Campbell Essential Biology, 4E Eric J Simon Solution Manuals

Instructor Guide for

Campbell Essential Biology Fifth Edition

&

Campbell Essential Biology with Physiology Fourth Edition

Simon • Dickey • Reece Edward J. Zalisko, Ph.D. Blackburn College

TABLE OF CONTENTS Chapter 1

Introduction: Biology Today .....................................................................

Chapter 2

Essential Chemistry for Biology ............................................................... 15

Chapter 3

The Molecules of Life ............................................................................... 27

Chapter 4

A Tour of the Cell ..................................................................................... 41

Chapter 5

The Working Cell ..................................................................................... 57

Chapter 6

Cellular Respiration: Obtaining Energy from Food ................................. 69

Chapter 7

Photosynthesis: Using Light to Make Food .............................................. 81

Chapter 8

Cellular Reproduction: Cells from Cells ................................................... 91

Chapter 9

Patterns of Inheritance .............................................................................. 107

Chapter 10

The Structure and Function of DNA ......................................................... 121

Chapter 11

How Genes Are Controlled ....................................................................... 137

Chapter 12

DNA Technology ...................................................................................... 151

Chapter 13

How Populations Evolve........................................................................... 167

Chapter 14

How Biological Diversity Evolves ........................................................... 185

Chapter 15

The Evolution of Microbial Life ............................................................... 199

Chapter 16

Plants, Fungi, and the Move onto Land .................................................... 215

Chapter 17

The Evolution of Animals ......................................................................... 231

Chapter 18

An Introduction to Ecology and the Biosphere......................................... 253

Chapter 19

Population Ecology ................................................................................... 271

Chapter 20

Communities and Ecosystems .................................................................. 285

Chapter 21

Unifying Concepts of Animal Structure and Function ............................. 303

Chapter 22

Nutrition and Digestion............................................................................. 317

Chapter 23

Circulation and Respiration ...................................................................... 331

Chapter 24

The Body’s Defenses ................................................................................ 349

Chapter 25

Hormones .................................................................................................. 361

Chapter 26

Reproduction and Development ............................................................... 371

Chapter 27

Nervous, Sensory, and Locomotor Systems ............................................. 387

Chapter 28

The Life of a Flowering Plant ................................................................... 409

Chapter 29

The Working Plant .................................................................................... 423

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Table of Contents

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INTRODUCTION

Author’s Foreword One of the greatest challenges facing instructors in any discipline is to remember what it was like before we understood the subject at hand. What were the mental obstacles we encountered on our way to understanding? What was it that we saw, heard, read, or touched that helped us make connections? What do we wish someone had said or explained?

Learning styles vary, and the experiences of our lives are unique. As teachers, we struggle to explain and connect the old to the new. The sections in this instructor’s guide titled “Student Misconceptions and Concerns” and “Teaching Tips” are intended to give teachers, old and new, something to think about as they prepare and teach their course.

Although these sections were written with a beginning instructor in mind, there should be something here for everyone to use. The field of biology is broad and fluid, offering new challenges in many diverse fields. For those of us with years of experience, a new twist or an opportunity to explain something in a different way can enliven our classes and refresh our efforts in the classroom.

It is my hope that you will find much here to consider, to make biology more meaningful and relevant to your students.

If you would like to share your insights and tips, for possible inclusion in future editions, your generous advice is most welcome and appreciated. We have so much to learn from each other.

ED ZALISKO, PH.D. PROFESSOR OF BIOLOGY BLACKBURN COLLEGE Forward suggestions to ezali@blackburn.edu. Please note Campbell Essential Biology Instructor Guide in the subject area of your email.

Instructor Exchange www.masteringbiology.com Click Instructor Resources in MasteringBiology and join other educators to learn more about creating an active learning environment for nonmajors and mixed-majors biology students. Retrieve and share ideas and experiences, ask questions, exchange tips and tricks, and engage in conversation with colleagues.

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CHAPTER

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Introduction: Biology Today

Why This Chapter Matters 1. We are living in the golden age of biology. Biological discoveries revolutionize medicine, change agriculture, and impact human culture.

2. Life is united not by a single trait, but by a common set of characteristics. Appreciating what it means to be living is as complex as life itself.

3. Life exists at many levels of biological organization. Understanding how these levels interrelate provides insight into the mechanisms of living systems.

4. The diversity of life is nested into groups that are united and interrelated by their shared evolutionary histories.

5. Science is a way of knowing and exploring our natural world. Most scientists use a combination of two main forms of inquiry: discovery science and hypothesis-driven science.

6. Understanding how science is done reveals the power and limits of this form of knowledge.

Chapter Objectives Biology and Society: Biology All Around Us 1. Describe three examples of how biology is woven into the fabric of society.

The Scope of Life 2. Describe seven properties or processes we associate with life.

3. List and give an example of each level of biological organization, starting with an ecosystem and ending with atoms.

4. Describe the two main dynamic processes in an ecosystem.

5. Compare the structure of prokaryotic and eukaryotic cells.

6. Distinguish between the three domains and four eukaryotic kingdoms of life.

Evolution: Biology’s Unifying Theme 7. Describe the two main points that Darwin made in his book On the Origin of Species by Means of Natural Selection.

8. Describe the two observations that led Darwin to his inescapable conclusion. State this conclusion.

9. Compare artificial and natural selection, noting similarities and differences.

The Process of Science 10. Compare discovery science and hypothesis-driven science. Provide examples of each regarding the study of trans fats in the human diet.

11. Distinguish between a hypothesis and a theory. Explain why natural selection qualifies as a scientific theory.

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13. Describe examples of the interdependence of technology and science.

Evolution Connection: Evolution in Our Everyday Lives 14. Explain how changes in the effectiveness of antibiotics illustrate natural selection.

Lecture Outline I. Biology and Society: Biology All Around Us 1. We are living in a golden age of biology 2. Scientists are studying a myriad of questions that are relevant to our lives a. How can errors in cell growth lead to cancer? b. How do plants trap solar energy? c. How do living creatures form ecological networks and how to human activities disrupt them? d. How did the great diversity of life on Earth evolve from the first microbes and how does such evolution have an impact on human health? e. How do mutations in genes lead to disease? f. How can DNA—the molecular basis of heredity—be used in forensic investigations?

II. The Scope of Life A. The Properties of Life 1. Biology is the scientific study of life 2. The study of biology encompasses a. a wide scale of size and b. a huge variety of life, both past and present.

B. Life at Its Many Levels 1. Biologists explore life at levels ranging from the biosphere to the molecules that make up cells C. Ecosystems 1. Each organism interacts continuously with its environment a. Organisms interact continuously with the living and nonliving factors in the environment. b. All the living organisms in a specific area, along with all of the non-living factors with which they interact, form an ecosystem.

2. The dynamics of any ecosystem depend on two main processes: a. recycling of chemical nutrients and b. flow of energy.

3. Within ecosystems a. nutrients are recycled but b. energy flows through.

D. Cells and Their DNA 1. The cell is the level at which the properties of life emerge 2. Cells are the lowest level of structure that can perform all activities required for life 3. All organisms are composed of cells 4. Cells are the subunits that make up multicellular organisms such as humans and trees 2

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5. All cells share many characteristics a. All cells are enclosed by a membrane that regulates the passage of materials between the cell and its surroundings. b. Every cell uses DNA as its genetic information.

6. We can distinguish two major types of cells: a. The prokaryotic cell is b. simpler and usually smaller and c. characteristic of bacteria. d. The eukaryotic cell is i. subdivided by internal membranes into different functional compartments called organelles and ii. found in plants and animals.

7. All cells use DNA as the chemical material of genes, the units of inheritance that transmit information from parents to offspring 8. The chemical language of DNA a. is common to all organisms and b. consists of just four molecular building blocks with names that are abbreviated as A, G, C, T. 9. Genetic engineering has transformed the pharmaceutical industry and extended millions of lives 10. The entire “book” of genetic instructions that an organism inherits is called its genome 11. The nucleus of each human cell packs a genome that is about 3 billion chemical letters long E. Life In Its Diverse Forms 1. Diversity is the hallmark of life a. The diversity of known life includes about 1.8 million species that biologists have identified and named. b. Estimates of the total number of species range from 10 million to over 100 million.

F. Grouping Species: The Basic Concept 1. Biodiversity can be beautiful but overwhelming 2. Categorizing life into groups helps us deal with this complexity 3. Taxonomy is the branch of biology that names and classifies species a. It formalizes the hierarchical ordering of organisms into broader and broader groups.

G. The Three Domains of Life 1. The three domains of life are a. Bacteria, b. Archaea, and c. Eukarya.

2. Bacteria and Archaea have prokaryotic cells 3. Eukarya have eukaryotic cells

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4. Eukarya include a. Kingdom Plantae, b. Kingdom Fungi, c. Kingdom Animalia, and d. Protists (multiple kingdoms).

5. Most plants, fungi, and animals are multicellular 6. Protists are generally single-celled 7. These three multicellular kingdoms are distinguished by how they obtain food a. Plants produce their own sugars and other foods by photosynthesis. b. Fungi are mostly decomposers, digesting dead organisms. c. Animals obtain food by ingesting (eating) and digesting other organisms.

H. Unity in the Diversity of Life 1. Underlying the diversity of life is a striking unity, especially at the lower levels of biological organization a. For example, all life uses the genetic language of DNA. 2. Biological evolution accounts for this combination of unity and diversity I. Evolution: Biology’s Unifying Theme 1. The history of life is a saga of a constantly changing Earth billions of years old a. Fossils document this history.

2. Life evolves a. Each species is one twig of a branching tree of life extending back in time through ancestral species more and more remote. b. Species that are very similar, such as the brown bear and polar bear, share a more recent common ancestor.

J. The Darwinian View of Life 1. The evolutionary view of life came into focus in 1859 when Charles Darwin published On the Origin of Species by Means of Natural Selection 2. Darwin’s book developed two main points: a. Species living today descended from a succession of ancestral species in what Darwin called “descent with modification,” capturing the duality of life’s i. unity (descent) and ii. diversity (modification). b. Natural selection is the mechanism for descent with modification.

K. Natural Selection 1. Darwin was struck by the diversity of animals on the Galápagos Islands 2. He thought that adaptation to the environment and the origin of new species were closely related processes a. As populations separated by a geographic barrier adapted to local environments, they became separate species.

L. Darwin’s Inescapable Conclusion 1. Darwin synthesized the theory of natural selection from two observations that were neither profound nor original a. Others had the pieces of the puzzle, but Darwin could see how they fit together.

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2. Observation 1: Overproduction and competition 3. Observation 2: Individual variation 4. Conclusion: Unequal reproductive success a. It is this unequal reproductive success that Darwin called natural selection. b. The product of natural selection is adaptation.

5. Natural selection is the mechanism of evolution M. Observing Artificial Selection 1. Artificial selection is the selective breeding of domesticated plants and animals by humans 2. In artificial selection, humans do the selecting instead of the environment N. Observing Natural Selection 1. There are many examples of natural selection in action a. Galápagos finches change beak size depending upon the size and shape of available seeds. b. Antibiotic-resistant bacteria have evolved in response to the overuse of antibiotics.

2. Darwin’s publication of The Origin of Species fueled an explosion in biological research a. Evolution is one of biology’s best demonstrated, most comprehensive, and longest-lasting theories. b. Evolution is the unifying theme of biology.

O. The Process of Science 1. The word science is derived from a Latin verb meaning “to know.” a. Science is a way of knowing, based on inquiry. b. Science developed from our curiosity about ourselves and the world around us.

2. There are two main scientific approaches: a. Discovery science is mostly about describing nature. b. Hypothesis-driven science is mostly about explaining nature.

P. Discovery Science 1. Science seeks natural causes for natural phenomena a. This limits the scope of science to the study of structures and processes that we can observe and measure directly or indirectly.

2. The dependence on observations that people can confirm demystifies nature and distinguishes science from belief in the supernatural 3. Verifiable observations and measurements are the data of discovery science a. In biology, discovery science enables us to describe life at its many levels, from ecosystems down to cells and molecules.

4. Discovery science a. can stimulate us to ask questions and seek explanations and b. uses a process of inquiry called the scientific method, consisting of a series of steps that provide a loose guideline for scientific investigations. c. Most modern scientific investigations can be described as hypothesis-driven science. i. A hypothesis is a tentative answer to a question — an explanation on trial. ii. Although we don’t think of it in those terms, we use hypotheses in solving everyday problems, like figuring out why a TV remote fails.

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Q. Hypothesis-Driven Science 1. Once a hypothesis is formed, an investigator can use logic to test it a. Then the hypothesis is tested by performing an experiment to see whether results are as predicted. b. This deductive reasoning takes the form of “If…then” logic.

III. The Process of Science: Are Trans Fats Bad for You? 1. One way to better understand how the process of science can be applied to real-world problems is to examine a case study, an in-depth examination of an actual investigation 2. Dietary fat comes in different forms 3. Trans fats are a non-natural form produced through manufacturing processes called hydrogenation 4. Trans fats a. add texture, b. increase shelf life, and c. are inexpensive to prepare.

5. A study of 120,000 female nurses found that a diet with high levels of trans fats nearly doubled the risk of heart disease 6. A hypothesis-driven study published in 2004 a. started with the observation that human body fat retains traces of consumed dietary fat, b. asked the question, Would the adipose tissue of heart attack patients be different from a similar group of healthy patients?, and c. formed the hypothesis that healthy patients’ body fat would contain less trans fats than the body fat in heart attack victims.

7. The researchers set up an experiment to determine the amounts of fat in the adipose tissue of 79 patients who had a heart attack 8. They compared these patients to the data for 167 patients who had not had a heart attack 9. This is an example of a controlled experiment, in which the control and experimental groups differ only in one variable—the occurrence of a heart attack 10. The results showed significantly higher levels of trans fats in the bodies of the heart attack patients 11. You would do well to read nutrition labels and avoid trans fats as much as possible in your own diet A. Theories in Science 1. What is a scientific theory, and how is it different from a hypothesis? a. A scientific theory is much broader in scope than a hypothesis. b. Theories only become widely accepted in science if they are supported by an accumulation of extensive and varied evidence.

2. Scientific theories are not the only way of “knowing nature.”

3. Science, religion, and art are very different ways of trying to make sense of nature B. The Culture of Science 1. Scientists build on what has been learned from earlier research a. They pay close attention to contemporary scientists working on the same problem.

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2. Cooperation and competition characterize the scientific culture a. Scientists check the conclusions of others by attempting to repeat experiments. b. Scientists are generally skeptics.

3. Science has two key features that distinguish it from other forms of inquiry. Science a. depends on observations and measurements that others can verify and b. requires that ideas (hypotheses) are testable by experiments that others can repeat.

C. Science, Technology, and Society 1. Science and technology are interdependent a. New technologies advance science. b. Scientific discoveries lead to new technologies. c. For example, the discovery of the structure of DNA about 60 years ago led to a variety of DNA technologies. d. Technology has improved our standard of living in many ways, but it is a double-edged sword. e. Technology that keeps people healthier has enabled the human population to double to 7 billion in just the past 40 years. f. The environmental consequences of this population growth may be devastating.

IV. Evolution Connection: Evolution in Our Everyday Lives 1. Antibiotics are drugs that help cure bacterial infections 2. When an antibiotic is taken, most bacteria are typically killed 3. Those bacteria most naturally resistant to the drug can still survive 4. Those few resistant bacteria can soon multiply and become the norm and not the exception 5. The evolution of antibiotic-resistant bacteria is a huge problem in public health 6. Antibiotics are being used more selectively 7. Many farmers are reducing the use of antibiotics in animal feed 8. It is important to note that the adaptation of bacteria to an environment containing an antibiotic does not mean that the drug created the antibiotic resistance. Instead, the environment screened the heritable variations that already existed among the existing bacteria

Chapter Guide to Teaching Resources The Scope of Life Student Misconceptions and Concerns 1. Many students enter our courses with a limited appreciation of the diversity of life. Ask any group of freshmen at the start of the semester to write down the first type of animal that comes to mind, and the most frequent response is a mammal. (In my courses, over a 21-year period, more than 98% of the examples have been mammals.) As the diversity of life is explored, the common heritage of biological organization can be less, and not more, apparent. The diverse forms, habits, and ecological interactions overwhelm our senses with differences. Emphasizing the diversity and unifying aspects of life is necessary for a greater understanding of the evolutionary history of life on Earth.

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2. We live in a world that is largely understood by what we can distinguish and identify with our naked senses. However, the diversity of life and the levels of biological organization extend well below the physical scale of our daily lives. For many students, appreciating the diversity of the microscopic world is abstract, nearly on par with an understanding of the workings of atoms and molecules. A laboratory opportunity to examine the microscopic details of objects from our daily lives (the surface of potato chips, the structure of table salt and sugar, the details of a blade of grass) can be an important sensory extension that prepares the mind for greater comprehension of these minute biological details.

Teaching Tips 1. Consider asking students to bring to class a page or two of an article about biology that appeared in the media in the last month. Alternatively, you could have each student e-mail a Web address of a recent biology-related news event to you. You might even have them e-mail relevant articles to you for each of the main topics you address throughout the semester.

2. The scientific organization Sigma Xi offers a free summary of the major science news articles each weekday. The first few paragraphs of each article are included with a hyperlink to the source of the entire article. The topics are most diverse and can be an excellent way to be aware of daily scientific announcements and reports. Typically, about ten articles are cited each weekday. Science In the News is part of the website at www.americanscientist.org/.

3. For a chance to add a little math to the biological levels of organization, consider calculating the general scale differences between each level of biological organization. For example, are cells generally 5, 10, 50, or 100 times more massive than organelles? Are organelles generally 5, 10, 50, or 100 times more massive than macromolecules? For some levels of organization, such as ecosystems, communities, and populations, size or scale differences are perhaps less relevant and more problematic to consider. However, at the smaller levels, the sense of scale might enhance an appreciation for levels of biological organization.

4. Help the class think through the diverse interactions between an organism and its environment.

In class, select an organism and have the class develop a list of environmental components that interact with the organism. This list should include living and nonliving categories.

5. The U.S. Census Bureau maintains updated population clocks that estimate the U.S. and world populations (www.census.gov/main/www/popclock.html). If students have a general idea of the human population of the United States, statistics about the number of people affected with a disease or disaster become more significant. For example, the current population of the United States is more than 311,000,000 (2011). It is currently estimated that at least 1 million people in the United States are infected with HIV. The number of people infected with HIV is impressive and concerning, but not perhaps as meaningful as the realization that this represents about one of every 311 people in the United States.

Although the infected people are not evenly distributed among geographic and ethnic groups, if you apply this generality to the enrollments in your classes, the students might better understand the tremendous impact of HIV infection.

6. The authors make an analogy between the four bases used to form genes and the 26 letters of the English alphabet used to create words and sentences. One could also make an analogy between the four bases and trains composed of four different types of railroad cars (perhaps an engine, boxcar, tanker, and flatcar). Imagine how many different types of trains one could make using just 100 rail cars of four different types. (The answer is 4 100.)

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7. An excellent introduction to the domains and kingdoms of life is presented at www.ucmp.berkeley.edu/exhibits/historyoflife.php.

Evolution: Biology’s Unifying Theme Student Misconceptions and Concerns 1. Students often believe that Charles Darwin was the first to suggest that life evolves; the early contributions by Greek philosophers and the work of Jean-Baptiste Lamarck may be unappreciated. Consider emphasizing this earlier work in your introduction to Darwin’s contributions.

2. Students often misunderstand the basic process of evolution and instead reflect a Lamarckian point of view. Organisms do not evolve structures deliberately or out of want or need. Individuals do not evolve. Evolution is a passive process in which the environment favors one or more variations of a trait that naturally exist within a population.

Teaching Tips 1. Many resources related to Charles Darwin are available on the Internet: a. General evolution resources: http://evolution.berkeley.edu/ http://nationalacademies.org/evolution/ http://ncse.com/ b. The complete works of Charles Darwin can be found at http://darwin-online.org.uk/ c. Details of Charles Darwin’s home are located at http://williamcalvin.com/bookshelf/down_hse.htm 2. There are many variations of games that model aspects of natural selection. Here is one that is appropriate for a laboratory exercise. Purchase several bags of dried grocery store beans of diverse sizes and colors. Large lima beans, small white beans, red beans, and black beans are all good options. Consider the beans “food” for the “predatory” students. To begin, randomly distribute (throw) 100 beans of each of four colors onto a green lawn. Allow individual students to collect beans over a set period, perhaps 3 minutes. Then count the total number of each color of bean collected. Assume that the beans remaining undetected (still in the lawn) reproduce by doubling in number. Calculate the number of beans of each color remaining in the field. For the next round, count out the number of each color to add to the lawn so that the new totals on the lawn will double the number of beans that students did not find in the first “generation.” Before each predatory episode, record the total number of each color of beans that have “survived” in the field. Then let your student “predators” out for another round of collection (generation).

Repeat the process for at least three or four “generations.” Note what colors of beans are favored by the environment. Apply Darwin’s “facts” and inescapable conclusions to this exercise. Ask students to speculate which colors might have been favored during another season or on a parking lot.

3. Many websites devoted to domesticated species can be used to illustrate the variety of forms produced by artificial selection. Those devoted to pigeons, chickens, and dogs have proven to be especially useful.

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The Process of Science Student Misconceptions and Concerns 1. Contrasting the concept of faith with the tentative nature of science can help to define and distinguish science from other ways of knowing. Students sometimes enter science classes expecting absolutes of facts and rigid dogma. Instead, scientific knowledge is tentative, reflecting degrees of confidence closely correlated to the strength of the evidence.

2. The authors’ distinction between natural and supernatural explanations is essential to understanding the power and limits of scientific explanations.

3. Some students think that variables are somehow restricted in a controlled experiment. That is, everything about the experiment is “controlled.” But as the textbook notes, controlled experiments limit the differences between experimental and control groups, with only one difference in most situations. That way, when a difference between the groups is identified, it can be explained by the single difference between the groups.

Teaching Tips 1. Consider using a laboratory exercise to have your students plan and perhaps conduct investigations using discovery science and a hypothesis-driven approach. Emphasize the processes and not the significance of the questions. Students can conduct descriptive surveys of student behavior (use of pens or pencils for taking notes, use of backpacks) or test hypotheses using controlled trials. Students may need considerable supervision and advice while planning and conducting their experiments.

2. Consider presenting your class with several descriptions of scientific investigations. Then ask students to categorize each type of experiment as discovery science or hypothesis-driven science. If students can work in small groups, encourage quick discussions to clarify these two types of scientific investigations.

3. You might also present to your class descriptions of several scientific investigations that you have written. Include in your descriptions numerous examples of improper methodology (small sample size, several variables existing between the control and experimental groups, failure to specifically test the hypothesis, and the like). Let small groups or individuals analyze the experiments in class to identify the flaws. This critical analysis allows students the opportunity to suggest the characteristics of good investigations in class.

4. Have your students explain why a coordinated “conspiracy” promoting a specific idea in science is unlikely to succeed. Have your students describe aspects of science that would check fraudulent or erroneous claims and/or political efforts.

5. The authors of Campbell’s Essential Biology note that the discovery of the structure and functions of DNA has led to a variety of DNA technologies. This technology is discussed in detail in Chapter 12.

Key Terms biology biosphere controlled experiment discovery science

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eukaryotic cell ecosystem genes hypothesis

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hypothesis-driven science life natural selection

prokaryotic cell science scientific method theory

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Word Roots bio = life (biology: the scientific study of life) eco = house (ecology: the study of how organisms interact with their environments) hypo = below (hypothesis: a tentative explanation) sphere = a ball (biosphere: the global ecosystem)

Relevant Songs to Play in Class “She Blinded Me with Science,” Thomas Dolby

“Put It to the Test,” They Might Be Giants

“Weird Science,” Oingo Boingo “The Scientist,” Coldplay

“(What a) Wonderful World” (“Don’t Know Much Biology. . .”), Sam Cooke

“Applied Science,” 311

“Biology,” Joe Jackson

“Science Is Real,” They Might Be Giants

“Alive,” P.O.D.

“The Sounds of Science,” Beastie Boys

Answers to End-of-Chapter Questions The Process of Science 1. Suggested answer: a. Hypothesis: Mice learn better when provided with food rewards.

Prediction: Over the course of several days, mice provided with food at the end of a maze will take less time to correctly navigate the maze than mice that are not provided with food at the end. b. The control group was the mice given no food reward and the experimental group was the mice provided with a food reward. A control group was needed for comparison. As can be seen in the graph, even mice that were not provided with a food reward learned to navigate the maze faster over time. c. Variables such as diet, time of day, age, and gender were probably controlled so as to minimize their effects on the results. Additional variables such as number of wrong turns and speed of the mouse will also have to be measured to determine whether they are actually learning better or just moving faster. For example, if both groups make the same number of wrong versus correct turns in the maze, but the control group is moving more slowly, then the time to completion may not be due to better learning, especially if the mice are hungry d. The data do support the above hypothesis because mice provided with food learned to navigate the maze faster with fewer wrong turns than mice that were not provided with food.

2. Suggested answer: If scientists understand and can control cell division in other fruits and vegetables, it may enable them to increase their size and marketability, like modern storebought tomatoes. All multicellular organisms, including humans, start as a single cell that repeatedly divides. Understanding the genetic control of this cell division will therefore help elucidate embryonic development, a fundamental component of eukaryotic biology.

Some diseases, such as cancer, are the result of problems with cell division, so understanding this process better may lead to treatments and cures for these diseases.

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Biology and Society 3. Students may get these stories from a variety of sources, such as the Internet, TV news and documentaries, magazines, and radio. Questions to consider for each story include: What is the biological connection? Does the reporting appear accurate? Are hypotheses being tested? What new questions arise from this story? Does this change how the audience perceives something afterward? Is there a connection to the students’ own life?

4. Some issues and questions to consider: Did the car have trouble starting or did you have to find a new way to school this morning? How did you work around the fact that your TV did not work today? Did you figure out what was wrong with your MP3 player? If students’ narrative description of their hypothesis-driven experiment is thorough enough, including their thought processes along the way, then the steps of the scientific method should become readily apparent.

Additional Critical Thinking Questions The Process of Science 1. Tobacco is the leading cause of preventable cancers today. In fact, there are very few known cancers for which smoking is not considered a risk factor. The relationship between cigarette smoking and disease has been studied for years. How can this problem be studied at many different levels of biological organization? Give some examples.

Suggested answer: A scientist may try to identify the molecules in tobacco that cause cancer and study how they affect cells (or DNA replication). At the organ level, a scientist may ask how the smoke and the chemicals in the smoke damage the lungs and other organs in the body.

The statistical relationship between tobacco smoke and the incidents of lung cancer can be studied at the population level. Finally, if a study on how smoke might affect organisms other than humans were considered, then this would be at the community level.

2. A newspaper headline reads “Scientific Study Shows That Coffee Can Cut Risk of Suicide.” The article states that in a 10-year study of 86,626 female nurses, there were 10 suicides among individuals who drank 2–3 cups of caffeinated coffee per day, compared with 21 suicides among individuals who almost never drank coffee. The researcher notes that these results were consistent with those of a previous study of 128,934 men and women done virtually the same way. The article also includes the following: (a) mention of a previous study indicating that the amount of caffeine in 2–3 cups of coffee tends to increase the drinker’s general energy level, sense of well-being, and motivation to work; (b) criticism by another scientist, who found the study flawed because it failed to address how many nurses used antidepressant drugs; and (c) mention that the researcher recorded the use of alcohol and tobacco by the nurses but did not record the number of nurses who were depressed and told by their physicians not to drink coffee. Do you think the conclusion in the headline is justified? Why or why not? How would you reword the headline to reflect more accurately the study as described? What key elements of the scientific process did the researcher use? Which ones were not used?

Suggested answer: The headline’s conclusion is not supported by the information in the article. Although there were about half as many suicides among caffeinated-coffeedrinking nurses, the study did not rule out the effects of other factors that could affect suicide rates, such as antidepressant drugs and a physician’s advice. Also, the amount of caffeine in a cup of coffee may vary; did the researcher take this into account (that is, determine if the amount of caffeine intake was significantly different between the two 12

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groups of nurses)? A headline such as “Preliminary Results May Point to Beneficial Effects of Caffeine” would be more appropriate. The researcher used observations (results of a previous study), then posed a question, a hypothesis (2–3 cups of coffee per day reduces the rate of suicide among nurses), a prediction of a test outcome, and a test (comparing the number of suicides in two groups of nurses). However, the study was flawed, and the scientific process compromised, by a failure to consider all possible factors influencing suicides. In addition to the concerns above, we cannot know about cause and effect. What if depression typically causes a person to avoid coffee? Correlations do not always lead to causes and effects.

3. Consider the following observation: A group of 10 overweight patients has high levels of LDL (low-density lipoprotein) cholesterol. Based on this limited information and using the scientific method, develop a question followed by a hypothesis. Design an experiment to test your hypothesis (make sure to indicate a control) and indicate predicted results.

Suggested answer: A possible question that could be asked is “Is weight a factor in developing high LDL cholesterol levels?” A possible hypothesis might be “Individuals who are overweight will develop high levels of LDL cholesterol.” In this experiment, it would be necessary to recruit overweight individuals for LDL cholesterol screening. The participants should be screened so that their diets and exercise levels are similar.

Individuals in the control group should be matched to those in the experimental group (exercise habits, diet habits) except that they are not overweight. Their LDL levels will also be monitored. The predicted results might be that factors other than weight contribute to elevated levels of LDL cholesterol. It should also be noted that this experiment does not test whether or not high LDL levels cause people to be overweight!

Biology and Society 1. Intelligent design theory is an argument used by some people to challenge the teaching of evolution in public schools. One of the supporters of this idea argues that certain biological structures, such as the bacterial flagellum, require so many complex parts working together in perfect synchronization that it is not possible that they could have evolved from simpler structures. This argument has arisen, in various forms for more than 200 years, states that a simpler structure could not perform the same function, which is evidence of “irreducible complexity.” This is cited as evidence for an intelligent designer. Do you consider this theory scientific? Why or why not? Would you support the inclusion of this theory in the science classroom? If so, would you also support contrasting this theory to the theory of evolution?

Some issues and questions to consider: Explain why intelligent design is not within the boundaries of science. What experiments could we perform to test for a designer? If flaws are discovered in evolutionary theory and other explanations are required, does that automatically support intelligent design theory (a false dichotomy)? Can structures have adaptive advantages that change as new parts are added or modified in the system? For example, can the bones in bird wings have served another function before they became adapted for flight?

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CHAPTER

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Essential Chemistry for Biology

Why This Chapter Matters 1. Many important biological questions can be reduced to aspects of chemistry.

2. Living organisms are, at their most basic level, chemical systems.

3. Understanding the chemical level of biology requires a basic understanding of chemistry.

4. Water’s unique life-supporting properties can be traced to the structure and interactions of its molecules.

Chapter Objectives Biology and Society: More Precious than Gold 1. Explain why water is precious to life and how droughts cause such damage.

Some Basic Chemistry 2. Distinguish between matter, chemical elements, and compounds. Give examples of each.

3. Explain the significance of trace elements to human health.

4. Describe the relative size, location, and electrical charge of protons, neutrons, and electrons within an atom. Explain how the atomic number and mass number are determined.

5. Define an isotope and explain how isotopes are used in biological research and medicine.

6. Explain how the location of electrons determines the chemical properties of an atom.

7. Distinguish between ionic, covalent, and hydrogen chemical bonds.

8. Describe the structure of water and explain how its shape makes water a polar molecule.

9. Write the chemical formula for the creation of water from hydrogen and oxygen. Identify the reactants and products of this reaction.

Water and Life 10. Describe the four life-supporting properties of water. Describe an example of how each property affects some form of life.

11. Describe the relationship between aerobic exercise and brain size.

12. Distinguish between the chemical properties of acids, bases, and neutral solutions.

Explain how buffers stabilize the pH of acidic and basic solutions.

13. Describe the potential impact of rising levels of carbon dioxide on the pH of the ocean.

Evolution Connection: The Search for Extraterrestrial Life 14. Explain why the search for extraterrestrial life centers on the search for water.

Lecture Outline I. Biology and Society: More Precious than Gold 1. A drought is a. a period of abnormally dry weather that changes the environment and b. one of the most devastating disasters. ..

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2. Droughts can cause a. severe crop damage, b. shortages of drinking water, c. dust storms, d. famine, e. habitat loss, and f. mass migration.

3. Throughout human history, droughts have helped wipe out societies and even whole civilizations 4. Droughts are catastrophic because life cannot exist without water

II. Some Basic Chemistry 1. Take any biological system apart, and you eventually end up at the chemical level 2. Chemical reactions are always occurring in the human body A. Matter: Elements and Compounds 1. Matter is anything that occupies space and has mass 2. Matter is found on Earth in three physical states: a. solid, b. liquid, and c. gas.

3. Matter is composed of chemical elements a. An element is a substance that cannot be broken down into other substances by chemical reactions. b. There are 92 naturally occurring elements on Earth.

4. All of the elements are listed in the periodic table 5. Twenty-five elements are essential to people 6. Four elements make up about 96% of the weight of most cells: a. oxygen, b. carbon, c. hydrogen, and d. nitrogen.

7. Trace elements are a. required in only very small amounts and b. essential for life.

8. An iodine deficiency causes goiter 9. Fluorine a. is added to dental products and drinking water and b. helps to maintain healthy bones and teeth.

10. Elements can combine to form compounds a. Compounds are substances that contain two or more elements in a fixed ratio. b. Common compounds include i. NaCl (table salt) and ii. H2O (water).

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B. Atoms 1. Each element consists of one kind of atom a. An atom is the smallest unit of matter that still retains the properties of an element.

2. The Structure of Atoms 3. Atoms are composed of subatomic particles a. A proton is positively charged. b. An electron is negatively charged. c. A neutron is electrically neutral.

4. Most atoms have protons and neutrons packed tightly into the nucleus a. The nucleus is the atom’s central core. b. Electrons orbit the nucleus.

5. Elements differ in the number of subatomic particles in their atoms a. The number of protons, the atomic number, determines which element it is. b. Mass is a measure of the amount of material in an object. c. An atom’s mass number is the sum of the number of protons and neutrons in its nucleus.

6. Isotopes 7. Isotopes are alternate mass forms of an element 8. Isotopes a. have the same number of protons and electrons but b. differ in their number of neutrons.

9. The nucleus of a radioactive isotope decays spontaneously, giving off particles and energy 10. Radioactive isotopes have many uses in research and medicine a. They can be used to determine the fate of atoms in living organisms. b. They are used in PET scans to diagnose heart disorders and some cancers.

11. Uncontrolled exposure to radioactive isotopes can harm living organisms by damaging DNA a. The 1986 Chernobyl nuclear accident released large amounts of radioactive isotopes. b. Naturally occurring radon gas may cause lung cancer.

12. Electron Arrangement and the Chemical Properties of Atoms 13. Of the three subatomic particles, only electrons are directly involved in the chemical activity of an atom 14. Electrons orbit the nucleus of an atom in specific electron shells 15. The farther an electron is from the nucleus, the greater its energy 16. The number of electrons in the outermost shell determines the chemical properties of an atom C. Chemical Bonding and Molecules 1. Chemical reactions enable atoms to give up or acquire electrons, completing their outer shells 2. Chemical reactions usually result in atoms a. staying close together and b. being held together by attractions called chemical bonds.

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3. Ionic Bonds 4. When an atom loses or gains electrons, it becomes electrically charged a. Charged atoms are called ions. b. Ionic bonds are formed between oppositely charged ions.

5. Covalent Bonds 6. A covalent bond forms when two atoms share one or more pairs of outer-shell electrons 7. Covalent bonds are the strongest of the various bonds 8. Covalent bonds hold atoms together in a molecule 9. The number of covalent bonds an atom can form is equal to the number of additional electrons needed to fill its outer shell 10. Hydrogen Bonds 11. Water is a compound in which the electrons in its covalent bonds are not shared equally a. This causes water to be a polar molecule, one with an uneven distribution of charge.

12. The polarity of water results in weak electrical attractions between neighboring water molecules a. These weak attractions are called hydrogen bonds.

D. Chemical Reactions 1. Cells constantly rearrange molecules by breaking existing chemical bonds and forming new ones a. Such changes in the chemical composition of matter are called chemical reactions. b. A simple example is the reaction between oxygen gas and hydrogen gas that forms water.

2. Chemical reactions include a. reactants, the starting materials, and b. products, the end materials.

3. Chemical reactions a. can rearrange matter b. but cannot create or destroy matter.

III. Water and Life 1. Life on Earth began in water and evolved there for 3 billion years a. Modern life remains tied to water. b. Your cells are composed of 70–95% water.

2. The abundance of water is a major reason Earth is habitable A. Water’s Life-Supporting Properties 1. The polarity of water molecules and the hydrogen bonding that results explain most of water’s life-supporting properties a. Water molecules stick together. b. Water has a strong resistance to change in temperature. c. Frozen water floats. d. Water is a common solvent for life.

2. The Cohesion of Water

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3. Water molecules stick together as a result of hydrogen bonding a. This tendency of molecules of the same kind to stick together is called cohesion. b. Cohesion is vital for the transport of water from the roots to the leaves of plants.

4. Surface tension is the measure of how difficult it is to stretch or break the surface of a liquid a. Hydrogen bonds give water an unusually high surface tension.

5. How Water Moderates Temperature 6. Because of hydrogen bonding, water has a strong resistance to temperature change 7. Heat and temperature are related, but different a. Heat is the amount of energy associated with the movement of the atoms and molecules in a body of matter b. Temperature measures the intensity of heat 8. Water can absorb and store large amounts of heat while only changing a few degrees in temperature 9. Water can moderate temperatures a. Earth’s giant water supply causes temperatures to stay within limits that permit life. b. Evaporative cooling occurs when a substance evaporates and the surface of the liquid remaining behind cools down.

10. The Biological Significance of Ice Floating 11. When water molecules get cold enough, they move apart, forming ice 12. A chunk of ice has fewer water molecules than an equal volume of liquid water 13. Ice floats because it is less dense than liquid water 14. If ice did not float, ponds, lakes, and even the oceans would freeze solid 15. Life in water could not survive if bodies of water froze solid 16. Water as the Solvent of Life 17. A solution is a liquid consisting of a homogeneous mixture of two or more substances a. The dissolving agent is the solvent. b. The dissolved substance is the solute.

18. When water is the solvent, the result is an aqueous solution B. The Process of Science: Can Exercise Boost Your Brain Power?

1. Observation: Human brains shrink as we age 2. Question: Can aerobic exercise slow or reverse brain loss?

3. Hypothesis: MRI scans will reveal differences between people who regularly exercised aerobically and those who did not 4. Prediction: Brains of active people shrink less than the brains of less active people 5. Experiment: Twenty-nine people in their 60s and 70s exercised for three one-hour sessions per week. A control group of 29 people engaged in non-aerobic stretching exercises for the same periods 6. Results: The aerobic group showed significant increases in brain volume compared to the non-aerobic group C. Acids, Bases, and pH 1. A chemical compound that releases H+ to a solution is an acid 2. A compound that accepts H+ and removes them from solution is a base

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3. To describe the acidity of a solution, chemists use the pH scale 4. Buffers are substances that resist pH change 5. Buffers a. accept H+ ions when they are in excess and b. donate H+ ions when they are depleted.

6. Increases in global CO2 concentrations may lead to a. the acidification of the oceans and b. ecological disasters.

D. Evolution Connection: The Search for Extraterrestrial Life 1. If life similar to ours has evolved elsewhere in the universe, then it too would depend upon water 2. Researchers at NASA missions have found evidence that water was once abundant on Mars 3. Microbial life may exist below the Martian surface

Chapter Guide to Teaching Resources Some Basic Chemistry Student Misconceptions and Concerns 1. The dangers posed by certain chemicals in our food and broader environment often mislead people to associate “chemicals” with harm. People might not want “chemicals” added to their food or in their environment. Students often fail to appreciate the chemical nature of our bodies and our world and the potential harm or benefits of naturally occurring chemistry. They often fail to understand why “natural” does not necessarily mean “good.” (Consider presenting a long list of naturally occurring toxins to make this point.) Your class may benefit from a class discussion of these misconceptions about our attitudes toward “chemicals.”

2. Students with limited backgrounds in chemistry and physics might struggle with basic concepts of mass, weight, compounds, elements, and isotopes. It may also be early in the semester when mature study habits have not yet developed. Consider passing along basic studying advice and tips to help students master these early chemistry concepts. In-class quizzes (graded or not) or a few homework problems will also provide reinforcing practice.

3. The half-lives of many radioactive substances, especially those used for dating fossils, might lead some students to expect very long periods of decay for any radioactive substance. This might even be alarming if students are someday asked to consume a radioactive substance for a medical test. However, some medically significant isotopes have relatively short half-lives. Radioactive iodine-131 is often used to diagnose or treat certain thyroid problems. Its half-life of 8 days means that it will decay quickly.

Teaching Tips 1. Students might be interested in the following aside: One of the challenges of raising captive, exotic animals is meeting the unique dietary requirements of the species. A zoo might have trouble keeping a particular animal because science has not fully determined what trace elements the animal requires.

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2. Many breakfast cereals are fortified with iron. A person can crush the cereal and extract distinct iron particles with a magnet. An overhead projector or video imagining device should clearly reveal the iron particles stuck to the magnet. This short practical demonstration can help connect an abstract concept to a concrete example.

3. Students with limited backgrounds in chemistry will benefit from a discussion of Figure 2.7 and the differences and limitations of diagrams of atomic structures. The contrasts in Figure 2.7 are a good beginning of such a discussion.

4. Here is a comparison that helps make the point about the differences in mass of protons and electrons. If a proton is as massive as a bowling ball, an electron will be the mass of a Life Saver candy. (This is calculated by considering a 15-pound bowling ball, a Life Saver with a mass of 0.12 ounces, and the textbook’s formula that an electron is 1/2,000 the mass of a proton.)

5. Here is an analogy regarding the size of a helium atom. If a helium atom were the size of Yankee Stadium, the nucleus would be about the size of a fly in center field, and the two electrons would be like tiny gnats buzzing around the stadium. This analogy helps to relate the great distances between parts of an atom. Consider modifying the analogy to any local stadium in your region.

6. After sharing teaching tips 4 and 5 above, consider asking your students to compare the mass of the gnat orbiting Yankee Stadium to the mass of the fly in center field. If a proton or neutron is about 2,000 times more massive than an electron, how does the mass of a helium nucleus compare to the mass of one of its electrons?

7. Have your students try to calculate the number of covalent bonds possible for a variety of atoms. Then provide the students with a list of elements and the number of outer electrons for each and have them make predictions about the chemical formula for many types of molecules.

8. Consider challenging your students to suggest relationships in human lives that are analogous to each of the three types of chemical bonds (covalent, ionic, and hydrogen).

Evaluating the accuracy of potential analogies requires careful analysis of the chemical bonding relationships and practices critical thinking skills. Small groups might provide immediate critiques before passing along analogies for the entire class to consider. The following is one example.

Ionic and covalent bonds are different types of relationships. Consider this analogy.

A woman taking out a loan has a specific relationship to her bank. She owes the bank money, something she got from the bank. A man shares an office with another man. Both look out the same window and answer the same phone. Ionic bonds are like a bank loan, in which something is borrowed. Covalent bonds are like sharing an office, with items (electrons) shared by both members of the relationship. After presenting this analogy, ask your students to modify the office analogy to represent a polar covalent bond. (Perhaps one man in the office sits closer to the window and the phone.)

9. As noted in the text, chemical reactions do not create or destroy matter. Instead, they rearrange the structure and form new relationships. This is much like shuffling and dealing cards. When playing poker, cards are not created nor destroyed. Instead, new combinations are formed as the cards are dealt to the players.

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Water and Life Student Misconceptions and Concerns 1. Students are unlikely to have carefully considered the four special properties of water that are apparent in our lives. However, these properties are of great biological significance and are often familiar. The connections between these properties and personal experiences can invest great meaning into a discussion of water’s properties. A homework assignment asking for three examples of each of these properties in each student’s experiences will require reflection and potentially produce meaningful illustrations. Similarly, quizzes or exam questions matching examples of each property to a list of the properties requires high-level evaluative analysis.

2. Students at all levels struggle with the distinction between heat and temperature. Students might also expect that all ice is about the same temperature, 0°C. Redefining and correcting misunderstandings often takes more class time and energy than introducing previously unknown concepts.

Teaching Tips 1. Here is a way to have your students think about the “sticky” nature of water in their lives.

Ask them to consider the need for a towel after a shower or a bath. Once we get out of the shower or bath, we have left the source of water. So why do we need the towel? The reason we need a towel to dry off is that water is still clinging to our bodies because water molecules are polar. The molecules on cell surfaces are also polar, so our skin and the water both “stick” to each other.

2. Some students may be intrigued if you tell them that you too can stand on the surface of water—when it is frozen. Thus, it is necessary to note a liquid water surface when talking about surface tension.

3. Have students compare the seasonal ranges of temperatures of Anchorage and Fairbanks, Alaska. (Many websites provide weather information about various cities.) These two northern cities have large differences in their annual temperature ranges. Make the point that the coastal location of Anchorage moderates the temperature.

4. Several versions of the following analogy are easy to relate to students. (a) Ask students how the average on an exam would be affected if the brightest students did not take the test. (b) The authors note that the performance of a track team would drop if the fastest sprinters didn’t compete. In both analogies, removing the top performers lowers the average just as the evaporation of the most active water molecules cools the evaporative surface.

5. “It is not the heat, it is the humidity.” The efficiency of evaporative cooling is affected by humidity. As humidity rises, the rate of evaporation decreases, making it more difficult to cool our heat-generating bodies on a warm and humid summer day.

6. Ask your students if the ocean levels would change if ice did not float or if all the floating ice in the oceans were to melt. They can try this experiment to find out. Place several large chunks of ice in a glass and fill the glass up completely with water to the top rim. Thus, the ice cubes should be sticking up above the top of the filled glass. Will the glass overflow when the ice melts? (No.) This phenomenon is important when we consider the potential consequences of global warming. If floating glaciers melt, ocean levels will not be affected. However, if the ice over land melts, we can expect increased ocean levels.

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7. Challenge students to think of other consequences from the expansion of water when it forms ice. (These include the ability to widen cracks in rocks, roads, and sidewalks!)

8. A simple demonstration of a solute dissolving in a solvent can focus students’ attention on the process when discussing solutions. Using colored water and white sugar or salt may make it easier to see and reference while you are discussing the process. Such simple visual aids add life to a lecture. (You might also add corn oil to the top of the solution to demonstrate the properties of hydrophobic substances, and challenge your class to explain why oil and water do not mix.)

9. Discussions of pH are enhanced by lab activities that permit students to test the pH of everyday items (foods and household solutions). If students do not have opportunities to conduct such tests in lab, consider testing a few items during your class (pH paper or a basic pH meter will, of course, be necessary).

10. The Environmental Protection Agency website www.epa.gov/acidrain/ includes good information about acid precipitation and teaching ideas.

11. The SETI (Search for Extraterrestrial Intelligence) Institute’s Mission is “to explore, understand and explain the origin, nature, and prevalence of life in the universe” (www.seti.org). Your students might enjoy exploring this respected scientific organization.

Key Terms acid aqueous solution atom atomic number base buffers chemical bonds chemical reactions cohesion

compounds covalent bond electron elements evaporative cooling heat hydrogen bonds ions ionic bond

isotopes mass mass number matter molecule neutron nucleus pH scale polar molecule

products proton radioactive isotope reactants solute solution solvent temperature trace elements

Word Roots aqua = water (aqueous: a type of solution in which water is the solvent) co = together; valent = strength (covalent bond: an attraction between atoms that share one or more pairs of outer-shell electrons) electro = electricity (electron: a subatomic particle with a single unit of negative electrical charge) iso = equal (isotope: an element having the same number of protons and electrons but a different number of neutrons) neutr = neither (neutron: a subatomic particle with a neutral electrical charge)

Relevant Songs to Play in Class “Neutron Dance,” Pointer Sisters

“Meet the Elements,” They Might Be Giants

“Better Living Through Chemistry,” Queens of the Stone Age

“Chemistry,” Rush

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“Opposites Attract,” Paula Abdul

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Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: Allow an animal to breathe radioactively labeled oxygen. After the animal has had ample time for aerobic respiration, test the carbon dioxide and water in the exhaled gases to see where the labeled oxygen is found. The primary location of the radioactively labeled oxygen should be in the water molecules formed during aerobic respiration.

12. Suggested answer: These two atoms would form an ionic bond. The potassium atom would donate an electron to the fluorine atom. As a result of this transfer of electrons, each atom would complete its outer electron shell and be chemically stable. However, they would become ions and therefore attract each other, resulting in an ionic compound otherwise known as a salt.

Biology and Society 13. Do chemicals produced by human technology differ from naturally occurring substances?

If so, how?

Suggested answer: A molecule of sugar, water, or carbon dioxide is the exact same whether or not it was made by a plant, animal or in a factory. They are made by the same elements regardless of the molecule’s origin. However, a potential problem may be contaminants from industrial cleaners found in highly processed food. Also, some processed foods may contain high amounts of fructose or trans fats that are not as healthy as naturally occurring foods that have more nutrients 14. Some issues and questions to consider: What chemicals are in the coal being burned?

How does burning the coal affect the chemicals (or what type of chemical reactions are taking place); what types of new chemicals are formed? How are these chemicals harmful to the environment? Which is less expensive, power from nuclear power plants or power from fossil-fuel plants? Does the price of electricity from nuclear versus coal fired plants reflect its actual cost, including environmental costs?

Which would be more harmful: the environmental effects of acid precipitation, ocean acidification, coal mining, and global warming from fossil-fuel power plants or the effects of nuclear wastes and potential nuclear accidents? What are the environmental impacts of mining coal or uranium; which one has more environmental impacts? How do we dispose of the waste from nuclear power plants and coal plants?

Additional Critical Thinking Questions The Process of Science 1. The atomic number for chlorine is 17 and the atomic number for potassium is 19. Draw electron shell diagrams for each atom. Predict what would happen with the electrons if a chlorine atom and a potassium atom came into contact. What kind of bond do you think they would form?

Suggested answer: Chlorine needs 1 electron for a full outer shell of 8, and if potassium loses 1 electron, its outer shell will have 8. Potassium will lose an electron (becoming a positive ion), and chlorine will pick it up (becoming a negative ion). The oppositely charged ions will attract to each other and form an ionic bond.

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2. A newspaper headline reads “Acid Precipitation Not a Threat.” The article states that the city’s air pollution control board has been monitoring sulfur oxides and nitrogen oxides in the air and recording the pH of precipitation for the past five years. Air samples have been collected daily at two sites: at the busiest downtown intersection and at the entrance to a privately owned electrical power–generating station. On most days, the power station is downwind from the downtown area. Over the period studied, sulfur oxides and nitrogen oxides have increased at both sites, with the power station always having higher levels than the downtown site. However, at no time in the past five years have any of the pollutant levels exceeded the nationally acceptable standards. Moreover, the pH of precipitation has remained essentially the same (slightly acidic) at both monitoring sites throughout the period. City officials have concluded that there is no immediate reason for alarm, that acid precipitation has not been a problem, but that monitoring should continue.

The news article, however, goes on to point out that not everyone agrees with the city officials. One resident living 10 miles outside the city is quoted: “The trees on our streets and in our yards are dying from acid precipitation. Five years ago, all our trees were healthy, but we’ve lost a dozen in this neighborhood in the past two years. We’re directly downwind from that power plant, and I know acid rain killed my trees. My neighbors and I are going to sue the power company for losses.”

Do you think these residents have the scientific evidence needed to win their lawsuit? Why or why not? Would they have a clear-cut case if a monitoring site had been set up in their neighborhood and data collected there showed an increase in acid precipitation during the five-year period? If the residents hired you as a scientific consultant, what advice would you give them?

Suggested answer: The situation is complex, and the residents’ case seems to be weak, at best. Assuming they are downwind from the city and the power plant, their air might be more polluted and their precipitation more acidic than air sampled at either collection site; however, there seems to be no evidence backing their claim. Evidence from sampling stations suggests that the city and the power plant are adding pollutants to the air, but there is no indication that the added pollution is causing acid precipitation. If samples collected at a monitoring station in the residents’ neighborhood showed an increase in acid precipitation, the residents’ case might still be weak (they could not tell if the power plant was the main source of pollutants if their air comes from both the city and the power plant). Also, the courts might not view the residents’ air pollution problem as serious unless the pollutant levels in their air exceeded national standards. Where would you place sampling stations to get the best idea of the source of air pollutants? Would the residents’ case be strengthened if they discovered that the power plant monitoring station was not downwind from the city or that for three of the five years, the wind actually blew in the other direction most days and nights? A scientific consultant might initially suggest a study to determine if other air pollutants, infectious diseases, insects, groundwater pollution, or other factors are responsible for the tree deaths. Would eliminating these factors as causative agents strengthen the acid precipitation case? Are the nationally accepted standards of pollutants based on what is safe for humans or for nature (nutrient concentrations for drinking water are based on consumption; however, higher nutrient concentrations in water that is safe for drinking can have large effects on freshwater communities. The pH of a soda is safe for consumption but is acidic enough to kill many species of plants and animals.

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Biology and Society 3. Many communities add fluoride to the drinking water supplies because of the ability of fluoride to bond with tooth enamel and prevent cavities, which are holes in the enamel caused by bacteria in the mouth. Fluoride is a negatively charged ion formed when a salt (such as sodium fluoride) is added to water. A tin salt, stannous fluoride, is a common ingredient in toothpaste. Is your water supply fluoridated? If you were choosing whether or not to drink fluoridated water, what questions or concerns would you have before making your decision?

Some issues and questions to consider: How strong is the evidence that fluoride reduces the rate of cavities in treated populations? What is the evidence that adding fluoride to the water supply is safe? Is there data suggesting that fluoride can have damaging effects on the body? If you discover some of these effects, keep in mind the importance of the concentration of the fluoride tested. How high is the fluoride concentration in fluoridesupplemented water? Since fluoride salts are a significant part of Earth’s crust, small amounts of fluoride are found in all groundwater. What is the range of normal concentrations found throughout the country? How does this concentration compare to the amount added artificially? Since fluoride’s effect is on the teeth, could applying fluoride directly to the teeth rather than ingesting it in the water be safer?

4. Considering the number of cases of food-borne illness each year, some people (including the U.S. Food and Drug Administration, FDA) have suggested that the irradiation of food is a solution to decreasing illness and death from contaminated foods. In addition, thisSS process helps to extend shelf life and prevent spoilage of perishable foods. During the process, foods are exposed to various types of radiation. This radiation damages and kills any cells that might be living on the surface (such as bacteria). Some people are against the use of irradiation without ever really understanding how the process works. Would you be willing to eat foods that have been irradiated? Should these foods have to be labeled as irradiated? Would you be willing to pay more for these products?

Some issues and questions to consider: Consider the lengthy history of testing irradiation on foods and the current use of radiation on spices. Do irradiated foods become radioactive? Is there any health risk associated with eating these products? Is the expense warranted? How much more will irradiated foods cost? Should the food be labeled to give consumers a choice? Will irradiated foods actually decrease illness and death from contaminated foods?

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CHAPTER

3

The Molecules of Life

Why This Chapter Matters 1. Biological molecules are the building blocks of cells, the fundamental units of life.

2. Knowing the structures, properties, and roles of the four major classes of organic molecules (carbohydrates, lipids, proteins, and nucleic acids) is essential to understanding the characteristics of life.

3. Carbohydrates, proteins, and lipids are vital components of human diets and the diets of most organisms.

4. Regional differences in lactose intolerance illustrate a medically significant aspect of human evolution.

Chapter Objectives Biology and Society: Got Lactose?

1. Describe the causes and consequences of lactose intolerance.

Organic Compounds 2. Describe the special bonding properties of carbon that allow it to form an endless variety of organic molecules.

3. Compare a dehydration reaction to hydrolysis.

Large Biological Molecules 4. Compare the structures and roles of monosaccharides, disaccharides, and polysaccharides in living organisms. Give examples of each.

5. Describe the unique properties of lipids.

6. Compare the structure and properties of saturated and unsaturated fatty acids.

7. Distinguish between steroids and anabolic steroids, and explain how the use of anabolic steroids can be dangerous to a person’s health.

8. Describe the structure of proteins. Distinguish between the primary structure and the final three-dimensional shape.

9. Describe and compare the structures of DNA and RNA.

Evolution Connection: Evolution and Lactose Intolerance in Humans 10. Explain why we think that lactose intolerance has a genetic basis.

11. Explain why lactose intolerance has evolved differently in humans spread throughout the world.

Lecture Outline I. Biology and Society: Got Lactose?

1. Lactose is the main sugar found in milk

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2. Lactose intolerance is the inability to properly digest lactose a. Instead of lactose being broken down and absorbed in the small intestine, b. lactose is broken down by bacteria in the large intestine, producing gas and discomfort.

3. Lactose intolerance can be addressed by a. avoiding foods with lactose or b. consuming lactase pills along with food.

II. Organic Compounds 1. A cell is mostly water 2. The rest of the cell consists mainly of carbon-based molecules 3. Carbon forms large, complex, and diverse molecules necessary for life’s functions 4. Organic compounds are carbon-based molecules A. Carbon Chemistry 1. Carbon is a versatile atom a. It has four electrons in an outer shell that holds eight electrons. b. Carbon can share its electrons with other atoms to form up to four covalent bonds.

2. Carbon can use its bonds to a. attach to other carbons and b. form an endless diversity of carbon skeletons varying in size and branching pattern.

3. The simplest organic compounds are hydrocarbons, which contain only carbon and hydrogen atoms 4. The simplest hydrocarbon is methane, a single carbon atom bonded to four hydrogen atoms 5. Larger hydrocarbons form fuels for engines 6. Hydrocarbons of fat molecules are important fuels for our bodies 7. Each type of organic molecule has a unique three-dimensional shape 8. The shapes of organic molecules relate to their functions 9. The unique properties of an organic compound depend on a. its carbon skeleton and b. the atoms attached to the skeleton.

10. The groups of atoms that usually participate in chemical reactions are called functional groups. Two common examples are a. hydroxyl groups (-OH) and b. carboxyl groups (-COOH).

11. Many biological molecules have two or more functional groups B. Giant Molecules from Smaller Building Blocks 1. On a molecular scale, many of life’s molecules are gigantic, earning the name macromolecules 2. Three categories of macromolecules are a. carbohydrates, b. proteins, and c. nucleic acids.

3. Most macromolecules are polymers

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4. Polymers are made by stringing together many smaller molecules called monomers 5. A dehydration reaction a. links two monomers together and b. removes a molecule of water.

6. Organisms also have to break down macromolecules 7. Digestion breaks down macromolecules to make monomers available to your cells 8. Hydrolysis a. breaks bonds between monomers, b. adds a molecule of water, and c. reverses the dehydration reaction.

III. Large Biological Molecules 1. There are four categories of large biological molecules: a. Carbohydrates, b. Lipids, c. Proteins, and d. Nucleic acids.

A. Carbohydrates 1. Carbohydrates include sugars and polymers of sugar. They include a. small sugar molecules in energy drinks and b. long starch molecules in spaghetti and French fries.

2. In animals, carbohydrates are a. a primary source of dietary energy and b. raw material for manufacturing other kinds of organic compounds.

3. In plants, carbohydrates serve as a building material for much of the plant body 4. Monosaccharides 5. Monosaccharides are a. simple sugars that cannot be broken down by hydrolysis into smaller sugars and b. the monomers of carbohydrates.

6. Common examples are a. glucose in sports drinks and b. fructose found in fruit.

7. Both glucose and fructose are found in honey 8. Glucose and fructose are isomers, molecules that have the same molecular formula but different structures 9. Monosaccharides are the main fuels for cellular work 10. In water, many monosaccharides form rings 11. Disaccharides 12. A disaccharide is a. a double sugar, b. constructed from two monosaccharides, and c. formed by a dehydration reaction.

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13. Disaccharides include a. lactose in milk, b. maltose in beer, malted milk shakes, and malted milk ball candy, and c. sucrose in table sugar.

14. Sucrose is a. the main carbohydrate in plant sap and b. rarely used as a sweetener in processed foods in the United States.

15. High-fructose corn syrup is made by a commercial process that converts a. natural glucose in corn syrup to b. much sweeter fructose.

16. The United States is one of the world’s leading markets for sweeteners 17. The average American consumes a. about 45 kg of sugar (about 100 lb) per year, b. mainly as sucrose and high-fructose corn syrup.

18. Polysaccharides 19. Polysaccharides are a. complex carbohydrates b. made of long chains of sugar units—polymers of monosaccharides.

20. Starch a. is a familiar example of a polysaccharide, b. is used by plant cells to store energy, and c. consists of long strings of glucose monomers.

21. Potatoes and grains are major sources of starch in our diet 22. Glycogen is a. used by animals cells to store energy and b. converted to glucose when it is needed.

23. Cellulose a. is the most abundant organic compound on Earth, b. forms cable-like fibrils in the walls that enclose plant cells, and c. cannot be broken apart by most animals.

24. Monosaccharides and disaccharides dissolve readily in water 25. Cellulose does not dissolve in water 26. Almost all carbohydrates are hydrophilic, or “water-loving,” adhering water to their surface B. Lipids 1. Lipids are a. neither macromolecules nor polymers and b. hydrophobic, unable to mix with water.

C. Fats 1. A typical fat, or triglyceride, consists of a. a glycerol molecule, b. joined with three fatty acid molecules, c. via a dehydration reaction.

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2. Fats perform essential functions in the human body including a. energy storage, b. cushioning, and c. insulation.

3. If the carbon skeleton of a fatty acid has a. fewer than the maximum number of hydrogens, it is unsaturated or b. the maximum number of hydrogens, it is saturated.

4. A saturated fat has a. no double bonds and b. all three of its fatty acids saturated.

5. Most animal fats a. have a high proportion of saturated fatty acids, b. can easily stack, tending to be solid at room temperature, and c. contribute to atherosclerosis, in which lipid-containing plaques build up along the inside walls of blood vessels.

6. Most plant and fish oils tend to be a. high in unsaturated fatty acids and b. liquid at room temperature.

7. Hydrogenation a. adds hydrogen, b. converts unsaturated fats to saturated fats, c. makes liquid fats solid at room temperature, and d. creates trans fat, a type of unsaturated fat that is particularly bad for your health.

8. Steroids 9. Steroids are very different from fats in structure and function a. The carbon skeleton is bent to form four fused rings. b. Steroids vary in the functional groups attached to this set of rings, and these chemical variations affect their function.

10. Cholesterol is a. a key component of cell membranes and b. the “base steroid” from which your body produces other steroids, such as estrogen and testosterone.

11. Synthetic anabolic steroids a. are variants of testosterone, b. mimic some of its effects, c. can cause serious physical and mental problems, d. may be prescribed to treat diseases such as cancer and AIDS, and e. are abused by athletes to enhance performance.

12. Most athletic organizations now ban the use of anabolic steroids because of their a. health hazards and b. unfairness, by providing an artificial advantage.

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D. Proteins 1. Proteins a. are polymers constructed from amino acid monomers, b. account for more than 50% of the dry weight of most cells, c. perform most of the tasks required for life, and d. form enzymes, chemicals that change the rate of a chemical reaction without being changed in the process.

2. The Monomers of Proteins: Amino Acids 3. All proteins are macromolecules constructed from a common set of 20 kinds of amino acids 4. Each amino acid consists of a central carbon atom bonded to four covalent partners 5. Three of those attachment groups are common to all amino acids: i. a carboxyl group (-COOH), ii. an amino group (-NH2), and iii. a hydrogen atom.

6. Proteins as Polymers 7. Cells link amino acids together a. by dehydration reactions, b. forming peptide bonds, and c. creating long chains of amino acids called polypeptides.

8. Your body has tens of thousands of different kinds of protein 9. Proteins differ in their arrangement of amino acids 10. The specific sequence of amino acids in a protein is its primary structure 11. A slight change in the primary structure of a protein affects its ability to function 12. The substitution of one amino acid for another in hemoglobin causes sickle-cell disease, an inherited blood disorder 13. Protein Shape 14. A functional protein consists of a. one or more polypeptide chains, b. precisely twisted, folded, and coiled into a molecule of unique shape 15. Proteins consisting of one polypeptide have three levels of structure 16. Proteins consisting of more than one polypeptide chain have a fourth level, quaternary structure 17. A protein’s three-dimensional shape a. typically recognizes and binds to another molecule and b. enables the protein to carry out its specific function in a cell.

18. What Determines Protein Shape?

19. A protein’s shape is sensitive to the surrounding environment 20. An unfavorable change in temperature and/or pH can cause denaturation of a protein, in which it unravels and loses its shape 21. High fevers (above 104ºF) in humans can cause some proteins to denature

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22. Misfolded proteins are associated with a. Alzheimer’s disease, b. mad cow disease, and c. Parkinson’s disease.

E. Nucleic Acids 1. Nucleic acids are macromolecules that a. store information, b. provide the directions for building proteins, and c. include DNA and RNA. 2. DNA resides in cells in long fibers called chromosomes 3. A gene is a specific stretch of DNA that programs the amino acid sequence of a polypeptide 4. The chemical code of DNA must be translated from “nucleic acid language” to “protein language.”

5. Nucleic acids are polymers made from monomers called nucleotides 6. Each nucleotide has three parts: a. a five-carbon sugar, b. a phosphate group, and c. a nitrogen-containing base.

7. Each DNA nucleotide has one of four possible nitrogenous bases: a. adenine (A), b. guanine (G), c. thymine (T), or d. cytosine (C).

8. Dehydration reactions a. link nucleotide monomers into long chains called polynucleotides, b. form covalent bonds between the sugar of one nucleotide and the phosphate of the next, and c. form a sugar-phosphate backbone.

9. Nitrogenous bases hang off the sugar-phosphate backbone 10. Two strands of DNA join together to form a double helix 11. Bases along one DNA strand hydrogen-bond to bases along the other strand 12. The functional groups hanging off the base determine which bases pair up: a. A only pairs with T and b. G can only pair with C. 13. RNA, ribonucleic acid, is different from DNA a. RNA uses the sugar ribose and the base uracil (U) instead of thymine (T). b. RNA is usually single-stranded, but DNA usually exists as a double helix.

F. The Process of Science: Does Lactose Intolerance Have a Genetic Basis?

1. Observation: Most lactose-intolerant people have a normal version of the lactase gene 2. Question: What is the genetic basis for lactose intolerance?

3. Hypothesis: Lactose-intolerant people have a mutation but not within the lactase gene

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4. Prediction: A mutation would be found near the lactase gene 5. Experiment: Genes of 196 lactose-intolerant people were examined 6. Results: Researchers found a 100% correlation between lactose intolerance and a nucleotide at a site approximately 14,000 nucleotides away from the lactase gene G. Evolution Connection: Evolution and Lactose Intolerance in Humans 1. Most people are lactose-intolerant as adults 2. Lactose intolerance is found in a. 80% of African Americans and Native Americans, b. 90% of Asian Americans, but c. only 10% of Americans of northern European descent.

3. Lactose tolerance appears to have evolved in northern European cultures that relied upon dairy products 4. Ethnic groups in East Africa that rely upon dairy products are also lactose tolerant but due to different mutations

Chapter Guide to Teaching Resources Organic Compounds Student Misconceptions and Concerns 1. General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension.

2. Students might need to be reminded about the levels of biological organization. The relationship between atoms, monomers, and polymers can be confusing as each is discussed. Consider noting these relationships somewhere in the classroom (such as on the board) where students can quickly glance for reassurance.

Teaching Tips 1. One of the great advantages of carbon is its ability to form up to four bonds, permitting the assembly of diverse components and branching configurations. Challenge your students to find another element that might also permit this sort of adaptability. (Like carbon, silicon has four electrons in its outer shell.)

2. Toothpicks and gumdrops (or any other pliable small candy) permit the quick construction of chemical models. Different candy colors can represent certain atoms. The model of the methane molecule in Figure 3.2 can thus easily be demonstrated (and consumed!)

3. A drill with interchangeable drill bits is a nice analogy to carbon skeletons with different functional groups. The analogy supports the role of different functions with different structures.

4. The author notes that a polymer is a like a pearl necklace made of many pearl “monomers.”

5. Train cars linking together to form a train is another nice analogy to monomers linking to form polymers. Consider adding that as the train cars are joined, a puff of steam appears—thus, the reference to water production and a dehydration reaction when linking molecular monomers.

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Large Biological Molecules Student Misconceptions and Concerns 1. The abstract nature of chemistry can be discouraging to many students. Consider starting out this section of the lecture by examining the chemical groups on a food nutrition label.

Candy bars with peanuts are particularly useful as they contain significant amounts of all three sources of calories (carbohydrates, proteins, and lipids).

2. Students might struggle to extrapolate the properties of lipids to their roles in an organism.

Ducks float because their feathers repel water instead of attracting it. Hair on your head remains flexible because of oils produced in your scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world.

3. The functional significance of protein shape is an abstract molecular example of form and function relationships, which might be new to some students. The binding of an enzyme to its substrate is a type of molecular handshake, which permits specific interactions. To help students think about form and function relationships, share some concrete analogies in their lives—perhaps flathead and Phillips screwdrivers that match the proper type of screws or the fit of a hand into a glove.

4. The evolution of lactose tolerance within human groups in East Africa does not represent a deliberate decision, yet this evolutionary change appears logical. Many students perceive adaptations as deliberate events with purpose. As students develop a better understanding of the mechanisms of evolution, it will be important to point out that mutations arise by chance, with the culling hand of natural selection favoring traits that convey an advantage.

Organisms cannot plan evolutionary change.

Teaching Tips 1. Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references; for example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included).

2. If your lectures will eventually include details of glycolysis and aerobic respiration, this is a good point to introduce the basic concepts of glucose as fuel. Just introducing this conceptual formula might help: eating glucose + breathing in oxygen (yields) water + usable energy (used to build ATP) + heat + exhaled CO2.

3. The section about our use of sugars may be of considerable interest to your students, who might not be expecting much interest in a lecture about organic chemistry. Consider an assignment for each student to bring to class a product label indicating high-fructose corn syrup (HFCS) as an ingredient.

4. Learning the definitions of word roots is invaluable when learning science. Learning the meaning of the prefix word roots “mono” (one), “di” (two), and “poly” (many) helps to distinguish the structures of various carbohydrates.

5. Consider an assignment for students to find reliable sources that discuss high sugar consumption in the modern diet. The key, of course, is in the quality of the resource.

Consider narrowing down the categories to certain nonprofit health organizations (American Cancer Society, American Heart Association, and the like) and peer-reviewed journals.

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6. A simple exercise demonstrates the enzymatic breakdown of starches into sugars.

If students place an unsalted cracker in their mouths, holding it in their mouths while it mixes well with saliva, they might soon notice that a sweeter taste begins to emerge. The salivary enzyme amylase begins the digestion of starches into disaccharides, which may be degraded further by other enzymes. These disaccharides are the source of the sweet taste.

7. The cellophane wrap often used to package foods is a biodegradable material derived from cellulose. Consider challenging students to create a list of other cellulose-derived products (such as paper).

8. An adult human may store about a half of a kilogram of glycogen in the liver and muscles of the body, depending on recent dietary habits. A person who begins dieting might soon notice an immediate weight loss of 2–4 pounds (1–2 kilograms) over several days, reflecting reductions in stored glycogen, water, and intestinal contents (among other factors).

9. Another simple demonstration can illustrate hydrophobic and hydrophilic substances. In front of the class, mix colored water and a yellow oil (corn or canola oil work well). Shake up the mixture and then watch as the two separate. (You may have a mixture already made that remains separated; however, the dyes may bleed between the oil and the water.)

10. Margarine in stores commonly comes in liquid squeeze containers, in tubs, and in sticks.

These forms reflect increasing amounts of hydrogenation, gradually increasing the stiffness from a liquid, to a firmer spread, to a firm stick of margarine. As noted in the text, recent studies have suggested that unsaturated oils become increasingly unhealthy as they are hydrogenated. Perhaps your students can find references to this correlation on the Internet.

11. Many analogies relate to students the diversity of proteins that can be made from just 20 amino acids. The authors note that our language uses combinations of 26 letters to form words. Proteins are much longer “words,” creating even more diversity. Another analogy is to trains. This builds on the earlier analogy when polymers were introduced. Imagine making different trains about 100 cars long, using any combination of 20 types of railroad cars. Mathematically, the number of possible trains is 20100, a number beyond imagination.

12. The functional significance of protein shape is an abstract molecular example of form and function relationships, which might be new to some students. The binding of an enzyme to its substrate is a type of “molecular handshake,” which permits specific interactions. To help students think about form and function relationships, share some concrete analogies in their lives—perhaps flathead and Phillips screwdrivers that match the proper type of screws or the fit of a hand into a glove.

13. The authors note that the difference between a polypeptide and a protein is analogous to the relationship between a long strand of yarn and a sweater knitted from yarn. Proteins are clearly more complex!

14. Most cooking results in changes in the texture and color of a food. The brown color of a steak is the product of the denaturation of proteins. Fixatives such as formalin also denature proteins and cause color changes. Students who have dissected vertebrates will realize that the brown color of the muscles makes it look as if the animal has been cooked.

15. Consider this assignment to wrap up the presence of organic molecules in our diets. Have students working individually or in small groups analyze a food label listing the components of a McDonald’s Big Mac. Note the most abundant organic molecule class (perhaps by weight) found in each component.

16. The “NA” in DNA and RNA represents “nucleic acid.” Students often do not make this association without assistance.

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Key Terms amino acid atherosclerosis carbohydrates cellulose dehydration reaction denaturation disaccharide DNA double helix fat functional groups

gene glycogen hydrocarbons hydrogenation hydrolysis hydrophilic hydrophobic isomers lipids macromolecules monomers

monosaccharides nucleic acids nucleotides organic compounds peptide bond polymers polypeptide polysaccharides primary structure protein RNA

saturated starch steroids sugar-phosphate backbone trans fat triglyceride unsaturated

Word Roots de = without or remove di = two; sacchar = sugar (disaccharide: two monosaccharides joined together) glyco = sweet; gen = producing (glycogen: a polysaccharide sugar used to store energy) hydro = water; lyse = break (hydrolysis: breaking chemical bonds by adding water) iso = equal; meros = part (isomer: molecules with similar molecular formulas but different structures) macro = big (macromolecules: a giant molecule in living organisms) mono = single (monosaccharide: simplest type of sugar) philic = loving (hydrophilic: water-loving property of a molecule) phobos = fearing (hydrophobic: water-repelling property of a molecule) poly = many (polymer: a chain made from smaller organic molecules) sclero = hard (atherosclerosis: hardening of the arteries) trans = across, through, or change (an unsaturated fat produced by the partial hydrogenation of a vegetable oil) tri = three (triglyceride: a glycerol molecule joined with three fatty acid molecules) un = not (unsaturated: fats that are not saturated)

Relevant Songs to Play in Class “Sugar, Sugar,” The Archies

“Sugar, We’re Going Down,” Fall Out Boy

“I’ve Got You Under My Skin,” Frank Sinatra

Answers to End-of-Chapter Questions The Process of Science 13. Suggested answer: A long hydrocarbon chain ending in a carboxyl group is a fatty acid.

Fatty acids and glycerol are the molecules that result when fats (triglycerides) are hydrolyzed. The evidence thus suggests that the cake mix does contain fat. To further support this hypothesis, intact fat molecules must be isolated from the mix. ..

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14. Suggested answer: Each mutant version of the lactase enzyme would need to be tested on lactose. The enzyme could be added to lactose and the products could be analyzed. If glucose and galactose were present, then the enzyme did in fact work; therefore, its shape has not been significantly altered. If glucose and galactose were not present after the enzyme had been added to lactose, then the shape of the enzyme has been significantly altered so that it can no longer do its job.

Biology and Society 15. Some additional issues and questions to consider: Is it fair for some athletes to have an “edge” over their competitors who are not using anabolic steroids? Is the competition so fierce that athletes are willing to assume the health risks for the athletic advantage? Should various private agencies and/or the government regulate the use of steroids? Should athletes randomly be tested for steroid use? Should athletes be disqualified from events if they have used anabolic steroids? Should all professional sports be subject to testing with similar penalties? Should steroids be legal in professional sports but not amateur sports?

What are the types of steroids and do they all have the same effects on athletic performance and health? Should other unregulated, but legal, substances—including creatine, caffeine, and even protein supplements, which can enhance athletic performance—be regulated or banned from sports?

16. Some additional issues and questions to consider: Should individuals be responsible for the consequences of their own actions? What, if any, distinctions can you make between people choosing to smoke versus people who consume fast food? Should courts be involved in such decisions? What can fast-food companies do to make the “dangers” of their products obvious to the consumers? Should insurance costs be raised to provide the money needed to care for the health of individuals who choose to smoke or eat unhealthy foods? If the fast-food companies are intentionally adding unhealthy or harmful substances, such as trans fats to improve taste and keep costs down, should they be held accountable? Should such unhealthy foods be taxed at a higher rate to pay for rising medical costs?

17. Some additional issues and questions to consider: How are these chemicals important in agriculture, medicine, and public health? How have they affected humans? Wildlife?

Natural vegetation? Would you use a chemical such as DDT to remove mosquitoes that spread malaria (one of the deadliest diseases to humans worldwide) knowing that it is harmful to birds of prey? Are the chemicals themselves harmful, or is the way that they are used harmful? What influences have shaped your opinions? The media? Personal experience? Reading? Friends and family? How might the opinion of a villager in a developing country differ from yours?

Additional Critical Thinking Questions The Process of Science 1. We always hear that starchy foods are a great source of nutrition because the glucose molecules that are contained within the starch can be used for energy. People often tell you to eat starchy foods prior to an athletic event. Cellulose (or fiber) is also made of many glucose molecules. Why don’t people tell you to eat lots of cellulose prior to an athletic event? Make sure your answer explains the chemical difference between starch and cellulose.

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Suggested answer: Although starch and cellulose are both made of glucose molecules, the difference between them is how those glucose molecules are bonded together. We have the enzymes to break the bonds in starch to release glucose, which can be used for energy. We are lacking enzymes to break the bonds in cellulose. This means that the glucose contained within cellulose can’t be used by humans.

2. Linus Pauling believed that large doses of vitamin C can help prevent the common cold, cancer, and other diseases. Imagine you have been given a research grant by the National Institutes of Health to evaluate Pauling’s claims. How would you go about setting up an experimental study to determine whether vitamin C can prevent colds? How would you evaluate the results of your study?

Some issues and questions to consider: How will you choose your test subjects? How many subjects should you have? Will you give them all vitamin C or just some of them?

What criteria will you use to divide the test subjects into groups? What is a control group?

Should the subjects know whether they are getting vitamin C or not? Should the experimenters who are giving out the drug and measuring the severity of cold symptoms know which of the subjects are getting vitamin C? What is a double-blind study? If there is a difference between your groups, how can you be sure it is due to vitamin C? 3. Answer the following based on the information provided on these nutritional labels.

Total fat Saturated fat Monounsaturated fat Polyunsaturated fat

Product A 30 g 8g 10 g 12 g

Product B 26 g 10 g 10 g 6g

Which product would you select if you were concerned about your health? Give two reasons why you would select that product. If the ingredient label of this product mentioned the term hydrogenated oils, what would that term mean? Manufacturers have gotten away with some fairly questionable labeling procedures to deceive consumers concerning the actual nutritional content of their products. Do you think that the U.S. Food and Drug Administration (FDA) should make some changes to the nutritional labels?

Suggested answer: Product A is the better choice. It has less saturated fat and more polyunsaturated fat. If hydrogenated oils were present, this would indicate that unsaturated fats have had hydrogens added, which essentially makes them the same as a saturated fat.

These hydrogenated fats are typically referred to as trans fats to deceive the consumer.

Product B may have less total fat, but higher saturated and monounsaturated fat, which is indicative of trans fats.

Biology and Society 4. Scientists are working on a radically new type of computer designed to use DNA as the information material rather than the silicon chips found in today’s computers. What is the basis for using DNA as an information storage and processing molecule? What are some of the potential advantages and disadvantages of this technology?

Some issues and questions to consider: Electronic computers with silicon chips store information in one of only two forms: on or off. DNA, however, has four different bases (A, T, C, and G). In addition, DNA is a very small molecule compared to a silicon chip;

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therefore, DNA might be able to dramatically reduce the size and increase the speed and storage capacity of computers. Most electronic computers work linearly—that is, they process data sets one after the other (much like your reading of this sentence). A DNA computer, however, is based on biochemical reactions using DNA as the reactant. These reactions can occur in parallel: Billions of DNA molecules can undergo a biochemical reaction (like copying the DNA) simultaneously. However, chemical reactions can be slow and may not occur faithfully. DNA is capable of mutation, so why not DNA computers?

Can we (as thinking human beings) be considered DNA computers? Would a DNA computer of the future be considered a living thing? Would they meet the definitions of life in Chapter 1, or would that definition have to be altered?

5. The term organic is perceived by most people to mean that such products are natural and harmless. Each year, industrial chemists develop and test thousands of new organic compounds for use as pesticides, fungicides, and weed killers. In what ways are these chemicals useful and important to us? In what ways can they be harmful? Is your general opinion of pesticides positive or negative?

Some issues and questions to consider: How are these chemicals important in agriculture, medicine, and public health? How have they affected humans? Wildlife? Natural vegetation? Are the chemicals themselves harmful, or is the way that they are used harmful? What influences have shaped your opinions? The media? Personal experience?

Reading? Friends and family? What are the differences between the biological term organic and the food industry’s definition of organic?

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CHAPTER

4

A Tour of the Cell

Why This Chapter Matters 1. Cells are the smallest entity that exhibits all the characteristics of life.

2. Cells are as fundamental to biology as atoms are to chemistry.

3. An understanding of cell structure and function is essential to understanding most human disease.

Chapter Objectives Biology and Society: Antibiotics: Drugs that Target Bacterial Cells 1. Explain how antibiotics specifically target bacteria while minimally harming the human host.

The Microscopic World of Cells 2. Compare the following pairs of terms, noting the most significant differences: light microscopes versus electron microscopes, scanning electron microscopes versus transmission electron microscopes, magnification versus resolution, prokaryotic cells versus eukaryotic cells, plant cells versus animal cells.

Membrane Structure 3. Describe the structure of the plasma membrane and other membranes of the cell. Explain why this structure is called a fluid mosaic.

4. Explain how MRSA bacteria disable human immune cells.

5. Compare the structures and functions of a plant cell wall and the extracellular matrix of an animal cell.

The Nucleus and Ribosomes: Genetic Control of the Cell 6. Explain how the genetic information in the nucleus is used to direct the production of proteins in the cytoplasm.

The Endomembrane System: Manufacturing and Distributing Cellular Products 7. Compare the structures and functions of the following components of the endomembrane system: rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.

Chloroplasts and Mitochondria: Energy Conversion 8. Compare the structure and function of chloroplasts and mitochondria. Describe the adaptive advantages of extensive folds in the grana of chloroplasts and the inner membrane of mitochondria.

The Cytoskeleton: Cell Shape and Movement 9. Describe the functions of the cytoskeleton. Compare the structures and functions of cilia and flagella.

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Evolution Connection: The Evolution of Antibiotic Resistance 10. Explain how and why antibiotic-resistant bacteria have evolved.

Lecture Outline I. Biology and Society: Antibiotics: Drugs that Target Bacterial Cells 1. Antibiotics were first isolated from mold in 1928 2. The widespread use of antibiotics drastically decreased deaths from bacterial infections 3. Most antibiotics kill bacteria while minimally harming the human host by binding to structures found only on bacterial cells 4. Some antibiotics bind to the bacterial ribosome, leaving human ribosomes unaffected 5. Other antibiotics target enzymes found only in the bacterial cells A. The Microscopic World of Cells 1. Organisms are either a. Single-celled, such as most prokaryotes and protists, or b. Multicelled, such as i. plants, ii. animals, and iii. most fungi.

B. Microscopes as Windows on the World of Cells 1. Light microscopes can be used to explore the structures and functions of cells 2. When scientists examine a specimen on a microscope slide, a. light passes through the specimen and b. lenses enlarge, or magnify, the image.

3. Magnification is an increase in the object’s image size compared to its actual size 4. Resolving power is the ability of an optical instrument to show two objects as separate 5. Cells were first described in 1665 by Robert Hooke 6. By the mid-1800s, the accumulation of scientific evidence led to the cell theory, which states that a. all living things are composed of cells and b. all cells come from other cells.

7. The electron microscope (EM) uses a beam of electrons, which results in 100-fold better resolution than light microscope 8. Two kinds of electron microscopes reveal different parts of cells 9. Scanning electron microscopes (SEMs) examine cell surfaces 10. Transmission electron microscopes (TEMs) are useful for studying the internal structure of a cell 11. The most powerful electron microscopes can a. magnify up to 100,000 times and b. distinguish between objects 0.2 nanometers apart.

12. Light microscopes are still very useful for studying living cells

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C. The Two Major Categories of Cells 1. The countless cells on Earth fall into two basic categories: a. Prokaryotic cells—Bacteria and Archaea and b. Eukaryotic cells—protists, plants, fungi, and animals.

2. All cells have several basic features a. They are all bounded by a thin plasma membrane. b. Inside all cells is a thick, jelly-like fluid called the cytosol, in which cellular components are suspended. c. All cells have one or more chromosomes carrying genes made of DNA. d. All cells have ribosomes, tiny structures that build proteins according to the instructions from the DNA. 3. Prokaryotic cells are older than eukaryotic cells a. Prokaryotes appeared about 3.5 billion years ago. b. Eukaryotes appeared about 2.1 billion years ago.

4. Prokaryotic cells are a. usually smaller than eukaryotic cells and b. simpler in structure.

5. Eukaryotes a. Only eukaryotic cells have organelles, membrane-enclosed structures that perform specific functions. b. The most important organelle is the nucleus, which i. houses most of a eukaryotic cell’s DNA and ii. is surrounded by a double membrane.

6. A prokaryotic cell lacks a nucleus. Its DNA is coiled into a nucleus-like region called the nucleoid, which is not partitioned from the rest of the cell by membranes D. An Overview of Eukaryotic Cells 1. Eukaryotic cells are fundamentally similar 2. The region between the nucleus and plasma membrane is the cytoplasm 3. The cytoplasm consists of various organelles suspended in the liquid cytosol 4. Unlike animal cells, plant cells have a. chloroplasts, which convert light energy to the chemical energy of food in the process of photosynthesis, and b. protective cell walls.

5. Only animal cells have lysosomes, bubbles of digestive enzymes surrounded by membranes

II. Membrane Structure 1. The plasma membrane separates the living cell from its nonliving surroundings A. The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins 1. The remarkably thin membranes of cells are composed mostly of a. lipids and b. proteins.

2. The lipids belong to a special category called phospholipids 3. Phospholipids form a two-layered membrane, the phospholipid bilayer 4. Most membranes have specific proteins embedded in the phospholipid bilayer ..

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5. These proteins help regulate traffic across the membrane and perform other functions 6. The plasma membrane is a fluid mosaic a. Fluid because molecules can move freely past one another. b. A mosaic because of the diversity of proteins in the membrane.

B. The Process of Science: What Makes a Superbug?

1. Particularly dangerous strains of bacteria, known as MRSA, are unaffected by several common antibiotics 2. Observation: Some bacteria use a protein called PSM to disable human immune cells by forming holes that rip apart the plasma membrane 3. Question: Does PSM play a role in MRSA infections?

4. Hypothesis: MRSA bacteria lacking the ability to produce PSM would be less deadly than normal MRSA strains 5. Experiment: Researchers infected a. seven mice with normal MRSA and b. eight mice with MRSA that does not produce PSM. 6. Results: a. All seven mice infected with normal MRSA died. b. Five of the eight mice infected with MRSA that does not produce PSM survived.

7. Conclusions: a. MRSA strains appear to use the membrane-destroying PSM protein, but b. factors other than PSM protein contributed to the death of mice (possibly other membrane-destroying proteins).

C. Cell Surfaces 1. Plant cells have rigid cell walls surrounding the membrane 2. Plant cell walls a. are made of cellulose, b. protect the cells, c. maintain cell shape, and d. keep cells from absorbing too much water.

3. Animal cells a. lack cell walls and b. typically have an extracellular matrix, which i. helps hold cells together in tissues and ii. protects and supports them.

4. The surfaces of most animal cells contain cell junctions, structures that connect cells together into tissues, allowing them to function in a coordinated way

III. The Nucleus and Ribosomes: Genetic Control of the Cell 1. The nucleus is the chief executive of the cell a. Genes in the nucleus store information necessary to produce proteins. b. Proteins do most of the work of the cell.

A. Structure and Function of the Nucleus 1. The nucleus is separated from the cytoplasm by a double membrane called the nuclear envelope 44

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2. Pores in the envelope allow materials to move between the nucleus and cytoplasm 3. The nucleus contains a nucleolus where ribosomes are made 4. Stored in the nucleus are long DNA molecules and associated proteins that form fibers called chromatin 5. Each long chromatin fiber constitutes one chromosome 6. The number of chromosomes in a cell depends on the species B. Ribosomes 1. Ribosomes are responsible for protein synthesis 2. Ribosome components are made in the nucleolus but assembled in the cytoplasm 3. Ribosomes may assemble proteins while the ribosomes are a. suspended in the fluid of the cytoplasm or b. attached to the outside of the nucleus or an organelle called the endoplasmic reticulum.

C. How DNA Directs Protein Production 1. DNA programs protein production in the cytoplasm by transferring its coded information into messenger RNA (mRNA) 2. Messenger RNA exits the nucleus through pores in the nuclear envelope 3. A ribosome moves along the mRNA, translating the genetic message into a protein with a specific amino acid sequence

IV. The Endomembrane System: Manufacturing and Distributing Cellular Products 1. Many membranous organelles forming the endomembrane system in a cell are interconnected either a. directly by their membranes or b. by transfer of membrane segments between them.

A. The Endoplasmic Reticulum 1. The endoplasmic reticulum (ER) is one of the main manufacturing facilities in a cell 2. The ER a. produces an enormous variety of molecules, b. is connected to the nuclear envelope, and c. is composed of smooth and rough ER. 3. Rough ER 4. The “rough” in rough ER refers to ribosomes that stud the outside of this portion of the ER membrane 5. These ribosomes produce membrane proteins and secretory proteins 6. Some products manufactured by rough ER are dispatched to other locations in the cell by transport vesicles, sacs made of membrane that bud off from the rough ER 7. Smooth ER 8. The smooth ER a. lacks surface ribosomes, b. produces lipids, including steroids, and c. helps liver cells detoxifys circulating drugs.

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B. The Golgi Apparatus 1. The Golgi apparatus a. works in partnership with the ER and b. receives, refines, stores, and distributes chemical products of the cell.

C. Lysosomes 1. A lysosome is a membrane-bound sac of digestive enzymes found in animal cells 2. Lysosomes are absent from most plant cells 3. Enzymes in a lysosome can break down large molecules such as a. proteins, b. polysaccharides, c. fats, and d. nucleic acids.

4. Lysosomes have several types of digestive functions a. Many cells engulf nutrients in tiny cytoplasmic sacs called food vacuoles. b. These food vacuoles fuse with lysosomes, exposing food to enzymes to digest the food. c. Small molecules from digestion leave the lysosome and nourish the cell.

5. Lysosomes can also a. destroy harmful bacteria, b. break down damaged organelles, and c. sculpt tissues during embryonic development, helping to form structures such as fingers.

D. Vacuoles 1. Vacuoles are large sacs of membrane that bud from the a. ER, b. Golgi apparatus, or c. plasma membrane.

2. Contractile vacuoles of protists pump out excess water in the cell 3. Central vacuoles of plants a. store organic nutrients, b. absorb water, and c. may contain pigments or poisons.

4. To review, the endomembrane system interconnects the a. nuclear envelope, b. ER, c. Golgi, d. lysosomes, e. vacuoles, and f. plasma membrane.

V. Chloroplasts and Mitochondira: Energy Conversion 1. Cells require a continuous energy supply to perform the work of life 2. Two organelles act as cellular power stations: a. chloroplasts and b. mitochondria.

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A. Chloroplasts 1. Most of the living world runs on the energy provided by photosynthesis 2. Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar and other organic molecules 3. Chloroplasts are a. unique to the photosynthetic cells of plants and algae and b. the organelles that perform photosynthesis.

4. Chloroplasts are divided into three major compartments by internal membranes: a. the space between the two membranes, b. the stroma, a thick fluid within the chloroplast, and c. the space within grana, membrane-enclosed discs and tubes that trap light energy and convert it to chemical energy.

B. Mitochondria 1. Mitochondria a. are the organelles of cellular respiration, b. are found in almost all eukaryotic cells, and c. produce ATP from the energy of food molecules.

2. An envelope of two membranes encloses the mitochondrion: a. an outer smooth membrane and b. an inner membrane that i. has numerous infoldings called cristae and ii. encloses a thick fluid called the matrix.

3. Mitochondria and chloroplasts contain their own DNA, which encodes some of their proteins 4. This DNA is evidence that mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past

VI. The Cytoskeleton: Cell Shape and Movement 1. The cytoskeleton is a network of fibers extending throughout the cytoplasm A. Maintaining Cell Shape 1. The cytoskeleton a. provides mechanical support to the cell and b. helps a cell maintain its shape.

2. The cytoskeleton contains several types of fibers made from different proteins: a. Microtubules are straight and hollow tubes that guide the movement of organelles and chromosomes. b. Intermediate filaments and microfilaments are thinner and solid.

3. The cytoskeleton provides anchorage and reinforcement for many organelles 4. The cytoskeleton is dynamic 5. Changes in the cytoskeleton contribute to the amoeboid (crawling) movements of a. the protist Amoeba and b. some of our white blood cells.

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B. Cilia and Flagella 1. Cilia and flagella are motile appendages that aid in movement a. Flagella propel the cell through their undulating, whiplike motion. b. Cilia move in a coordinated back-and-forth motion. c. Cilia and flagella have the same basic architecture, but cilia are generally shorter and more numerous than flagella.

2. Cilia may extend from nonmoving cells 3. On cells lining the human trachea, cilia help sweep mucus with trapped debris out of the lungs C. Evolution Connection: The Evolution of Antibiotic Resistance 1. Many antibiotics disrupt cellular structures of invading microorganisms 2. Introduced in the 1940s, penicillin worked well against such infections 3. But over time, bacteria that were resistant to antibiotics, such as the MRSA strain, were favored 4. The widespread use and abuse of antibiotics continue to favor bacteria that resist antibiotics

Chapter Guide to Teaching Resources The Microscopic World of Cells Student Misconceptions and Concerns 1. Students typically cannot distinguish between resolution and magnification. However, pixels and resolution of digital images can help “clarify” the distinction. Consider printing the same image at high and low resolution or enlarging the same image at two different levels of resolution. Teaching Tip 2 below suggests another related exercise.

2. Students frequently equate the functions of mitochondria and chloroplasts as alternative ways to acquire usable energy. This often leads to the conclusion that animal cells have mitochondria but not chloroplasts and that plant cells have chloroplasts but not mitochondria. Plant cells have both.

Teaching Tips 1. Here is a chance to challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, and so on. Students can be assigned the task of preparing a short report on one of these technologies.

2. Here is a way to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, and so on. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes. (They need not state their answers publicly, to avoid embarrassment.)

3. Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope and a “compound” light microscope using microscope slides. The way these scopes function parallels the workings of EMs. Dissection microscopes are like an

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SEM—both rely on a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material.

If you have an overhead or other strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye—the way a compound light microscope or TEM works!

4. Even in college, students still struggle with the metric system. When discussing the scale of life, consider bringing a meter stick to class. The ratio of a meter to a millimeter is the same as the ratio of a millimeter to a micron: 1,000 to 1.

5. This is a place where a visual image comparing a prokaryotic and eukaryotic cell can be very helpful. These cells are strikingly different in size and composition. A visual reference point instead of just abstract ideas and traits will be a continual reminder for your students during your discussion of these cells.

6. Students might wrongly conclude that prokaryotes are typically one-tenth the volume of eukaryotic cells. A difference in diameter by a factor of ten translates into a much greater difference in volume. Students might be challenged to recall enough geometry to calculate the difference in the volume of two cells with diameters that differ by a factor of ten.

7. Germs—here is a term that we learn early in our lives but that is rarely well defined.

Students may appreciate a biological explanation. The general use of germs is a reference to anything that causes disease. This may be a good time to sort the major disease-causing agents into three categories: (a) bacteria (prokaryotes), (b) viruses (not yet addressed), and (c) single-celled and multicellular eukaryotes (athlete’s foot is a fungal infection; malaria is caused by a unicellular eukaryote).

8. Some instructors have reported great success by challenging their students to make analogies to the functions of the many organelles discussed. Students may wish to construct one inclusive analogy between a society or factory (used in the text) and a cell or to construct separate analogies for each organelle. As with any analogy, it is important to list the similarities and differences/exceptions.

9. This might be a good time to discuss the evolution of antibiotic resistance. Teaching tips and ideas for related lessons can be found at www.pbs.org/wgbh/evolution/educators/lessons/lesson6/act1.html.

Membrane Structure Student Misconceptions and Concerns 1. Students often think of the function of cell membranes as mainly containment, like that of a plastic bag. Consider relating the functions of membranes to our human skin. For example, membranes and our skin (a) detect stimuli, (b) engage in gas exchange, and (c) serve as sites of excretion and absorption.

Teaching Tips 1. The hydrophobic and hydrophilic ends of a phospholipid molecule naturally create a lipid bilayer. The hydrophobic edges of the layer will seal to other such edges, eventually wrapping a sheet into a sphere that can enclose water (a simple cell). Further, because of these hydrophobic properties, lipid bilayers are naturally self-healing. That all of this organization naturally emerges from the properties of phospholipids is worth sharing with your students. ..

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2. You might wish to share a very simple analogy that seems to work with some students.

A cell membrane is a little like a peanut butter and jelly sandwich with jellybeans poked into it. The bread represents the hydrophilic portions of the bilayer (and bread does indeed quickly absorb water). The peanut butter and jelly represent the hydrophobic regions (and peanut butter, containing plenty of oil, is generally hydrophobic). The jellybeans stuck into the sandwich represent proteins variously embedded partially into or completely through the membrane. Transport proteins would be like the jellybeans that poke completely through the sandwich. Analogies are rarely perfect. Challenge your students to critique this analogy to find exceptions. (For example, this analogy does not include a model of the carbohydrates on the cell surface.)

The Nucleus and Ribosomes: Genetic Control of the Cell Student Misconceptions and Concerns 1. Students often enter college with misunderstandings about the interrelationship between DNA, a chromosome, and a replicated chromosome often photographed just prior to mitosis or meiosis. Consider specifically distinguishing between these important cellular components early in your discussions of the nucleus.

2. Noting the main flow of genetic information from DNA to RNA to protein on the board will provide a useful reference for students when explaining these processes. As a review, have students note where new molecules of DNA, RNA, and proteins are produced in a cell.

Teaching Tips 1. Some of your more knowledgeable students may like to guess the exceptions to 46 chromosomes per human cell. These exceptions include gametes, some of the cells that produce them, and red blood cells in non-fetal mammals.

2. If you wish to continue the text’s factory analogy, nuclear pores might be said to function most like the doors to the boss’s office.

3. If you want to challenge your students further, ask them to consider the adaptive advantage of using mRNA to direct the production of proteins instead of using DNA directly. Some biologists suggest that DNA is better protected in the nucleus and that mRNA, exposed to more damaging cross-reactions in the cytosol, is the temporary “working copy” of the genetic material. In some ways, this is similar to making a working photocopy of an important document, keeping the original copy safely stored away.

4. Consider challenging your students to explain how we can have four main types of organic molecules functioning in specific roles in our cells, yet DNA and RNA only specifically dictate the generation of proteins (and more copies of DNA and RNA). How is the production of specific types of carbohydrates and lipids in cells controlled? (Answer: primarily by the specific properties of enzymes.)

The Endomembrane System: Manufacturing and Distributing Cellular Products Student Misconceptions and Concerns 1. Students might have trouble connecting the diverse functions to the organelles. The pathway of secretory proteins is a good process to use to introduce the primary organelle 50

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functions. The movement of information and products extends generally from the central nucleus to the interconnected rough ER, to the more peripherally located Golgi, and finally to the outer plasma membrane. Introducing the steps of this process with the central to peripheral flow may help students better see the interrelationships and recall the sequence.

2. Conceptually, some students seem to benefit from the well-developed factory-like-a-cell analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships.

Teaching Tips 1. The endoplasmic reticulum is continuous with the outer nuclear membrane. This explains why the ER is usually found close to the nucleus.

2. Students often learn that a human body can build up a tolerance to a drug. Here in chapter 4, students learn about one of the specific mechanisms of this response. Liver cells exposed to certain toxins or drugs increase the amount of smooth ER, which functions in the processing of these chemicals. Thus, there is a structural and functional explanation to the development of drug tolerance.

3. Some people think the Golgi apparatus looks like a stack of pita bread.

4. If you continue the factory analogy, the addition of a molecular tag is like adding address labels in the shipping department of a factory.

5. Lysosomes help to recycle damaged cell components. Challenge your students to explain why this is adaptive. Recycling, whether in human society or in our cells, can be an efficient way to reuse materials. The recycled components, which enter the lysosomes in a highly organized form, would require a much greater investment to produce from “scratch.”

Chloroplasts and Mitochondria: Energy Conversion Student Misconceptions and Concerns 1. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They may falsely think that cells either have mitochondria or they have chloroplasts.

You might challenge this thinking by asking how plant cells generate ATP at night.

2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small size of these organelles, similar to the size of a prokaryote.

Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons.

Teaching Tips 1. ATP functions in cells much like money functions in modern societies. Each holds value that can be generated in one place and “spent” in another. This analogy has been very helpful for many students.

2. Mitochondria and chloroplasts are each wrapped by multiple membranes. In both organelles, the innermost membranes are the sites of greatest molecular activity and the outer membranes have fewer significant functions. This makes sense when we consider that the outer membranes correspond to the plasma membrane of the eukaryotic cells that originally wrapped the free-living prokaryotes during endocytosis. Biology makes sense in light of evolution.

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3. Mitochondria and chloroplasts are not cellular structures that are synthesized in a cell like ribosomes and lysosomes. Instead, mitochondria only come from other mitochondria and chloroplasts only come from other chloroplasts. This is further evidence of the independent evolution of these organelles from free-living ancestral forms.

The Cytoskeleton: Cell Shape and Movement Student Misconceptions and Concerns 1. Students often regard the fluid of the cytoplasm as little more than cell broth, a watery fluid that suspends the organelles. The diverse functions of thin, thick, and intermediate filaments are rarely appreciated before college.

2. Students often think that the cilia on the cells lining our trachea function like a comb, removing debris from the air. Except in cases of disease or damage, these respiratory cilia are covered by mucus. Cilia do not reach the air to comb it free of debris. Instead, these cilia sweep dirty mucus up our respiratory tracts to be expelled or swallowed. (See also Teaching Tip 1 below.)

3. The dynamic, weblike structure of the cytoskeleton is very different from the skeletons that students may already know. Their dynamic structures (see Teaching Tip 2 below) are quite unlike any human designs. Students have much to gain from vivid illustrations of cytoskeletal diversity. Consider sharing some impressive images from a Google image search or other resources.

Teaching Tips 1. Students might enjoy this brief class activity. Have everyone in the class clear their throats at the same time. Wait a few seconds. Have them notice that after clearing, they swallowed. The mucus that trapped debris is swept up the trachea by cilia. When we clear our throats, this dirty mucus is disposed of down our esophagus and among the strong acids of our stomach!

2. Analogies between the infrastructure of human buildings and the cytoskeleton are limited by the dynamic nature of the cytoskeleton. Few human structures have their structural framework routinely constructed, deconstructed, and then reformed in a new configuration on a regular basis. (Tents are often constructed, deconstructed, and then re-formed repeatedly but typically rely upon the same basic design.) Thus, caution is especially warranted in such analogies.

Key Terms cell junctions cell theory central vacuole chloroplasts chromatin chromosomes cilia cristae cytoplasm cytoskeleton cytosol electron microscope (EM) 52

endomembrane system endoplasmic reticulum (ER) eukaryotic cells extracellular matrix flagella fluid mosaic Golgi apparatus grana light microscope (LM) lysosome magnification matrix

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microtubules mitochondria nuclear envelope nucleoid nucleolus nucleus organelles phospholipids phospholipid bilayer plasma membrane prokaryotic cells resolving power ribosomes

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rough ER scanning electron microscope (SEM) smooth ER stroma transmission electron microscope (TEM) transport vesicles vacuoles

Word Roots chloro = green (chloroplast: the green organelle of photosynthesis) chromo = color (chromosome: a threadlike, darkly staining structure packaging DNA in the nucleus) cili = small hair (cilium: a short, hairlike cellular appendage with a microtubule core) cyto = cell (cytoplasm: cell region between the nucleus and the plasma membrane) endo = inner (endomembrane system: an internal system of membranous organelles) eu = true (eukaryotic: cell type with a membrane-enclosed nucleus and other organelles) extra = outside (extracellular: the substance around animal cells) flagell = whip (flagellum: a long, whiplike cellular appendage that moves cells) micro = small (microtubule: microscopic tubular filaments contributing to the cytoskeleton) plasm = molded (plasma membrane: the thin layer that sets a cell apart from its surroundings) pro = before (prokaryotic: the first cells, lacking a membrane-enclosed nucleus and other organelles) reticul = network (endoplasmic reticulum: membranous network where proteins are produced) trans = across (transport vesicles: membranous spheres that move materials across a cell) vacu = empty (vacuole: sac that buds from the ER, Golgi apparatus, or plasma membrane)

Relevant Songs to Play in Class “Tainted Love,” Soft Cell

“Insane in the Brain,” Cyprus Hill

“Golgi Apparatus,” Phish

“Cells,” They Might Be Giants

Answers to End-of-Chapter Questions The Process of Science 12. Suggested answer: In the cell membrane, phospholipids are facing either the aqueous environment outside the cell or the aqueous environment inside the cell. Since the polar “heads” of the phospholipids are hydrophilic, they orient toward water. Therefore, two layers are necessary. The membranes that enclose oil droplets face only an aqueous environment on the exterior of the droplet. This means that one layer of phospholipids is sufficient. The polar heads point outward, whereas the hydrophobic fatty acids point inward toward the oil.

13. Suggested answer: Upon initial inspection, one would expect to see cells containing indigestible substances accumulated in the lysosomes. The symptoms of lysosomal storage diseases can be diverse, depending on the specific digestive enzyme that is not present or functioning correctly. A wide battery of blood tests and a physical exam might reveal some of these specific symptoms. In addition, some of the disease symptoms might also exist in one of the parents of the child.

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Biology and Society 14. Some issues and questions to consider: Were the cells Moore’s property, a gift, or just surplus? Was Moore asked to donate the cells? Was he informed about how the cells might be used? Is it important to ask permission or inform the patient in such a case? How much did the researchers modify the cells? What did they have to do to them to sell the product?

Do the researchers and the university have a right to make money from Moore’s cells? Is the fact that they saved Moore’s life a factor here? Does Moore have the right to sell his cells? Would Moore have been able to sell the cells without the researchers’ help?

Additional Critical Thinking Questions The Process of Science 1. You are comparing two cells. One cell is very small, and the other cell is huge. Under which conditions would you expect the larger cell to be more successful, or the small cell to be more successful? What would your answer be? Give a specific explanation for your answer.

Suggested answer: The smaller cell would be expected to be more successful when resources are abundant. It will have a greater surface-to-volume ratio. This makes it easier for the cell to acquire nutrients, remove wastes, and communicate faster between the nucleus and cytoplasm. Larger cells do have a large surface area; however, they also have a larger volume, allowing them to store materials when resources are not as abundant, enabling them to survive in harsher times.

2. Several lines of evidence support the hypothesis that mitochondria and chloroplasts evolved from parasitic prokaryotic cells living in the cytoplasm of primitive eukaryotic cells. What types of evidence would you look for to support or refute this hypothesis?

Suggested answer: Prokaryotes, like eukaryotes, contain DNA. One would expect, therefore, to find DNA in mitochondria and chloroplasts. Such DNA is found. You would expect that DNA found within mitochondrial or chloroplast DNA are more similar to prokaryotic DNA than they are to equivalent eukaryotic DNA. Mitochondrial DNA is circular and found on one chromosome like prokaryotes. Prokaryotes carry out protein synthesis, as do mitochondria and chloroplasts, which have their own ribosomes. One curious feature of mitochondria and chloroplasts is their double membrane. Although prokaryotes do not have a double membrane, you might imagine how the envelopment of a prokaryote by a eukaryotic cell would wrap a second “outer membrane” around the cell.

Thus, the inner membrane would represent the original prokaryotic membrane, and the outer membrane would represent the remains of the eukaryotic membrane.

3. The inside of lysosomes is acidic with a pH (5.0) significantly lower than the slightly basic pH of the cytoplasm. As you might expect, the hydrolytic enzymes stored inside the lysosome work best at this low pH. Can you think of a hypothesis to explain why such a pH difference was important in the evolution of the cell? How would you test your hypothesis?

Suggested answer: Lysosomes are important organelles for breaking down organic molecules because of their large arsenal of enzymes capable of digesting virtually any macromolecule produced by the cell. Were a lysosome to leak, the potential damage to the cell would be great. It is inevitable that a few lysosomes rupture, either because of accident or because of age. Because of the pH difference, leaked enzymes would be unable to work in the pH of the cytoplasm, and no damage would be done to the cell. To test your hypothesis, you could isolate enzymes from lysosomes and measure their activity at 54

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several different controlled pHs. If your hypothesis were correct, you would expect that the activity of the enzymes at the pH of the cytoplasm would be very low.

4. You have isolated a new prokaryotic organism, and now you want to determine whether it is photosynthetic. It is too small to visualize with the microscopes you have available.

Design an experiment to determine whether the new cell actively uses photosynthesis.

Suggested answer: You could provide this new cell with the ingredients needed for photosynthesis and see what happens. For example, you could provide the cells with water in which the oxygen has been radioactively labeled. If the cells photosynthesize, those water molecules will be split, and radioactive oxygen gas will be released. You could also provide the cells with radioactively labeled carbon dioxide. If the cells perform photosynthesis, the radioactivity should be found in glucose in the cells.

Biology and Society 5. Panspermia is an old idea that living cells did not evolve on Earth, but instead came to Earth from space. The Greek philosopher Anaxagoras was the first to consider the possibility that living seeds arrived on Earth from another world. Several famous scientists have also held this view. The Swedish chemist Svante Arrhenius, a Nobel Prize winner, published a book in 1907 in which he argued that living spores escaped from the upper atmosphere of living planets and traveled to other planets through space. The astronomer Fred Hoyle, famous for the steady-state universe theory, argued that life originated in comets, which seeded the Earth on impact. Frances Crick, codiscoverer of the structure of DNA, argued in a 1981 book that life was sent to Earth on rocket ships by intelligent beings elsewhere in the universe, a process he termed directed pangenesis. What objections to this theory would its supporters have to consider? Do you consider this idea a reasonable explanation of how living cells evolved? How would such an idea change your view of your position in the universe?

Some issues and questions to consider: Could living cells or spores survive the long journey through space? Would they be damaged by the intense radiation and extreme temperatures found in space? What force could eject cells from their home planet? Would the force of such an ejection damage the cells? Could cells survive passage through Earth’s atmosphere? Assuming cells survived this journey inside a protected environment (such as the center of a large comet), how would they exit this environment upon arrival? Could they survive the environment of their new home? If there are supportive data for each of these concerns, does the hypothesis merely push back the question of how life evolved? If it did not evolve on Earth, then how did it evolve in some other corner of the universe? If cells did evolve elsewhere in the universe, the most important conclusion would be that indeed we are not alone in the universe. Perhaps our universe is teeming with life.

6. Explain why animal cells would be unable to exist without the presence of plant cells. Is this relationship reciprocal?

Some issues and questions to consider: What things do plants produce via photosynthesis that animal cells require? Do animals produce anything that plants need? What would happen to animals if plant cells all died? What would happen to plant cells if animal cells all died?

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CHAPTER

5

The Working Cell

Why This Chapter Matters 1. Biological systems rely on several forms of energy.

2. Living systems require an input of energy to maintain order and survive.

3. Energy coupling enables cells to transfer energy from reactions that yield energy to processes that consume energy.

4. Enzymes promote specific chemical reactions in cells. Without enzymes, life would not be possible.

5. Membranes specifically regulate the passage of materials into and out of a cell and enable cells to respond to their environments. These interactions are essential to life and an understanding of many forms of disease.

Chapter Objectives Biology and Society: Harnessing Cellular Structures 1. Explain how nanotechnology might be used to power microscopic robots.

Some Basic Energy Concepts 2. Define the terms energy, kinetic energy, potential energy, and the principle of conservation of energy.

3. Explain the relationship between heat and entropy.

4. Compare the processes by which a car and a human use “fuel” to perform work.

5. Compare the amount of energy in a calorie, kilocalorie, and Calorie. Which is most commonly used on food labels?

ATP and Cellular Work 6. Explain how ATP powers cellular work.

7. Explain how ATP is recycled.

Enzymes 8. Explain why enzymes are needed in living organisms.

9. Explain how enzymes are able to speed up specific chemical reactions.

10. Explain how inhibitors and poisons can affect enzyme activity.

Membrane Function 11. Define and distinguish between the following pairs of terms: diffusion versus osmosis, passive transport versus active transport, hypertonic versus hypotonic, endocytosis versus exocytosis, and phagocytosis versus pinocytosis.

12. Explain how signal transduction pathways permit environmental stimuli to impact the activities inside of a cell.

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Evolution Connection: The Origin of Membranes 13. Explain why phospholipids were probably some of the first organic compounds to form as life emerged on Earth.

Lecture Outline I. Biology and Society: Harnessing Cellular Structures 1. Cells control their chemical environment using a. energy, b. enzymes, and c. the plasma membrane.

2. Cell-based nanotechnology may be used to power microscopic robots

II. Some Basic Energy Concepts 1. Energy makes the world go around 2. But what is energy?

A. Conservation of Energy 1. Energy is defined as the capacity to cause change a. Some forms of energy are used to perform work. b. Energy is the ability to rearrange a collection of matter.

2. Kinetic energy is the energy of motion 3. Potential energy is stored energy. It is energy that an object has because of its a. location or b. structure.

4. Machines and organisms can transform kinetic energy to potential energy and vice versa 5. In all such energy transformations, total energy is conserved a. Energy cannot be created or destroyed. b. Energy can be converted from one form to another. c. This is the principle of conservation of energy.

B. Entropy 1. Every energy conversion releases some randomized energy in the form of heat 2. Heat is a a. type of kinetic energy and b. product of all energy conversions.

3. Scientists use the term entropy as a measure of disorder, or randomness, in a system 4. All energy conversions increase the entropy of the universe C. Chemical Energy 1. Molecules store varying amounts of potential energy in the arrangement of their atoms 2. Organic compounds are relatively rich in such chemical energy 3. Chemical energy a. arises from the arrangement of atoms and b. can be released by a chemical reaction.

4. Living cells and automobile engines use the same basic process to make chemical energy do work 58

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5. Cellular respiration is a. the energy-releasing chemical breakdown of fuel molecules and b. the storage of that energy in a form the cell can use to perform work.

6. Humans convert about 34% of the energy in food to useful work, such as the contraction of muscles 7. About 66% of the energy released by the breakdown of fuel molecules generates body heat D. Food Calories 1. A calorie is the amount of energy that can raise the temperature of one gram of water by 1 degree Celsius 2. Food Calories are kilocalories, equal to 1,000 calories 3. The energy of calories in food is burned off by many activities

III. ATP and Cellular Work 1. Chemical energy is a. released by the breakdown of organic molecules during cellular respiration and b. used to generate molecules of ATP. 2. ATP a. acts like an energy shuttle, b. stores energy obtained from food, and c. releases it later as needed.

A. The Structure of ATP 1. ATP (adenosine triphosphate) a. consists of an organic molecule called adenosine plus a tail of three phosphate groups and b. is broken down to ADP and a phosphate group, releasing energy.

B. Phosphate Transfer 1. ATP energizes other molecules by transferring phosphate groups 2. This energy helps cells perform a. mechanical work, b. transport work, and c. chemical work.

C. The ATP Cycle 1. Cellular work spends ATP continuously 2. ATP is recycled from ADP and a phosphate group through cellular respiration 3. A working muscle cell spends and recycles up to 10 million ATP molecules per second

IV. Enzymes 1. Metabolism is the total of all chemical reactions in an organism 2. Most metabolic reactions require the assistance of enzymes, proteins that speed up chemical reactions 3. All living cells contain thousands of different enzymes, each promoting a different chemical reaction

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A. Activation Energy 1. Activation energy a. activates the reactants and b. triggers a chemical reaction.

2. Enzymes reduce the amount of activation energy required to break bonds of reactant molecules B. The Process of Science: Can Enzymes Be Engineered?

1. Observation: Genetic sequences suggest that many of our genes were formed through a type of molecular evolution 2. Question: Can laboratory methods mimic this process through artificial selection?

3. Hypothesis: An artificial process could be used to modify the gene that codes for lactase into a new gene coding for an enzyme with a new function 4. Experiment: Using the process of directed evolution, many copies of the lactase gene were randomly mutated and tested for new activities 5. Results: Directed evolution produced a new enzyme with a novel function C. Induced Fit 1. An enzyme is very selective in the reaction it catalyzes 2. Each enzyme recognizes a substrate, a specific reactant molecule a. The active site fits to the substrate, and the enzyme changes shape slightly. b. This interaction is called induced fit because the entry of the substrate induces the enzyme to change shape slightly.

3. Enzymes can function over and over again, a key characteristic of enzymes 4. Many enzymes are named for their substrates, but with an –ase ending D. Enzyme Inhibitors 1. Enzyme inhibitors can prevent metabolic reactions by binding a. to the active site or b. near the active site, resulting in changes to the enzyme’s shape so that the active site no longer accepts the substrate.

2. Some products of a reaction may inhibit the enzyme required for its production a. This is called feedback regulation. b. It prevents the cell from wasting resources.

3. Many beneficial drugs work by inhibiting enzymes a. Penicillin blocks the active site of an enzyme that bacteria use in making cell walls. b. Ibuprofen inhibits an enzyme involved in sending pain signals. c. Many cancer drugs inhibit enzymes that promote cell division.

V. Membrane Function 1. Cells must control the flow of materials to and from the environment 2. Membrane proteins perform many functions 3. Transport proteins a. are located in membranes and b. help move substances across a cell membrane.

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2. Diffusion is the movement of molecules so that they spread out evenly into the available space 3. Passive transport is the diffusion of a substance across a membrane without the input of energy 4. Cell membranes are selectively permeable, allowing only certain substances to pass 5. Substances diffuse down their concentration gradient, a region in which the substance’s density changes 6. Some substances do not cross membranes spontaneously or cross slowly a. These substances can be transported via facilitated diffusion. b. Specific transport proteins act as selective corridors. c. No energy input is needed.

B. Osmosis and Water Balance 1. The diffusion of water across a selectively permeable membrane is osmosis 2. Compared to another solution, a. a hypertonic solution has a higher concentration of solute, b. a hypotonic solution has a lower concentration of solute, and c. an isotonic solution has an equal concentration of solute.

3. Water Balance in Animal Cells 4. Osmoregulation is the control of water balance within a cell or organism 5. Water Balance in Plant Cells 6. Plants have rigid cell walls 7. Plant cells are healthiest in a hypotonic environment, which keeps their walled cells turgid 8. As a plant cell loses water, a. it shrivels and b. its plasma membrane may pull away from the cell wall in the process of plasmolysis, which usually kills the cell.

C. Active Transport: The Pumping of Molecules across Membranes 1. Active transport requires that a cell expend energy to move molecules across a membrane D. Exocytosis and Endocytosis: Traffic of Large Molecules 1. Exocytosis is the secretion of large molecules within transport vesicles 2. Endocytosis takes material in via vesicles that bud inward from the plasma membrane 3. In the process of phagocytosis (“cellular eating”), a cell engulfs a particle and packages it within a food vacuole 4. Other times a cell “gulps” droplets of fluid into vesicles 5. Endocytosis can also be triggered by the binding of certain external molecules to specific receptor proteins built into the plasma membrane E. The Role of Membranes in Cell Signaling 1. The plasma membrane helps convey signals a. between cells and b. between cells and their environment.

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F. Evolution Connection: The Origin of Membranes 1. Phospholipids a. are key ingredients of membranes, b. were probably among the first organic compounds that formed from chemical reactions on early Earth, and c. self-assemble into simple membranes.

Chapter Guide to Teaching Resources Some Basic Energy Concepts Student Misconceptions and Concerns 1. Students with limited exposure to physics may have never understood the concepts of “energy” and “the conservation of energy” or distinguished between potential and kinetic energy.

Understanding such broad and new abstract concepts requires time and concrete examples.

2. Although typically familiar with the concept of dietary Calories, students often struggle to think of Calories as a source of potential energy. For many students, it is not immediately clear how energy is stored as Calories in food.

Teaching Tips 1. In our daily lives, we rely upon many energy transformations. On our classroom walls, a clock converts electrical energy to mechanical energy to sweep the hands around the clock’s face (unless it is digital!). Our physical (mechanical) activities walking to and from the classroom rely upon the chemical energy from our diet. This chemical energy in our diet also helps us maintain a steady body temperature (heat). Consider challenging your students to come up with additional examples of such common energy conversions in their lives.

2. Some students can relate well to the concept of entropy as it relates to the room where they live. Despite cleaning up and organizing the room on a regular (or irregular) basis, the room increasingly becomes disorganized, a victim of entropy, until another energy input (or effort) is exerted to make the room more orderly again. Students might even get to know “entropy” as the “dorm room effect.”

3. All too often we hear or read that some thing or reaction creates energy. We might hear or read that a power plant “produces” energy or that mitochondria “make” energy. Even in our classroom conversations, we may occasionally slip into this error. When discussing the first law of thermodynamics, consider emphasizing the inaccuracy of such statements.

4. The heat produced by the engine of a car is typically used to heat the car during cold weather. But is this same heat available in warmer weather? Students are often unaware that their car “heater” works very well in the summer too. Just as exercise can warm us when it is cold, the same extra heat is released when we exercise in warm conditions. A car engine in the summer struggles to dissipate heat in the same way that a human struggles to cool off after exercising when weather is warm.

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5. Here is a question that might make cellular respiration a little more meaningful to your students. Ask your students why they feel warm when it is 30°C (86°F) outside if their core body temperature is about 37°C (98.6°F). Shouldn’t they feel cold? The answer is, our bodies are always producing heat. At these higher temperatures, we are producing more heat than we need to maintain a body temperature around 37°C. Thus, we sweat and behave in ways that help release our extra heat generated in cellular respiration.

6. Here is a calculation that has impressed some students. Depending on the size and activity of a person, a human might burn 2,000 dietary Calories (kilocalories) a day. This is enough energy to raise the temperature of 20 L of liquid water from 0° to 100°C. This is something to think about the next time you heat water on the stove! If you can bring in ten 2-L bottles you can help students visualize how much liquid water can be raised from 0° to 100°C. (Note: 100 Calories raises about 1 L of water 100°C; but it takes much more energy to melt ice or to convert boiling water into steam.)

7. The same mass of fat (about 9 kcal per gram) stores nearly twice as many Calories as an equivalent mass of protein or carbohydrates (about 4.5–5 kcal per gram). Thus, when comparing equal masses of fat, protein, and lipid, the fat has nearly twice the potential energy. Fat is therefore an efficient way to store energy in animals and many plants. To store an equivalent amount of energy in the form of carbohydrates or proteins would require about twice the mass, adding a significant burden to the organism’s structure.

(For example, if you were 20 pounds overweight, you would be nearly 40 pounds overweight if the same energy were stored as carbohydrates or proteins instead of fat.)

ATP and Cellular Work Student Misconceptions and Concerns 1. Although students might already understand mechanical and chemical work in a cell, the idea of transport work might be new to them. Chapter 6, in a section on the electron transport system, develops an analogy between transport work and water behind a dam. Therefore, at this point you might consider making an analogy between transport work (against a gradient) and pumping water up into a reservoir (against gravity)—perhaps into a water tower.

2. Energy shuttling at the cellular level may be new to many students, but it is a familiar concept when related to the use of money in our society. Students might be discouraged if the only benefit of work was the ability to make purchases from your employer. (Most of us would soon tire of a fast-food job that pays its employees only in free food!) Money permits the generation of value (a paycheck) analogous to an energy-releasing reaction to be coupled to an energy (money)-consuming reaction, making purchases in distant locations. This idea of “earn and spend” is a common concept most students know well.

Teaching Tips 1. The authors suggest an analogy between ATP and a spring. When a phosphate group is attached to ADP, it is like compressing the spring. When a phosphate group is lost, the spring is relaxed, and energy is released.

2. When introducing ATP and ADP, consider having students think of the terms as A-3-P and A-2-P, noting that the word roots “tri” means 3 and “di” means 2. It might help students to keep track of the number of phosphates more easily.

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recycled, and ADP is recycled. Several advantages are common to both human recycling of components of garbage and cellular recycling. For example, both save energy by avoiding the need to remanufacture the basic units, and both avoid an accumulation of waste products that could interfere with other “environmental” chemistry (the environment of the cell or the environment of the human population).

Enzymes Student Misconceptions and Concerns 1. For students not previously familiar with activation energy, analogies can make all the difference. Activation energy can be thought of as a small input that is needed to trigger a large output. This is like (a) an irritated person who needs only a bit more frustration to explode in anger, (b) small waves that lift debris over a dam, or (c) lighting a match around lighter fluid. In each situation, the output was much greater than the input.

2. The specific interactions of enzymes and substrates can be illustrated with simple physical models. Many students new to these concepts will benefit from several forms of explanation, including diagrams such as those in the textbook, physical models, and the opportunity to manipulate or create their own examples. New concepts, like pitching a tent, are best constructed with many lines of support.

Teaching Tips 1. The text notes that the relationship between an enzyme and its substrate is like a handshake, with each hand generally conforming to the shape of the other. This induced fit is also like the change in shape of a glove when a hand is inserted. The glove’s general shape matches the hand, but the final “fit” requires some additional adjustments.

2. Enzyme inhibitors that block the active site are like (a) a person sitting in your assigned theater seat or (b) a car parked in your parking space. Analogies for inhibitors that change the shape of the active site are more difficult to imagine. Consider challenging your students to think of such analogies. (Perhaps someone adjusting the driver seat of the car differently from your preferences and then leaving it that way when you try to use the car.)

3. Feedback regulation relies on the negative feedback of the accumulation of a product. Ask students in class to suggest other products of reactions that inhibit the process that made them, when the product reaches high enough levels. (Gas station pumps routinely shut off when a high level of gasoline is detected. Furnaces typically turn off when enough heat has been produced, and toilets stop running when the tank is refilled.)

4. Consider challenging your class to suggest advantages to using specific enzyme inhibitors as insect poisons. Many advantages exist and include (a) the ability to target chemical reactions of only certain types of pest organisms and (b) the ability to target chemical reactions that are found in insects but not in humans.

5. The information in DNA is used to direct the production of RNA, which in turn directs the production of proteins. Yet in Chapter 3, four different types of biological molecules were noted as significant components of life. Students who think this through might wonder, and you could point out, that DNA does not directly control the production of carbohydrates and lipids. So how does DNA exert its influence over the synthesis of these two chemical groups? The answer is largely by way of enzymes, which are proteins with the ability to control the production of carbohydrates and lipids.

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Membrane Function Student Misconceptions and Concerns 1. For students with limited science backgrounds, concepts such as diffusion and osmosis can take considerable time to fully understand and apply. Instructors often struggle to remember a time in their lives when they did not know about such fundamental scientific principles. Consider spending extra time to illustrate and demonstrate these key processes to the class. Consider short interactive class exercises in which students create analogies or think of examples of these principles in their lives.

2. Students easily confuse the terms hypertonic and hypotonic. One challenge is to understand that these are relative terms, such as heavier, darker, or fewer. No single solution is “heavier,” no single cup of coffee is “darker,” and no single bag of M & M’s has “fewer” candies. Such terms only apply when comparing two or more items. A solution with a higher concentration is “hypertonic.” But the same solution might also be “hypotonic” to a third solution.

Teaching Tips 1. Students often benefit from reminders of diffusion in their lives. Smells can usually be traced back to their sources—the smell of dinner on the stove, the scent of a perfume or cologne to its bottle, the smoke drifting away from a campfire. These scents are strongest nearest the source and weaker as we move away.

2. Consider demonstrating simple diffusion. A large jar of water and a few drops of darkcolored dye work well over the course of a lecture period. Or release a strong scent of cologne or peppermint or peel part of an orange in the classroom and have students raise their hands as they first detect the smell. Students nearest the source will raise their hands before students farther away. The fan from an active overhead projector or overhead vent may bias the experiment a bit, so be aware of any directed movements of air in your classroom that might disrupt this demonstration.

3. The word root “hypo” means “below.” Thus, a hypodermic needle injects substances below the dermis. Students might best remember that hypotonic solutions have concentrations below that of the other solution(s).

4. After introducing the idea of hypertonic and hypotonic solutions, you may wish to challenge your students with the following: A marine salmon moves from the ocean up a freshwater stream to reproduce. The salmon is moving from a _____ environment to a _____ environment. (Answers: hypertonic to a hypotonic) 5. Your students may have noticed that their fingers wrinkle after taking a long shower or bath, or washing dishes. The skin wrinkles because it is swollen with water but still tacked down at some points. Oils inhibit the movement of water into our skin. Thus, soapy water results in wrinkling faster than plain water since the soap removes the natural layer of oil from our skin. Our skin is hypertonic to the solutions that produce the swelling that appears as large wrinkles.

6. The effects of hypertonic and hypotonic solutions are easily demonstrated if students soak carrot sticks, long slices of potato, or celery in hypertonic and hypotonic solutions. These also make nice class demonstrations.

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7. The three stages of cell signaling can be compared to a human reaction. Consider someone calling your name. (1) Reception—The sound waves of someone’s voice hitting and changing the shape of your eardrum. (2) Transduction—Your ear converts sound waves to nerve impulses and sends a signal to your brain, which registers that your name has been called. (3) Response—You look around to see who is calling.

8. The hydrophobic and hydrophilic ends of a phospholipid molecule create a lipid bilayer.

The hydrophobic edges of the layer will also seal to other such edges, eventually wrapping a sheet into a sphere that can enclose water. Furthermore, because of these hydrophobic properties, lipid bilayers are naturally self-healing. All of these properties emerge from the structure of phospholipid.

Key Terms activation energy active site active transport ADP ATP calorie chemical energy concentration gradient conservation of energy

diffusion endocytosis energy entropy enzyme enzyme inhibitor exocytosis facilitated diffusion heat

hypertonic hypotonic induced fit isotonic kinetic energy metabolism osmoregulation osmosis passive transport

phagocytosis potential energy signal transduction pathway solute substrate transport proteins

Word Roots endo = within, inner; cyto = cell (endocytosis: taking material into a cell) exo = outside (exocytosis: eliminating some materials outside of a cell) hyper = excessive (hypertonic: in comparing two solutions, it refers to the one with the greater concentration of solutes) hypo = lower (hypotonic: in comparing two solutions, it refers to the one with the lower concentration of solutes) iso = same (isotonic: solutions with equal concentrations of solutes) kinet = move (kinetic: type of energy, it is the energy of motion) phago = eat (phagocytosis: cellular eating) tonus = tension (isotonic: solutions with equal concentrations of solutes) trans = across (transport proteins: membrane proteins that help move substances across a cell membrane)

Relevant Songs to Play in Class “Tainted Love,” Soft Cell

“Insane in the Brain,” Cyprus Hill

“Golgi Apparatus,” Phish

“Cells,” They Might Be Giants

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Answers to End-of-Chapter Questions The Process of Science 13. Suggested answer: DNA uses the bases A, C, G, and T, whereas RNA uses A, C, G, and U. As the viral RNA is converted to DNA, the AZT will be present in each location that should have a T. This will render the viral DNA nonfunctional.

14. Suggested answer: You would need to run approximately 28 miles to burn 3,500 Calories.

This would take approximately 4 hours. You would need to swim about 13 miles, which would take about 6–7 hours. Walking would take about 22.15 hours and the distance would be about 66.5 miles.

Biology and Society 15. Some issues and questions to consider: If carbohydrates are eliminated from the body, what will the cells use for fuel for cellular respiration? Will any stored nutrients in the body be utilized? What are the problems associated with elevated levels of fat and protein in the diet? Can you see any long-term problems that might develop from this diet? What sorts of clinical studies have been done to back up these claims? What was the sample size and were the experiments well controlled? Is it the role of the government to regulate every fad diet that appears? Should the government regulate the diet and sport supplement industry to protect the consumer?

16. Some issues and questions to consider: Does a pregnant woman have a right to work in an unsafe environment, even if it may put her child at risk? What are the rights of the child?

Does the company have the right to protect women who are not pregnant? Is the company trying to protect the mother and child or protect itself from a potential lawsuit? Who is responsible for protecting employees and their children? The employees? The company?

The government? Suppose a woman risks lead exposure and bears an intellectually disabled child. Who is responsible if, 20 years from now, the child decides to sue?

Additional Critical Thinking Questions The Process of Science 1. A patient in a local hospital suffered extensive hemolysis (lysis of red blood cells) when distilled water was mistakenly given to him intravenously (into his vein). Explain how the hemolysis occurred.

Suggested answer: Distilled water without solutes is hypotonic to red blood cells. When distilled water is mixed with cells in the blood, water will move from the solution into the cells. The cells will swell and lyse (burst).

2. Imagine that organisms composed of cells with unusual and novel structures have just invaded our planet. You as a scientist are asked to create a drug that inhibits their growth or kills them but does not harm currently existing life-forms on Earth. Outline how you would go about designing such a drug.

Suggested answer: First, you would have to investigate the cell structure of the organisms and try to isolate unique structures and/or enzymes vital to their growth, reproduction, and survival. These structures and enzymes must be different from those found in existing lifeforms on Earth. You would then proceed to design and test chemicals that would inhibit

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any unique enzymes or destroy any unique structures vital to their survival. This would leave life that already exists on Earth safe from the action of these chemicals.

3. An individual can die after experiencing a high fever for a prolonged period of time. Using what you know about enzymes, explain why an individual who enters the emergency room with a high fever might be given an ice bath to lower his or her temperature.

Suggested answer: High temperatures can cause the enzymes in the body to denature. If the body temperature is extremely high, the fastest way to lower it is by using an ice bath.

Lowering the body temperature quickly would ensure that the enzymes do not denature.

Biology and Society 4. High cholesterol is a significant problem, especially in developed countries. You as a pharmacologist would like to design a drug to help alleviate this problem. What kinds of approaches could you consider?

Some issues and questions to consider: You could try to develop a compound that binds to low-density lipoproteins in the blood, converting them into a harmless substance that can be excreted from the body, thus lowering their level in the blood.

5. Your roommate goes out and buys some new nutritional supplements. The bottle claims that the supplements will give her lots of energy, increase her metabolism, and help her lose weight. For the next eight weeks she takes the supplement every day but does not work out. Thinking that your experience in this class has made you an expert in biology, she asks you to explain why she is not losing any weight. Be specific and complete in your answer. What are some of the best scientific ways to lose weight?

Some issues and questions to consider: Nutritional supplements are not regulated by the FDA and provide false claims and have no ability to do what they claim. Others may help temporarily but can have very serious side effects due to high doses of stimulants such as caffeine and ephedra or other thermogenic products, which increase body temperature. In addition, these products will have no effect once they are discontinued. The best ways to ensure weight loss are to reduce Calories consumed (especially processed foods and refined sugars) and increase activity level via exercise, including weight lifting and cardiovascular work.

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CHAPTER

6

Cellular Respiration: Obtaining Energy from Food

Why This Chapter Matters 1. Photosynthesis powers chemical processes that make organic molecules. We can trace the energy in all of our food to the sun.

2. The mechanisms of cellular respiration are fundamental to the lives of most organisms on Earth and reveal their basic evolutionary relationships.

3. Fermentation is used by our cells in times of temporary oxygen shortage and by humans to produce foods and beverages.

Chapter Objectives Biology and Society: Marathoners versus Sprinters 1. Explain how differences in muscle fibers relate to athletic performance.

Energy Flow and Chemical Cycling in the Biosphere 2. Explain why photosynthesis is important to most ecosystems.

3. Define and compare autotrophs and heterotrophs, producers and consumers.

4. Explain how the processes of photosynthesis and cellular respiration are complementary to each other.

Cellular Respiration: Aerobic Harvest of Food Energy 5. Compare the processes of cellular respiration and breathing.

6. Write and explain the overall equation for cellular respiration.

7. Explain how the processes of oxidation and reduction are used to transfer electrons from food molecules to NADH, the electron transport chain, and oxygen.

8. Compare the reactants, products, location in the cell, and energy yield of the three stages of cellular respiration (glycolysis, citric acid cycle, and electron transport chain).

Fermentation: Anaerobic Harvest of Food Energy 9. Compare the reactants, products, and energy yield of aerobic metabolism versus fermentation in human cells. Indicate where this process occurs in each type of cell.

Evolution Connection: Life before and after Oxygen 10. Describe the lines of evidence that suggest that glycolysis is a primitive form of metabolism.

Lecture Outline I. Biology and Society: Marathoners versus Sprinters 1. Sprinters do not usually compete at short and long distances 2. Natural differences in the muscles of these athletes favor sprinting or long-distance running 3. The muscles that move our legs contain two main types of muscle fibers: a. slow-twitch and b. fast-twitch. ..

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4 Slow-twitch fibers a. last longer, b. do not generate a lot of quick power, and c. generate ATP using oxygen (aerobically).

5. Fast-twitch fibers a. contract more quickly and powerfully, b. fatigue more quickly, and c. can generate ATP without using oxygen (anaerobically).

6. All human muscles contain both types of fibers but in different ratios

II. Energy Flow and Chemical Cycling in the Biosphere 1. Animals depend on plants to convert the energy of sunlight to: a. chemical energy of sugars and b. other organic molecules we consume as food.

2. Photosynthesis uses light energy from the sun to a. power a chemical process and b. make organic molecules.

A. Producers and Consumers 1. Plants and other autotrophs (self-feeders) a. make their own organic matter from inorganic nutrients.

2. Heterotrophs (other-feeders) a. include humans and other animals that cannot make organic molecules from inorganic ones.

3. Autotrophs are producers because ecosystems depend upon them for food 4. Heterotrophs are consumers because they eat plants or other animals B. Chemical Cycling between Photosynthesis and Cellular Respiration 1. The ingredients for photosynthesis are carbon dioxide (CO2) and water (H2O) a. CO2 is obtained from the air by a plant’s leaves. b. H2O is obtained from the damp soil by a plant’s roots.

2. Chloroplasts in the cells of leaves use light energy to rearrange the atoms of CO2 and H2O, which produces a. sugars (such as glucose), b. other organic molecules, and c. oxygen gas.

3. Plant and animal cells perform cellular respiration, a chemical process that a. primarily occurs in mitochondria, b. harvests energy stored in organic molecules, c. uses oxygen, and d. generates ATP. 4. The waste products of cellular respiration are a. CO2 and H2O, b. used in photosynthesis.

5. Animals perform only cellular respiration

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6. Plants perform a. photosynthesis and b. cellular respiration.

7. Plants usually make more organic molecules than they need for fuel. This surplus provides material that can be a. used for the plant to grow or b. stored as starch in potatoes.

III. Cellular Respiration: Aerobic Harvest of Food Energy 1. Cellular respiration is a. the main way that chemical energy is harvested from food and converted to ATP and b. an aerobic process—it requires oxygen.

2. Cellular respiration and breathing are closely related a. Cellular respiration requires a cell to exchange gases with its surroundings. i. Cells take in oxygen gas. ii. Cells release waste carbon dioxide gas. b. Breathing exchanges these same gases between the blood and outside air.

A. The Simplified Equation for Cellular Respiration 1. A common fuel molecule for cellular respiration is glucose 2. Cellular respiration can produce up to 32 ATP molecules for each glucose molecule consumed 3. The overall equation for what happens to glucose during cellular respiration is a. glucose & oxygen ➔ CO2, H2O, & a release of energy B. The Role of Oxygen in Cellular Respiration 1. During cellular respiration, hydrogen and its bonding electrons change partners from sugar to oxygen, forming water as a product 2. Redox Reactions 3. Chemical reactions that transfer electrons from one substance to another are called a. oxidation-reduction reactions or b. redox reactions for short.

4. The loss of electrons during a redox reaction is oxidation 5. The acceptance of electrons during a redox reaction is reduction 6. During cellular respiration a. glucose is oxidized and b. oxygen is reduced.

7. Why does electron transfer to oxygen release energy? a. When electrons move from glucose to oxygen, it is as though the electrons were falling. b. This “fall” of electrons releases energy during cellular respiration.

8. Cellular respiration is a. a controlled fall of electrons and b. a stepwise cascade much like going down a staircase.

9. NADH and Electron Transport Chains

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10. The path that electrons take on their way down from glucose to oxygen involves many steps 11. The first step is an electron acceptor called NAD+ a. NAD is made by cells from niacin, a B vitamin b. The transfer of electrons from organic fuel to NAD+ reduces it to NADH 12. The rest of the path consists of an electron transport chain, which a. involves a series of redox reactions and b. ultimately leads to the production of large amounts of ATP. C. An Overview of Cellular Respiration 1. Cellular respiration is an example of a metabolic pathway, which is a series of chemical reactions in cells 2. All of the reactions involved in cellular respiration can be grouped into three main stages: a. glycolysis, b. the citric acid cycle, and c. electron transport.

D. The Three Stages of Cellular Respiration 1. With the big-picture view of cellular respiration in mind, let’s examine the process in more detail 2. Stage 1: Glycolysis 3. A six-carbon glucose molecule a. is split in half to form two molecules of pyruvic acid.

4. These two molecules then a. donate high energy electrons to NAD+, forming NADH. 5. Glycolysis a. uses two ATP molecules per glucose to split the six-carbon glucose and b. makes four additional ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP. 6. Thus, glycolysis produces a net of two molecules of ATP per glucose molecule 7. Stage 2: The Citric Acid Cycle 8. In the citric acid cycle, pyruvic acid from glycolysis is first “prepped.” a. Each pyruvic acid loses a carbon as CO2. b. The remaining fuel molecule, with only two carbons left, is acetic acid.

9. Oxidation of the fuel generates NADH 10. Finally, each acetic acid is attached to a molecule called coenzyme A to form acetyl CoA 11. The CoA escorts the acetic acid into the first reaction of the citric acid cycle 12. The CoA is then stripped and recycled 13. The citric acid cycle a. extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2, b. uses some of this energy to make ATP, and c. forms NADH and FADH2.

14. Stage 3: Electron Transport

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15. Electron transport releases the energy your cells need to make the most of their ATP 16. The molecules of the electron transport chain are built into the inner membranes of mitochondria 17. The chain a. functions as a chemical machine, which b. uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane, and c. uses these ions to store potential energy.

18. When the hydrogen ions flow back through the membrane, they release energy a. The hydrogen ions flow through ATP synthase. b. ATP synthase i. takes the energy from this flow and ii. synthesizes ATP. 19. Cyanide is a deadly poison that a. binds to one of the protein complexes in the electron transport chain, b. prevents the passage of electrons to oxygen, and c. stops the production of ATP. E. The Results of Cellular Respiration 1. Cellular respiration can generate up to 32 molecules of ATP per molecule of glucose 2. In addition to glucose, cellular respiration can “burn” a. diverse types of carbohydrates, b. fats, and c. proteins.

VI. Fermentation: Anaerobic Harvest of Food Energy 1. Some of your cells can actually work for short periods without oxygen 2. Fermentation is the anaerobic (without oxygen) harvest of food energy A. Fermentation in Human Muscle Cells 1. After functioning anaerobically for about 15 seconds, muscle cells begin to generate ATP by the process of fermentation 2. Fermentation relies on glycolysis to produce ATP 3. Glycolysis a. does not require oxygen and b. produces two ATP molecules for each glucose broken down to pyruvic acid.

4. Pyruvic acid, produced by glycolysis, a. is reduced by NADH, b. producing NAD+, which c. keeps glycolysis going.

5. In human muscle cells, lactic acid is a by-product B. The Process of Science: What Causes Muscle Burn?

1. Observation: Muscles produce lactic acid under anaerobic conditions 2. Question: Does the buildup of lactic acid cause muscle fatigue?

3. Hypothesis: The buildup of lactic acid would cause muscle activity to stop

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4. Experiment: Tested frog muscles under conditions when lactic acid a. could and b. could not diffuse away.

5. Results: When lactic acid could diffuse away, performance improved greatly 6. Conclusion: Lactic acid accumulation is the primary cause of failure in muscle tissue 7. However, recent evidence suggests that the role of lactic acid in muscle function remains unclear C. Fermentation in Microorganisms 1. Fermentation alone is able to sustain many types of microorganisms 2. The lactic acid produced by microbes using fermentation is used to produce a. cheese, sour cream, and yogurt, b. soy sauce, pickles, and olives, and c. sausage meat products.

3. Yeast is a microscopic fungus that a. uses a different type of fermentation and b. produces CO2 and ethyl alcohol instead of lactic acid.

4. This type of fermentation, called alcoholic fermentation, is used to produce a. beer, b. wine, and c. breads.

D. Evolution Connection: Life before and after Oxygen 1. Glycolysis could be used by ancient bacteria to make ATP a. when little oxygen was available, and b. before organelles evolved.

2. Today, glycolysis: a. occurs in almost all organisms and b. is a metabolic heirloom of the first stage in the breakdown of organic molecules.

Chapter Guide to Teaching Resources Energy Flow and Chemical Cycling in the Biosphere Student Misconceptions and Concerns 1. Students should be cautioned against making statements that “energy is created” when it is converted from one form to another. This might be a good time to review the principle of conservation of energy (the first law of thermodynamics).

2. Students frequently think that plants have chloroplasts instead of mitochondria. Care should be taken to point out the need for mitochondria in plants when photosynthesis is not efficient or possible (such as during the night).

Teaching Tips 1. You might wish to elaborate on the amount of solar energy striking Earth. Every day Earth is bombarded with solar radiation equal to the energy of 100 million atomic bombs. Of the tiny fraction of light that reaches photosynthetic organisms, only about 1% is converted to chemical energy by photosynthesis.

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2. You might share with your students that it takes about 10 million ATP molecules per second to power one active muscle cell.

3. Energy coupling at the cellular level may be new to many students, but it is a familiar concept when related to the use of money in our society. Students might be discouraged if the only benefit of work was the ability to make purchases from the employer. (We all might soon tire of a fast-food job that pays its employees only in food!) Money permits the coupling of the generation of value (a paycheck, analogous to an energy-releasing reaction) to an energy-consuming reaction (money, which enables us to make purchases in distant locations). This idea of “earn and spend” is a common concept we all know well.

Cellular Respiration: Aerobic Harvest of Food Energy Student Misconceptions and Concerns 1. Perhaps more than anywhere else in general biology, students studying aerobic metabolism fail to see “the forest for the trees.” Students often focus on the details of each stage of aerobic metabolism and devote little attention to the overall process and products.

Consider emphasizing the products, locations, and energy yields associated with glycolysis, the citric acid cycle, and electron transport before detailing the specifics of each reaction. Figure 6.6 can be especially helpful to provide physical orientation to these cellular processes.

2. Students often fail to realize that aerobic metabolism is a process generally similar to the burning of wood in a fireplace or campfire. Pointing out the general similarities can help students comprehend the overall reaction and heat generation associated with both processes.

3. The advantage of the gradual degradation of glucose may not be obvious to some students.

Many analogies exist that reveal the advantages of short and steady steps. Fuel in an automobile is burned slowly to best utilize the energy released from the fuel. A few fireplace logs release gradual heat to keep a room temperature steady. In both situations, excessive use of fuel can be wasteful, reducing the efficiencies of the systems.

Teaching Tips 1. During cellular respiration, our cells convert about 40% of our food energy to useful work. The other 60% of the energy is released as heat. We use this heat to maintain a relatively steady body temperature near 37°C (98–99°F). This is about the same amount of heat generated by a 100-watt incandescent lightbulb (depending upon the size of the person). If you choose to include a discussion of heat generated by aerobic metabolism, consider the following: a. Ask your students why they feel warm when it is 30°C (86°F) outside if their core body temperature is 37°C (98.6°F). Shouldn’t they feel cold? The answer is, our bodies are always producing heat. At these higher temperatures, we are producing more heat than we need to maintain a body temperature around 37°C. Thus, we sweat and behave in ways that help us get rid of the extra heat from cellular respiration. b. Share this calculation with your students. Depending on the size and activity of a person, a human might burn 2,000 dietary Calories (kilocalories) a day. This is enough energy to raise the temperature of 20 L of liquid water from 0 to 100°C. This is something to think about the next time you heat water on the stove! (Note: Consider bringing a 2-L bottle as a visual aid, or ten 2-L bottles to make the point above; 100 Calories raises 1 L of water 100°C. Note: It takes much more energy to melt ice or evaporate water as steam.)

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2. The location within a cell of each of the following reactions is often lost in the details of the processes; yet the locations are important. The “Evolution Connection” section at the end of this chapter discusses the significance of glycolysis occurring in the cytosol. To emphasize the location of each stage, consider pointing to Figure 6.6, with mitochondrial detail, as you discuss cellular respiration.

3. As you relate the structure of the inner mitochondrial membrane to its functions, challenge the students to suggest an adaptive advantage of the many folds of this inner membrane.

These folds greatly increase the membrane region available for the associated reactions.

4. The production of NADH by glycolysis and the citric acid cycle, instead of just the direct production of ATP, can get confusing for students. Help students understand that NADH molecules have energy “value,” to be “cashed in” by the electron transport chain. The NADH can therefore be thought of as casino chips, accumulated along the way to be cashed in at the “electron transport” cashier.

5. The authors developed an analogy between the function of the inner mitochondrial membrane and a dam. A reservoir of hydrogen ions is built up between the mitochondrial membranes, like a dam holding back water. As the hydrogen ions move down their concentration gradient, they “spin” the ATP synthase, which helps generate ATP. In a dam, water rushing downhill turns giant turbines, which generate electricity.

6. Students should be reminded that the ATP yield per glucose molecule of up to 32 ATP is only a potential. The complex chemistry of aerobic metabolism can only yield this amount under ideal conditions, when every substrate and enzyme is immediately available. Such circumstances may only rarely occur in a working cell.

Fermentation: Anaerobic Harvest of Food Energy Student Misconceptions and Concerns 1. Some students might expect that fermentation produces alcohol and perhaps carbon dioxide. Care should be taken to clarify the different possible products of fermentation in muscle cells and alcoholic fermentation used in the food and beverage industry.

2. The text notes that some microbes are useful in the dairy industry because they produce lactic acid. However, the impact of acids on milk may not be obvious to many students.

Consider a simple demonstration mixing about equal portions of milk (skim or 2%) with some acid (vinegar will work). Notice the accumulation of strands of milk curd (protein) on the side of the container and stirring device.

Teaching Tips 1. The carbon dioxide released from fermentation also makes beer and champagne bubbly.

2. Dry wines are produced when the yeast cells use up all or most of the sugar available.

Sweet wines result when the alcohol accumulates enough to inhibit fermentation before the sugar is depleted.

3. Exposing fermenting yeast to oxygen will slow or stop the process, because the yeast will switch back to aerobic respiration. When fermentation is rapid, the carbon dioxide produced drives away the immediate oxygen above the wine. However, as fermentation slows down, the wine must be sealed to prevent oxygen exposure and permit the fermentation process to finish.

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Key Terms aerobic anaerobic ATP synthase autotrophs cellular respiration

citric acid cycle glycolysis consumers heterotrophs electron transport NADH electron transport chain oxidation fermentation photosynthesis

producers redox reaction reduction

Word Roots aero = air (aerobic: chemical reaction using oxygen) auto = self; troph = food (autotroph: organism that makes its own organic matter) glyco = sweet; lysis = split (glycolysis: process that splits glucose into two molecules) hetero = other (heterotroph: an organism that cannot make its own organic food from inorganic ingredients, “other feeder”) photo = light (photosynthesis: process using light energy to make organic molecules)

Relevant Songs to Play in Class “Breathe,” Pink Floyd “Amber (is the color of your energy),” 311

“The Energy Blues,” (Schoolhouse Rock!

Rocks), Biz Markie

“Stayin’ Alive,” Bee Gees

“Hemorrhage,” Fuel

“The Energy,” Audiovent

“Fuel,” Metallica

Answers to End-of-Chapter Questions The Process of Science 12. Suggested answer: NADH and FADH2 are needed to pick up the electrons from the oxidation of a glucose molecule during glycolysis and the citric acid cycle. Ten NAD+ molecules are needed in the breakdown of one glucose molecule. However, NADH and FADH2 are recycled between electron transport, glycolysis, and the citric acid cycle.

Therefore, we need a small additional supply to replace those that are lost or damaged.

Biology and Society 13. Some issues and questions to consider: Perhaps microbes such as yeast had accidentally been sealed in an anaerobic environment. This environment would be conducive for alcoholic fermentation to occur. Alcoholic beverages were probably easier to store for longer periods without worry of bacterial contamination due to the high alcohol content.

Additionally, people were unlikely to contract sicknesses from drinking beverages containing alcohol.

14. Some issues and questions to consider: Is your customer aware of the danger? Do you have an obligation to protect the customer, even against her wishes? Does your employer have the right to dismiss you for informing the customer or for refusing to serve the customer?

Could you or the restaurant later be held liable for injury to the fetus? Is the mother responsible for willfully disregarding warnings about drinking?

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Additional Critical Thinking Questions The Process of Science 1. For pyruvic acid to enter the citric acid cycle, it must first be oxidized to acetyl CoA. The acetyl CoA then joins with a molecule of oxaloacetic acid to form citric acid in the citric acid cycle. After one turn of the citric acid cycle, the citric acid regenerates the oxaloacetic acid molecule consumed. Many of the intermediates of the citric acid cycle are used for other purposes. Succinyl CoA, for example, is used in the production of heme, the iron-containing molecule in hemoglobin and in the cytochromes of electron transport. This use of citric acid cycle intermediates reduces the amount of oxaloacetic acid available to join with acetyl CoA. If acetyl CoA cannot enter the citric acid cycle, it is converted to ketone bodies that are eliminated in the urine. When oxaloacetic acid is low, an enzyme converts pyruvic acid to oxaloacetic acid. Dr. Atkins’ diet is a popular weight-loss program. The principle is for dieters to consume large quantities of fats and protein, but to avoid carbohydrates. How does this diet cause weight loss? Hint: Consider the steps of cellular respiration and think about what other molecules would be missing if there was no glucose to begin the process.

Suggested answer: Fats and some amino acids are converted directly to acetyl CoA. There is no way for the acetyl CoA to be converted directly to pyruvic acid. If the diet is low in carbohydrates, little pyruvic acid is made by glycolysis, and the oxaloacetic acid cannot be replaced. The result is that the acetyl CoA produced by the fats and protein cannot be oxidized. Instead, the acetyl CoA is converted to ketone bodies, and the Calories are excreted from the body. This diet can be dangerous since many of the ketone bodies are acids that can lower the pH of the blood. Uncontrolled diabetics cannot make pyruvic acid because without the hormone insulin, glucose cannot enter the cells. They are subject to diabetic comas caused by ketone bodies. One of the ketone bodies is acetone. Acetone is very volatile and has a distinctly sweet smell. Some dieters complain of breath odors when they are on this diet.

2. An average adult human requires 2,200 kilocalories (kcal) of energy per day (however, this number can vary based on age, gender, and weight). Suppose your diet provides an average of 2,300 kcal per day. How many hours per week would you have to walk to burn off the extra 100 Calories consumed?

Suggested answer: 100 kcal per day is 700 kcal per week. Based on Figure 5.3 in your textbook, walking 3 miles per hour would use 245 Calories per hour. This would require 700 Calories / 245 Calories per hour = 2.86 hours of walking.

3. Although your body can convert excess carbohydrates in the diet to fats, it cannot convert a carbohydrate into protein. What is missing in the carbohydrate that is necessary to convert it to a protein?

Suggested answer: The amino acids that make up proteins have amino groups containing nitrogen atoms. Amino groups are lacking in carbohydrates and must be added to carbohydrates to make amino acids for making proteins.

Biology and Society 4. Obesity is a serious epidemic in the United States. According to the Centers for Disease Control and Prevention (CDC), obesity in the U.S. population increased from about 12% in 1991 to about 34% in 2006. The highest increase occurred in 18- to 29-year-olds.

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our overconsumption of abundant processed food products, many of which are high in fat and sugar content. Fat tastes good to most people, and the temptation to eat too much is ever present. Why do you think this is so? Consider the fact that our appetites and digestive systems evolved over time under very different circumstances. Are there advantages to our tendency to eat too much that would have been selected for in the course of human evolution? How can we, as a society, deal with the problem?

Some issues and questions to consider: Take an anonymous survey of the class using a website (www.cdc.gov/nccdphp/dnpa/healthyweight/assessing/bmi/index.htm) that calculates a person’s body mass index (BMI). A BMI over 30 is considered obese; a BMI between 25 and 30 is defined as overweight. What percentage of the class is obese? Does this fit the CDC data? Consider the conditions experienced by our prehistoric ancestors.

Was food plentiful or scarce for hunter-gatherers? If a group came upon an infrequent source of food, would there be an advantage to eating heartily? Fatty foods have the largest concentration of Calories. Would this give a selective advantage to those individuals who found fat flavorful? Women tend to have a higher fat content than men. Is this related to pregnancy? Consider the fact that women with a very low body-fat content—for example, those who suffer from anorexia—stop menstruating. Why? 5. We are regularly bombarded with advertisements for supplements that will help us lose that ugly fat the fast and easy way with no diet or exercise required. Your roommate insists on purchasing every new supplement that hits the market in the hopes of shedding a few pounds. As a scientifically educated person, you know that the Food and Drug Administration does not regulate these supplement companies and that their claims are typically not backed by good scientific evidence. Explain to your roommate some of the risks associated with taking these supplements (based on what you know about cellular respiration and metabolism) and what will work best to lose weight.

Some issues and questions to consider: Since the supplement industry is not regulated, there really is no strong evidence that their claims are true. In fact, many supplements have caused serious health problems such as high blood pressure and death (ephedra, for example). Moreover, the abuse of frequent fad diets and supplements can cause long-term slowing of the metabolism. The best way to lose weight is to increase your activity (and thus your ATP demands) by exercise and to decrease the consumption of Calories, especially processed foods and refined sugars that lack nutrients and minerals.

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CHAPTER

7

Photosynthesis: Using Light to Make Food

Why This Chapter Matters 1. About 160 billion metric tons of organic material are produced on Earth each year by photosynthesis.

2. All of the food consumed by humans can be traced to photosynthetic plants.

3. Photosynthesis provides materials used for clothing, housing, heating, pharmaceuticals, and cooking.

4. The chemistry of photosynthesis affects our global environment.

Chapter Objectives Biology and Society: Biofuels 1. Describe the advantages of biofuels over fossil fuels.

The Basics of Photosynthesis 2. Describe the structure of chloroplasts and indicate where the chlorophyll molecules are located. Explain how carbon dioxide and oxygen move in and out of leaves.

3. Explain how the process of photosynthesis is similar to the reverse of cellular respiration.

4. Compare the reactants and products of the light reactions and the Calvin cycle.

The Light Reactions: Converting Solar Energy to Chemical Energy 5. Define wavelength and the electromagnetic spectrum. Identify the wavelengths that are absorbed by and reflected from an object that appears green.

6. Explain how Theodor Engelmann was able to determine that only certain wavelengths of light are used in photosynthesis.

7. Compare the functions of chlorophyll a, chlorophyll b, and carotenoids.

8. Explain how the energy of photons is transferred within a photosystem.

9. Compare the water-splitting and NADPH-producing processes of the light reactions.

10. Compare the process of ATP production in the inner mitochondrial membrane to the thylakoid membrane of chloroplasts.

The Calvin Cycle: Making Sugar from Carbon Dioxide 11. Describe the reactants and products of the Calvin cycle. Explain why this cycle is dependent on the light reactions.

Evolution Connection: Solar-Driven Evolution 12. Compare the mechanisms that C3, C4, and CAM plants use to obtain carbon dioxide.

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Lecture Outline I. Biology and Society: Biofuels 1. Wood has historically been the main fuel used to produce a. heat and b. light.

2. Industrialized societies replaced wood with fossil fuels including a. coal, b. gas, and c. oil.

3. To limit the damaging effects of fossil fuels, researchers are investigating the use of biomass (living material) as efficient and renewable energy sources 4. There are several types of biofuels a. Bioethanol is a type of alcohol produced by the fermentation of glucose made from starches in crops such as grains, sugar beets, and sugar cane. b. Bioethanol may be used i. directly as a fuel source in specially designed vehicles or ii. as a gasoline additive. c. Cellulosic ethanol is a type of bioethanol made from cellulose in nonedible plant material such as wood or grass. d. Biodiesel is made from plant oils or recycled frying oil.

A. The Basics of Photosynthesis 1. Photosynthesis a. is used by plants, algae (protists), and some bacteria, b. transforms light energy into chemical energy, and c. uses carbon dioxide and water as starting materials.

2. The chemical energy produced via photosynthesis is stored in the bonds of sugar molecules 3. Organisms that use photosynthesis are a. photosynthetic autotrophs and b. the producers for most ecosystems.

B. Chloroplasts: Sites of Photosynthesis 1. Chloroplasts are: a. the site of photosynthesis and b. found mostly in the interior cells of leaves.

2. Inside chloroplasts are interconnected, membranous sacs called thylakoids, which are suspended in a thick fluid called stroma 3. Thylakoids are concentrated in stacks called grana 4. The green color of chloroplasts is from chlorophyll, a light-absorbing pigment that plays a central role in converting solar energy to chemical energy 5. Stomata are tiny pores in leaves where a. carbon dioxide enters and b. oxygen exits.

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C. The Simplified Equation for Photosynthesis 1. In the overall equation for photosynthesis, notice that the reactants of photosynthesis are the waste products of cellular respiration 2. In photosynthesis, a. sunlight provides the energy, b. electrons are boosted “uphill” and added to carbon dioxide, and c. sugar is produced.

3. During photosynthesis, water is split into a. hydrogen and b. oxygen.

4. Hydrogen is transferred along with electrons and added to carbon dioxide to produce sugar 5. Oxygen escapes through stomata into the atmosphere D. A Photosynthesis Road Map 1. Photosynthesis occurs in two multistep stages: a. the light reactions convert solar energy to chemical energy and b. the Calvin cycle uses the products of the light reactions to make sugar from carbon dioxide.

2. The initial incorporation of carbon from the atmosphere into organic compounds is called carbon fixation a. This lowers the amount of carbon in the air. b. Deforestation reduces the ability of the biosphere to absorb carbon by reducing the amount of photosynthetic plant life.

E. The Light Reactions: Converting Solar Energy to Chemical Energy 1. Chloroplasts a. are chemical factories powered by the sun and b. convert sunlight into chemical energy.

F. The Nature of Sunlight 1. Sunlight is a type of energy called radiation, or electromagnetic energy 2. The distance between the crests of two adjacent waves is called a wavelength 3. The full range of radiation is called the electromagnetic spectrum G. The Process of Science: What Colors of Light Drive Photosynthesis?

1. Observation: In 1883, German biologist Theodor Engelmann saw that certain bacteria tend to cluster in areas with higher oxygen concentrations 2. Question: Could this information determine which wavelengths of light work best for photosynthesis?

3. Hypothesis: Oxygen-seeking bacteria will congregate near regions of algae performing the most photosynthesis 4. Experiment: Engelmann a. laid a string of freshwater algal cells in a drop of water on a microscope slide, b. added oxygen-sensitive bacteria to the drop, and c. used a prism to create a spectrum of light shining on the slide.

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5. Results: Bacteria a. mostly congregated around algae exposed to red-orange and blue-violet light and b. rarely moved to areas of green light.

6. Conclusion: Chloroplasts absorb light mainly in the blue-violet and red-orange part of the spectrum H. Chloroplast Pigments 1. Chloroplasts contain several pigments: a. Chlorophyll a i. absorbs mainly blue-violet and red light and ii. participates directly in the light reactions. b. Chlorophyll b i. absorbs mainly blue and orange light and ii. participates indirectly in the light reactions.

2. Carotenoids a. absorb mainly blue-green light, b. participate indirectly in the light reactions, and c. absorb and dissipate excessive light energy that might damage chlorophyll.

3. The spectacular colors of fall foliage are due partly to the yellow-orange light reflected from carotenoids I. How Photosystems Harvest Light Energy 1. Light behaves as photons, a fixed quantity of light energy 2. Chlorophyll molecules absorb photons a. Electrons in the pigment gain energy. b. As the electrons fall back to their ground state, energy is released as heat or light.

3. In the thylakoid membrane, chlorophyll molecules are organized with other molecules into photosystems 4. A photosystem is a cluster of a few hundred pigment molecules that function as a light-gathering antenna 5. The reaction center of the photosystem consists of chlorophyll a molecules that sit next to another molecule called a primary electron acceptor, which traps the lightexcited electron from chlorophyll a 6. Another team of molecules built into the thylakoid membrane then uses that trapped energy to make a. ATP and b. NADPH. J. How the Light Reactions Generate ATP and NADPH 1. Two types of photosystems cooperate in the light reactions: a. the water-splitting photosystem and b. the NADPH-producing photosystem.

2. The light reactions are located in the thylakoid membrane

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3. An electron transport chain a. connects the two photosystems and b. releases energy that the chloroplast uses to make ATP. K. The Calvin Cycle: Making Sugar from Carbon Dioxide 1. The Calvin cycle a. functions like a sugar factory within a chloroplast and b. regenerates the starting material with each turn.

L. Evolution Connection:Solar-Driven Evolution 1. C3 plants a. use CO2 directly from the air and b. are very common and widely distributed.

2. C4 plants a. close their stomata to save water during hot and dry weather and b. can still carry out photosynthesis.

3. CAM plants a. are adapted to very dry climates and b. open their stomata only at night to conserve water.

Chapter Guide to Teaching Resources The Basics of Photosynthesis Student Misconceptions and Concerns 1. Students often do not fully understand how the burning of fossil fuels contributes to global warming. They might wonder, “How does the burning of fossil fuels differ from the burning of ethanol produced from crops?” Students might not realize that the carbon in fossil fuels was removed from the atmosphere hundreds of millions of years ago, while the carbon in crops was removed much more recently, when the crops were grown. The use of ethanol as an alternative is complicated by the typical reliance upon fossil fuels for ethanol production.

2. Some students do not realize that plant cells also have mitochondria. Instead, they assume that the chloroplasts are sufficient for the plant cell’s needs. But nearly 50% of the carbohydrates produced by plant cells are used for cellular respiration (involving mitochondria).

3. Students may not connect the growth in plant mass to the fixation of carbon during the Calvin cycle. It can be difficult for many students to appreciate that molecules in air can contribute significantly to the mass of plants.

4. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange.

5. Students who have not read all of Chapter 7 may not realize that glucose is not the direct product of photosynthesis. Although glucose is shown as a product of photosynthesis, a three-carbon sugar is directly produced (G3P). A plant can use G3P to make many types of organic molecules, including glucose. (The authors address the production of G3P under the section “The Calvin Cycle” later in this chapter.)

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Teaching Tips 1. When introducing the diverse ways that plants impact our lives, consider challenging your students to come up with a list of products made from plants that they encounter regularly.

Perhaps you might only list those encountered in a single day of college life. The list can be surprising and help to build up your “catalog of examples.”

2. The living world contains many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle seen elsewhere to the extensive folding of the thylakoid membranes.

3. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis.

4. You might wish to discuss the evolution of chloroplasts from photosynthetic prokaryotes if you will not address this subject elsewhere in your course.

5. Figure 7.3 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates.

6. The thylakoid space and the intermembrane space of a mitochondrion have analogous roles. Students might be encouraged to create a list of the similarities in structure and function of mitochondria and chloroplasts through these related chapters.

The Light Reactions: Converting Solar Energy to Chemical Energy Student Misconceptions and Concerns 1. The authors note that sunlight is a type of radiation. Many students think of radiation as a result of radioactive decay, a serious threat to health. The diverse types of radiation and the varying energy associated with each, might need to be explained.

2. The authors note that electromagnetic energy travels through space in waves that are like those made by a pebble dropped in a pond. This wave imagery is helpful, but can confuse students when energy is also thought of as discrete packets called photons. The dual nature of light as a wave and particle may need to be discussed further, if students are to do more than just accept the definitions.

3. The light reactions are not solely responsible for all of the products in the general chemical equation of photosynthesis. Point out that oxygen is generated in the light reactions but that glucose results from products of the Calvin cycle.

4. Even at the college level, students struggle to understand why we perceive certain colors.

The authors discuss the specific absorption and reflection of certain wavelengths of light, noting which colors are absorbed and which are reflected (and thus available for our eyes to detect). Consider spending time to make sure that your students understand how photosynthetic pigments absorb and reflect certain wavelengths.

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Teaching Tips 1. Consider bringing a prism to class and demonstrating the spectrum of visible light. Depending on what you have available, it can be a dramatic reinforcement of this key concept. You might show an image of a rainbow if you are willing to explain how it is produced.

2. Consider bringing a glow stick to class just to help illustrate the authors’ note about the lightgenerating reactions in glow sticks. Small demonstrations break up lectures and stir attention.

3. The authors discuss a phenomenon that most students have noticed: Dark surfaces heat up faster in the sun than lighter-colored surfaces. This is an opportunity to demonstrate to your students the various depths of scientific explanations and help them appreciate their own educational progress. In elementary school, they might have learned that the sun heats darker surfaces faster than lighter surfaces. In high school, they may have learned about light energy and the fact that dark surfaces absorb more of this energy than lighter surfaces. Now, in college, they are learning that at the atomic level, darker surfaces absorb the energy of more photons, exciting more electrons, which then fall back to a lower state, releasing more heat.

4. The authors develop a mechanical analogy to the energy levels and movement of electrons in the light reaction. Figure 7.12 equates the height of an electron with its energy state.

Thus, electrons captured at high levels carry more energy than electrons in lower positions.

Although this figure can be very effective, students might need to be carefully led through the analogy to understand precisely what is represented.

The Calvin Cycle: Making Sugar from Carbon Dioxide Student Misconceptions and Concerns 1. Glucose is not the direct product of the Calvin cycle, as might be expected from the general equation for photosynthesis. Instead, G3P, as noted in the text, is the main product.

Clarify for students the diverse uses of G3P in the production of many important plant molecules and the advantages of producing a molecule with this flexibility.

Teaching Tips 1. If you can find examples of potted C3, C4, and CAM plants, consider bringing them to class. Referring to living plants in class helps students understand these abstract concepts.

Nice photographs can serve as a substitute.

2. Relate the properties of C3 and C4 plants to the regions of the country where each is grown.

Students might generally understand that crops have specific requirements, but may not specifically relate these physiological differences to their geographic sites of production or specific evolutionary histories.

Key Terms C3 plants C4 plants Calvin cycle CAM plants carbon fixation chlorophyll

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chlorophyll a chloroplast electromagnetic spectrum grana light reactions

NADPH photon photosynthesis photosystem primary electron acceptor

reaction center stomata stroma thylakoids wavelength

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Word Roots chloro = green; plast = formed or molded (chloroplast: the organelle of photosynthesis) electro = electricity; magne = magnetic (electromagnetic spectrum: the full range of radiation) photo = light; syn = with or together (photosynthesis: the process whereby plants transform light energy into chemical energy) phyll = leaf (chlorophyll: photosynthetic pigment in chloroplasts) stoma = mouth (stomata: tiny pores in leaves through which gases are exchanged) thylac = a sac or pouch (thylakoids: membranous sacs suspended in the stroma)

Relevant Songs to Play in Class “High Hopes (Rubber Tree Plant),” Doris Day

“Here Comes the Sun,” The Beatles

“Blinded by the Light,” Manfred Mann

“Sunshine,” Matt Costa

“Photosynthesis,” They Might Be Giants

“You Are the Sunshine of My Life,” Stevie Wonder

“The Last Remaining Light,” Audioslave “Don’t Turn Off the Lights,” Enrique Iglesias

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: Although the plants in the rain forest produce large amounts of oxygen, there are many reasons that all of this oxygen does not result in a net surplus. Oxygen is consumed by (a) the combustion of organic matter when rain forests are cleared, (b) other heterotrophic rain forest organisms that need this oxygen to perform aerobic cellular respiration, and (c) the consumption of oxygen by plants to perform aerobic cellular respiration.

12. Suggested answer: The oxygen atoms in glucose come from CO2. You could give some plants CO2 containing the isotope oxygen-18 and H2O containing ordinary oxygen (oxygen-16) and see whether the oxygen-18 ended up in glucose or in O2 gas. You could then use H2O labeled with oxygen-18 and unlabeled CO2. Only oxygen-18 from labeled CO2 would end up in glucose.

Biology and Society 13. Some issues and questions to consider: Would voluntary efforts have enough effect to lessen CO2 levels? Should businesses get a tax break for participating? Should the financial status of the countries involved be a factor? Would you be willing to pay increased taxes if the Kyoto agreement were actively enforced? Would the initial investments required to reduce CO2 emissions eventually become cost-effective? What are the possible consequences to the economy and poor nations if climate change leads large-scale flooding in coastal areas in the next hundred years compared to not making changes? Should we make drastic policy changes based on scientific models or adopt a wait and see approach to climate change?

14. Some issues and questions to consider: What are the benefits of each type of energy? What are the disadvantages of each type? Will the initial investment needed for biomass energy eventually become cost effective? Who should regulate a wide-scale conversion to biomass energy? Can this energy source produce enough energy to be cost-effective?

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Additional Critical Thinking Questions The Process of Science 1. Why is it beneficial for plants to have two types of chlorophyll instead of just one? What would you expect concerning the rate of photosynthesis for a plant that had only one type of chlorophyll?

Suggested answer: Having two types of chlorophyll enables the plant to utilize additional wavelengths of light to drive the light reactions. A plant with only one type of chlorophyll should have a slower rate of photosynthesis since fewer wavelengths of light would be absorbed.

2. Predict what will happen in the following experiment based on what you know about photosynthesis and cellular respiration. a. You place a plant alone in a covered airtight container in the presence of sunlight. Assume a watering system is provided. What will happen to the plant (will it live or die), and why? b. You place a mouse alone in a covered airtight container with food and a source of water. What will happen to the mouse, and why? c. You place a plant and a mouse together in a covered airtight container with food, water, and sunlight. What will happen to the plant and the mouse, and why?

Suggested answers: a. The plant will die due to a lack of CO2, which is needed to perform the Calvin cycle and ultimately produce glucose for the plant. b. The mouse will die due to a lack of O2, which is needed to perform aerobic cellular respiration. c. They should both live (at least temporarily). The plant will produce O2 needed by the mouse during the light reactions, and the mouse will exhale CO2 needed by the plant for the dark reactions.

3. A group of students is investigating the effect of light quality on photosynthesis in the aquatic plant Elodea. During the course of the experiment, the plant produces a stream of O2 bubbles as it photosynthesizes. Very specifically, explain where these bubbles of O2 are coming from.

Suggested answer: The O2 is being produced on the thylakoid membranes of chloroplasts by the light reactions of photosynthesis, as solar energy is used to split water molecules.

Biology and Society 4. Cattle ranching is a major cause of rain forest destruction in South America, especially in Brazil. Rain forest destruction contributes to global warming by releasing large amounts of CO2 and eliminating plants that use CO2 for photosynthesis. Ranchers slash and burn rain forests to create pastures for cattle herds. The meat is frozen and exported to industrialized countries such as the United States. A leading consumer of frozen meat is the fast-food industry. One estimate claims that for every quarter-pound hamburger made from rain forest cattle, 55 square feet of rain forest must be cleared. What is your demand and society’s demand for frozen beef? Should it be reduced, or is this the price we must pay for a plentiful food supply? Is it reasonable to expect people to voluntarily reduce meat consumption, or should other incentives be developed?

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Some issues and questions to consider: Consider the health benefits of reducing your consumption of fatty meats. Is this a greater reason to reduce meat consumption than the destruction of the rain forests? Has learning about this use of rain forest land altered your attitude toward excessive meat consumption? Could alternative uses of the rain forest, such as sustainable harvesting, decrease the meat production incentive for cattle ranchers? Do we have the ability to affect corporate policy? Visit the following website to review McDonald’s statement on this issue: www.mcspotlight.org/company/statements/rainforests_policy.html.

Why do you think that McDonald’s has posted its position on this issue on its website? Is this a reflection of the impact of information and the public’s reactions to business practices? What other fast-food companies have provided similar statements?

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CHAPTER

8

Cellular Reproduction: Cells from Cells

Why This Chapter Matters 1. Cell replication is a normal part of maintaining a healthy body.

2. Mitosis and meiosis permit asexual and sexual reproduction.

3. Errors in cell division can lead to cancer, infertility, abortion, or the production of children with serious genetic disorders.

4. Understanding the details of cell division helps us recognize the causes of these problems and helps us develop better strategies to address the challenges they produce.

Chapter Objectives Biology and Society: Virgin Birth of a Dragon 1. Explain what is unusual about Komodo dragon reproduction.

What Cell Reproduction Accomplishes 2. Describe the roles of cell division in living organisms.

3. Compare the cellular processes and cellular products of asexual and sexual reproduction.

The Cell Cycle and Mitosis 4. Describe the basic structure of a chromosome. Explain how DNA is packaged into an elaborate, multilevel system of coiling and folding.

5. Explain how and when chromosomes are duplicated.

6. Describe the key events of each phase of the cell cycle.

7. Describe the key events of each phase of mitosis.

8. Compare the processes of cytokinesis in animal and plant cells.

9. Describe how the cell cycle control system normally functions and explain the consequences of errors in this system.

10. Explain how cancer cells are different from healthy cells of the body.

11. Distinguish between benign and malignant tumors. Explain what is meant by the “slash, burn, and poison” approach to treating cancer.

12. Explain how you can reduce your risks of developing cancer.

Meiosis, the Basis of Sexual Reproduction 13. Distinguish between the following pairs of terms: sex chromosomes versus autosomes, somatic cells versus gametes, and diploid versus haploid cells.

14. Explain why the production of haploid gametes is necessary in sexually reproducing organisms.

15. Compare the processes and products of meiosis I and meiosis II. 16. Compare the overall processes and products of meiosis and mitosis.

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17. Explain how independent assortment of chromosomes during meiosis, random fertilization, and crossing over contribute to genetic diversity in offspring.

18. Describe the consequences of nondisjunction in autosomes and sex chromosomes.

Evolution Connection: The Advantages of Sex 19. Explain why asexual and sexual reproduction are adaptive.

Lecture Outline I. Biology and Society: Virgin Birth of a Dragon 1. In 2002, zookeepers at the Chester Zoo were surprised to discover that their Komodo Dragon laid eggs a. The female dragon had not been in the company of a male. b. The eggs developed without fertilization, in a process called parthenogenesis. c. DNA analysis confirmed that her offspring had genes only from her.

2. A second European Komodo dragon is now known to have reproduced a. asexually, via parthenogenesis, and b. sexually.

II. What Cell Reproduction Accomplishes 1. Reproduction a. may result in the birth of new organisms but b. more commonly involves the production of new cells.

2. When a cell undergoes reproduction, or cell division, two “daughter” cells are produced that are genetically identical a. to each other and b. to the “parent” cell.

3. Before a parent cell splits into two, it duplicates its chromosomes, the structures that contain most of the cell’s DNA 4. During cell division, each daughter cell receives one identical set of chromosomes from the lone, original parent cell 5. Cell division plays important roles in the lives of organisms 6. Cell division a. replaces damaged or lost cells, b. permits growth, and c. allows for reproduction.

7. In asexual reproduction, a. single-celled organisms reproduce by simple cell division and b. there is no fertilization of an egg by a sperm.

8. Some multicellular organisms, such as sea stars, can grow new individuals from fragmented pieces 9. Growing a new plant from a clipping is another example of asexual reproduction 10. In asexual reproduction, the lone parent and its offspring have identical genes

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11. Mitosis is the type of cell division responsible for a. asexual reproduction and b. growth and maintenance of multicellular organisms.

12. Sexual reproduction requires fertilization of an egg by a sperm using a special type of cell division called meiosis 13. Thus, sexually reproducing organisms use a. meiosis for reproduction and b. mitosis for growth and maintenance.

14. In a eukaryotic cell a. most genes are located on chromosomes in the cell nucleus and b. a few genes are found in DNA in mitochondria and chloroplasts.

III. The Cell Cycle and Mitosis 1. In a eukaryotic cell: 2. most genes are located on chromosomes in the cell nucleus and 3. a few genes are found in DNA in mitochondria and chloroplasts A. Eukaryotic Chromosomes 1. Each eukaryotic chromosome contains one very long DNA molecule, typically bearing thousands of genes 2. The number of chromosomes in a eukaryotic cell depends on the species 3. Chromosomes are a. made of chromatin, fibers composed of roughly equal amounts of DNA and protein molecules and b. not visible in a cell until cell division occurs.

4. The DNA in a cell is packed into an elaborate, multilevel system of coiling and folding 5. Histones are proteins used to package DNA in eukaryotes 6. Nucleosomes consist of DNA wound around histone molecules 7. Before a cell divides, it duplicates all of its chromosomes, resulting in two copies called sister chromatids containing identical genes 8. Two sister chromatids are joined together tightly at a narrow “waist” called the centromere 9. When the cell divides, the sister chromatids of a duplicated chromosome separate from each other 10. Once separated, each chromatid is a. considered a full-fledged chromosome and b. identical to the original chromosome.

B. The Cell Cycle 1. A cell cycle is the ordered sequence of events that extend a. from the time a cell is first formed from a dividing parent cell b. to its own division into two cells.

2. The cell cycle consists of two distinct phases: a. interphase and b. the mitotic phase.

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3. Most of a cell cycle is spent in interphase 4. During interphase, a cell a. performs its normal functions, b. doubles EVERYTHING in its cytoplasm, and c. grows in size.

5. The mitotic (M) phase includes two overlapping processes: a. mitosis, in which the nucleus and its contents divide evenly into two daughter nuclei and b. cytokinesis, in which the cytoplasm is divided in two.

C. Mitosis and Cytokinesis 1. During mitosis the mitotic spindle, a football-shaped structure of microtubules, guides the separation of two sets of daughter chromosomes 2. Spindle microtubules grow from structures within the cytoplasm called centrosomes 3. Mitosis consists of four distinct phases: a. Prophase b. Metaphase c. Anaphase d. Telophase 4. Cytokinesis usually a. begins during telophase, b. divides the cytoplasm, and c. is different in plant and animal cells.

5. In animal cells cytokinesis a. is known as cleavage and b. begins with the appearance of a cleavage furrow, an indentation at the equator of the cell.

6. In plant cells, cytokinesis a. begins when vesicles containing cell wall material collect at the middle of the cell and then fuse, forming a membranous disk called the cell plate.

D. Cancer Cells: Growing Out of Control 1. Normal plant and animal cells have a cell cycle control system that consists of specialized proteins, which send “stop” and “go-ahead” signals at certain key points during the cell cycle 2. What Is Cancer?

3. Cancer is a disease of the cell cycle 4. Cancer cells do not respond normally to the cell cycle control system.

5. Cancer cells can form tumors, abnormally growing masses of body cells 6. If the abnormal cells remain at the original site, the lump is called a benign tumor 7. The spread of cancer cells beyond their original site of origin is metastasis 8. Malignant tumors can a. spread to other parts of the body and b. interrupt normal body functions.

9. A person with a malignant tumor is said to have cancer

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10. Cancer Treatment 11. Cancer treatment can involve a. radiation therapy, which damages DNA and disrupts cell division, and b. chemotherapy, the use of drugs to disrupt cell division.

12. Cancer Prevention and Survival 13. Certain behaviors can decrease the risk of cancer: a. not smoking, b. exercising adequately, c. avoiding exposure to the sun, d. eating a high-fiber, low-fat diet, e. performing self-exams, and f. regularly visiting a doctor to identify tumors early.

E. Meiosis, the Basis of Sexual Reproduction 1. Sexual reproduction a. depends on meiosis and fertilization and b. produces offspring that contain a unique combination of genes from the parents.

F. Homologous Chromosomes 1. Different individuals of a single species have the same a. number and b. types of chromosomes.

2. A human somatic cell a. is a typical body cell and b. has 46 chromosomes.

3. A karyotype is an image that reveals an orderly arrangement of chromosomes 4. Homologous chromosomes a. are matching pairs of chromosomes that b. can possess different versions of the same genes.

5. Humans have a. two different sex chromosomes, X and Y, and b. 22 pairs of matching chromosomes, called autosomes.

G. Gametes and the Life Cycle of a Sexual Organism 1. The life cycle of a multicellular organism is the sequence of stages leading from the adults of one generation to the adults of the next 2. Humans are diploid organisms with a. body cells containing two sets of chromosomes and b. haploid gametes that have only one member of each homologous pair of chromosomes.

3. In humans, a haploid sperm fuses with a haploid egg, during fertilization to form a diploid zygote 4. Sexual life cycles involve an alternation of diploid and haploid stages 5. Meiosis produces haploid gametes, which keeps the chromosome number from doubling every generation

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H. The Process of Meiosis 1. In meiosis, a. haploid daughter cells are produced in diploid organisms, b. interphase is followed by two consecutive divisions, meiosis I and meiosis II, and c. crossing over occurs.

I. Review: Comparing Mitosis and Meiosis 1. In mitosis and meiosis, the chromosomes duplicate only once, during the preceding interphase 2. The number of cell divisions varies: a. Mitosis uses one division and produces two diploid cells. b. Meiosis uses two divisions and produces four haploid cells.

3. All the events unique to meiosis occur during meiosis I J. The Origins of Genetic Variation 1. Offspring of sexual reproduction are genetically different from their parents and one another 2. Independent Assortment of Chromosomes 3. When aligned during metaphase I of meiosis, the side-by-side orientation of each homologous pair of chromosomes is a matter of chance 4. Every chromosome pair orients independently of all of the others at metaphase I 5. For any species, the total number of chromosome combinations that can appear in the gametes due to independent assortment is a. 2n, where n is the haploid number.

6. For a human, a. n = 23. b. With n = 23, there are 8,388,608 different chromosome combinations possible in a gamete.

K. Random Fertilization 1. A human egg cell is fertilized randomly by one sperm, leading to genetic variety in the zygote 2. If each gamete represents one of 8,388,608 different chromosome combinations, at fertilization, humans would have 8,388,608 × 8,388,608, or more than 70 trillion different possible chromosome combinations 3. So we see that the random nature of fertilization adds a huge amount of potential variability to the offspring of sexual reproduction 4. Crossing Over 5. In crossing over, a. nonsister chromatids of homologous chromosomes exchange corresponding segments and b. genetic recombination, the production of gene combinations different from those carried by parental chromosomes, occurs.

L. The Process of Science: Do All Animals Have Sex? 1. Observation: No scientists have ever found male bdelloid rotifers, a microscopic freshwater invertebrate

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2. Question: Does this entire class of animals reproduce solely by asexual means?

3. Hypothesis: Bdelloid rotifers have thrived for millions of years despite a lack of sexual reproduction 4. Prediction: Bdelloid rotifers would display much more variation in their pairs of homologous genes than most organisms 5. Experiment: Researchers compared sequences of a particular gene in bdelloid and non-bdelloid rotifers 6. Results: a. Non-bdelloid sexually reproducing rotifers had a nearly identical homologous gene, differing by only 0.5% on average. b. The two versions of the same gene in asexually reproducing bdelloid rotifers differed by 3.5–54%.

7. Conclusion: Bdelloid rotifers have evolved for millions of years without any sexual reproduction M. When Meiosis Goes Awry 1. What happens when errors occur in meiosis?

2. Such mistakes can result in genetic abnormalities that range from mild to fatal 3. How Accidents during Meiosis Can Alter Chromosome Number 4. In nondisjunction, a. the members of a chromosome pair fail to separate at anaphase, b. producing gametes with an incorrect number of chromosomes.

5. Nondisjunction can occur during meiosis I or II 6. If nondisjunction occurs, and a normal sperm fertilizes an egg with an extra chromosome, the result is a zygote with a total of 2n + 1 chromosomes 7. If the organism survives, it will have a. an abnormal karyotype and b. probably a syndrome of disorders caused by the abnormal number of genes.

8. Down Syndrome: An Extra Chromosome 21 9. Down syndrome a. is also called trisomy 21, b. is a condition in which an individual has an extra chromosome 21, and c. affects about one out of every 700 children.

10. The incidence of Down syndrome in the offspring of normal parents increases markedly with the age of the mother 11. Abnormal Numbers of Sex Chromosomes 12. Nondisjunction in meiosis a. can lead to ABNORMAL numbers of sex chromosomes but b. seems to upset the genetic balance less than unusual numbers of autosomes, perhaps because the Y chromosome is very small and carries relatively few genes.

N. Evolution Connection: The Advantages of Sex 1. Asexual reproduction conveys an evolutionary advantage when plants are a. sparsely distributed and unlikely to be able to exchange pollen or b. superbly suited to a stable environment.

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2. Asexual reproduction also eliminates the need to expend energy a. forming gametes and b. copulating with a partner.

3. Sexual reproduction may convey an evolutionary advantage by a. speeding adaptation to a changing environment or b. allowing a population to more easily rid itself of harmful genes.

Chapter Guide to Teaching Resources What Cell Reproduction Accomplishes Student Misconceptions and Concerns 1. Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling can be prevented if each gamete has only half the genetic material of the adult cells.

2. Some basic familiarity or faint memory of mitosis and meiosis might result in a lack of enthusiasm for mitosis and meiosis in some of your students. Consider beginning such lectures with important topics related to cellular reproduction. For example, cancer cells reproduce uncontrollably, stem cells have the capacity to regenerate lost or damaged tissues, and the study of embryonic stem cells holds great potential but is variously restricted and regulated.

3. As the authors note, biologists use the term daughter to indicate offspring and not gender.

Students with little experience in this terminology can easily become confused.

Teaching Tips 1. The authors do not use the word clone in this chapter. You might wish to point out to your students that asexual reproduction produces clones.

2. Consider pointing out that asexual reproduction is common in prokaryotes and singlecelled organisms.

3. You might want to get your students thinking by asking them why eggs and sperm are different. (This depends on the species, but within vertebrates, eggs and sperm are specialized for different tasks. Sperm are adapted to move to an egg, donate a nucleus, and activate development of the egg. Eggs contain a nucleus and most of the cytoplasm of the future zygote. Thus, eggs are typically larger, nonmotile, and full of cellular resources to sustain cell division and support growth.)

4. Virchow’s principle of “Every cell from a cell” (not specifically addressed in this chapter) is worth thinking through with your class. Students might expect that like automobiles, computers, and cell phones, cell parts are constructed de novo and cells are assembled. In our society, few nonliving products are generated from only existing products (try to think of such examples). For example, you do not need a painting to paint or a house to construct a house. Yet, this common expectation exists in biology.

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The Cell Cycle and Mitosis Student Misconceptions and Concerns 1. Students often seem confused by the difference between a DNA molecule and a chromosome.

This is especially problematic in this chapter when discussing DNA replication.

2. Students are often confused by photographs of chromosomes. A chromosome is often described as a single strand, yet photographs typically show duplicated chromosomes appearing like the letter “X.” It remains unclear to many students why (a) chromosome structure is typically different between interphase G1 and stages of division and (b) why chromosomes are not photographed during interphase (the stage in which chromosomes are typically first discussed) before the chromosomes replicate.

3. Students do not typically know that all cancers are genetically based. Consider making this clear early in your discussions. Challenge your students to explain how certain viruses can lead to cancer (such as HPV, human papillomavirus associated with genital warts and cervical cancer).

Teaching Tips 1. Mitochondrial DNA is widely used to analyze evolutionary relationships. Students might be challenged to search the Internet for examples of its use in tracing human evolutionary history.

2. Consider this additional analogy between histones and DNA. DNA is like a very long piece of thread wrapped around a series of spools (histones). The DNA wraps one spool, then extends to another spool, repeating this many hundreds of times—all with one continuous strand of thread.

3. The concepts of DNA replication and sister chromatids are often obstacles for many students. If you can find twist ties or other bendable wire, you can demonstrate or have students model the difference between (a) a chromosome before DNA replication and (b) sister chromatids after DNA replication. One piece of wire will represent a chromosome before replication. Two twist ties twisted about each other can represent sister chromatids (even though this is not the actual physical relationship between sister chromatids). In the model, we have doubled the DNA, but the molecules remain attached.

(You might also want to point out that when sister chromatids are separated, they are considered separate chromosomes.)

4. In G1, the chromosomes have not replicated. But by G2, chromosomes consist of sister chromatids. If you have created a demonstration of sister chromatids, relate DNA replication and sister chromatids to the cell cycle.

5. The cell cycle control system is somewhat like the control device of an automatic washing machine. Each has a control system that triggers and coordinates key events in the cycle.

However, the components of the control system of a cell cycle are not located in one place, like a washing machine.

6. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPMAT. The first letters of interphase, prophase, metaphase, anaphase, and telophase are represented in this made-up word.

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7. Many students think of mitosis and cytokinesis as one process. In some situations, mitosis occurs without subsequent cytokinesis. Challenge your students to predict the outcome of mitosis without cytokinesis (multinuclear cells called a syncytium). One place this occurs is in human development during the formation of the placenta.

8. The authors make an analogy between a drawstring and the mechanism of cytokinesis in animal cells. Students seem to appreciate this analogy. Have your students think of a person tightening the drawstring of sweatpants so tight that they pinch themselves in two, or perhaps nearly so! The analogy is especially good because the drawstring is just beneath the surface of the sweatpants, and the microfilaments are just beneath the surface of the cell’s plasma membrane.

9. Chemotherapy has some disastrous side effects. The drugs used to fight cancer attack rapidly dividing cells. Unfortunately for men, the cells that make sperm are also rapidly dividing. In some circumstances, chemotherapy can leave a man infertile (unable to produce viable sperm) but still able to produce an erection.

10. Many other approaches (such as cancer vaccines) are under consideration to fight cancers.

You may wish to explore these as sidelights to your lecture. Good resources include cell biology and development textbooks.

Meiosis, the Basis of Sexual Reproduction Student Misconceptions and Concerns 1. How meiosis results in four haploid cells yet mitosis yields two diploid cells is often memorized but not understood. It can be explained like this. In mitosis and meiosis, the processes begin with replicated pairs of chromosomes. The two pairs include four items.

Sort this group into two subgroups, and you are back to two pairs. Divide again, and you have separated four items into four groups of one. All of the details of these two processes, although eventually addressed, can get in the way of seeing the overall process.

2. Most people have difficulty comprehending large numbers. See Teaching Tips 8–10 below to help relate these large numbers to aspects of students’ lives.

Teaching Tips 1. Sometimes the most basic questions can challenge students and get them focused on the subject at hand. Consider asking your students why we expect that dogs produce dogs, cats produce only more cats, and chickens only produce chickens. Why does “like produce like”?

2. Consider helping students through mitosis and meiosis by developing an analogy to pairs of shoes. In this case, any given species that is diploid has a certain number of pairs of shoes, or homologous chromosomes.

3. In the shoe analogy, females have 23 pairs of matching shoes, males have 22 matching pairs and one odd pair—maybe a sandal and a sneaker!

4. You may wish to ask the class why meiosis is necessary. Why not have a male diploid cell fertilize a diploid female cell? In short, the answer is that, if this were true, at every fertilization, we would have genetic doubling.

5. If you wish to continue the shoe analogy, crossing over is somewhat like exchanging the shoelaces in a pair of shoes. A point to make is that the shoes (chromosomes) before

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crossing over are what you inherited—either from the sperm or the egg; but, as a result of crossing over, you no longer pass along exactly what you inherited. Instead, you pass along a combination of homologous chromosomes (or shoes with switched shoelaces). In this shoe analogy, after exchanging shoelaces, we have recombinant shoes!

6. You might consider emphasizing a crucial difference between the processes of mitosis and meiosis. In mitosis, sister chromatids separate at metaphase. In meiosis I metaphase, sister chromatids stay together, and homologous chromosomes separate. After discussing mitosis and meiosis in class, consider asking your students to sketch the alignment of the chromosomes at mitosis metaphase and meiosis metaphase I. 7. The number 223 is 8,388,608. This number squared is more than 70 trillion. The authors rounded down to 8 million for 223 and squared this to estimate 64 trillion possible combinations. But more precisely, the number of possible zygotes produced by a single pair of reproducing humans, based solely on independent assortment and random fertilization, is over 70 trillion!

8. There are currently about 315 million humans living in the United States. If every person in the United States received $222,222, it would equal $70 trillion. Here is another way to think of it. If you lived to be 100 years old, and spent $22,181.66 every second of your life, (or a million dollars every 45 seconds) you would spend about $70 trillion dollars.

9. The impressive nature of such large numbers is lost on most of us who cannot comprehend such quantities. There are about 64 trillion seconds in 2 million years (actually, 2,028,000 years).

10. Depending on the size of your class, it is likely that at least one of your students is related to a person with Down syndrome. A student in your class may even enjoy the chance to talk about their Down syndrome friend or relative.

Key Terms anaphase asexual reproduction autosome benign tumor cancer cell cycle cell cycle control system cell division cell plate centromere centrosome chemotherapy

chiasma chromatin chromosome cleavage furrow crossing over cytokinesis diploid Down syndrome fertilization gamete genetic recombination haploid histone

homologous chromosome interphase karyotype life cycle malignant tumor meiosis metaphase metastasis mitosis mitotic (M) phase mitotic spindle nucleosome

nondisjunction prophase radiation therapy sex chromosome sexual reproduction sister chromatid somatic cell telophase trisomy 21 tumor zygote

Word Roots a = not or without (asexual: type of reproduction not involving fertilization) ana = again (anaphase: mitotic stage when sister chromatids separate) auto = self (autosomes: the chromosomes that do not determine gender) centro = the center; mere = a part (centromere: the centralized region joining two sister chromatids)

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chemo = chemical (chemotherapy: type of cancer therapy using drugs that disrupt cell division) chiasm = cross-mark (chiasma: the sites where crossing over has occurred) chroma = colored (chromosome: DNA-containing structure) cyto = cell; kinet = move (cytokinesis: division of the cytoplasm) di = two (diploid: cells that contain two homologous sets of chromosomes) fertil = fruitful (fertilization: process of fusion of sperm and egg cell) gamet = a wife or husband (gamete: egg or sperm) haplo = single (haploid: cells that contain only one chromosome of each homologous pair) homo = like (homologous: like chromosomes that form a pair) inter = between (interphase: time when a cell metabolizes and performs its various functions) karyo = nucleus (karyotype: a display of the chromosomes of a cell) mal = bad or evil (malignant: type of tumor that migrates away from its site of origin) mei = less (meiosis: the division of a diploid nucleus into four haploid daughter nuclei) meta = between (metaphase: mitotic stage when the chromosomes are lined up in the cell’s middle) mito = a thread (mitosis: the division of a diploid cell into two diploid cells) non = not; dis = separate (nondisjunction: the result when paired chromosomes fail to separate) pro = before (prophase: mitotic stage when the nuclear membrane first breaks up) soma = body (somatic: body cells with 46 chromosomes in humans) telo = end (telophase: final mitotic stage when the nuclear envelope re-forms) tri = three (trisomy 21: a condition in which a person has three number 21 chromosomes)

Relevant Songs to Play in Class “Miserable Bastard” (from the album Zygote), John Popper

“Two Kinds of Seagulls,” Tom Chapin

“Reproduction,” Grease 2 Soundtrack

“Love Will Tear Us Apart,” Joy Division

“I Want Your Sex,” George Michael

“Imitosis,” Andrew Bird

“Let’s Talk About Sex,” Salt-N-Pepa

Answers to End-of-Chapter Questions The Process of Science 13. Suggested answer: Each chromosome lines up singly in mitosis; chromosome replication and the separation of sister chromatids occur independently for each horse or donkey chromosome. Therefore, mitotic divisions, starting with the zygote, are not impaired. In meiosis, however, homologous chromosomes must pair in prophase I. This pairing of homologous chromosomes cannot occur properly because horse and donkey chromosomes do not match in number or content. Further, when the homologous pairs line up in metaphase I of meiosis, there will be one extra chromosome, which will be unpaired.

14. Suggested answer: (a) metaphase, (b) anaphase, (c) telophase, (d) prophase.

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Biology and Society 15. Some issues and questions to consider: Could it be that less money is spent on prevention because effective prevention is so much cheaper? Or because prevention has been tried, and it does not work well? Are lifestyle changes the kind of measures that could benefit from a shift in resources? Is prevention an individual matter of avoiding exposure or a social matter of preventing exposure? How might the answer to this question shape prevention policy? If more money were devoted to prevention, how could it be used to encourage you or others to make lifestyle changes? Would prevention work better for younger or older people? Might older people, already exposed to cancer-causing agents, actually be harmed by a shift of resources to prevention?

16. Some issues and questions to consider: Is this an issue that needs to be legally regulated? If one person agrees to such an arrangement, should that person’s right to sell gametes be halted by laws against this process? Do you think the financial motivation interferes with a person’s normal judgment on an issue such as this? Sperm donation has virtually no risks to the donor, but egg donation can be very risky for the donor. What are the risks of removing eggs? Should there be separate rules for male and female gamete donation?

Should eggs be considered more valuable based on the considerable risk to the donor?

Additional Critical Thinking Questions The Process of Science 1. Down syndrome is one of the few genetic conditions involving an alteration of chromosome number that allows fetal development to be completed. Nondisjunction of autosomes other than chromosome 21 can also occur but is rarely seen in full-term infants because of spontaneous abortions during fetal development. Why would a child with trisomy 21 be more likely to come to term than a child with, say, trisomy 3?

Suggested answer: Chromosome 21 is the smallest autosome, so it may be that having additional copies of the smaller number of genes on 21 is not lethal (though it does have detrimental effects). The larger the chromosome, the more genes it is likely to have; and the more additional copies of genes there are, the more likely it is that there will be resulting problems. Trisomy of large chromosomes, like chromosome 3, is more likely to be lethal to the developing fetus.

2. Suppose you read in the newspaper that a genetic engineering laboratory has developed a procedure for fusing two gametes from the same person (two eggs or two sperm) to form a zygote. The article mentions that an early step in the procedure prevents crossing over from occurring during the formation of the gametes in the donor’s body. The researchers are in the process of determining the genetic makeup of one of their new zygotes. Which of the following predictions do you think they would make? Justify your choice, and explain why you rejected each of the other choices. a. The zygote would have 46 chromosomes, all of which came from the gamete donor (its one parent), so the zygote would be genetically identical to the gamete donor. b. The zygote could be genetically identical to the gamete donor, but it is much more likely that it would have an unpredictable mixture of chromosomes from the gamete donor’s parents. c. The zygote would not be genetically identical to the gamete donor, but it would be genetically identical to one of the donor’s parents. d. The zygote would not be genetically identical to the gamete donor, but it would be genetically identical to one of the donor’s grandparents.

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Suggested answers: Answer a: No. For this to happen, all of the chromosomes of the two gametes that fused would have to represent a complete set of the donor’s maternal chromosomes (the ones that originally came from the donor’s mother) and a complete set of the donor’s paternal chromosomes (from the donor’s father). It is much more likely that the zygote would be missing one or more maternal chromosomes and would have an excess of paternal chromosomes, or vice versa.

Answer b: Correct. Consider what would have to happen to produce a zygote genetically identical to the gamete donor: The zygote would have to have a complete set of the donor’s maternal chromosomes and a complete set of the donor’s paternal chromosomes.

The first gamete in this union could contain any mixture of maternal and paternal chromosomes, but once that first gamete was “chosen,” the second one would have to have one particular combination of chromosomes—the combination that supplies whatever the first gamete did not supply. So, for example, if the first three chromosomes of the first gamete were maternal, maternal, and paternal, the first three of the second gamete would have to be paternal, paternal, and maternal. The chance that all 23 chromosome pairs would be complementary in this way is only one in 223 (or one in 8,388,608). Because of independent assortment, it is much more likely that the zygote would have an unpredictable combination of chromosomes from the donor’s father and mother.

Answer c: No. First, the zygote could be genetically identical to the gamete donor (see b).

Second, the zygote could not be identical to either of the gamete donor’s parents because the donor only has half the genetic material of each of his or her parents. For example, even if the zygote were formed by two gametes containing only paternal chromosomes, the combined set of chromosomes could not be identical to that of the donor’s father because it would still be missing half of the father’s chromosomes.

Answer d: No; see answer c.

3. Typical neurons are not able to perform mitosis after maturity. A patient has just been diagnosed with brain cancer and is undergoing treatment. Based on what you know about cell division and cancer, why does this seem unusual?

Suggested answer: Since cancer is unregulated cell division, it would seem unusual that brain cells would become cancerous since they are not supposed to be dividing at all. Most likely, the cancer has metastasized from another location or originated in glial (supporting) cells in the brain.

Biology and Society 4. The recent availability of genetic tests for susceptibility to some types of cancer has led some patients to take extreme measures, such as having a mastectomy when there is a risk, though not a certainty, of developing breast cancer. If you were a doctor, how would you advise a patient found to be at high risk for breast cancer?

Some issues and questions to consider: Does the doctor have the responsibility of educating the patient about all of the preventive and diagnostic measures? Should the patient’s wishes always be followed, regardless of the outcome? How accurate are the testing measures for susceptibility? What is the risk of developing breast cancer versus the risk of having a mastectomy?

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5. As women age, the cells in their ovaries that ultimately produce eggs also age. The older a woman is when she becomes pregnant, the older that egg cell is and the more likely it is that chromosomal damage has occurred. If this is the case and the embryo has a chromosomal abnormality, the mother’s system may spontaneously abort; however, the aborting mechanism also becomes defective with age. This is one reason why older women are more likely to have children born with birth defects than younger women. At menopause, the woman stops releasing eggs, which ends her fertility. Some postmenopausal women are now using reproductive technology to go to extreme measures to have their own biological child. How do you feel about the use of this technology?

Some issues and questions to consider: How risky is pregnancy at an older age? If the body has naturally stopped releasing eggs, should this be overridden by technology? How likely is it that the child will have a birth defect? How expensive is the technology? What are the consequences to a child having much older parents?

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CHAPTER

9

Patterns of Inheritance

Why This Chapter Matters 1. Humans have long relied on selective breeding to produce specialized breeds of livestock and pets. Mendel’s principles of inheritance are fundamental to the workings of artificial selection.

2. Variations of Mendel’s laws explain the inheritance patterns of many human traits and diseases.

3. Determining the probability of genetic diseases by following patterns of inheritance enables us to anticipate disease and better address its consequences. Pedigrees and genetic testing are an increasingly common part of modern medicine.

4. Genetics and the inheritance of traits are fundamental to understanding evolution by natural selection.

Chapter Objectives Biology and Society: Our Longest-Running Genetic Experiment: Dogs 1. Explain how human experiences breeding dog and food crops can provide insights into principles of genetics.

Heritable Variation and Patterns of Inheritance 2. Define and distinguish between self-fertilization, cross-fertilization, purebred organisms, hybrids, the P generation, the F1 generation, and the F2 generation.

3. Define and distinguish between the following pairs of terms: heterozygous versus homozygous, dominant allele versus recessive allele, genotype versus phenotype, and phenotypic ratio versus genotypic ratio.

4. Define the law of segregation and explain how it applies to reproduction.

5. Define Mendel’s law of independent assortment and explain how it applies to a dihybrid cross.

6. Explain how a testcross can be performed to determine an organism’s genotype.

7. Explain how and when the rule of multiplication should be used to determine the probability of an event.

8. Explain how a pedigree is used to determine how a particular human trait is inherited.

Define a carrier and explain how carriers are revealed in human pedigrees.

9. Compare the frequency and method of inheritance of recessive and dominant disorders.

Explain how a dominant lethal allele can be inherited.

Variations on Mendel’s Laws 10. Define and distinguish between complete dominance, incomplete dominance, and codominance.

11. Describe the selective advantage of people who are heterozygous for sickle-cell disease.

12. Define and distinguish between pleiotropy and polygenic inheritance. Describe examples of each.

13. Explain how the environment influences the expression of traits.

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The Chromosomal Basis of Inheritance 14. Define the chromosome theory of inheritance and explain how linked genes are inherited differently from nonlinked genes.

15. Explain why researchers used fruit flies and how they created linkage maps.

Sex Chromosomes and Sex-Linked Genes 16. Explain how chromosomes determine the sex of a human.

17. Explain why sex-linked diseases are more common in male humans.

18. Describe the general characters of the following sex-linked disorders in humans: redgreen colorblindness and hemophilia.

Evolution Connection: Barking Up the Evolutionary Tree 19. Describe the relationships between the many breeds of dogs.

Lecture Outline I. Biology and Society: Our Longest-Running Genetic Experiment: Dogs 1. People have selected and mated dogs with preferred traits for more than 15,000 years 2. Over thousands of years, such genetic tinkering has led to the incredible variety of body types and behaviors in dogs today 3. The biological principles underlying genetics have only recently been understood A. Heritable Variation and Patterns of Inheritance 1. Heredity is the transmission of traits from one generation to the next 2. Genetics is the scientific study of heredity 3. Gregor Mendel a. worked in the 1860s, b. was the first person to analyze patterns of inheritance, and c. deduced the fundamental principles of genetics.

B. In an Abbey Garden 1. Mendel studied garden peas because they a. were easy to grow, b. came in many readily distinguishable varieties, c. are easily manipulated, and d. can self-fertilize.

2. A character is a heritable feature that varies among individuals 3. A trait is a variant of a character 4. Each of the characters Mendel studied occurred in two distinct traits 5. Mendel a. created purebred varieties of plants and b. crossed two different purebred varieties.

6. Hybrids are the offspring of two different purebred varieties a. The parental plants are the P generation. b. Their hybrid offspring are the F1 generation. c. A cross of the F1 plants forms the F2 generation.

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C. Mendel’s Law of Segregation 1. Mendel performed many experiments 2. He tracked the inheritance of characters that occur as two alternative traits 3. Monohybrid Crosses 4. A monohybrid cross is a cross between purebred parent plants that differ in only one character 5. Mendel developed four hypotheses from the monohybrid cross, listed here using modern terminology (including “gene” instead of “heritable factor”) 6. The alternative versions of genes are called alleles 7. For each inherited character, an organism inherits two alleles, one from each parent a. An organism is homozygous for that gene if both alleles are identical. b. An organism is heterozygous for that gene if the alleles are different.

8. If two alleles of an inherited pair differ, a. then one determines the organism’s appearance and is called the dominant allele and b. the other has no noticeable effect on the organism’s appearance and is called the recessive allele.

9. Gametes carry only one allele for each inherited character a. The two alleles for a character segregate (separate) from each other during the production of gametes. b. This statement is called the law of segregation.

10. Do Mendel’s hypotheses account for the 3:1 ratio he observed in the F2 generation?

11. A Punnett square highlights a. the four possible combinations of gametes and b. the four possible offspring in the F2 generation.

12. Geneticists distinguish between an organism’s physical appearance and its genetic makeup a. An organism’s physical appearance is its phenotype. b. An organism’s genetic makeup is its genotype.

13. Genetic Alleles and Homologous Chromosomes 14. A gene locus is a specific location of a gene along a chromosome 15. Homologous chromosomes have alleles (alternate versions) of a gene at the same locus D. Mendel’s Law of Independent Assortment 1. A dihybrid cross is the mating of parental varieties differing in two characters 2. What would result from a dihybrid cross? Two hypotheses are possible: a. dependent assortment or b. independent assortment.

3. Mendel’s dihybrid cross supported the hypothesis that each pair of alleles segregates independently of the other pairs during gamete formation 4. Thus, the inheritance of one character has no effect on the inheritance of another 5. This is called Mendel’s law of independent assortment 6. Independent assortment is also seen in two hereditary characters in Labrador retrievers

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E. Using a Testcross to Determine an Unknown Genotype 1. A testcross is a mating between a. an individual of dominant phenotype (but unknown genotype) and b. a homozygous recessive individual.

F. The Rules of Probability 1. Mendel’s strong background in mathematics helped him understand patterns of inheritance 2. The rule of multiplication states that the probability of a compound event is the product of the separate probabilities of the independent events G. Family Pedigrees 1. Mendel’s principles apply to the inheritance of many human traits 2. Dominant traits are not necessarily a. normal or b. more common.

3. Wild-type traits are a. those seen most often in nature and b. not necessarily specified by dominant alleles.

4. A family pedigree a. shows the history of a trait in a family and b. allows geneticists to analyze human traits.

H. Human Disorders Controlled by a Single Gene 1. Many human traits a. show simple inheritance patterns and b. are controlled by single genes on autosomes.

2. Recessive Disorders 3. Most human genetic disorders are recessive 4. Individuals who have the recessive allele but appear normal are carriers of the disorder 5. Cystic fibrosis is a. the most common lethal genetic disease in the United States and b. caused by a recessive allele carried by about one in 31 Americans.

6. Prolonged geographic isolation of certain populations can lead to inbreeding, the mating of close relatives 7. Inbreeding increases the chance of offspring that are homozygous for a harmful recessive trait 8. Dominant Disorders 9. Some human genetic disorders are dominant a. Achondroplasia is a form of dwarfism. i. The homozygous dominant genotype causes death of the embryo. ii. Thus, only heterozygotes have this disorder. b. Huntington’s disease, which leads to degeneration of the nervous system, does not usually begin until middle age.

I. Process of Science: What Is the Genetic Basis of Coat Variation in Dogs?

1. Observation: Dogs come in a wide variety of physical types

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2. Question: What is the genetic basis for canine coats?

3. Hypothesis: A comparison of genes of a wide variety of dogs with different coats would identify the genes responsible 4. Prediction: Mutations in just a few genes account for the coat appearance 5. Experiment: Compared DNA sequences of 622 dogs from dozens of breeds 6. Results: Three genes in different combinations produced seven different coat appearances, from very short hair to full, thick, wired hair 7. Genetic Testing 8. Today many tests can detect the presence of disease-causing alleles 9. Most genetic tests are performed during pregnancy a. Amniocentesis collects cells from amniotic fluid. b. Chorionic villus sampling removes cells from placental tissue.

10. Genetic counseling helps patients understand the results and implications of genetic testing

III. Variations on Mendel’s Laws 1. Some patterns of genetic inheritance are not explained by Mendel’s laws A. Incomplete Dominance in Plants and People 1. In incomplete dominance, F1 hybrids have an appearance between the phenotypes of the two parents 2. Hypercholesterolemia a. is a human trait that is an example of incomplete dominance b. is characterized by dangerously high levels of cholesterol in the blood.

3. In hypercholesterolemia, heterozygotes have blood cholesterol levels about twice normal, and a. homozygotes have about five times the normal amount of blood cholesterol and may have heart attacks as early as age 2.

B. ABO Blood Groups: An Example of Multiple Alleles and Codominance 1. The ABO blood groups in humans are an example of multiple alleles 2. The immune system produces blood proteins called antibodies that bind specifically to foreign carbohydrates 3. If a donor’s blood cells have a carbohydrate (A or B) that is foreign to the recipient, the blood cells may clump together, potentially killing the recipient 4. The clumping reaction is the basis of a blood-typing lab test 5. The human blood type alleles IA and IB are codominant, meaning that both alleles are expressed in heterozygous individuals who have type AB blood C. Pleiotropy and Sickle-Cell Disease 1. Pleiotropy is when one gene influences several characters 2. Sickle-cell disease a. exhibits pleiotropy, b. results in abnormal hemoglobin proteins, and c. causes disk-shaped red blood cells to deform into a sickle shape with jagged edges.

D. Polygenic Inheritance 1. Polygenic inheritance is the additive effects of two or more genes on a single phenotype

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E. The Role of Environment 1. Many human characters result from a combination of a. heredity and b. environment.

2. Only genetic influences are inherited

IV. The Chromosomal Basis of Inheritance 1. The chromosome theory of inheritance states that a. genes are located at specific positions (loci) on chromosomes and b. the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns.

2. It is chromosomes that a. undergo segregation and independent assortment during meiosis and b. account for Mendel’s laws.

A. Linked Genes 1. Linked genes a. are located close together on a chromosome and b. tend to be inherited together.

2. Thomas Hunt Morgan a. used the fruit fly Drosophila melanogaster and b. determined that some genes were linked based on the inheritance patterns of their traits.

B. Genetic Recombination: Crossing Over 1. Crossing over can a. separate linked alleles, b. produce gametes with recombinant gametes, and c. produce offspring with recombinant phenotypes.

2. The percentage of recombinant offspring among the total is called the recombination frequency C. Linkage Maps 1. Early studies of crossing over were performed using the fruit fly Drosophila melanogaster 2. Alfred H. Sturtevant, a student of Morgan, a. developed a method for mapping the relative gene locations, b. which resulted in the creation of linkage maps.

V. Sex Chromosomes and Sex-Linked Genes 1. Sex chromosomes influence the inheritance of certain traits. For example, humans that have a pair of sex chromosomes designated a. X and Y are male or b. X and X are female.

A. Sex Determination in Humans 1. Nearly all mammals have a pair of sex chromosomes designated X and Y. a. Males have an X and Y. b. Females have XX.

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B. Sex-Linked Genes 1. Any gene located on a sex chromosome is called a sex-linked gene a. Most sex-linked genes are found on the X chromosome. b. Red-green colorblindness is i. a common human sex-linked disorder and ii. caused by a malfunction of light-sensitive cells in the eyes.

2. Hemophilia a. is a sex-linked recessive blood-clotting trait that may result in excessive bleeding and death after relatively minor cuts and bruises and b. has plagued the royal families of Europe.

C. Evolution Connection: Barking Up the Evolutionary Tree 1. About 15,000 years ago in East Asia, people began to cohabit with ancestral canines that were predecessors of modern wolves and dogs 2. As people settled into geographically distinct populations, a. different canines became separated and b. eventually became inbred.

3. A 2010 study indicated that small dogs were developed within the first permanent agricultural settlements of the Middle East around 12,000 years ago 4. Continued over millennia, genetic tinkering has resulted in a diverse array of dog body types and behaviors

Chapter Guide to Teaching Resources Heritable Variation and Patterns of Inheritance Student Misconceptions and Concerns 1. Students might think that dominant alleles are naturally (a) more common, (b) more likely to be inherited, and (c) better for an organism. The text notes that this is not necessarily true. However, this might need to be emphasized further in lecture.

2. Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. Just as we would expect that any six playing cards dealt might be half black and half red, we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling reflects expected ratios.

3. The authors note that Mendel’s work was published in 1866, seven years after Darwin published On the Origin of Species. Consider challenging your students to consider whether Mendel’s findings were supportive of Darwin’s ideas. Some scientists have noted that Darwin often discussed the evolution of traits by matters of degree. Yet, Mendel’s selection of pea plant traits typically showed complete dominance. Mendel’s pea traits did not show the possibility for such gradual inheritance.

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Teaching Tips 1. Medical technology raises many ethical issues. Consider asking your students this practical question. How much routine fetal testing do we want our insurance companies to cover and at what cost for insurance? Ultrasound, for example, is routinely performed on pregnant women as a normal part of prenatal care. What other tests should be standard? Who should decide? Who should pay?

2. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress.

3. Consider this analogy for dominance of a trait in the heterozygous condition, which may help struggling students. Two people are trying to make a decision about where to eat tonight. One person wants to eat at a restaurant, the other wants to eat a meal at home. If this “heterozygous” couple eats at home, the dominant allele “wins.”

4. Many students benefit from a little quick practice with a Punnett square. Have them try these crosses for practice: (a) PP × pp and (b) Pp × pp.

5. Understanding dihybrid crosses may be the most difficult concept in this chapter. Consider spending additional time to make these ideas very clear. As the text indicates, dihybrid crosses are essentially two monohybrid crosses.

6. Consider challenging your students to explain why a testcross of two black Labs of unknown genotypes might not reveal the genotype of each dog. Explanation: If both dogs are heterozygous, or homozygous, the results would reveal the genotypes because the offspring would either be three black and one chocolate or all black. But if one black Lab was homozygous and the other heterozygous, we could not determine which Lab has which genotype.

7. Many students have trouble with basic statistics. Give your students some practice. Consider having them work in pairs, each with a pair of dice (for large class sizes, this can be done in laboratories). Let them calculate the odds of rolling three sixes in a row and other possibilities.

8. The 2/3 fraction noted in the discussion of carriers of a recessive disorder (and in Figure 9.14) often catches students off guard, as they may be expecting odds of 1/4, 1/2, or 3/4. However, we eliminate the dd (deaf) possibility, as it would not be a carrier.

So, the odds are based out of the remaining three genotypes Dd, dD, and DD. 9. Genetic tests are now available to inform a person whether he or she has the Huntington’s allele. The test is especially important to the children of a parent with Huntington’s disease. Consider asking your class: (a) what are the odds of developing Huntington’s disease if a parent has this disease (50%) and (b) whether or not they would want this genetic test.

The Huntington Disease Society website (www.hdsa.org) offers many additional details. It is a good starting point for those who want to explore this disease in more detail.

10. As a simple test of comprehension, ask students to explain why lethal alleles are not eliminated from a population. Several possibilities exist: The lethal allele might be recessive, persisting in the population due to the survival of carriers, or the lethal allele might be dominant, but is not expressed until after the age of reproduction.

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Variations on Mendel’s Laws Student Misconceptions and Concerns 1. As these variations of Mendel’s laws are introduced, students are likely to get confused and become uncertain about the prior definitions. Consider keeping a clear definition of these different patterns of inheritance available for the class to refer to as new patterns are discussed.

2. As your class size increases, the chances increase that at least one student will have a family member with one of the genetic disorders discussed. Some students may find this embarrassing, but others might have a special interest in learning more about these topics, and may even be willing to share some of their family’s experiences with the class.

Teaching Tips 1. Incomplete dominance is analogous to a compromise, or a gray shade. The key concept is that both “sides” have input. Complete dominance is more analogous to an authoritarian style, overruling others and insisting on things being a certain way. Although these analogies might seem obvious to us, many students new to genetics appreciate them.

2. Another analogy for cholesterol receptors is fishing poles. The more fishing poles you use, the more fish you will likely catch. Heterozygotes for hypercholesterolemia have fewer “fishing poles” for cholesterol. Thus, fewer “fish” are caught and more “fish” remain in the water.

3. Students can think of blood types as analogous to socks on their feet. You can have socks that match, a sock on one foot but not the other, you can wear two socks that do not match, or you can even go barefoot (type O blood)! Developed further, think of Amber and Blue socks. Type A blood can have an Amber sock with either another Amber sock or a bare foot (or “zero” sock). Blue socks work the same way. One Amber and one Blue sock is like the AB blood type. No socks, as already noted, represent type O. 4. Consider specifically comparing the principles of codominance (expression of both alleles) and incomplete dominance (expression of one intermediate trait). Students will likely benefit from this direct comparison.

5. The American Sickle Cell Anemia Association’s website (www.ascaa.org) is a good place to get additional details.

6. Polygenic inheritance makes it possible for children to inherit genes to be taller, or shorter, than either parent. Similarly, skin tones can be darker or lighter than either parent. The environment also contributes significantly to the final phenotype for both of these traits.

7. The authors note that polygenic inheritance is the converse of pleiotropy. This is worth noting in lecture as these concepts are discussed. We often remember concepts better when they are contrasted in pairs.

8. As the authors are careful to note, although genetics and the environment both contribute to the final phenotypes, only the genetic factors are inherited. This distinction is important to understanding the limitations of Lamarck’s mechanisms of evolution. If you will address principles of evolution soon after this chapter, this may be an important distinction to reinforce in lecture. References to tattoos, piercing, and circumcision may also help to distinguish between acquired traits and those which are inherited. Students with tattoos will not produce children born with tattoos! After thousands of years, circumcised men have never produced sons who are born circumcised!

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The Chromosomal Basis of Inheritance Student Misconceptions and Concerns 1. This section of the chapter relies on a good understanding of the chromosome sorting process of meiosis. If students were not assigned Chapter 8, and meiosis was not otherwise addressed, it will be difficult for students to understand the chromosomal basis of inheritance or linked genes.

2. The nature of linked genes builds on our natural expectations that items that are closer together are less likely to be separated. Yet, students may find such concepts initially foreign. Whether it is parents holding the hands of children or people and their pets, we generally know that separation is more likely when things are farther apart. You might demonstrate this simply by drawing a line down a page of text. The likelihood that the line separates any pair of words increases, as the distance between the words grows farther apart.

Teaching Tips 1. Building on the shoe analogy developed in Chapter 8, linked genes are like a shoe and its shoelaces. The two are usually transferred together but can be moved separately under special circumstances.

2. Crossing over (from Chapter 8) is like randomly editing out a minute of film from two movies and swapping them. Perhaps the fifth minute of Bambi is swapped for the fifth minute of Gone With the Wind. Clearly, the closer that two frames of film are together, the more likely they are to move or remain together.

Sex Chromosomes and Sex-Linked Genes Student Misconceptions and Concerns 1. The prior discussion of “linked genes” addresses a different relationship than the use of the similar termed sex-linked genes. The nature of the linkage is quite different. Consider emphasizing this distinction for your students.

2. The likelihood that at least some students are colorblind in larger classes is very high.

Some of these students might find this interesting and want to discuss it further. However, others might be embarrassed by what might be perceived as a defect.

Teaching Tips 1. In some ways, sex-linked genes reflect the risk of not having a backup copy of a file on your computer. If you only have one copy, and it is damaged, you have to live with the damaged file. Having two X chromosomes in females provides a “backup copy” that can function if one of the sex-linked genes is damaged.

2. Hemophilia and other genetic diseases may also result from spontaneous mutations in a family with no known history of the disease. Although rare, this possibility should always be considered when tracing the history of an inherited disease.

3. Female hemophiliacs are very rare because both X chromosomes would need to have the recessive trait. Although very unlikely, female hemophiliacs are known. Students may enjoy searching for details of these rare cases. For additional information about hemophilia, consider visiting the website of the National Hemophilia Foundation at www.hemophilia.org.

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Key Terms ABO blood groups achondroplasia alleles carrier character chromosome theory of inheritance codominant cross cystic fibrosis (CF) dihybrid cross dominant allele F1 generation

F2 generation genetics genotype hemophilia heredity heterozygous homozygous Huntington’s disease hybrid hypercholesterolemia inbreeding incomplete dominance

law of independent assortment law of segregation linkage map linked genes locus monohybrid cross pedigree P generation phenotype pleiotropy polygenic inheritance Punnett square

recessive allele recombination frequency red-green colorblindness rule of multiplication sex-linked gene sickle-cell disease testcross trait wild-type traits

Word Roots co = together (codominance: phenotype in which both dominant alleles in a heterozygous individual are expressed) di = two (dihybrid: a type of cross that mates varieties differing in two characters) geno = offspring (genotype: an organism’s genetic makeup) hemo = blood; philia = love (hemophilia: a human genetic disease caused by excessive bleeding following an injury) hetero = different (heterozygous: when an organism has different alleles for a gene) homo = alike (homozygous: when an organism has the same alleles for a gene) hyper = excessive (hypercholesterolemia: a condition of incomplete dominance resulting in elevated blood cholesterol levels) mono = one (monohybrid: a type of cross between organisms that differ in only one trait) pheno = appear (phenotype: an organism’s physical traits) pleio = more; trop = change (pleiotropy: when a single gene impacts more than one character) poly = many; gen = produce (polygenic: type of inheritance in which two or more genes affect a single trait)

Relevant Songs to Play in Class “I Think I’m Going Bald,” Rush “Behind Blue Eyes,” The Who (original) or Limp Bizkit (2003 cover)

“Pass the Peas,” James Brown or Maceo Parker “X&Y,” Coldplay “Genetic,” Sonic Youth

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Answers to End-of-Chapter Questions The Process of Science 18. Suggested answer: Start out by breeding the cat to get a population to work with. If the curl allele is recessive, two curl cats can have only curl kittens. If the allele is dominant, curl cats can have “normal” kittens. If the curl allele is sex-linked, ratios will differ in male and female offspring of some crosses. If the curl allele is autosomal, the same ratios will be seen among males and females. Once you have established that the curl allele is dominant and autosomal, you can determine if a particular curl cat is true-breeding (homozygous) by doing a testcross with a normal cat. If the curl cat is homozygous, all offspring of the testcross will be curl; if heterozygous, half the offspring will be curl and half normal.

19. Suggested answer: You could start by taking one strain of fruit flies, crossing them with the wild type, and analyzing the offspring. Those offspring could be bred to create the F2 generation; the F2 generation could be bred to create the F3 generation, and so forth. This same procedure could be followed to cross each of the other nine strains against the wild type for multiple generations. Further, the ten strains could be crossed with each other for multiple generations. By examining the results of such crosses, you should be able to determine (a) which traits are dominant and recessive, (b) which traits are sex-linked, and (c) recombination frequencies could be used to create linkage maps.

Biology and Society 20. Some issues and questions to consider: Do biologists actually see the structures and molecules of cells? What about past evolutionary processes, the origin of life, the physical appearance or behavior of dinosaurs? In other fields of science, what is the evidence for atoms, subatomic particles, the formation of stars, the composition of Earth’s interior, and the past positions of the continents? How clear does evidence have to be before it is acceptable?

What prompts a scientist to propose an explanation? What if more than one explanation can account for the observations? Is it possible to be absolutely sure that an explanation is correct? That it is incorrect? What is the place of words like correct, incorrect, fact, theory, scientific law, and truth in science? Can some of the facts in this textbook be “wrong”?

21. Some issues and questions to consider: Do you agree with genetic testing at any level? Is testing for genetic diseases in embryos any different from testing for Huntington’s disease in adults, or from testing two potential parents to see if they are carriers of a genetic disease? If multiple embryos are created during the in vitro process and only some can be used, should the “best” ones be selected using gene testing? If you agree with the process, should guidelines be developed to prevent abuse of the technology so that parents are not selecting features such as the sex of the child, eye color, or skin tone?

Additional Critical Thinking Questions The Process of Science 1. Two parents consult a genetic counselor. They do not understand why all of their sons are colorblind (an X-linked trait) but none of their daughters are colorblind. Both of the parents appear normal. How would you explain this to the parents?

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Suggested answer: Sons always get their X chromosome from their mother and the Y from their father. In this case, the mother was the carrier of colorblindness. She appeared normal, as did the father (who did not have colorblindness). When they had children, half of mom’s gametes contained the X chromosome with the trait for colorblindness. When fertilized by a Y chromosome, sons were produced. Half of them will be colorblind. For the daughters to be colorblind, they would have had to receive an afflicted X from both their mother and their father. (Red-green colorblindness is a recessive trait found on the X-chromosome.)

2. Cystic fibrosis is a recessive genetic disease. Two parents do not have cystic fibrosis; however, their child does. Fully explain how this could have happened.

Suggested answer: In this case, both parents are heterozygous and carriers of the defective allele. Since this is a recessive trait, they appear normal; however, half of their gametes contain the defective allele. When an egg with the defective allele is fertilized by a sperm with a defective allele, the embryo will have two defective (recessive) copies and will have the disease. The odds of these heterozygous parents producing a child with cystic fibrosis are 25%.

3. A mother is unsure who the father is of her newborn. Before doing DNA analysis, a simple blood test is performed to give some preliminary information. In this case, two men are the potential father so their blood is also collected. Here is the summary: mom—O, the baby—B, potential father 1—A, potential father 2—AB. Which man is the most likely father? Write an explanation to justify your answer.

Suggested answer: The mom is type O, which is recessive (ii). Since the baby is type B blood, his genotype must be (IBi). The real father had to have contributed the IB allele since mom contributed the i allele. Potential father 2 is the only possible dad in this case who has the IB allele to give.

Biology and Society 4. Why would it be difficult to develop a genetic test for a polygenic disorder?

Some issues and questions to consider: For polygenic traits, different mutations in different genes may have the same or similar phenotypic effects. It would be difficult to test for all possible mutations for all genes involved. However, if a specific mutation is known to run in a family, members of that family can be tested for that specific mutation.

5. As the Human Genome Project progresses, we are learning more and more about genetic differences that cause genetic disease. Some people advocate the use of this knowledge to ultimately develop gene therapy. The goal of gene therapy would be to find alleles that are “faulty” and to correct them with normal alleles. Ideally, to “fix” every cell in an individual, this process would need to occur in embryos. Let’s suppose a couple found out that later in their embryo’s life, their baby would develop an incurable disease such as Alzheimer’s disease. Would you advocate the use of gene therapy in the embryo to correct the problem before the child was ever born? What if the embryo did not appear likely to develop a genetic disease, but the parents decided that they would really prefer that their child have blue eyes as opposed to brown. Would you advocate the use of gene therapy in this case? Should the use of this therapy be limited? Who should decide those limits?

Some issues and questions to consider: How do we decide what is “serious” versus what is not critical? If the technology existed, should there be any reason not to use it in any situation? Who should set the limitations to prevent abuse of the technology?

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CHAPTER

10

The Structure and Function of DNA

Why This Chapter Matters 1. Hereditary information is stored in the chemical language of DNA. 2. DNA directs the biochemical, cellular, anatomical, and physiological activities of the human body.

3. Scientists can manipulate the DNA of cells to modify the traits of crops, transform the characteristics of cells, and treat and potentially prevent disease.

4. Viruses play a key role in the history of molecular biology and continue to be important pathogens in humans, bacteria, plants, and animals.

5. Treatments and cures for viral infections are likely to be the products of research into molecular biology.

Chapter Objectives Biology and Society: Mix-and-Match Viruses 1. Explain how the H1N1 virus evolved, the global response, and the dangers of influenza viruses over the past 100 years.

DNA: Structure and Replication 2. Explain what was and was not known about DNA by the early 1950s.

3. Describe and compare the chemical compositions of DNA and RNA. 4. Describe the key features of the overall shape of a DNA molecule. Explain how Watson and Crick determined the structure of DNA. 5. Describe the process of DNA replication.

The Flow of Genetic Information from DNA to RNA to Protein 6. Define transcription and translation. Explain why the hypothesis “one gene–one enzyme” is not correct.

7. Explain how the language of DNA directs the production of polypeptides.

8. Explain how codons are used to construct polypeptides.

9. Describe the steps of transcription and the processing of RNA before it leaves the nucleus.

10. Compare the structures and functions of mRNA, tRNA, and rRNA. 11. Describe in detail the process of translation.

12. Distinguish between insertion, deletion, and substitution mutations. Explain how mutations can be harmful or beneficial to organisms.

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Viruses and Other Noncellular Infectious Agents 13. Compare the lytic and lysogenic cycles of bacteriophages.

14. Compare the life cycles of RNA and DNA viruses. Describe the spread, symptoms, and prevention of viral diseases in plants and animals.

15. Describe the reproductive cycle of retroviruses such as HIV and the mechanisms by which AZT and protease inhibitors limit AIDS. 16. Explain how viroids and prions cause disease.

Evolution Connection: H1N1 and Other Emerging Viruses 17. Describe the processes that contribute to the emergence of viral disease.

Lecture Outline I. Biology and Society: Mix-and-Match Viruses 1. In 2009, a cluster of unusual flu cases broke out around Mexico City 2. In June 2009, the World Health Organization (WHO) a. declared H1N1 a pandemic (global epidemic) and b. unveiled a massive effort to contain it.

3. Scientists soon determined that H1N1 was a hybrid flu strain, made when a. a known flu virus mixed with b. an Asian swine flu virus.

4. The hybrid H1N1 flu strain had a combination of genes that infected young, healthy people instead of the elderly or people who were already sick 5. Many countries produced a coordinated response, and the WHO declared the pandemic over in August 2010 6. Each year in the United States, over 20,000 people die from influenza infection 7. From 1918 to 1919, the deadliest pandemic killed about 40 million people worldwide in just 18 months A. DNA: Structure and Replication 1. DNA a. was known to be a chemical in cells by the end of the nineteenth century, b. has the capacity to store genetic information, and c. can be copied and passed from generation to generation.

2. The discovery of DNA as the hereditary material ushered in the new field of molecular biology, the study of heredity at the molecular level B. DNA and RNA Structure 1. DNA and RNA are nucleic acids a. They consist of chemical units called nucleotides. b. A nucleotide polymer is a polynucleotide. c. Nucleotides are joined by covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar-phosphate backbone.

2. The sugar in DNA is deoxyribose. thus, the full name for DNA is deoxyribonucleic acid

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3. The four nucleotides found in DNA differ in their nitrogenous bases. These bases are a. thymine (T), b. cytosine (C), c. adenine (A), and d. guanine (G).

4. RNA has uracil (U) in place of thymine C. Watson and Crick’s Discovery of the Double Helix 1. James Watson and Francis Crick determined that DNA is a double helix 2. Watson and Crick used X-ray crystallography data to reveal the basic shape of DNA 3. Rosalind Franklin produced the X-ray image of DNA 4. The model of DNA is like a rope ladder twisted into a spiral a. The ropes at the sides represent the sugar-phosphate backbones b. Each wooden rung represents a pair of bases connected by hydrogen bonds 5. DNA bases pair in a complementary fashion: a. adenine (A) pairs with thymine (T) and b. cytosine (C) pairs with guanine (G).

D. DNA Replication 1. When a cell reproduces, a complete copy of the DNA must pass from one generation to the next 2. Watson and Crick’s model for DNA suggested that DNA replicates by a template mechanism 3. DNA can be damaged by X-rays and ultraviolet light 4. DNA polymerases a. are enzymes, b. make the covalent bonds between the nucleotides of a new DNA strand, and c. are involved in repairing damaged DNA. 5. DNA replication ensures that all the body cells in multicellular organisms carry the same genetic information 6. DNA replication in eukaryotes a. begins at specific sites on a double helix (called origins of replication) and b. proceeds in both directions.

E. The Flow of Genetic Information from DNA to RNA to Protein 1. DNA provides instructions to a. a cell and b. an organism as a whole.

F. How an Organism’s Genotype Determines Its Phenotype 1. An organism’s genotype is its genetic makeup, the sequence of nucleotide bases in DNA 2. The phenotype is the organism’s physical traits, which arise from the actions of a wide variety of proteins 3. DNA specifies the synthesis of proteins in two stages: a. transcription, the transfer of genetic information from DNA into an RNA molecule and b. translation, the transfer of information from RNA into a protein.

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4. The major breakthrough in demonstrating the relationship between genes and enzymes came in the 1940s from the work of American geneticists George Beadle and Edward Tatum with the break mold Neurospora crassa 5. Beadle and Tatum a. studied strains of mold that were unable to grow on the usual growth medium, b. determined that these strains lacked an enzyme in a metabolic pathway that synthesized arginine, c. showed that each mutant was defective in a single gene, and d. hypothesized that the function of an individual gene is to dictate the production of a specific enzyme.

6. The one gene–one enzyme hypothesis has since been modified 7. The function of a gene is to dictate the production of a polypeptide 8. A protein may consist of two or more different polypeptides G. From Nucleotides to Amino Acids: An Overview 1. Genetic information in DNA is a. transcribed into RNA, then b. translated into polypeptides, c. which then fold into proteins.

2. What is the language of nucleic acids? a. In DNA, it is the linear sequence of nucleotide bases. b. A typical gene consists of thousands of nucleotides in a specific sequence 3. When a segment of DNA is transcribed, the result is an RNA molecule 4. RNA is then translated into a sequence of amino acids in a polypeptide 5. Experiments have verified that the flow of information from gene to protein is based on a triplet code 6. A codon is a triplet of bases, which codes for one amino acid H. The Genetic Code 1. The genetic code is the set of rules that convert a nucleotide sequence in RNA to an amino acid sequence 2. Of the 64 triplets, a. 61 code for amino acids and b. 3 are stop codons, instructing the ribosomes to end the polypeptide.

3. Because diverse organisms share a common genetic code, it is possible to program one species to produce a protein from another species by transplanting DNA I. Transcription: From DNA to RNA 1. Transcription a. makes RNA from a DNA template, b. uses a process that resembles the synthesis of a DNA strand during DNA replication, and c. substitutes uracil (U) for thymine (T).

2. RNA nucleotides are linked by the transcription enzyme RNA polymerase

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J. Initiation of Transcription 1. The “start transcribing” signal is a nucleotide sequence called a promoter, which is a. located in the DNA at the beginning of the gene and b. a specific place where RNA polymerase attaches.

2. The first phase of transcription is initiation, in which a. RNA polymerase attaches to the promoter and b. RNA synthesis begins.

K. RNA Elongation 1. During the second phase of transcription, called elongation, a. the RNA grows longer and b. the RNA strand peels away from its DNA template.

L. Termination of Transcription 1. During the third phase of transcription, called termination, a. RNA polymerase reaches a special sequence of bases in the DNA template, called a terminator signaling the end of the gene, b. polymerase detaches from the RNA and the gene, and c. the DNA strands rejoin.

M. The Processing of Eukaryotic RNA 1. In the cells of prokaryotes, RNA transcribed from a gene immediately functions as messenger RNA (mRNA), the molecule that is translated into protein 2. The eukaryotic cell a. localizes transcription in the nucleus and b. modifies, or processes, the RNA transcripts in the nucleus before they move to the cytoplasm for translation by ribosomes.

3. RNA processing includes a. adding a cap and tail consisting of extra nucleotides at the ends of the RNA transcript, b. removing introns (noncoding regions of the RNA), and c. RNA splicing, joining exons (the parts of the gene that are expressed) together to form messenger RNA (mRNA).

4. RNA splicing is believed to play a significant role in humans a. in allowing our approximately 21,000 genes to produce many thousands more polypeptides and b. by varying the exons that are included in the final mRNA. N. Translation: The Players 1. Translation is the conversion from the nucleic acid language to the protein language O. Messenger RNA (mRNA) 1. Translation requires a. mRNA, b. ATP, c. enzymes, d. ribosomes, and c. transfer RNA (tRNA).

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P. Transfer RNA (tRNA) 1. Transfer RNA (tRNA) a. acts as a molecular interpreter, b. carries amino acids, and c. matches amino acids with codons in mRNA using anticodons, a special triplet of bases that is complementary to a codon triplet on mRNA. Q. Ribosomes 1. Ribosomes are organelles that a. coordinate the functions of mRNA and tRNA and b. are made of two subunits.

2. Each subunit is made up of a. proteins and b. a considerable amount of another kind of RNA, ribosomal RNA (rRNA).

3. A fully assembled ribosome holds tRNA and mRNA for use in translation R. Translation: The Process 1. Translation is divided into three phases: a. initiation, b. elongation, and c. termination.

S. Initiation 1. Initiation brings together a. mRNA, b. the first amino acid with its attached tRNA, and c. two subunits of the ribosome.

2. The mRNA molecule has a cap and tail that help the mRNA bind to the ribosome 3. Initiation occurs in two steps a. An mRNA molecule binds to a small ribosomal subunit, then a special initiator tRNA binds to the start codon, where translation is to begin on the mRNA. b. A large ribosomal subunit binds to the small one, creating a functional ribosome.

T. Elongation 1. Elongation occurs in three steps a. Step 1: Codon recognition. The anticodon of an incoming tRNA pairs with the mRNA codon at the A site of the ribosome. b. Step 2: Peptide bond formation. i. The polypeptide leaves the tRNA in the P site and attaches to the amino acid on the tRNA in the A site. ii. The ribosome catalyzes the bond formation between the two amino acids. c. Step 3: Translocation. i. The P site tRNA leaves the ribosome. ii. The tRNA carrying the polypeptide moves from the A to the P site.

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U. Termination 1. Elongation continues until a. a stop codon reaches the ribosome’s A site, b. the completed polypeptide is freed, and c. the ribosome splits back into its subunits.

V. Review: DNA→ RNA→ Protein 1. In a cell, genetic information flows from a. DNA to RNA in the nucleus and b. RNA to protein in the cytoplasm.

2. As it is made, a polypeptide a. coils and folds and b. assumes a three-dimensional shape, its tertiary structure.

3. Transcription and translation are how genes control the structures and activities of cells W. Mutations 1. A mutation is any change in the nucleotide sequence of DNA 2. Mutations can change the amino acids in a protein 3. Mutations can involve a. large regions of a chromosome or b. just a single nucleotide pair, as occurs in sick-cell disease.

4. Mutations within a gene can be divided into two general categories: a. nucleotide substitutions (the replacement of one base by another) and b. nucleotide deletions or insertions (the loss or addition of a nucleotide).

5. Insertions and deletions can a. change the reading frame of the genetic message and b. lead to disastrous effects.

X. Mutagens 1. Mutations may result from a. errors in DNA replication or recombination or b. physical or chemical agents called mutagens.

2. Mutations a. are often harmful but b. are useful in nature and the laboratory as a source of genetic diversity, which makes evolution by natural selection possible.

Y. Viruses and Other Noncellular Infectious Agents 1. Viruses share some, but not all, characteristics of living organisms. Viruses a. possess genetic material in the form of nucleic acids wrapped in a protein coat, b. are not cellular, and c. cannot reproduce on their own.

Z. Bacteriophages 1. Bacteriophages, or phages, are viruses that attack bacteria 2. Phages consist of a molecule of DNA, enclosed within an elaborate structure made of proteins

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3. Phages have two reproductive cycles a. In the lytic cycle, i. many copies of the phage are produced within the bacterial cell, and ii. then the bacterium lyses (breaks open). b. In the lysogenic cycle, i. the phage DNA inserts into the bacterial chromosome and ii. the bacterium reproduces normally, copying the phage at each cell division.

AA. Plant Viruses 1. Viruses that infect plants can a. stunt growth and b. diminish plant yields.

2. Most known plant viruses have RNA rather than DNA as their genetic material 3. Many of them, like the tobacco mosaic virus, are rod-shaped with a spiral arrangement of proteins surrounding the nucleic acid 4. Viral plant diseases a. have no cure and b. are best prevented by producing plants that resist viral infection.

BB. Animal Viruses 1. Viruses that infect animals cells a. are a common cause of disease and b. may have RNA or DNA genomes.

2. Many animal viruses have an outer envelope made of phospholipid membrane, with projecting spikes of protein 3. The reproductive cycle of an enveloped RNA virus can be broken into seven steps CC. The Process of Science: Do Flu Vaccines Protect the Elderly?

1. Observation: Vaccination rates among the elderly rose from 15% in 1980 to 65% in 1996 2. Question: Do flu vaccines decrease the mortality rate among those elderly people who receive them?

3. Hypothesis: Elderly people who were immunized would have fewer hospital stays and deaths during the winter after vaccination 4. Experiment: Tens of thousands of people over the age of 65 were followed during the ten flu seasons of the 1990s 5. Results: People who were vaccinated had a a. 27% less chance of being hospitalized during the next flu season and b. 48% less chance of dying.

DD. HIV, the AIDS Virus 1. The devastating disease AIDS (acquired immunodeficiency syndrome) is caused by HIV (human immunodeficiency virus), an RNA virus with some special twists 2. HIV is a retrovirus, an RNA virus that reproduces by means of a DNA molecule 3. Retroviruses use the enzyme reverse transcriptase to catalyze reverse transcription, the process of synthesizing DNA on an RNA template 4. The behavior of HIV nucleic acid in an infected cell can be broken into six steps

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5. HIV infects and eventually kills several kinds of white blood cells that are important in the body’s immune system 6. While there is no cure for AIDS, its progression can be slowed by two categories of medicine that interfere with the reproduction of the virus EE. Viroids and Prions 1. Two classes of pathogens are smaller than viruses a. Viroids are small, circular RNA molecules that infect plants b. Prions are misfolded proteins that somehow convert normal proteins to the misfolded prion version, leading to disease 2. Prions are responsible for neurodegenerative diseases including a. mad cow disease, b. scrapie in sheep and goats, c. chronic wasting disease in deer and elk, and d. Creutzfeldt-Jakob disease in humans.

FF. Evolution Connection: Emerging Viruses 1. Emerging viruses are viruses that have suddenly come to the attention of science Examples are a. H1N1 and b. avian flu.

2. Avian flu a. infects birds, b. infected 18 people in Hong Kong in 1997, and c. since has spread to Europe and Africa, infecting over 400 people and killing more than 240 of them.

3. Over 100 million birds have either a. died from the disease or b. been killed to prevent the spread of infection.

4. If avian flu mutates to a form that can easily spread between people, the potential for a major human outbreak is significant 5. New viruses can arise by a. the mutation of existing viruses or b. the spread of existing viruses to a new host species.

Chapter Guide to Teaching Resources DNA: Structure and Replication Student Misconceptions and Concerns 1. If your class has not yet studied Chapter 3, consider assigning the Chapter 3 section on “Nucleic Acids” before addressing the contents of Chapter 10.

2. The text describes but does not specifically point out that DNA replication is semiconservative. Tell your students about an experiment in which a DNA molecule is labeled, and then replicated. How will the two DNA molecules compare with regard to the location/distribution of the original DNA molecule? Will one DNA molecule be the original and the other the new copy? Or is there another possibility? Half of each of the ..

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two DNA molecules is new and half is the original; thus, it used semiconservative replication. Analogies for semiconservative replication can be a challenge. But in a sense, DNA replication is similar to parents getting divorced and then each parent remarrying someone else. The two new couples represent “half old parent and half new person.”

3. Students often confuse the terms nucleic acids, nucleotides, and bases. It helps just to note the hierarchy of relationships: Nucleic acids consist of long chains of nucleotides, and nucleotides include bases as part of their structure.

Teaching Tips 1. Consider comparing DNA, RNA, and proteins to a train (polymer). DNA and RNA are like a train of various lengths and combinations of four types of train cars (monomers). Proteins are also “trains” of various lengths but made of a combination of 20 types of train cars.

2. The descriptions of the discovery of DNA’s structure are a good time to point out that science is a collaborative effort. You might remind your class of all the prior research (identifying DNA as the genetic material and clues to its structure) that brought Watson and Crick to their historic conclusions.

3. The authors note that the structure of DNA is analogous to a twisted rope ladder. In class, challenge your students to explain what the parts of the ladder represent. The wooden rungs represent a base pair and each rope the sugar-phosphate backbone.

4. Demonstrate the complementary base pairing within DNA. Present students with the base sequence to one side of a DNA molecule and have them work quickly at their seats to determine the sequence of the complementary strand. For some students, these sorts of quick practice are necessary to reinforce a concept and break up a lecture.

5. To explain the adaptive advantage of multiple replication sites over a single site of replication, ask your students to imagine copying, by hand, the first ten chapters of your biology textbook.

The task would certainly go faster if ten students each copied a different chapter!

6. There are about 2 million characters (letters or numbers) in the Campbell Essential Biology with Physiology textbook. The accuracy of DNA replication would be like copying every letter and number in this textbook by hand 500 times and writing just one letter or number incorrectly, making one error in every 1 billion characters!

7. The information in DNA is used to direct the production of RNA, which in turn directs the production of proteins. However, in Chapter 3, four different types of biological molecules were noted as significant components of life. Students who think this through might wonder, and you could point out, that DNA does not directly control the production of carbohydrates and lipids. So how does DNA exert its influence over the synthesis of these other chemical groups? The answer is largely by way of enzymes, proteins with the ability to promote the production of carbohydrates and lipids.

The Flow of Genetic Information from DNA to RNA to Protein Student Misconceptions and Concerns 1. Less experienced students are often intensely focused on writing detailed notes. The risk is that they miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process.

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2. Consider placing on the board Figure 10.8, noting the sequence, products, and locations of transcription and translation in eukaryotic cells. This reminder can create a quick concept check for students as they learn additional detail.

3. Mutations are often discussed as part of evolution mechanisms. In this sense, mutations may be considered a part of a positive creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified.

Teaching Tips 1. It has been said that “Everything about an organism is an interaction between the genome and the environment.” You might wish to challenge your students to explain the significance and validity of this statement.

2. The authors note that the sequential information in DNA and RNA is analogous to the sequential information in the letters of a sentence. This analogy is also helpful when explaining the impact of insertion or deletion mutations that cause a shift in the reading frame.

3. The transcription of DNA into RNA is like a reporter who transcribes a political speech.

In both situations, the language remains the same, although in the case of the reporter, it changes form from spoken to written.

4. A parallel can be drawn between the discovery in 1799 of the Rosetta stone, which provided the key that enabled scholars to crack the previously indecipherable hieroglyphic code, and the cracking of the genetic code in 1961. Consider challenging your students to explain what part of the genetic code is similar to the Rosetta stone. This could be a short in-class activity for small groups.

5. Another advantage to the use of RNA to direct protein synthesis is that the original code (DNA) remains safely within the nucleus, away from the many potentially damaging chemicals in the cytoplasm. This is like making photocopies of important documents for study, keeping the originals safely stored away (much like how we deal with the U.S. Constitution).

6. The production of proteins is like a machine requiring fuel. The molecular machinery (ribosomes and tRNA) used in many cellular processes also requires an input of energy in the form of ATP. 7. If you were using a train analogy for the assembly of monomers into polymers, at this point the DNA and RNA “trains” are traded in 3 for 1 for the polypeptide “train.” Thus, in general, polypeptides have about 1/3 as many monomers as the mRNA that coded for them. (It might be a good challenge to have your students explain why proteins do not have exactly a third of monomers of the corresponding mRNA.) 8. After translation is addressed, consider asking your students (working singly or in small groups) to list all of the places where base pairing is used (in the construction of a DNA molecule during DNA replication, in transcription, and during translation when the tRNA attaches).

9. Many analogies can be developed to represent the selective expression of a gene requiring the deletion of introns. Instructors that only assign some modules of a chapter are treating the chapters like sections of exons and introns, portions to be read and portions to be skipped.

Alternately, students who highlight a chapter might be thought of as editing the book into exons, portions to be reviewed, and introns, nonhighlighted sections that will not be studied.

Both analogies are imperfect, but may still convey the concept of selective reading.

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10. Students might want to think of the A and P sites as stages in an assembly line. The A site is where a new amino acid is brought in, according to the blueprint of the codon on the mRNA. The P site is where the growing product/polypeptide is anchored as it is being built. To help them better remember details of translation, students might think of the letters for the two sites to mean “A” for addition, where an amino acid is added, and “P” for polypeptide, where the growing polypeptide is located.

11. A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. But look what happens when a letter is added (2) or deleted (3). The “reading frame,” or triplet groupings, are re-formed into nonsense.

(1) The big red pig ate the red rag.

(2) The big res dpi gat eth ere dra g.

(3) The big rep iga tet her edr ag.

12. The authors have noted elsewhere that “A random mutation is like a shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!”

Viruses and Other Noncellular Infectious Agents Student Misconceptions and Concerns 1. Students and many parents with young children expect a treatment of antibiotics for many respiratory infections, even though such infections may result from a virus. Students will benefit by a thorough explanation of the inappropriate use of antibiotics for viral infections and the risks of overuse of antibiotics leading to increased numbers of antibiotic-resistant bacteria.

2. The success of modern medicine has perhaps led to overconfidence in our ability to treat disease. Students often do not understand that there are few successful treatments for viral infections. Instead, the best defense against viruses is prevention by reducing the chances of contacting the virus and the use of vaccines.

3. Many misconceptions about AIDS exist. A list of 18 common misconceptions is located at www.gng.org/currents/teachers/hiv101/misconceptions.html.

Teaching Tips 1. Students (and instructors) might enjoy thinking of a prophage as a smudge mark on the master copy of a class handout. The smudge is replicated every time the original is copied!

2. A phage functions like a needle and syringe, injecting a drug. The needle and syringe are analogous to the protein components of the phage. The drug to be injected is analogous to the phage DNA. 3. Viruses can spread throughout a plant by moving through plasmodesmata (not specifically discussed in this chapter). This is like smoke spreading throughout a building by moving through air ducts.

4. There is an interesting relationship between the speed at which a virus kills or debilitates a host and the extent to which it spreads from one organism to another. This is something to consider for a class discussion. Compare two viral infections. Infection A multiplies within the host, is spread by the host to other people through casual contact, but does not cause its lethal symptoms until 5–10 years after infection. Virus B kills the host within 1–2 days of infection, is easily transmitted, and causes severe symptoms within hours of contact.

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Which virus is likely to spread the fastest through the human population on Earth? Which might be considered the most dangerous to humans?

5. Students often do not understand the disproportionate distribution of HIV infections and AIDS in our world. Consider an Internet assignment, asking students to identify the regions of the world most affected by HIV-AIDS. The Centers for Disease Control and Prevention has extensive information about AIDS at www.cdc.gov/hiv/.

Key Terms adenine (A) AIDS anticodon bacteriophages cap codon cytosine (C) DNA DNA polymerase double helix emerging viruses exons

genetic code guanine (G) HIV introns lysogenic cycle lytic cycle messenger RNA (mRNA) molecular biology mutagen mutation nucleotide

phages polynucleotide prion promoter prophage provirus retrovirus reverse transcriptase ribosomal RNA (rRNA) RNA polymerase RNA splicing

start codon stop codon sugar-phosphate backbone tail terminator thymine (T) transcription transfer RNA (tRNA) translation uracil (U) virus

Word Roots muta = change; gen = producing (mutagen: a physical or chemical agent that causes mutations) phage = eat (bacteriophages: viruses that attack bacteria) poly = many (polynucleotide: a polymer of many nucleotides) pro = before (prophage: phage DNA inserted into the bacterial chromosome before viral replication) retro = backward (retrovirus: an RNA virus that reproduces by first transcribing its RNA into DNA then inserting the DNA molecule into a host’s DNA) trans = across; script = write (transcription: the transfer of genetic information from DNA into an RNA molecule)

Relevant Songs to Play in Class “The Jean Genie,” David Bowie

“Cat DNA,” Ozric Tentacles

“Billy Jean,” Michael Jackson

“Express Yourself,” Madonna

“In Those Jeans,” Ginuwine

Answers to End-of-Chapter Questions The Process of Science 12. Suggested answer: In this case, two of the daughter cells will have a double helix in which both strands are radioactive. The other two daughter cells will have a double helix in which one strand is radioactive and the other is nonradioactive.

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13. Suggested answer: In this experiment one would expect to find the proteins (tagged with radioactive sulfur) outside of the bacterial cells, whereas the viral DNA (tagged with radioactive phosphorus) would be found inside the bacterial cells. This experiment indicates that the viral DNA is the infectious particle as it was the only thing to enter the bacterial cells.

Biology and Society 14. Some issues and questions to consider: Is it fair to issue a patent for a gene or gene product that occurs naturally in every human being? Or, should a patent be issued only for something new that is invented rather than found? Suppose another scientist slightly modifies the gene or protein. How different does the gene or protein have to be so that the patent is not infringed? Might patents encourage secrecy and interfere with the free flow of scientific information? What are the benefits to the holder of a patent? When research discoveries cannot be patented, what are the scientists’ incentives for doing the research?

What are the incentives for the institution or company that is providing financial support?

15. Tanning by exposure to ultraviolet light causes mutations in skin cells exposed to the light. These mutations increase the risks of developing skin cancer.

Additional Critical Thinking Questions The Process of Science 1. What would be the effect of the following mutations on the production of the protein for which a gene codes? a. A mutation in the promoter of a gene, so that RNA polymerase cannot bind to it b. A mutation in an intron of a gene c. A mutation of codon CGA to codon AGA in an exon d. A mutation of a stop codon to one coding for an amino acid Suggested answers: a. A mutation in the promoter, preventing RNA polymerase binding, would mean that the gene is never transcribed, and the protein is never made. b. Since an intron is cut out of mRNA before it is translated, a mutation in an intron of a gene would have no effect on the protein or its production. c. Both of these codons correspond to the amino acid arginine, so there would be no effect on the protein or its production. d. The translation of the protein would not terminate properly but would continue until a stop codon is reached. This would likely produce a protein with an altered function or no function.

2. The base sequence of the gene coding for a short polypeptide is T A C G C T A G G C G A T T G A C T. What would be the base sequence of the mRNA transcribed from this gene? Using the genetic code in Figure 10.11, state the amino acid sequence of the polypeptide translated from this mRNA. Suggested answer: mRNA: AUGCGAUCCGCUAACUGA. Amino acids: Met-Arg-Ser-Ala-Asn. 3. In the early 1950s, scientists considered several different hypotheses about how DNA is replicated. One hypothesis, called conservative replication, was that the double-stranded parental DNA molecule is conserved intact but somehow directs the synthesis of a daughter DNA molecule consisting of two entirely new strands. Another hypothesis, semiconservative replication, was that the two strands of the parental DNA separate and each acts as a template for the construction of a new strand, yielding two daughter molecules, that each have one old and one new strand. This hypothesis turned out to be correct. Assume you grow bacteria in a 134

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medium containing radioactive phosphorus, so all their DNA is labeled, and then you transfer them to a medium containing only nonradioactive phosphorus. After precisely one cell division in the nonradioactive medium, you test the bacterial DNA for radioactivity. a. The results that would support the conservative replication hypothesis would be that: b. The results that would support the semiconservative replication hypothesis would be that: (For the two questions above, select one of the answers below, state why you chose it, and state why you rejected each of the other choices.) a. None of the DNA would be radioactive; all the DNA would be radioactive. b. All the DNA would be radioactive; half the DNA would be radioactive. c. Half the DNA would be radioactive; all the DNA would be radioactive. d. None of these. This experiment would not be able to distinguish between the two hypotheses.

Suggested answers: a. No. The conservative replication theory would predict that after one cell division, the DNA of half the cells would be entirely radioactive, and the DNA of the other half of the cells would be all new and completely nonradioactive. b. No. This is the reverse of the correct answer; see answer c. c. Correct. The conservative replication hypothesis predicts that after one cell division, half the cells will contain entirely new, nonradioactive DNA, and half the cells will contain entirely old, radioactive DNA. The semiconservative replication hypothesis predicts that each cell will have DNA consisting of one old strand (radioactive) and one new strand (nonradioactive) and therefore that all the DNA molecules in all the cells will contain some radioactivity. d. No. This experiment could distinguish very well between the hypotheses.

Biology and Society 4. Our civilization generates many potentially mutagenic chemicals (pesticides, for example) and modifies the environment in ways that increase exposure to other mutagens, notably ultraviolet (UV) radiation. What role should government play in identifying mutagens and regulating their release to the environment?

Some issues and questions to consider: Does the government have an obligation to protect the health of its citizens? Can too much government regulation stifle the economy? What is the proper balance between protection from harm and government regulation? Is it possible to identify and monitor every possible mutagen? Should we try?

5. There are many environmental mutagens whose effects have been clearly noted in humans.

Some examples include the chemicals in cigarette smoke and UV exposure. Knowing that the risks of exposure carry such high odds of a dangerous outcome such as cancer, many people still voluntarily expose themselves to these mutagens. Should people be responsible for regulating their own activities, or should there be more legislation to prevent this? If people choose to smoke and then develop lung cancer or choose to overexpose themselves to the sun and develop malignant melanoma, should they be held accountable for their actions? If so, should they pay more for health care? Should their insurance cover the expense? Should these people be able to sue others for financial gain when they were fully aware of the dangers associated with the exposure?

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Some issues and questions to consider: How responsible is a person for his or her own actions?

How might the actions of another person indirectly affect others (for example, higher healthcare costs)? If the dangers are clearly indicated and the person makes his or her own choice, should the individual suffer the consequences? Should insurance companies be responsible for paying for claims that were derived in this manner? Should they be allowed to deny coverage for these people? If so, where do they draw the line? Are you willing to pay higher insurance premiums to cover these costs? Should the government do more to deter people from habits such as smoking?

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CHAPTER

11

How Genes Are Controlled

Why This Chapter Matters 1. Gene regulation explains how cells become specialized and how cellular activity can change over time. This information is essential to understanding the development of cancer and many other forms of disease.

2. DNA microarray analysis is an exciting molecular tool enabling the broad detection of gene activity in healthy and diseased tissues. Its use and significance continue to expand.

3. The manipulation of stem cells has the potential to treat many forms of disease.

4. Cancer is now one of the leading causes of death in the United States. Identifying known cancer risks and understanding the mechanisms of this disease can greatly improve human health.

Chapter Objectives Biology and Society: Tobacco’s Smoking Gun 1. Describe the evidence that suggests that cigarette smoking causes lung cancer.

How and Why Genes Are Regulated 2. Explain how the many types of adult human cells are formed.

3. Explain how the lac operon works.

4. Explain how DNA packing influences gene expression.

5. Explain how transcription is regulated in eukaryotes. Compare transcriptional regulation in eukaryotes and prokaryotes.

6. Explain how RNA is processed in eukaryotes before it leaves the nucleus. Explain how this processing can result in different proteins from the same gene.

7. Describe the mechanisms used to regulate gene expression after eukaryotic mRNA is transported to the cytoplasm.

8. Describe the significance of cell signaling in multicellular organisms.

9. Explain how homeotic genes help us understand animal evolution and development.

10. Explain how DNA microarrays help scientists visualize gene expression.

Cloning Plants and Animals 11. Explain how every cell has the potential to act like every other cell. Illustrate with examples.

12. Explain how plants are cloned, what this reveals about cell differentiation, and why growers clone plants.

13. Explain how nuclear transplantation can be used to clone animals. Describe advantages of reproductive cloning of animals.

14. Compare the properties of embryonic and adult stem cells. Explain why embryonic stem cells may be better to produce replacement tissues in adults.

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The Genetic Basis of Cancer 15. Explain how mutations in proto-oncogenes and tumor suppressor genes can lead to cancer.

16. Explain how personal habits and individual choices can affect a person’s risk of developing cancers.

Evolution Connection: The Evolution of Cancer in the Body 17. Explain how populations of cancer cells evolve.

Lecture Outline I. Biology and Society: Tobacco’s Smoking Gun 1. During the 1900s, doctors noticed that a. smoking increased and b. lung cancer increased.

2. In 1996, researchers studying lung cancer found that, in human lung cells growing in the lab, a component of tobacco smoke, BPDE, binds to DNA within a gene called p53, which codes for a protein that normally helps suppress the formation of tumors.

3. This work directly linked a chemical in tobacco smoke with the formation of human lung tumors.

A. How and Why Genes Are Regulated 1. Every somatic cell in an organism contains identical genetic instructions. a. they all share the same genome. b. so what makes cells different from one another?

2. In cellular differentiation, cells become specialized in a. structure and b. function.

3. Certain genes are turned on and off in the process of gene regulation.

B. Patterns of Gene Expression in Differentiated Cells 1. In gene expression, a. a gene is turned on and transcribed into RNA and b. information flows from c. genes to proteins and d. genotype to phenotype.

2. Information flows from DNA to RNA to proteins.

3. The great differences among cells in an organism must result from the selective expression of genes.

C. Gene Regulation in Bacteria 1. Natural selection has favored bacteria that express a. only certain genes b. only at specific times when the products are needed by the cell.

2. So how do bacteria selectively turn their genes on and off?

3. An operon includes a. a cluster of genes with related functions and b. the control sequences that turn the genes on or off.

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4. The bacterium E. coli uses the lac operon to coordinate the expression of genes that produce enzymes used to break down lactose in the bacterium’s environment.

5. The lac operon uses a. a promoter, a control sequence where the transcription enzyme attaches and initiates transcription, b. an operator, a DNA segment that acts as a switch that is turned on or off, and c. a repressor, which binds to the operator and physically blocks the attachment of RNA polymerase and transcription.

D. Gene Regulation in Eukaryotic Cells 1. Eukaryotic cells have more complex gene regulating mechanisms with many points where the process can be turned on or off.

2. The multiple mechanisms that control gene expression are like the many control valves along a water supply.

E. The Regulation of DNA Packing 1. Cells may use DNA packing for long-term inactivation of genes.

2. X chromosome inactivation a. takes place early in embryonic development, b. occurs in female mammals, and c. is when one of the two X chromosomes in each cell is inactivated at random.

3. All of the descendants of each cell will have the same X chromosome turned off.

4. If a female is heterozygous for a gene on the X chromosome, a. about half her cells will express one allele and b. the others will express the alternate allele.

F. The Initiation of Transcription 1. The initiation of transcription is the most important stage for regulating gene expression.

2. In prokaryotes and eukaryotes, regulatory proteins a. bind to DNA and b. turn the transcription of genes on and off.

3. Transcription in eukaryotes, unlike in prokaryotes, is complex, involving many proteins, called transcription factors, that bind to DNA sequences called enhancers.

4. Repressor proteins called silencers a. bind to DNA and b. inhibit the start of transcription.

5. Activators a. are more typically used by EUKARYOTES than silencers and b. turn genes on by binding to DNA. G. RNA Processing and Breakdown 1. The eukaryotic cell a. localizes transcription in the nucleus and b. processes RNA in the nucleus.

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3. In alternative RNA splicing, exons may be spliced together in different combinations, producing more than one type of polypeptide from a single gene.

4. A typical human gene contains about ten exons, with a. nearly all human genes spliced in at least two different ways and b. some spliced hundreds of different ways!

5. Eukaryotic mRNAs a. can last for hours to weeks to months and b. are all eventually broken down and their parts recycled.

H. microRNAs 1. Small single-stranded RNA molecules, called microRNAs (miRNAs), bind to complementary sequences on mRNA molecules in the cytoplasm. a. Some trigger the breakdown of their target mRNA, and others block translation.

2. It has been estimated that miRNAs may regulate the expression of up to one-third of all human genes, yet miRNAs were unknown 20 years ago!

I. The Initiation of Translation 1. The process of translation offers additional opportunities for regulation by regulatory molecules.

J. Protein Activation and Breakdown 1. Post-translational control mechanisms in eukaryotes a. occur after translation and b. often involve cutting polypeptides into smaller, active final products.

2. The selective breakdown of proteins is another control mechanism operating after translation.

K. Cell Signaling 1. In a multicellular organism, gene regulation can cross cell boundaries.

2. A cell can produce and secrete chemicals, such as hormones, that affect gene regulation in another cell.

L. Homeotic genes 1. Master control genes called homeotic genes regulate groups of other genes that determine what body parts will develop in which locations.

2. Mutations in homeotic genes can produce bizarre effects.

3. Similar homeotic genes help direct embryonic development in nearly every eukaryotic organism examined so far.

M. DNA Microarrays: Visualizing Gene Expression 1. A DNA microarray allows visualization of gene expression.

2. The pattern of glowing spots enables the researcher to determine which genes were being transcribed in the starting cells.

3. Researchers can thus learn which genes are active a. in different tissues or b. in tissues from individuals in different states of health.

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II. Cloning Plants and Animals: The Genetic Potential of Cells 1. Differentiated cells a. all contain a complete genome and b. have the potential to express all of an organism’s genes.

2. Differentiated plant cells can develop into a whole new organism.

3. The somatic cells of a single plant can be used to produce hundreds or thousands of identical organisms—clones from a single plant.

4. Plant cloning demonstrates that cell differentiation in plants a. is reversible and b. does not cause irreversible changes in the DNA. 5. Plant cloning is now used extensively in agriculture.

6. Regeneration a. is the regrowth of lost body parts and b. occurs, for example, in the regrowth of the legs of salamanders.

7. During regeneration of the leg, cells in the leg stump a. reverse their differentiated state, b. divide, and c. then differentiate again to give rise to a new leg.

A. Reproductive Cloning of Animals 1. Nuclear transplantation involves a. replacing the nucleus of an egg cell with the nucleus from a differentiated cell from an adult body and b. allowing the egg to develop into an adult.

2. In 1997, Scottish researchers PRODUCED Dolly, a sheep, by replacing the nucleus of an egg cell with the nucleus of an adult somatic cell. a. This procedure is called reproductive cloning, because it results in the birth of a new animal.

B. Practical Applications of Reproductive Cloning 1. Since Dolly, reproductive cloning has been used to clone many species of mammals, including mice, horses, dogs, mules, cows, pigs, rabbits, ferrets, and cats.

2. Reproductive cloning has been used to restock populations of endangered species including a. a wild mouflon (a small European sheep), b. a banteng (a Javanese cow), c. a gaur (an Asian ox), and d. gray wolves.

3. However, cloning does not increase genetic diversity, which may be essential to long-term species survival.

C. Human Cloning 1. Cloning of mammals a. has heightened speculation about human cloning and b. is very difficult and inefficient.

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D. Therapeutic Cloning and Stem Cells 1. The purpose of therapeutic cloning is a. not to produce a viable organism but b. to produce embryonic stem cells.

E. Embryonic Stem Cells 1. Embryonic stem cells (ES cells) a. are derived FROM blastocysts and b. can give rise to all the specialized cells in the body.

F. Adult Stem Cells 1. Adult stem cells a. are cells in adult tissues and b. generate replacements for some of the body’s cells.

2. Unlike embryonic ES cells, adult stem cells a. are partway along the road to differentiation and b. usually give rise to only a few related types of specialized cells.

G. Umbilical Cord Blood Banking 1. Umbilical cord blood a. can be collected at birth, b. contains partially differentiated stem cells, and c. has had limited success in the treatment of a few diseases.

2. The American Academy of Pediatrics recommends cord blood banking only for babies born into families with a known genetic risk.

H. The Genetic Basis of Cancer 1. Cancer is a variety of diseases in which cells a. experience changes in gene expression and b. escape from the control mechanisms that normally limit their growth and division.

I. Genes That Cause Cancer 1. As early as 1911, certain viruses were known to cause cancer.

2. Oncogenes are a. genes that cause cancer and b. found in viruses.

J. Oncogenes and Tumor-Suppressor Genes 1. Proto-oncogenes are a. normal genes with the potential to become oncogenes, b. found in many animals, and c. often genes that code for growth factors, proteins that stimulate cell division.

2. A cell can acquire an oncogene a. from a virus or b. from the mutation of one of its own proto-oncogenes.

3. Tumor-suppressor genes a. inhibit cell division, b. prevent uncontrolled cell growth, and c. may be mutated and contribute to cancer.

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4. Researchers have identified many mutations in both tumor-suppressor and growth factor genes that are associated with cancer.

K. The Process of Science: Are Childhood Tumors Special 1. Observations: Specific mutations can lead to cancer.

2. Question: Are different kinds of cancer associated with specific mutations?

3. Hypothesis: Young patients with medulloblastoma (MB) harbor unique mutations.

(MB is the most common pediatric brain cancer and the deadliest form of childhood cancer.)

4. Prediction: The genetic map of MB cells from childhood tumors would have cancerassociated mutations not found in adult brain cancer tissue.

5. Experiment: Researchers sequenced all the genes in tumors from 22 pediatric MB patients and compared the genes with normal tissue from these same patients.

6. Results: a. Each tumor had an average of 11 mutations. b. This is 5–10 times fewer mutations than are found in adult MB patients. c. Therefore, younger MB patients have fewer but more deadly mutations.

L. The Progression of a Cancer 1. Nearly 150,000 Americans will be stricken by cancer of the colon (the main part of the large intestine) this year.

2. Colon cancer, like many cancers, a. spreads gradually and b. is produced by more than one mutation.

3. The development of a malignant tumor is accompanied by a gradual accumulation of mutations that a. convert proto-oncogenes to oncogenes and b. knock out tumor-suppressor genes.

M. “Inherited” Cancer 1. Most mutations that lead to cancer arise in the organ where the cancer starts.

2. In familial or inherited cancer, a. a cancer-causing mutation occurs in a cell that gives rise to gametes and b. the mutation is passed on from generation to generation.

3. Breast cancer a. is usually not associated with inherited mutations and b. in some families can be caused by inherited BRCA1 cancer genes.

N. Cancer Risk and Prevention 1. Cancer a. is the second leading cause of death (after heart disease) in most industrialized countries and b. can be caused by carcinogens, cancer-causing agents, found in the environment, including i. tobacco products, ii. alcohol, and iii. exposure to ultraviolet light from the sun.

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2. Exposure to carcinogens a. is often an individual choice and b. can be avoided.

3. Some studies suggest that certain substances in fruits and vegetables may help protect against a variety of cancers.

O. Evolution Connection: The Evolution of Cancer in the Body 1. Evolution drives the growth of a tumor.

2. Like individuals in a population of organisms, cancer cells in the body a. have the potential to produce more offspring than can be supported by the environment and b. show individual variation, which i. affects survival and reproduction and ii. can be passed on to the next generation of cells.

3. Some researchers are attempting to “prime” tumors for treatment by increasing the reproductive success of only those cells that will be susceptible to a chemotherapy drug.

Chapter Guide to Teaching Resources How and Why Genes Are Regulated Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation.

2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating.

The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation.

Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type.

2. The lactose operon is turned on by removing the repressor—a sort of double negative.

Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor.

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3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch.

4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role.

5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression.

6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away.

7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing.

(Answer: the award for best editing.)

8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door.

9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation.

10. Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction.

11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles.

Cloning Plants and Animals Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material.

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2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype.

3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s).

Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton.

2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts!

3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use.

Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells.

4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans.

This viral DNA might not otherwise have the capacity for transmission to humans.

5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact.

The Genetic Basis of Cancer Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level.

Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text).

2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association.

3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds.

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Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function.

2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection (www.cancer.gov/cancertopics/factsheet/Risk/HPV).

3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited.

4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer.

5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease.

6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society (http://www.cancer.org/Cancer/CancerCauses/TobaccoCancer/index).

Key Terms activators adult stem cells alternative RNA splicing carcinogens cellular differentiation complementary DNA (cDNA) DNA microarray

embryonic stem cells (ES cells) enhancers gene expression gene regulation growth factors homeotic genes nuclear transplantation oncogene

operator operon promoter proto-oncogene regeneration repressor reproductive cloning signal transduction pathway

silencers therapeutic cloning transcription factors tumor-suppressor genes X chromosome inactivation

Word Roots gen = producing (carcinogen: a cancer-causing agent) onkos = tumor (oncogene: a gene that causes cancer) proto = first (proto-oncogene: a normal gene with the potential to become an oncogene)

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Relevant Songs to Play in Class “Cancer,” Filter “I Ain’t Afraid of Cancer” (contains expletives), George Carlin “Cancer,” Joe Jackson

“I Think I’m a Clone Now,” Weird Al Yankovic “Hello, Dolly!” (Broadway musical), Barbra Streisand “Express Yourself,” Madonna

Answers to End-of-Chapter Questions The Process of Science 13. Suggested answers: a. If the mutated repressor could still bind to the operator on the DNA, it would continuously repress the operon; enzymes for lactose utilization would not be made, whether or not lactose was present. b. The lac genes would continue to be transcribed and the enzymes made, whether or not lactose was present. c. Same predicted result as for b. d. RNA polymerase would not be able to transcribe the genes; no proteins would be made, whether or not lactose was present.

14. Suggested answer: In this case, one possibility would be to isolate mRNAs from the cells.

From there, cDNA could be created using reverse transcriptase. These cDNA molecules could then be tested to see if they pair with DNA isolated from various genes.

15. Suggested answer: XXY. 16. Suggested answer: Follow the general procedure for microarray analysis described in this chapter, comparing the sets of mRNA transcribed from genes in each type of cell. The two types of genes of interest are those that are not expressed in the cancer cell and those that are expressed in the cancer cell.

Biology and Society 17. Some issues and questions to consider: The protein to which dioxin binds in the cell is probably a transcription factor that regulates multiple genes. If the binding of dioxin influences the activity of this transcription factor (either activating or inactivating it), dioxin could thereby affect multiple genes and thus have a variety of effects on the body.

The varying effects in different animals might be explained by variations in genetic details of the particular species. It would be extremely difficult to demonstrate conclusively that dioxin exposure was the cause of illness in a particular individual, even if dioxin had been shown to be present in the person’s tissues. However, if you had detailed information about how dioxin affects patterns of gene expression in humans and were able to show dioxin-specific abnormal patterns in the patient (perhaps using a DNA microarray), you might be able to establish a strong link between dioxin and the illness.

18. Some issues and questions to consider: If the cancer cannot be prevented by lifestyle changes, do you want to know the results? Would the results change the way you live your life? Can you be certain that a positive test will definitely lead to cancer? Is it possible that the test results could be used against you (for example, being denied coverage by an insurance company)? Would you take preventative measures such as a mastectomy if you knew you had that type of cancer?

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Additional Critical Thinking Questions The Process of Science 1. The random inactivation of one X chromosome in female mammals means that females who are heterozygous for an X-linked gene should have two different types of cells, each expressing one of the two different alleles. One enzyme in particular, glucose-6-phosphate dehydrogenase (G6PD), has two different forms that can be distinguished by gel electrophoresis. The gene for G6PD is expressed in white blood cells. Women heterozygous for these two forms, therefore, have two different types of white blood cells circulating in their blood. If these women develop leukemia, it is observed that all of the cells of the cancer have the same form of G6PD. What does this fact teach us about cancer?

Suggested answer: Since the random X chromosome inactivation that occurs in a cell is inherited by the cell’s descendants, the fact that all the leukemia cells express the same enzyme allele suggests that all of the cells of the leukemia derived from one cell. This is a fundamental finding in the study of cancer, since it means that we can understand tumors as clones of cells that share many of the same characteristics as the original cell from which they arose.

2. Homeotic genes have segments that are nearly identical in very diverse organisms. When you find the same DNA segments in various species, what does that tell you about the importance of the gene? Explain your answer.

Suggested answer: This suggests that the gene is critical to growth and development leading to survival. The reason no variation is observed may be because if mutations occur, the protein is nonfunctional and the organism does not complete development.

3. Genetic mutation is the ultimate source of variation, the raw material for evolution by natural selection. The shuffling of genes that occurs during meiosis and the “luck of the draw” at fertilization also increases variation. Without the variation that mutation produces, there would not be inherited variations in the offspring on which natural selection could act. Cancer is a disease caused by mutation. Does this mean that cancer is inevitable if we simply live long enough?

Suggested answer: Yes. One of the best bits of evidence for this is the fact that the frequency of developing cancer increases with age. For example, a woman has a one in 257 chance of developing breast cancer between the ages of 30 and 40. The odds increase to one in 28 for women between 60 and 70. Similarly, autopsy studies have found prostate cancer in over half of men older than 80 who died of other causes. These findings are consistent with the observation that tumors become more malignant as the number of oncogene and tumor-suppressor gene mutations increase.

Biology and Society 4. Recently, three scientists argued that confusion about the word cloning is responsible for much of the public fear of this technology. They argue that we should adopt the term somatic cell nuclear transfer to describe those circumstances in which the technique is used for purposes other than the creation of an adult organism, such as the creation of stem cells for use in medical therapy. The term therapeutic cloning confuses the issue since it is easily confused with reproductive cloning. However, could the cloning of a human being be seen as a therapy for infertility? Do you agree with this suggestion?

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Some issues and questions to consider: How important are the words we use to describe important and controversial issues in society? Can you think of any words or phrases concerning science that are “loaded” in that they may mislead an unsuspecting person to wrong conclusions? How about the war on cancer? In the specific case addressed in this question, do the words somatic cell nuclear transfer obscure the fact that an embryo will be destroyed as a result of the technique? Or do they make a valid distinction between two very different procedures?

5. The goal of gene therapy is to correct flawed genes so that they no longer express defective proteins, which cause the symptoms of genetic disease. This has been attempted on a limited basis for a few genetic diseases but the ultimate goal is to “correct” the genes in the embryo, which has not yet been achieved. Another option for attempting to deal with genetic diseases is to use “genetic drugs” to block faulty genes so that they can no longer express defective proteins. In limited cases, this too has the potential to at least alleviate symptoms of a genetic disease. Do you agree with research that promotes gene therapy in embryos? What about research into genetic drugs? If your answers to these questions are different, explain why.

Some issues and questions to consider: Are gene therapy and genetic drugs equivalent technologies? Is one more “ethical” than the other? Does it make a difference that the goal of gene therapy may be to alter embryonic DNA, whereas the goal of using genetic drugs is simply to block gene expression? Where would you draw the line with altering embryonic DNA?

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CHAPTER

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DNA Technology

Why This Chapter Matters 1. DNA technology has quickly revolutionized the field of forensics.

2. Beyond the courtroom, DNA technology is responsible for some of the most remarkable scientific advances in recent years.

3. DNA technology offers great promise in agriculture and medicine but raises serious social, legal, and ethical issues.

Chapter Objectives Biology and Society: DNA, Guilt, and Innocence 1. Explain how DNA profiling is used in criminal trials.

Recombinant DNA Technology 2. Explain how recombinant DNA technology can be used to produce useful products.

3. Explain how recombinant DNA techniques are used to mass-produce a protein from an isolated gene.

4. Explain how genetic engineering is used to produce Humulin, human growth hormone, erythropoietin, vaccines, crops, and “pharm” animals.

5. Describe the process of cloning genes using plasmids.

6. Explain how the “shotgun” approach produces a genomic library.

7. Explain how restriction enzymes and DNA ligase are used to create recombinant DNA.

DNA Profiling and Forensic Science 8. Describe the ways that DNA profiling can be used in our society.

9. Explain how the polymerase chain reaction (PCR), short tandem repeat (STR) analysis, restriction fragment length polymorphism (RFLP), and gel electrophoresis are used in the process of DNA profiling.

Genomics and Proteomics 10. Describe the types of organisms that have been the subject of recent sequencing efforts.

Explain why these particular organisms have been examined.

11. Describe the goals of the Human Genome Project. Explain why our genome presents a major challenge.

12. Explain how comparative genomics has been used to investigate acts of bioterrorism, track the spread of disease, and study evolutionary relationships.

13. Explain why scientists study DNA and proteins to better understand the functioning of cells and organisms.

Human Gene Therapy 14. Describe the steps used to treat severe combined immunodeficiency (SCID) using human gene therapy. ..

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Safety and Ethical Issues 15.

Describe the potential benefits, risks, and concerns of producing genetically modified foods.

16.

Describe the concerns for the abuse of genetic information and technology as it relates to human society.

Evolution Connection: The Y Chromosome as a Window on History 17.

Describe the surprising results of DNA profiling of the human Y chromosome.

Lecture Outline I. Biology and Society: DNA, Guilt, and Innocence 1. DNA profiling is the analysis of DNA samples that can be used to determine whether the samples come from the same individual.

2. DNA profiling can therefore be used in courts to indicate if someone is guilty of a crime.

3. DNA technology has led to other advances in the a. creation of genetically modified crops and b. identification and treatment of genetic diseases.

A. Recombinant DNA Technology 1. Biotechnology a. is the manipulation of organisms or their components to make useful products and b. has been used for thousands of years to i. make bread using yeast and ii. selectively breed livestock for desired traits.

2. Biotechnology today means the use of DNA technology, techniques for a. studying and manipulating genetic material, b. modifying specific genes, and c. moving genes between organisms.

3. Recombinant DNA is constructed when scientists combine pieces of DNA from two different sources to form a single DNA molecule.

4. Recombinant DNA technology is widely used in genetic engineering, the direct manipulation of genes for practical purposes.

B. Applications: From Humulin to Foods to “Pharm” Animals 1. By transferring the gene for a desired protein into a bacterium or yeast, proteins that are naturally present in only small amounts can be produced in large quantities.

2. Making Humulin.

3. In 1982, the world’s first genetically engineered pharmaceutical product was sold.

4. Humulin, human insulin a. was produced by genetically modified bacteria and b. is used today by more than 4 million people with diabetes.

5. Today, humulin is continuously produced in gigantic fermentation vats filled with a liquid culture of bacteria.

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6. DNA technology is used to produce medically valuable molecules, including a. human growth hormone (HGH), b. the hormone erythropoietin (EPO), which stimulates production of red blood cells, and c. vaccines, harmless variants or derivatives of a pathogen used to prevent infectious diseases.

7. Genetically Modified (GM) Foods.

8. Today, DNA technology is quickly replacing traditional breeding programs.

9. Scientists have produced many types of genetically modified (GM) organisms, organisms that have acquired one or more genes by artificial means.

10. A transgenic organism contains a gene from another organism, typically of another species.

11. In the United States today, roughly half of the corn crop and more than three-quarters of the soybean and cotton crops are genetically modified.

12. Corn has been genetically modified to resist insect infestation, attack by an insect called the European corn borer.

13. Strawberry plants produce bacterial proteins that act as a natural antifreeze, protecting the plants from cold weather.

14. Potatoes and rice have been modified to produce harmless proteins derived from the cholera bacterium and may one day serve as edible vaccines.

15. “Golden rice 2” is a transgenic variety of rice that carries genes from daffodils and corn and could help prevent vitamin A deficiency and resulting blindness.

16. “Pharm” Animals.

17. A transgenic pig has been produced that carries a gene for human hemoglobin, which can be a. isolated and b. used in human blood transfusions.

18. In 2006, genetically modified pigs carried roundworm genes that produce proteins that convert less healthy fatty acids to omega-3 fatty acids.

19. However, unlike transgenic plants, no transgenic animals are yet sold as food.

C. Recombinant DNA Techniques 1. Bacteria are the workhorses of modern biotechnology.

2. To work with genes in the laboratory, biologists often use bacterial plasmids, small, circular DNA molecules that replicate separately from the larger bacterial chromosome.

3. Plasmids a. can carry virtually any gene, b. can act as vectors, DNA carriers that move genes from one cell to another, and c. are ideal for gene cloning, the production of multiple identical copies of a gene-carrying piece of DNA. 4. Recombinant DNA techniques can help biologists produce large quantities of a desired protein.

5. A Closer Look: Cutting and Pasting DNA with Restriction Enzymes.

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6. Recombinant DNA is produced by combining two ingredients: a. a bacterial plasmid and b. the gene of interest.

7. To combine these ingredients, a piece of DNA must be spliced into a plasmid.

8. This splicing process can be accomplished by a. using restriction enzymes, which cut DNA at specific nucleotide sequences (restriction sites), and b. producing pieces of DNA called restriction fragments with “sticky ends” important for joining DNA from different sources.

9. DNA ligase connects the DNA pieces into continuous strands by forming bonds between adjacent nucleotides.

10. A Closer Look: Obtaining the Gene of Interest.

11. How can a researcher obtain DNA that encodes a particular gene of interest? a. A “shotgun” approach can yield millions of recombinant plasmids carrying many different segments of foreign DNA. b. A collection of cloned DNA fragments that includes an organism’s entire genome (a complete set of its genes) is called a genomic library.

12. Once a genomic library is created, the bacterial clone containing the desired gene is identified using a nucleic acid probe consisting of a short single strand of DNA with a complementary sequence and labeled with either a radioactive isotope or a fluorescent dye 13. Another way to obtain a gene of interest is to a. use reverse transcriptase and b. synthesize the gene by using an mRNA template.

14. Another approach is to a. use an automated DNA-synthesizing machine and b. synthesize a gene of interest from scratch.

II. DNA Profiling and Forensic Science 1. DNA profiling a. can be used to determine if two samples of genetic material are from a particular individual and b. has rapidly revolutionized the field of forensics, the scientific analysis of evidence from crime scenes.

2. To produce a DNA profile, scientists compare sequences in the genome that vary from person to person.

A. Investigating Murder, Paternity, and Ancient DNA 1. DNA profiling can be used to a. test the guilt of suspected criminals, b. identify tissue samples of victims, c. resolve paternity cases, d. identify contraband animal products, and e. trace the evolutionary history of organisms

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B. DNA Profiling Techniques 1. The Polymerase Chain Reaction (PCR) 2. The polymerase chain reaction (PCR) a. is a technique to copy quickly and precisely a specific segment of DNA and b. can generate enough DNA, from even minute amounts of blood or other tissue, to allow DNA profiling.

3. Short Tandem Repeat (STR) Analysis.

4. How do you test if two samples of DNA come from the same person?

5. Repetitive DNA a. makes up much of the DNA that lies between genes in humans and b. consists of nucleotide sequences that are present in multiple copies in the genome.

6. Short tandem repeats (STRs) are a. short sequences of DNA and b. repeated many times, tandemly (one after another), in the genome.

7. STR analysis a. is a method of DNA profiling and b. compares the lengths of STR sequences at specific sites in the genome.

8. Gel Electrophoresis.

9. STR analysis a. compares the lengths of DNA fragments and b. uses gel electrophoresis, a method for sorting macromolecules—usually proteins or nucleic acids—primarily by their i. electrical charge and ii. size.

10. The DNA fragments are visualized as “bands” on the gel.

11. The differences in the locations of the bands reflect the different lengths of the DNA fragments.

12. RFLP Analysis.

13. Gel electrophoresis may also be used for RFLP analysis, in which DNA molecules are exposed to a restriction enzyme, producing fragments that are compared and made visible by gel electrophoresis.

III. Genomics and Proteomics 1. Genomics is the study of complete sets of genes (genomes). a. The first targets of genomics research were bacteria. b. As of 2011, i. the genomes of more than 1,700 species have been published and ii. more than 8,000 more are in progress.

A. The Human Genome Project 1. Begun in 1990, the Human Genome Project was a massive scientific endeavor to a. determine the nucleotide sequence of all the DNA in the human genome and b. identify the location and sequence of every gene.

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2. At the completion of the project, a. more than 99% of the genome had been determined to 99.999% accuracy, b. about 3 billion nucleotide pairs were identified, c. about 21,000 genes were found, and d. about 98% of the human DNA was identified as noncoding.

3. The Human Genome Project can help map the genes for specific diseases such as a. Alzheimer’s disease and b. Parkinson’s disease.

B. Tracking the Anthrax Killer 1. In October 2001, a. a Florida man died after inhaling anthrax and b. by the end of the year, four other people had also died from anthrax.

2. In 2008, investigators a. completed a whole-genome analysis of the spores used in the attack, b. found four unique mutations, and c. traced the mutations to a single flask at an Army facility.

3. Although never charged, an army research scientist suspected in the case, committed suicide in 2008 and the case remains officially unsolved.

4. The anthrax investigation is just one example of the new field of bioinformatics, the application of computational tools to molecular biology. Additional examples include a. evidence that a Florida dentist transmitted HIV to several patients, b. tracing the West Nile virus outbreak in 1999 to a single natural strain of virus infecting birds and people, and c. determining that our closest living relative, the chimpanzee (Pan troglodytes), shares 96% of our genome.

C. Genome-Mapping Techniques 1. Genomes are most often sequenced using the whole-genome shotgun method, in which a. the entire genome is chopped into fragments using restriction enzymes, b. all the fragments are cloned and sequenced, and c. computers running specialized mapping software reassemble the millions of overlapping short sequences into a single continuous sequence for every chromosome—an entire genome.

D. The Process of Science: Can Genomics Cure Cancer?

1. Observation: A few patients responded quite dramatically to a new drug, gefitinib, which a. targets a protein called EGFR found on the surface of cells that line the lungs and b. is used to treat lung cancer.

2. Question: Are genetic differences among lung cancer patients responsible for the differences in gefitinib’s effectiveness?

3. Hypothesis: Mutations in the EGFR gene were causing the different responses to gefitinib.

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4. Prediction: DNA profiling that focuses on the EGFR gene would reveal different DNA sequences in the tumors of responsive patients compared with the tumors of unresponsive patients.

5. Experiment: The EGFR gene was sequenced in the cells extracted from the tumors of a. five patients who responded to the drug and b. four who did not.

6. Results: The results were quite striking. a. All five tumors from gefitinib-responsive patients had mutations in EGFR. b. None of the other four tumors did. c. These results suggest that doctors can use DNA profiling techniques to screen lung cancer patients for those who are most likely to benefit from treatment with this drug.

E. Proteomics 1. Success in genomics has given rise to proteomics, the systematic study of the full set of proteins found in organisms.

2. To understand the functioning of cells and organisms, scientists are studying a. when and where proteins are produced and b. how they interact.

IV. Human Gene Therapy 1. Human gene therapy a. is a recombinant DNA procedure, b. seeks to treat disease by altering the genes of the afflicted person, and c. often replaces or supplements the mutant version of a gene with a properly functioning one.

2. Severe combined immunodeficiency (SCID) is a. a fatal inherited disease and b. caused by a single defective gene that prevents the development of the immune system.

3. SCID patients quickly die unless treated with a. a bone marrow transplant or b. gene therapy.

4. From 2000 to 2011, gene therapy has cured 22 children with inborn SCID. 5. However, there have been some serious side effects. Four of the children developed leukemia, and proved fatal to one.

A. Safety and Ethical Issues 1. As soon as scientists realized the power of DNA technology, they began to worry about potential dangers such as the a. creation of hazardous new pathogens and b. transfer of cancer genes into infectious bacteria and viruses.

2. Strict laboratory safety procedures have been designed to a. protect researchers from infection by engineered microbes and b. prevent microbes from accidentally leaving the laboratory.

B. The Controversy over Genetically Modified Foods 1. GM strains account for a significant percentage of several staple crops in the United States.

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2. Advocates of a cautious approach are concerned that a. crops carrying genes from other species might harm the environment, b. GM foods could be hazardous to human health, and/or c. transgenic plants might pass their genes to close relatives in nearby wild areas.

3. Negotiators from 130 countries (including the United States) agreed on a Biosafety Protocol that a. requires exporters to identify GM organisms present in bulk food shipments and b. allows importing countries to decide whether the shipments pose environmental or health risks.

4. In the United States, all projects are evaluated for potential risks by a number of regulatory agencies, including the a. Food and Drug Administration, b. Environmental Protection Agency, c. National Institutes of Health, and d. Department of Agriculture.

C. Ethical Questions Raised by DNA Technology 1. DNA technology raises legal and ethical questions—few of which have clear answers. a. Should genetically engineered human growth hormone be used to stimulate growth in HGH-deficient children? b. Should we try to eliminate genetic defects in our children and their descendants? c. Should people use mail-in kits that can tell healthy people their relative risk of developing various diseases?

2. DNA technologies raise many complex issues that have no easy answers.

3. We as a society and as individuals must become educated about DNA technologies to address the ethical questions raised by their use.

D. Evolution Connection: The Y Chromosome as a Window on History 1. Barring mutations, the human Y chromosome passes essentially intact from father to son.

2. By comparing Y DNA, researchers can learn about the ancestry of human males.

3. DNA profiling of the Y chromosome has revealed that a. nearly 16 million men currently living may be descended from Genghis Khan, b. nearly 10% of Irish men were descendants of Niall of the Nine Hostages, a warlord who lived during the 1400s, and c. the Lemba people of southern Africa are descended from ancient Jews.

Chapter Guide to Teaching Resources Recombinant DNA Technology Student Misconceptions and Concerns 1. Student comprehension of restriction enzymes, nucleic acid probes, and many other aspects of recombinant DNA techniques depend upon a comfortable understanding of basic molecular genetics. Consider addressing Chapter 12 after an exam that addresses the content in Chapters 10 and 11.

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2. Students might bring some awareness and/or concerns about biotechnology to the classroom, for example, in their reactions to the controversies regarding genetically modified (GM) foods. This experience can be used to generate class interest and to highlight the importance of good information when making judgments. Consider starting class with a headline addressing one of these issues. The recent process of FDA approval for genetically engineered salmon raised for food might be particularly useful and relevant.

Teaching Tips 1. Annual flu vaccinations are a common example of using vaccines to prevent diseases that cannot be easily cured. However, students might not understand why many people receive the vaccine every year. A new annual vaccine is necessary because the flu viruses keep evolving.

2. Genetically engineered organisms are controversial, creating various degrees and directions of social resistance; yet many debates around issues of science are confused by misinformation. This may be an opportunity for you to make an extra credit or regular assignment for students to take a position, on one side or the other, on some aspect of this or related issues. The science would need to be accurate. Students might debate whether a food product made from GM/transgenic organisms should be labeled as such, or students can discuss the risks or advantages of producing GM organisms.

3. The origin of the name “restriction enzymes” may be of interest. In nature, these enzymes protect bacterial cells against foreign DNA. Thus, these enzymes “restrict” the invasion of foreign genetic material.

4. The ability to swap genes between prokaryotes and eukaryotes using the technologies described in this chapter reveal the fundamental genetic mechanisms shared by all forms of life. This very strong evidence of common descent is a lesson about evolution that may be missed by your students.

5. Students might think you are just making a bad joke by noting that laboratory synthesized genes are “designer genes,” but this is a common term. Search the Internet using the keywords “designer genes,” and many scientific (and unscientific) sites will be found.

6. A genomic library of the sentence you are now reading would be all of the sentence fragments that make up the sentence. One could string together all of the words of this first sentence, without spaces between letters, and then conduct a word-processing edit placing a space between any place where an “e” is followed by the letter “n.” The resulting fragments of this original sentence would look like this, and would be similar to a type of “genomic library.”

Age nomic library of these nte nce you are now reading would be all of these nte nce fragments that made up these nte nce.

7. Some Internet search programs rely on a methodology similar in one way to the use of a nucleic acid probe. For example, if you want to find the lyrics to a particular song, but you do not know the song title or artist, you might search the Internet using a unique phrase from the song. (For example, search using “yellow submarine.”) The search engine will scan millions of web pages to identify those sites containing that particular phrase. However, unlike a nucleic acid probe, you would search for the song by using a few of the lyrics. A nucleic acid probe would search using a sequence complementary to the desired sequence.

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8. Roundup Ready Corn, a product of Monsanto, is resistant to the herbicide Roundup. The general strategy for farmers is to spray fields of Roundup Ready Corn with the herbicide Roundup, killing weeds but not the corn. A search of the Internet will quickly reveal the controversy associated with this and other genetically modified organisms (GMOs), which can encourage interesting discussions and promote critical thinking skills.

9. As gene therapy technology expands, our ability to modify the genome in human embryos, created through in vitro fertilization, permits genetic modification at the earliest stages of life. Future generations of humans, like our crops today, may include those with and without a genetically modified ancestry. The benefits and challenges of these technologies raise issues many students have never considered. Our students, and the generations soon to follow, will face the potential of directed human evolution.

DNA Profiling and Forensic Science Student Misconceptions and Concerns 1. Television programs might lead some students to expect that DNA profiling is quick and easy. Ask students to consider why DNA profiling actually takes many days or weeks to complete.

2. Students might expect DNA profiling for criminal investigations to involve an analysis of the entire human genome. Consider explaining why such an analysis is unrealistic and unnecessary.

3. The many forms of DNA technology discussed in this chapter provide powerful evidence of evolution. Although not addressed regularly in this chapter, consider reminding students that these techniques continue to reinforce and inform our understandings of the common descent of life on Earth.

Teaching Tips 1. In most legal cases, the probability of two people having identical DNA profiles can be one in 10 billion or more. However, eyewitness testimony has been a standard part of the justice system. If you want to make the point about the unreliability of eyewitnesses in a trial, compared to techniques such as genetic profiling, consider this exercise. Arrange for a person who is not well known to the class to run into your classroom, take something you have placed near you (perhaps a bag, stack of papers, box), and leave quickly. You need to take care that no one in the class is so alarmed as to do something dangerous. Once the “thief” is gone, tell the class that this was planned but not to speak. Have them each write a description of the person, including height, hair color, clothing, facial hair, behavior, and so on. Many students will be accurate, but some will likely get details wrong. This is also an effective exercise to demonstrate the need for large sample sizes and accurate recording devices for good scientific technique.

2. Although the statistical odds of a DNA-profiling match can exceed one in 10 billion, the odds of a mistake in the collecting and testing procedures can be much greater. This is an important distinction. An error as simple as mislabeling a sample can confuse the results.

Unfortunately, the odds of human error will vary and are difficult to determine.

3. In PCR, the product becomes another master copy. Imagine that while you are photocopying, every copy is used as a master at another copy machine. (This would require many copy machines.)

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4. Students might need a little more practice understanding the products of restriction enzymes.

Consider these two words, equilibrium and equalibrium. Imagine that a mutation produced the spelling error of the second word. If we used a “restriction enzyme” that splits these words between “u” and “i,” how will the fragments compare in size and number? equilibrium = equ ilibri um (three fragments of three, six, and two letters) equalibrium = equalibri um (two fragments of nine and two letters) 5. Separating marker ink using paper chromatography is a simple experiment that approximates some of what occurs in gel electrophoresis. Consider doing this as a class demonstration while addressing electrophoresis. Cut a large piece of filter paper into a rectangle or square. Use markers to color large dots about 2 cm away from the edge of the paper. Separate the dots from each other by 3–4 cm. Place the paper on edge, dots down, into a beaker containing about 1 cm of ethanol or isopropyl alcohol (50% or higher will do). The dots should not be in contact with the pool of alcohol in the bottom of the beaker.

As the alcohol is drawn up the filter paper by capillary action, the alcohol will dissolve the ink dots. As the alcohol continues up the paper, the ink follows. Not all of the ink components move at the same speed, based on their size and chemical properties. If you begin the process at the start of class, you should have some degree of separation by the end of a 50-minute period. Experiment with the technique a day or two before class to fine-tune the demonstration, and experiment with different types of ink. (Save and air-dry these samples for your class.) Consider using brown, green, and black markers, as these colors are often made by color combinations.

Genomics and Proteomics Student Misconceptions and Concerns 1. The text notes that there are 24 chromosomes in the human genome. Students might initially find this confusing, as it is common knowledge that humans have 23 pairs of chromosomes. Consider making the statement that we have 24 different types of chromosomes and asking your students to explain why this is true.

2. The similarities of the genotypes and phenotypes of members of a human family tree are expected and understood by most students. Yet, for many students, these same relationships are often poorly extrapolated to phylogenetic relationships of other groups.

The use of genomics to test phylogenetic relationships is an enormously powerful tool used in modern systematics. Genomics is a significant test of the other overwhelming types of evidence for evolution.

Teaching Tips 1. The first targets of genomics were prokaryotic pathogenic organisms. Consider asking your students in class to suggest why this was a good choice. Students may note that the genomes of these organisms are smaller than eukaryotes and that many of these organisms are of great medical significance.

2. The authors note that there are about 3 billion nucleotide pairs in the human genome.

There are about 3 billion seconds in about 95 years. This simple reference might add meaning to the significance of these large numbers.

3. The main U.S. Department of Energy Office website in support of the Human Genome Project is found at http://genomics.energy.gov.

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4. The website for the National Center for Biotechnology Information is www.ncbi.nlm.nih.gov/. The center, established in 1988, serves as a national resource for biomedical information related to genomic data.

5. Challenge students to explain why a complete understanding of an organism’s genome and the resulting proteins produced is still not enough to understand the full biology of an organism. Challenge them to consider the role of the environment in development and physiology. (One striking example of the influence of the environment is that the sex of some reptiles is determined not by genetics, but by incubation temperature!)

6. With a better understanding of the diverse and still unknown roles of many sections of DNA, consider discussing some of the difficulties of “resurrecting” extinct organisms from incomplete DNA sequences.

Human Gene Therapy Student Misconceptions and Concerns 1. Using gene therapy to “fix” genetic problems relies on a thorough understanding of the roles of genes and alleles. Students might benefit from a discussion of the extent to which we as a society might want to consider directing our own genetics.

Teaching Tips 1. Ethical, legal, and social issues related to the Human Genome Project are directly addressed at the Department of Energy Human Genome website at www.ornl.gov/sci/techresources/Human_Genome/elsi/elsi.shtml.

2. The Biology and Society end-of-chapter textbook questions address some of the issues raised in this chapter section.

Safety and Ethical Issues Student Misconceptions and Concerns 1. The many issues raised in this chapter are of great potential significance and remain unresolved. An informed debate about rights, responsibilities, and possibilities continues regarding these scientific issues.

The Genetic Information Nondiscrimination Act was passed in May 2008. Details about this important legislation can be found at www.ornl.gov/sci/techresources/Human_Genome/elsi/legislat.shtml.

Teaching Tips 1. Genetically engineered organisms are controversial, creating various degrees of concern; yet many debates around issues of science are confused by misinformation. This may be an opportunity for you to make an extra credit or regular assignment for students to take a position, on one side or the other, on some aspect of genetic engineering. The science would need to be accurate. Students might debate whether a food product made from GM/transgenic organisms should be labeled as such, or students can discuss the risks or advantages of producing GM organisms.

2. Consider a person who opposes GM food by stating “I do not want any DNA in my food.”

You might want to have your students respond to this person’s concerns.

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Key Terms biotechnology clone DNA ligase DNA profiling DNA technology forensics gel electrophoresis gene cloning genetic engineering

genetically modified (GM) organism genomic library genomics human gene therapy Human Genome Project nucleic acid probe plasmids

polymerase chain reaction (PCR) proteomics recombinant DNA repetitive DNA restriction enzymes restriction fragments restriction site

short tandem repeat (STR) STR analysis transgenic organism vaccine vectors whole-genome shotgun method

Word Roots bio = life (biotechnology: the manipulation of living organisms to perform useful tasks) liga = tied (DNA ligase: the enzyme that permanently “pastes” together NA fragments) trans = across; genic = producing (transgenic organism: an organism that contains genes from another organism)

Relevant Songs to Play in Class “Who Are You,” (aka theme to the TV show CSI), The Who

“Fingerprint File,” The Rolling Stones “Fuel,” Innocent

“Won’t Get Fooled,” Again (aka theme to the TV show CSI: Miami), The Who

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: The biochemist could start with DNA isolated from liver cells (the entire genome) and carry out the procedure outlined in Figure 12.8 to produce a collection of recombinant bacterial clones, each carrying a small piece of liver cell DNA. To find the clone with the desired gene, the biochemist could then make a probe of radioactive RNA with a nucleotide sequence complementary to part of the gene: GACCUGACUGU. This probe would bind to the gene, labeling it, and identifying the clone that carries it.

Alternatively, the biochemist could start with messenger RNA (mRNA) isolated from liver cells and use it as a template to make DNA (using reverse transcriptase). Cloning this DNA rather than the entire genome would yield a smaller library of genes to be screened— only those active in liver cells. Furthermore, the genes would lack introns, making the desired gene easier to manipulate after isolation.

12. Suggested answer: Determining the nucleotide sequences is just the first step. Once researchers have written out the DNA “book,” they will have to try to figure out what it means—what the nucleotide sequences code for and how they work. In addition, researchers will attempt to use this information to help identify alleles that cause specific disease and ultimately hope to be able to use this information to cure genetic diseases. Sequencing the human genome is the equivalent of generating a road map, but without any labels. Scientists still have to determine where genes are located and how they interact with each other—for instance, humans produce nearly 100,000 proteins but have approximately 21,000 genes. ..

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Biology and Society 13. Some issues and questions to consider: What kinds of impact will gene therapy have on the individuals who are treated? On society? Who will decide what patients and diseases will be treated? What costs will be involved, and who will pay them? How do we draw the line between treating disorders and “improving” the human species? If we can treat mental diseases such as schizophrenia, is it ethical to increase that person’s memory or alter eye color?

14. Some issues and questions to consider: What are some of the unknowns in recombinant DNA experiments? Do we know enough to anticipate and deal with possible unforeseen and negative consequences? Do we want this kind of power over evolution? Who should make these decisions? If scientists doing the research were to make the decisions about guidelines, what factors might shape their judgment? What might shape the judgment of business executives in the decision-making process? Does the public have a right to a voice in the direction of scientific research? Does the public know enough about biology to get involved in this decision-making process? Who represents “the public”? What are the possible benefits compared to the possible risks of recombinant DNA technology?

15. Some issues and questions to consider: Who made the decision about the safety of the corn?

Was it an individual or more than one person? Did these scientists analyze the safety data available? Is using the corn a better option than allowing people to die from starvation? Did the corn actually contain GM kernels (it is indicated that it was “likely”)? What might be the associated health risks and could they be as bad as dying from starvation?

16. Some issues and questions to consider: How often are these mistakes made? How many people are on death row who had a trial that lacked any DNA evidence at the time? Who should pay for the testing? Would you be willing to pay higher taxes to cover the cost of this expensive testing? If a person had been convicted in a trial using DNA evidence, should they get to appeal and have further testing done? The current number of states banning the death penalty can be found at www.deathpenaltyinfo.org/documents/FactSheet.pdf.

Additional Critical Thinking Questions The Process of Science 1. PCR is a technology that has many useful applications with biotechnology. What are some of those applications? What are the advantages of PCR over gene cloning for generating many copies of a DNA fragment?

Suggested answer: The polymerase chain reaction can be used in a variety of settings ranging from amplifying DNA from fossils, to forensics, to genetic testing. PCR requires only a very small amount of DNA as starting material and usually takes only a few hours.

Gene cloning requires larger amounts of DNA for successful transformation of bacterial cells and requires at least a day for growth of cell cultures.

2. Humans are almost identical in the protein-coding sections of the genome, yet each individual has a unique DNA profile. Explain how this is possible.

Suggested answer: Large portions of the human genome consist of noncoding DNA. The highly variable genomic regions analyzed for DNA profiling are located in these noncoding portions. Humans can still be very similar in their protein-coding regions.

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Biology and Society 3. Today, parents at risk of having children with a particular genetic disorder can make use of preimplantation genetic diagnosis. In this process, a number of embryos are produced by in vitro fertilization using the parents’ gametes, and a few cells are removed from each embryo for genetic testing. Those embryos that do not carry the disorder are selected for implantation, ensuring that children will be free of the disorder. What limits, if any, do you feel should be put on the use of this procedure?

Some issues and questions to consider: If embryos can be screened for specific genetic disorders, they can be screened for any specific genetic sequences. It is possible for embryos to be tested for genetic variations that are not detrimental to health, such as hair color or intelligence. Parents could select a preferred combination of traits in their potential offspring. Could this be a “slippery slope” to allowing engineering of traits not carried by the parents? What is to be done with the healthy embryos that are rejected?

Where would you draw the line on screening for embryos with certain combinations? Is it inevitable that in the near future people will screen their embryos?

4. The possibility of extensive genetic testing raises questions about how personal genetic information should be used. For example, should employers or potential employers have access to such information? Why or why not? Should the information be available to insurance companies? Why or why not? Is there any reason for the government to keep genetic files? Is there any obligation to warn relatives who might share a bad gene? Might some people avoid being tested for fear of being labeled genetic outcasts or for fear that they will not get or keep health insurance? Or might they be compelled to be tested against their wishes? Can you think of other reasons to proceed with caution?

Some issues and questions to consider: Should genetic testing be mandatory or voluntary?

Under what circumstances? Why might employers and insurance companies be interested in genetic data? Since genetic characteristics differ among ethnic groups and between the sexes, might such information be used to discriminate? Which of these questions do you think is most important? Which issues are likely to be the most serious in the future?

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CHAPTER

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How Populations Evolve

Why This Chapter Matters 1. Evolution integrates and informs all of biology.

2. Applications of evolutionary biology are transforming medicine, agriculture, biotechnology, and conservation biology.

3. Evolution helps us understand the historical context of life through common descent.

Chapter Objectives Biology and Society: Mosquitoes, Microbes, and Malaria 1. Explain how pesticide-resistant insect populations evolve.

2. Explain why an understanding of evolution is important.

Charles Darwin and The Origin of Species 3. Compare the ideas of Aristotle, Lamarck, Wallace, and Darwin on the ability of species to change.

4. Explain how Darwin’s voyages on the Beagle influenced the development of his thoughts on evolution.

5. Explain how Lyell’s ideas impacted Darwin’s thinking.

6. Describe the circumstances that led to the presentation of Darwin’s and Wallace’s ideas in 1858 and the publication of Darwin’s work, The Origin of Species.

7. Describe Darwin’s two main points in The Origin of Species.

Evidence of Evolution 8. Explain how each of the following provides evidence that evolution occurs: the fossil record, biogeography, comparative anatomy, comparative embryology, and molecular biology.

Natural Selection 9. Describe Darwin’s two main observations that led to the concept of natural selection.

10. Explain how natural selection is more a process of editing than a creative mechanism.

11. Explain how evolutionary trees are constructed and what they represent.

The Modern Synthesis: Darwinism Meets Genetics 12. Explain what is meant by the phrases “modern synthesis” and “population genetics.”

Further, define a population, describe its properties, and explain why a population is the smallest unit of evolution.

13. Explain the relative importance of mutation and sexual reproduction in the evolution of life.

14. Explain how the Hardy-Weinberg formula can be used to determine the frequency of genotypes in a gene pool. Explain why this formula is a model for genetic equilibrium.

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Mechanisms of Evolution 15. Distinguish between the following concepts: genetic drift versus gene flow; the founder effect versus bottleneck effect; directional selection, disruptive selection, and stabilizing selection; and sexual selection and natural selection.

Evolution Connection: An Evolutionary Response to Malaria 16. Explain how humans have evolved in response to malaria.

Lecture Outline I. Biology and Society: Mosquitoes, Microbes, and Malaria 1. In the 1960s, the World Health Organization (WHO) launched a campaign to eradicate the mosquitoes that transmit malaria.

2. It used DDT, to which some mosquitoes have evolved resistance.

3. The evolution of pesticide-resistant insects is just one of the ways that evolution affects our lives.

4. An understanding of evolution informs every field of biology, for example, a. medicine, b. agriculture, c. biotechnology, and d. conservation biology.

II. Charles Darwin and The Origin of Species 1. Biology came of age on November 24, 1859. Charles Darwin published On the Origin of Species by Means of Natural Selection, an assemblage of facts about the natural world.

2. Darwin made three observations from these facts. a. Life shows rich diversity. b. There are similarities in life that allow the classification of organisms into groups nested within broader groups. c. Organisms display many striking ways in which they are suited for their environments.

3. In The Origin of Species, Darwin a. proposed a hypothesis, a scientific explanation for his observations, b. used hundreds of pages in his book to describe the evidence supporting his hypothesis, c. made testable PREDICTIONS, and d. reported the results of numerous experiments he had performed.

4. Darwin hypothesized that a. present-day species are the descendants of ancient ancestors that they still resemble in some ways and b. change occurs as a result of “descent with modification,” with natural selection as the mechanism.

5. Natural selection is a process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are individuals with other characteristics.

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6. As a result of natural selection, a population, a group of individuals of the same species living in the same place at the same time, changes over generations.

7. Natural selection leads to evolutionary adaptation, a population’s increase in the frequency of traits suited to the environment.

8. Natural selection thus leads to evolution, seen either as a. a change in the genetic composition of a population over time or b. on a grander scale, the entire biological history, from the earliest microbes to the enormous diversity of organisms that live on Earth today.

9. Natural selection leads to a. a population (a group of individuals of the same species living in the same place at the same time) changing over generations and b. evolutionary adaptation.

10. In one modern definition of evolution, the genetic composition of a population changes over time.

A. Darwin’s Cultural and Scientific Context 1. The Origin of Species was fundamentally different from the prevailing scientific and cultural views of Darwin’s time.

2. Let’s place Darwin’s ideas in their historical context.

B. The Idea of Fixed Species 1. The Greek philosopher Aristotle held the belief that species are fixed and do not evolve.

2. The Judeo-Christian culture fortified this idea with a. a literal interpretation of the biblical book of Genesis and b. the suggestion that Earth may only be 6,000 years old.

3. At the same time, naturalists were grappling with the interpretation of fossils, imprints or remains of organisms that lived in the past.

4. Lamarck and Evolutionary Adaptations 5. Naturalists compared fossil forms with living species and noted patterns of similarities and differences.

6. In the early 1800s, French naturalist Jean Baptiste Lamarck suggested that life evolves and explained this evolution as the refinement of traits that equip organisms to perform successfully in their environment.

7. Lamarck suggested a mechanism that we now know is wrong.

8. Lamarck proposed that by using or not using its body parts, an individual may develop certain TRAITS that it passes on to its offspring, thus, acquired traits are inherited.

9. Lamarck helped set the stage for Darwin by proposing that species evolve as a result of interactions between organisms and their environment.

10. The Voyage of the Beagle 11. Darwin was born on February 12, 1809, the same day that Abraham Lincoln was born.

12. In December 1831, Darwin left Great Britain on the HMS Beagle on a five-year voyage around the world.

13. On his journey on the Beagle, Darwin a. collected thousands of specimens and b. observed various adaptations in organisms.

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14. Darwin was intrigued by a. the geographic distribution of organisms on the Galápagos Islands and b. similarities between organisms in the Galápagos and those in South America.

15. Darwin was strongly influenced by the writings of geologist Charles Lyell.

16. Lyell suggested that Earth a. is very old and b. was sculpted by gradual geological processes that continue today.

17. Darwin reasoned that the extended time scale would allow for gradual changes to occur a. in species and b. in geologic features.

C. Descent with Modification 1. Darwin made two main points in The Origin of Species. a. Organisms inhabiting Earth today descended from ancestral species. b. Natural selection is the mechanism for descent with modification.

D. Evidence of Evolution 1. Evolution leaves observable signs.

2. We will examine five of the many lines of evidence in support of evolution: a. the fossil record, b. biogeography, c. comparative anatomy, d. comparative embryology, and e. molecular biology.

E. The Fossil Record 1. Fossils are a. imprints or remains of organisms that lived in the past b. often found in sedimentary rocks.

2. The fossil record a. is the ordered sequence of fossils as they appear in rock layers, b. reveals the appearance of organisms in a historical sequence, and c. fits with the molecular and cellular evidence that prokaryotes are the ancestors of all life.

3. Paleontologists (scientists who study fossils) have discovered many transitional forms that link past and present.

4. Transitional fossils include evidence that a. birds descended from one branch of dinosaurs and b. whales descended from four-legged land mammals.

F. Biogeography 1. Biogeography, the study of the geographic distribution of species, first suggested to Darwin that today’s organisms evolved from ancestral forms.

2. Darwin noted that Galápagos animals resembled species of the South American mainland more than they resembled animals on similar but distant islands.

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3. Many examples from biogeography would be difficult to understand, except from an evolutionary perspective.

4. One example is the distribution of marsupial mammals in Australia.

G. Comparative Anatomy 1. Comparative anatomy a. is the comparison of body structure between different species and b. attests that evolution is a remodeling process in which ancestral structures become modified as they take on new functions.

2. Homology is a. the similarity in structures due to common ancestry and b. illustrated by the remodeling of the pattern of bones forming the forelimbs of mammals for different functions.

3. Vestigial structures a. are remnants of features that served important functions in an organism’s ancestors and b. now have only marginal, if any, importance.

H. Comparative Embryology 1. Early stages of development in different animal species reveal additional homologous relationships. a. For example, pharyngeal pouches appear on the side of the embryo’s throat, which i. develop into gill structures in fish and ii. form parts of the ear and throat in humans. b. Comparative embryology of vertebrates supports evolutionary theory.

I. Molecular Biology 1. The hereditary background of an organism is documented in a. its DNA and b. the proteins encoded by the DNA. 2. Evolutionary relationships among species can be determined by comparing a. genes and b. proteins of different organisms.

III. Natural Selection 1. Darwin noted the close relationship between adaptation to the environment and the origin of new species.

2. The evolution of finches on the Galápagos Islands is an excellent example.

3. Darwin’s Theory of Natural Selection 4. Darwin based his theory of natural selection on two key observations. a. All species tend to produce excessive numbers of offspring. b. Organisms vary, and much of this variation is heritable.

5. Observation 1: Overproduction and competition a. All species have the potential to produce many more offspring than the environment can support. b. This leads to inevitable competition among individuals.

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6. Observation 2: Individual variation a. Variation exists among individuals in a population. b. Much of this variation is heritable.

7. Inference: Unequal reproductive success (natural selection) a. Those individuals with traits best suited to the local environment generally leave a larger share of surviving, fertile offspring.

A. Natural Selection in Action 1. Examples of natural selection include a. pesticide-resistant insects, b. antibiotic-resistant bacteria, and c. drug-resistant strains of HIV. B. The Process of Science: Does Predation Drive the Evolution of Lizard Horn Length?

1. Observation: Flat-tailed horned lizards defend against attack by a. thrusting their heads backward and b. stabbing a shrike with the spiked horns on the rear of their skull.

2. Question: Are longer horn length and spread a survival advantage?

3. Hypothesis: Longer horn length and spread are a survival advantage.

4. Prediction: Live horned lizards have longer and more widely spread horns than dead ones.

5. Experiment: Measure the horn lengths and the tip-to-tip spread distance of side horns from the skulls of a. 29 killed and b. 155 living lizards.

6. Results: The average horn length and spread of live lizards is about 10% greater than that of killed lizards.

C. Evolutionary Trees 1. Darwin saw the history of life as analogous to a tree. a. The first forms of life on Earth form the common trunk. b. At each fork is the last common ancestor to all the branches extending from that fork. c. The tips of millions of twigs represent the species living today.

IV. The Modern Synthesis: Darwinism Meets Genetics 1. The modern synthesis is the fusion of a. genetics with b. evolutionary biology.

A. Populations as the Units of Evolution 1. A population is a. a group of individuals of the same species, living in the same place at the same time and b. the smallest biological unit that can evolve.

2. The total collection of alleles in a population at any one time is the gene pool.

3. When the relative frequency of alleles changes over a number of generations, evolution is occurring on its smallest scale.

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B. Genetic Variation in Populations 1. Individual variation abounds in all species. a. Not all variation in a population is heritable. b. Only the genetic component of variation is relevant to natural selection.

2. Variable traits in a population may be a. polygenic, resulting from the combined effects of several genes, or b. determined by a single gene.

3. Polygenic traits tend to produce phenotypes that vary more or less continuously.

4. Single-gene traits tend to produce only a few distinct phenotypes.

C. Sources of Genetic Variation 1. Genetic variation results from processes that both involve randomness: a. mutations, changes in the nucleotide sequence of DNA, and b. sexual recombination, the shuffling of alleles during meiosis.

2. For any given gene locus, mutation alone has little effect on a large population in a single generation.

3. Organisms with very short generation spans, such as bacteria, can evolve rapidly with mutation as the only source of genetic variation.

D. Analyzing Gene Pools 1. A gene pool a. consists of all the alleles in a population at any one time and b. is a reservoir from which the next generation draws its alleles.

2. Alleles in a gene pool occur in certain frequencies.

3. Alleles can be symbolized by a. p for the relative frequency of the dominant allele in the population, b. q for the frequency of the recessive allele in the population, and c. p + q = 1.

4. Note that if we know the frequency of either allele in the gene pool, we can subtract it from 1 to calculate the frequency of the other allele.

5. Genotype frequencies can be calculated from allele frequencies (if the gene pool is stable = not evolving).

6. The Hardy-Weinberg formula a. p2 + 2pq + q2 = 1 b. can be used to calculate the frequencies of genotypes in a gene pool from the frequencies of alleles.

E. Population Genetics and Health Science 1. The Hardy-Weinberg formula can be used to calculate the percentage of a human population that carries the allele for a particular inherited disease.

2. PKU a. is a recessive allele that prevents the breakdown of the amino acid phenylalanine and b. occurs in about one out of every 10,000 babies born in the United States.

3. People with PKU must strictly regulate their dietary intake of the amino acid phenylalanine.

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F. Microevolution as Change in a Gene Pool 1. How can we tell if a population is evolving?

2. A non-evolving population is in genetic equilibrium, a. called the Hardy-Weinberg equilibrium, meaning the population’s gene pool is constant over time.

3. From a genetic perspective, evolution can be defined as a generation-to-generation change in a population’s frequencies of alleles, sometimes called microevolution.

G. Mechanisms of Evolution 1. The main causes of evolutionary change are a. genetic drift, b. gene flow, and c. natural selection.

2. Natural selection is the most important, because it is the only process that promotes adaptation.

H. Genetic Drift 1. Genetic drift is a change in the gene pool of a small population due to chance.

I. The Bottleneck Effect 1. The bottleneck effect a. is an example of genetic drift and b. results from a drastic reduction in population size.

2. Passing through a “bottleneck,” a severe reduction in population size, a. decreases the overall genetic variability in a population because at least some alleles are lost from the gene pool, and b. results in a loss of individual variation and hence adaptability.

3. Cheetahs appear to have experienced at least two genetic bottlenecks: a. during the last ice age, about 10,000 years ago, and b. during the 1800s, when farmers hunted the animals to near extinction.

4. With so little variability, cheetahs today have a reduced capacity to adapt to environmental challenges.

J. The Founder Effect 1. The founder effect is likely when a few individuals colonize an isolated habitat.

2. This represents genetic drift in a new colony.

3. The founder effect explains the relatively high frequency of certain inherited disorders in some small human populations.

K. Gene Flow 1. Gene flow a. is another source of evolutionary change, b. is separate from genetic drift, c. is genetic exchange with another population, d. may result in the gain or loss of alleles, and e. tends to reduce genetic differences between populations.

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L. Natural Selection: A Closer Look 1. Of all causes of microevolution, only natural selection promotes adaptation.

2. Evolutionary adaptation results from a. chance, in the random generation of genetic variability, and b. sorting, in the unequal reproductive success among the varying individuals.

M. Darwinian Fitness 1. Relative fitness is a. the contribution an individual makes to the gene pool of the next generation b. relative to the contributions of other individuals.

N. Three General Outcomes of Natural Selection 1. If we graph the coat color of a population of mice, we get a bell-shaped curve.

2. If natural selection favors certain fur-color phenotypes, a. the populations of mice will change over the generations and b. three general outcomes are possible.

3. Directional selection shifts the overall makeup of a population by selecting in favor of one extreme phenotype.

4. Disruptive selection can lead to a balance between two or more contrasting phenotypic forms in a population.

5. Stabilizing selection favors intermediate phenotypes, occurs in relatively stable environments, and is the most common.

O. Sexual Selection 1. Sexual selection is a form of natural selection in which individuals with certain traits are more likely than other individuals to obtain mates.

2. Sexual dimorphism is a distinction in appearance between males and females not directly associated with reproduction or survival.

P. Evolution Connection: An Evolutionary Response to Malaria 1. We can see the results of past natural selection in present-day humans.

2. Malaria first emerged as a serious threat to people in Africa just 10,000 years ago, a. long after humans had established populations around the globe, b. therefore only producing evolutionary responses in malarial regions.

3. Sickle hemoglobin a. is a mutation that denies the malarial parasite essential access to human hemoglobin and b. distorts the shape of red blood cells.

4. Individuals with one copy of this sickle allele (heterozygotes) are relatively resistant to malaria. a. Individuals with two copies (homozygotes) are usually fatally ill.

5. In the African tropics, a. malaria is most common and b. the frequency of the sickle-cell allele is highest.

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Chapter Guide to Teaching Resources Charles Darwin and The Origin of Species Student Misconceptions and Concerns 1. Students often believe that Charles Darwin first suggested that life evolves: The early contributions by Greek philosophers (such as Anaximander) and the work of Jean Baptiste Lamarck remain unappreciated. Consider emphasizing this earlier work.

2. Students often misunderstand the basic process of evolution and instead express a Lamarckian point of view. Species do not evolve because of need. Biological diversity exists, and the environment selects. Students must understand that the environment does the selecting (editing) in natural selection. Evolution is not deliberate, it is reactive. As teachers, we must be careful in how we express evolution to best reflect this process. For example, the statement “Birds evolved wings” may make it sound as if birds did something deliberately. “Wings evolved in birds” is more accurate, in that something happened to birds through a process. This use of the passive voice in our descriptions of evolution better reflects the nature of evolution.

3. Students often think that the application of pesticides or presence of antibiotics somehow causes the changes necessary for members of a species to survive, again reflecting a Lamarckian point of view. It is important to point out to students that selection simply favors traits already present. The short phrase, “first diversity, then selection,” can help students remember this important point.

4. Students often think of evolution as a process that improves. However, an adaptation in one context might be a handicap in another. Bats are not better animals than sharks. Neither could survive long in the other’s environment. Instead, the adaptations found in bats best reflect their terrestrial environment, distinct from the aquatic lifestyle and adaptations of sharks.

5. Evolution also does not produce perfection. Despite often heard statements about “perfectly adapted” organisms, perfection is not possible for many reasons: (a) Adaptations occur together within organisms, often with competing advantages— hearing and chewing, for example, are often in conflict in mammals; (b) Biological materials are limited—turtles do not have titanium shells; and (c) Adaptations arise by remodeling ancestral plans, not de novo in an ideal world. Much like renovating a home, the new structure will be limited by the design of the original home.

6. Students might become confused by some scientific debates. Evolution can be considered on three levels, sometimes referred to as (a) fact, (b) course, and (c) mechanism: (a) Does evolution occur? (b) Who gave rise to whom? and (c) Is natural selection the only mechanism of evolution that produces adaptations? Students who listen to scientific debates about the course of evolution might think that evolution itself is under attack.

Doubts about ancestry can be misconstrued as doubts about evolution itself. Consider sharing these distinctions with your class.

Teaching Tips 1. Consider beginning your unit on evolution by asking each student to explain how a particular adaptation evolved. The evolution of flight in birds is a good example.

Reviewing these student explanations can provide great insight into the misconceptions that students may bring to the class.

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2. Many resources related to Charles Darwin are available on the Internet. The following are only a few examples: www.ucmp.berkeley.edu/history/evolution.html and ncse.com are extensive sites rich with details and references. www.literature.org/authors/darwin-charles/ includes the texts of The Voyage of the Beagle, The Origin of Species first and sixth editions, and The Descent of Man. http://williamcalvin.com/bookshelf/down_hse.htm includes details of Charles Darwin’s home.

3. Consider asking your students to consider “Can individuals evolve?” Sometimes such simple questions require complex answers. Might Lamarck have answered this question differently than Darwin?

Evidence of Evolution Student Misconceptions and Concerns 1. Students who struggle with the concept of evolution may also bring personal objections to the classroom. Distinguishing between the processes of science and the use of supernatural forces in explanations helps distinguish between scientific explanations and those that are not scientific. The evidence of evolution permits a demonstration of the scientific method, in which confidence in our conclusions increases based on multiple, independent lines of evidence. Science requires evidence and cannot rely upon faith or supernatural explanations.

2. Students might expect that every living organism will leave fossils and that we should be able to find them. Furthermore, they might falsely conclude that the absence of evidence is evidence of absence. Understanding the rare circumstances under which fossils form (the scientific study of fossil formation is referred to as taphonomy), the geological processes that distort and destroy layers (for example, earthquakes and glaciers), and the long odds against the discovery of fossils, help students understand why the fossil record is limited.

3. The experiences of beginning college students with the subject of fossils are likely to be uneven and weak. For example, the many ways that fossil ages are determined also demonstrates the strength of independent lines of evidence and consistency. Here is a chance to describe the many ways that a fossil’s age can be determined (for example, radiometric dating, association with other fossils of known age in the same layer, correlation to other strata of known ages).

Teaching Tips 1. If you have any sort of a fossil, it makes a nice visual aid (of course, the larger the better).

Many shops in natural history museums carry large and common fossils that can be purchased for less than $50.00. Crinoid stems or other marine fossils from the Midwest are the types of fossils that make the point that life and ecosystems change over time.

Selecting fossils that are common in your region may stimulate students to search for their own.

2. The sequence, but not absolute ages, is revealed by the stratifications in sedimentary rocks.

This is like peeling the layers of wallpaper from the walls of a very old house that has been inhabited by many owners. By the sequence, we can tell which layers are older, but not the absolute ages of each layer.

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3. Another popular example of biogeography is the distribution of lungfish in Australia, southern South America, and southern Africa. At one time, these three continents were united as Gondwana.

4. One striking example of evolutionary remodeling is the shell of turtles, primarily made from vertebrae and modified ribs. If you find an old turtle shell and soak it in water, the shell may come apart with some effort, leaving isolated ribs that make interesting visual aids.

5. The evolution of the three inner ear bones in mammals, the malleus and incus joining the stapes (already present as the columella in reptiles), is another wonderful transitional sequence in the fossil record.

6. Building on the earlier point about the evolution of the middle ear bones from the lower jaw of reptiles, consider the conflicting problems of hearing while chewing. Ask your students to consider the problems of chewing carrots and listening to a lecture. The mammalian hearing apparatus clearly conflicts with the crunching noises of chewing, one of the costs of remodeling. Adaptations typically represent a compromise of functions and not perfection.

7. You can have some fun with this analogy to molecular evidence for evolution. As teachers, we have to be keenly aware of cheating. Certainly, if two students turn in written assignments that differ by just a few words, we would conclude that they had a “common heritage” or that one was derived from the other.

Natural Selection Student Misconceptions and Concerns 1. Students must understand that the environment does the selecting (editing) in natural selection. Species do not evolve because of want or need. Biological diversity exists and the environment selects. Evolution is not deliberate, it is reactive.

2. A related point is what we learn from extinction. As Darwin noted, species become extinct because they do not get what they want or need!

3. The authors note that evolution is not goal directed and does not lead to perfectly adapted organisms. These excellent points represent two misunderstandings: (a) Instructors need to be clear that evolutionary change is a consequence of an immediate advantage, not a distant goal. Three-chambered hearts in amphibians evolved from two-chambered fish hearts because the three-chambered hearts conveyed an advantage, not because evolution was directed toward producing a four-chambered heart! (b) Evolutionary change only reflects “improvement” in the context of the immediate environment. What is better “today” may not be better “tomorrow.” Thus, species do not steadily get “better,” they respond to the environment or go extinct.

4. Students require practice with evolutionary trees to understand their meaning. For example, students may struggle to see the relationships as a family tree, or understand how time is represented.

Teaching Tips 1. An analogy might be made between the specialized functions of finch beaks and the many types of screwdrivers that exist today. Each type of screwdriver (Phillips, flathead, longhandled, interchangeable tips) represents a specialization for a particular job.

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2. Based on the human condition, students are likely to think that reproduction is largely a choice, and less a consequence of good health or other adaptations. Yet, in our natural world, there are thousands of examples of the overproduction of offspring and resulting death or failure to reproduce. Thousands of acorns hanging from one tree, millions of spores escaping from a puffball, or a salmon spawning thousands of eggs, are all easy examples of overproduction. Provide a few solid illustrations from your geographic region to bring home this point.

3. Challenge students to explain whether the evolutionary tree in Figure 13.17 would be different if the group of “Ostriches” and “Hawks” was reversed, such that the “Hawk” group would be positioned closer to “crocodiles.” It would not.

4. Consider pointing out that evolutionary trees are testable hypotheses about evolutionary relationships.

The Modern Synthesis: Darwinism Meets Genetics Student Misconceptions and Concerns 1. Students may suggest that individuals evolve. As this chapter section clarifies, populations are the smallest units that can evolve. Individuals cannot have diversity from which to select. However, individuals can change during their lifetime in response to activities.

Muscles can grow stronger because of use. However, these individual changes are not passed on to the next generation (after all, boys have been circumcised for thousands of years but are still born with a foreskin).

2. Another misperception is that evolution results from need. Challenge your students to explain how “need” and “want” have nothing to do with evolution (because neither “need” nor “want” can generate genetic variation!).

3. Students may think of mutations in a positive sense, as if they come as needed; yet mutations in key genes are the cause of cancer and other diseases. Only rarely does a mutation lead to a change that increases the chances for survival. However, these rare events can become significant if given enough time. (As the authors note: A random mutation is like a shot in the dark; it is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance.)

Teaching Tips 1. It might be interesting to discuss with students whether the Internet would have helped Mendel and Darwin. Is the Internet facilitating scientific communication? Has this technology created new problems in the process?

2. Try to find good, local examples of populations. If you live near a seashore, the many invertebrate populations (starfish, sea urchin, and kelp) would be great. Further inland we find somewhat isolated populations of fish and continuous and clumped populations of squirrels, separated by vast fields of corn, wheat, or soybeans! Bring the subject home with local examples.

3. No doubt about it, the Hardy-Weinberg equation is problematic for some students.

Students should create a quick reference key to the definitions of the elements. Consider some practice problems varying the value of p and q.

4. Heterozygotes can form in two ways, the recessive from mom, the dominant from dad—or the reverse. This should serve to remind students that the 2pq portion of the equation represents the heterozygotes. ..

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5. Another example that can be used for Hardy-Weinberg practice is cystic fibrosis. Cystic fibrosis strikes about one out of every 3,300 Caucasian children. It results from the homozygous recessive condition. Thus, q2 would equal 1/3,300 = 0.000303 and q = the square root of 0.000303 = 0.0174. The frequency of carriers = 2pq = 2 × 0.0174 × 0.9826 = 0.0342 = 3.42%, about one in every 29 Caucasian people. (Source of information is Fertil. Steril. 2006 Jan 85(1): 135–8.)

Mechanisms of Evolution Student Misconceptions and Concerns 1. The concept of a genetic bottleneck contributing to a loss of diversity can be difficult for some students to understand. Without an appreciation for population genetics, students might think that a recovery in sheer numbers of individuals is all that is needed; yet the loss of genetic diversity might doom a population eventually faced with widespread disease.

2. Sampling error can be difficult for some students to immediately understand. Have students work in pairs to flip a penny 10 times. For each pair, list the number of heads on the board as just a long list of numbers (no need to keep track of heads and tails). This can be done quickly as long as you have been sure to bring enough pennies. Now analyze the results. There should be considerable variation from the expected five. Now determine the average of all the groups, and the collective sample size. By pooling the results, and increasing the sample size, the means should be closer to five.

Teaching Tips 1. The loss of genetic diversity in a population because of the bottleneck effect is a significant problem in conservation. When a species is reduced to relatively few individuals, and then is brought back to abundance by extraordinary efforts, the species is not fully recovered. The lost genetic diversity may be a prerequisite for the long-term survival of the species. Consider challenging your students to identify modern endangered species that might suffer from a genetic bottleneck despite increasing numbers.

2. Students might best relate to the bias of the founder effect by this example. Just for the sake of explanation, consider that you and all the students present in today’s class are the only survivors of some global catastrophe. Would your class adequately represent the biological diversity of the current human population?

3. Challenge your students to explain why evolution primarily addresses only organisms that reproduce. Like people who vote, reproduction contributes to change. Moreover, like nonvoters who influence opinions of voters, nonreproducing organisms can still influence the actions of those who do reproduce. Challenge your students to suggest how organisms that do not reproduce might influence the evolution of a species. (One such example is the benefit of a sibling helping to raise its nieces/nephews.)

4. Students are often surprised to learn that overweight human newborns can be as unhealthy as underweight newborns. Thus, stabilizing selection favors human birth weights clustered narrowly around a mean weight.

5. Consider challenging your students to distinguish between natural selection generally, sexual selection specifically, and artificial selection. One criterion for comparison is the nature of the selective environment. In natural selection, the interaction is between the organism and its immediate environment. In sexual selection, competition occurs within a species for access to mates. In artificial selection, humans act as the environment, favoring traits of human interest.

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6. At the conclusion of this chapter information, it might be a good time to remind your students that most species that have ever lived are now extinct. Species do not have a mechanism to get what they need to survive. The natural variation inherited from the immediate ancestors and the new variations that emerge from mutations and genetic combinations are the raw materials for survival. No amount of need can influence the variety upon which selection must act. It is, therefore, quite possible that the variety in any generation is insufficient for survival, especially during periods of relatively fast environmental change.

7. Finally, you might share with your students that we are all the product of an unbroken lineage of ancestors who beat the odds and reproduced successfully, producing fertile offspring. Each of our family histories, going back hundreds of millions of years to the first animals, is one amazing “winning streak”!

Key Terms biogeography evolutionary tree bottleneck effect fossil record comparative anatomy fossils directional selection founder effect disruptive selection gene flow evolution gene pool evolutionary adaptation genetic drift

Hardy-Weinberg equilibrium homology microevolution modern synthesis natural selection population

relative fitness sexual selection sexual dimorphism stabilizing selection vestigial structures

Word Roots bio = life; geo = the earth (biogeography: the geographic distribution of species) di = separate; morph = form (dimorphism: a distinction in appearance based on secondary sexual characteristics) homo = alike (homology: traits that appear similar due to common ancestry) micro = small (microevolution: evolution at its smallest scale) vestigi = trace (vestigial: historical remnants of structures that had important functions in ancestors)

Relevant Songs to Play in Class “Do the Evolution,” Pearl Jam

“Darwin,” Third Eye Blind

“Walk the Dinosaur,” Was (Not Was)

Answers to End-of-Chapter Questions The Process of Science 12. Suggested answer: The unstriped snails appear to be better adapted. Striped snails make up 47% of the living population but 56% of the broken shells. Assuming all the broken shells result from the meals of birds, we would predict that bird predation would reduce the frequency of striped snails, and the frequency of unstriped individuals would increase.

13. Suggested answer: Using the Hardy-Weinberg principles, the frequency of the dominant allele is 0.527 and the frequency of the recessive allele is 0.473. The genotypic frequency of heterozygotes would be 0.499.

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Biology and Society 14. Some issues and questions to consider: Human advances in medicine, shelter, and food production enable the survival of members of the population that might be weak or have traits not conducive to survival under primitive conditions. Therefore, they are able to reproduce in some cases, keeping deleterious or less “fit” genes in the gene pool. In addition, humans have the ability to test embryos for certain traits and abort embryos that have “undesirable” traits. What are the pros and cons of this ability? Who has the right to decide who is genetically “fit” and who is not?

Additional Critical Thinking Questions The Process of Science 1. Why is the fossil record said to be incomplete? What organisms might be most underrepresented in the fossil record? Why? Suggested answer: Only those organisms that die in an environment that is favorable for fossil formation (for example, an aquatic environment that is quickly covered by sediment at the bottom) will be in the fossil record, whereas other organisms will be absent. Softbodied, terrestrial organisms (lacking bones, cartilage, or cellulose material) will be most underrepresented in the fossil record.

2. It has been noted that with the ability to clone animals, such as endangered species, their population numbers can be increased in a short time. How would this impact these populations from the perspective of the gene pool?

Suggested answer: Cloning would create an artificial bottleneck similar to natural bottlenecks that have occurred in nature (for example, in the cheetah population). Genetic variability would be very low so the gene pool would not contain many variations of different traits. Also, sexual reproduction with genetically similar organisms would not significantly increase variability.

3. Use some of the principles of evolutionary theory from this chapter to explain how the overuse of antibiotics has altered the course of evolution for bacteria that have evolved antibiotic resistance.

Suggested answer: Antibiotic resistance evolved in bacteria as the result of spontaneous mutations at a low frequency. In nature, this enables them to survive in the presence of antibiotics that would normally kill the bacteria. If those antibiotics are not present, then the percentage of antibiotic-resistant bacteria does not increase because there is not a selective advantage to this trait under these conditions. However, when an antibiotic is overused, it destroys the nonresistant bacteria, leaving the resistant population to multiply and reproduce. Under these selective pressures, the resistance trait in the population increases very quickly.

Biology and Society 4. School districts in several states have been criticized by groups demanding that science classes give “equal time” to nonscientific explanations of the origin and history of life.

They argue that it is only fair to let students hear all sides of the debate. Do you think nonscientific views about the origin of species should receive the same emphasis as evolution in science courses? Why or why not?

Some issues and questions to consider: Who should decide the curriculum, “experts” or members of the community? Are the two alternatives both scientific ideas? Who judges what is scientific? If it is fairer to consider alternatives, should the door be open to all 182

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alternatives? Are constitutional issues (separation of church and state) involved here? Can a teacher be compelled to teach an idea he or she thinks is wrong? Should a student be required to learn an idea he or she thinks is wrong? What does it mean to be scientific?

Should nonscientific ideas be taught in a science class? Should science be open to all explanations? Are certain interest groups attempting to redefine what it means to be scientific by teaching nonscientific alternatives?

5. Each of us tends to have a preconceived notion concerning the theory of evolution. These preconceived notions tend to be the result of years of various influences. Has any of the information presented in this chapter changed your perception of the theory of evolution?

If so, how have your views been altered?

Some issues and questions to consider: Does having the proper scientific “facts” provide any clarity on the theory of evolution? Does any of the presented information explain something that you have observed in real life (such as antibiotic-resistant bacteria)? Is it possible to assimilate parts of this theory into your current beliefs?

6. Recent advances in molecular techniques have allowed scientists to successfully extract proteins and DNA fragments from extinct animals found in museum collections or the recent fossil record. In the near future, it may be possible to clone previously extinct organisms such as the dodo, great auk, passenger pigeon, or maybe even mammoths. What are your opinions on cloning extinct species?

Some issues and questions to consider: Is it ethical to clone an extinct species? Is it worth the time, money, and resources? What if the species went extinct due to people’s activities, such as occurred with the dodo or passenger pigeon? What about animals that went extinct naturally, such as mastodons? Could the reintroduction of extinct animals have an impact on today’s ecosystems?

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CHAPTER

14

How Biological Diversity Evolves

Why This Chapter Matters 1. Recognizing the types of life on Earth and relationships between them helps us understand the similarities and differences of organisms.

2. Life on Earth has a long and dynamic history. Understanding how Earth has changed helps us understand the processes occurring on Earth today.

Chapter Objectives Biology and Society: The Sixth Mass Extinction 1. Explain why scientists think we may be at the start of the sixth mass extinction in the last 540 million years.

The Origin of Species 2. Define speciation and the biological species concept. Explain its limitations when applied to all types of living organisms.

3. Describe examples of prezygotic and postzygotic reproductive barriers.

4. Distinguish between allopatric and sympatric speciation, noting examples of each.

5. Compare the punctuated equilibria model to the graduated model of evolution. Relate a “sudden” geologic appearance to our “human” sense of time.

The Evolution of Biological Novelty 6. Distinguish between microevolution and macroevolution.

7. Explain the concept of exaptations and describe an example.

8. Explain how duplications and mutations of homeotic genes can result in major evolutionary change.

9. Explain how paedomorphosis contributes to speciation. Describe some of the paedomorphic traits of humans.

Earth History and Macroevolution 10. List, in order, the four broad divisions in the history of Earth and its life. Explain how the boundaries of each division are defined.

11. Explain how analyzing sedimentary rock layers and radiometric dating help us understand the fossil history of life on Earth.

12. Explain how the formation and breakup of the supercontinent Pangaea affected the evolution of life on Earth.

13. Explain how an extraterrestrial object could have caused the mass extinction around 65 million years ago. Explain how mass extinctions can be seen as times of great opportunity.

Classifying the Diversity of Life 14. Define and distinguish between taxonomy and systematics. Explain how the binomial system is used to identify species. Finally, list the levels of taxonomic groups in order, beginning with species and ending at domain. ..

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15. Explain and interpret the relationships indicated in phylogenetic trees.

16. Explain how homologies are used to create classification systems. Distinguish between homologous and analogous structures. Explain how convergent evolution can make interpreting homologies difficult.

17. Define cladistics and describe how it is used to create classification systems.

18. Distinguish between the two-kingdom, five-kingdom, and three-domain systems of classification. Explain why classification systems are revised.

Evolution Connection: Rise of the Mammals 19. Explain how the extinction of most of the dinosaurs affected mammalian evolution.

Lecture Outline I. Biology and Society: The Sixth Mass Extinction 1. Over the past 540 million years, the fossil record reveals five periods of extinction when 50–90% of living species suddenly died out.

2. Our current rate of extinction, over the past 400 years, indicates that we may be living in, and contributing to, the sixth mass extinction period.

3. Mass extinctions pave the way for the evolution of new and diverse forms, but it takes millions of years for Earth to recover.

II. The Origin of Species 1. When Darwin visited the Galápagos Islands, he realized that he was visiting a place of origins. a. Although the volcanic islands were geologically young, they were home to many plants and animals known nowhere else in the world. b. Darwin thought it unlikely that all of these species could have been among the original colonists of the islands.

2. In the 150 years since the publication of Darwin’s book On the Origin of Species by Means of Natural Selection, new discoveries and technological advances have given scientists a wealth of new information about the evolution of life.

3. The diversity of life evolved through speciation, the process in which one species splits into two or more species.

A. What Is a Species?

1. Species is a Latin word meaning a. “kind” or b. “appearance.”

2. The biological species concept defines a species as “A group of populations whose members have the potential to interbreed with one another in nature to produce fertile offspring.”

3. The biological species concept cannot be applied in all situations, including a. fossils and b. asexual organisms.

4. Some other definitions of species are based on a. measurable physical traits, b. the use of ecological resources, or c. unique adaptations to particular roles in a biological community.

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B. Reproductive Barriers between Species 1. Prezygotic barriers prevent mating or fertilization between species.

2. Prezygotic barriers include a. temporal isolation, b. habitat isolation, c. behavioral isolation, d. mechanical isolation, and e. gametic isolation.

3. Postzygotic barriers operate if a. interspecies mating occurs and b. hybrid zygotes form.

4. Postzygotic barriers include a. reduced hybrid viability, b. reduced hybrid fertility, and c. hybrid breakdown.

C. Mechanisms of Speciation 1. A key event in the potential origin of a species occurs when a population is somehow cut off from other populations of the parent species.

2. Species can form by a. allopatric speciation, due to geographic isolation, or b. sympatric speciation, without geographic isolation.

3. Allopatric Speciation 4. Geologic processes can a. fragment a population into two or more isolated populations and b. contribute to allopatric speciation.

5. Speciation occurs with the evolution of reproductive barriers between a. the isolated population and b. its parent population.

6. Even if the two populations should come back into contact at some later time, the reproductive barriers will keep them as separate species.

7. Sympatric Speciation.

8. Sympatric speciation occurs in populations that live in the same geographic area.

9. An accident during cell division that results in an extra set of chromosomes is a common route to sympatric speciation in plants.

10. any polyploid species arise from the hybridization of two parent species.

11. any domesticated plants are the result of sympatric speciation, including a. oats, b. potatoes, c. bananas, d. peanuts, e. apples, f. coffee, and g. wheat. ..

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D. What Is the Tempo of Speciation?

1. There are two contrasting patterns for the pace of evolution: a. the gradual pattern, in which big changes (speciations) occur by the steady accumulation of many small changes and b. the punctuated equilibria pattern, in which there are i. long periods of little apparent change, (equilibria) interrupted (punctuated) by ii. relatively brief periods of rapid change.

III. The Evolution of Biological Novelty 1. What accounts for the dramatic differences between dissimilar groups?

A. Adaptation of Old Structures for New Functions 1. Birds a. are derived from a lineage of earthbound reptiles and b. evolved flight from flightless ancestors.

2. An exaptation is a. a structure that evolves in one context but becomes adapted for another function and b. a type of evolutionary remodeling.

3. Exaptations can account for the evolution of novel structures.

4. Bird wings are modified forelimbs that were previously adapted for non-flight functions, such as a. thermal regulation, b. courtship displays, and/or c. camouflage.

5. The first flights may have been only glides or extended hops as the animal pursued prey or fled from a predator.

B. Evo-Devo: Development and Evolutionary Novelty 1. Evo-devo, evolutionary developmental biology, is the study of the evolution of developmental processes in multicellular organisms.

2. Homeotic genes are master control genes that regulate a. the rate, b. timing, and c. spatial pattern of changes in an organism’s form as it develops from a zygote into an adult.

3. Mutations in homeotic genes can profoundly affect body form.

4. Paedomorphosis a. is the retention into adulthood of features that were solely juvenile in ancestral species and b. has occurred in the evolution of i. axolotl salamanders and ii. humans.

IV. Earth History and Macroevolution 1. Macroevolution is closely tied to the history of Earth.

A. Geologic Time and the Fossil Record

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1. The fossil record is a. the sequence in which fossils appear in rock strata and b. an archive of macroevolution.

2. Geologists have established a geologic time scale that divides Earth’s history into a consistent sequence of geologic periods.

3. Fossils are reliable chronological records only if we can determine their ages, using a. the relative age of fossils, revealing the order in which groups of species evolved, and/or b. the absolute age of fossils, requiring other methods such as radiometric dating.

4. Radiometric dating a. is the most common method for dating fossils, b. is based on the decay of radioactive isotopes, and c. helped establish the geologic time scale.

B. Plate Tectonics and Macroevolution 1. The continents are not locked in place. a. Continents drift about Earth’s surface on plates of crust floating on a flexible layer of hot, underlying material called the mantle.

2. Japan sits atop four different plates. a. A tsunami, caused by an earthquake off the coast of Japan, resulted in the disaster of March 2011. b. Frequent earthquakes occur as the plates move and bump against each other.

3. About 250 million years ago, a. plate movements formed the supercontinent Pangaea, b. the total amount of shoreline was reduced, c. ocean basins increased in depth, d. sea levels dropped, e. the dry continental interior increased in size, and f. many extinctions occurred.

4. About 180 million years ago, a. Pangaea began to break up, b. large continents drifted increasingly apart, c. climates changed, and d. the organisms of the different biogeographic realms diverged.

5. Plate tectonics helps to explain a. why Mesozoic reptiles in Ghana (West Africa) and Brazil look so similar and b. how marsupials were free to evolve in isolation in Australia.

C. Mass Extinctions and Explosive Diversifications of Life 1. The fossil record reveals that five mass extinctions have occurred over the last 540 million years.

2. The Permian mass extinction a. occurred at about the time the merging continents formed Pangaea (250 million years ago) and b. claimed about 96% of marine species.

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3. The Cretaceous extinction a. occurred at the end of the cretaceous period, about 65 million years ago, b. included the extinction of all the dinosaurs except birds, and c. permitted the rise of mammals.

D. The Process of Science: Did a Meteor Kill the Dinosaurs?

1. The fossil record reveals that five mass extinctions have occurred over the last 540 million years.

2. In each of these events, 50% or more of Earth’s species died out.

3. Of all the mass extinctions, those marking the ends of the Permian and Cretaceous periods have been the most intensively studied.

4. Observation: About 65 million years ago, the fossil record shows that a. the climate cooled, b. seas were receding, c. many plant species died out, d. dinosaurs (except birds) became extinct, and e. a thin layer of clay rich in iridium was deposited.

5. Question: Is the iridium layer the result of fallout from a huge cloud of dust that billowed into the atmosphere when a large meteor or asteroid hit Earth?

6. Hypothesis: The mass extinction 65 million years ago was caused by the impact of an extraterrestrial object.

7. Prediction: A huge impact crater of the right age should be found somewhere on Earth’s surface.

8. Results: Near the Yucatán Peninsula, a huge impact crater was found that a. dated from the predicted time, b. was about the right size, and c. was capable of creating a cloud that could have blocked enough sunlight to change the Earth’s climate for months.

V. Classifying the Diversity of Life 1. Systematics focuses on a. classifying organisms and b. determining their evolutionary relationships.

2. Taxonomy is the a. identification, b. naming, and c. classification of species.

3. Systematics includes taxonomy.

A. Some Basics of Taxonomy 1. Scientific names ease communication by a. unambiguously identifying organisms and b. making it easier to recognize the discovery of a new species.

2. Carolus Linnaeus (1707–1778) proposed the current taxonomic system based upon a a. two-part name for each species and b. hierarchical classification of species into broader groups of organisms.

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3. Naming Species 4. Each species is assigned a two-part Latinized name or binomial, consisting of a. the genus and b. a name unique for each species.

5. The scientific name for humans is Homo sapiens, a. a two part name, italicized, b. given a Latin ending, and c. with the first letter of the genus capitalized.

6. Hierarchical Classification.

7. Species that are closely related are placed into the same genus.

8. The taxonomic hierarchy extends to progressively broader categories of classification, from genus to a. family, b. order, c. class, d. phylum, e. kingdom, and f. domain.

B. Classification and Phylogeny 1. The goal of systematics is to have classification reflect evolutionary relationships.

2. Biologists use phylogenetic trees to a. depict hypotheses about the evolutionary history of species and b. reflect the hierarchical classification of groups nested within more inclusive groups.

3. Sorting Homology from Analogy 4. Homologous structures a. reflect variations of a common ancestral plan and b. are one of the best sources of information used to i. develop phylogenetic trees and ii. classify organisms according to their evolutionary history.

5. Convergent evolution involves superficially similar structures from different evolutionary branches that result from natural selection shaping analogous adaptations.

6. Similarity due to convergence is called analogy, not homology.

7. To develop phylogenetic trees and classify organisms according to their evolutionary history, we use only homologous similarities.

8. Molecular Biology as a Tool in Systematics.

9. Molecular systematics a. compares nucleotide and amino acid sequences between organisms and b. can reveal evolutionary relationships.

10. The more recently two species have branched from a common ancestor, the more similar their nucleotide and amino acid sequences should be.

11. Some fossils are preserved in such a way that DNA fragments can be extracted for comparison with living organisms.

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C. The Cladistic Revolution 1. In cladistics, organisms are grouped by common ancestry.

2. A clade consists of an ancestral species and all its evolutionary descendants and forms a distinct branch in the tree of life.

3. Cladistics is based on the Darwinian concept of “descent with modification from a common ancestor.”

4. To identify clades, scientists compare an ingroup with an outgroup.

5. Cladistics has changed the traditional classification of some organisms, including the relationships between a. dinosaurs, b. birds, c. crocodiles, d. lizards, and e. snakes.

D. Classification: A Work in Progress 1. Phylogenetic trees are hypotheses about evolutionary history.

2. Linnaeus divided all known forms of life between the plant and animal kingdoms. a. this two-kingdom system prevailed in biology for over 200 years.

3. In the mid-1900s, the two-kingdom system was replaced by a five-kingdom system that a. placed all prokaryotes in one kingdom and b. divided the eukaryotes among four other kingdoms.

4. In the late 1900s, molecular studies and cladistics led to the development of a three-domain system, recognizing a. two domains of prokaryotes (Bacteria and Archaea) and b. one domain of eukaryotes (Eukarya).

E. Evolution Connection: Rise of the Mammals 1. Mass extinctions a. have repeatedly occurred throughout Earth’s history and b. were followed by a period of evolutionary change.

2. Fossil evidence indicates that a. mammals first appeared about 180 million years ago but b. the number of mammalian species i. remained steady and low in number until about 65 million years ago and ii. greatly increased after most of the dinosaurs became extinct.

3. Throughout the process of evolution by natural selection, this pattern of death and renewal is repeated throughout the history of life on Earth.

Chapter Guide to Teaching Resources The Origin of Species Student Misconceptions and Concerns 1. Students may think that species evolve because of need. However, need has no role in biological evolution. Biological diversity exists and the environment selects. Evolution is not 192

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deliberate. It is reactive. Species do not deliberately change. There is no plan. As teachers, we must be careful in how we express evolution to best reflect this process. This use of the passive voice in our descriptions of evolution better reflects the nature of this fundamental process.

2. The concept of “sudden” in geologic terms is likely misunderstood. Events such as major floods, earthquakes, or asteroid impacts, which might be so rare as to occur every 1,000 years, are actually common in geologic terms. Students might not realize that 1,000 such events would be expected to occur in a million years.

3. Students might not have considered how species are “naturally” kept separate and unique.

Instead, students are more likely to consider species as fixed entities, especially the species to which they belong. As instructors of biology, it can become increasingly difficult to empathize with this perspective. To help ease students into the topic, consider pointing out that species of life do not reflect an even spectrum of diversity. Instead, there are many clear groups of related organisms (fungi, flowers, owls, sharks, beetles, butterflies, and frogs, for example). Ask students to consider why such clumping exists. Is it in any way due to the same reason that a particular human family is distinct from other families? Can this grouping of kinds be related to shared common ancestors?

Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples help to bring a point home.

2. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species.

3. The isolation of a few individuals from a parent population may result from a catastrophic weather or geologic event. Ask your students to think back to news footage of torrential rains, massive debris rocketed down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events.

Dramatic weather and geologic events may be rare in our lifetimes, but are frequent enough to play a role in speciation.

4. Challenge your students to explain why the field of paleontology has largely been concerned with macroevolution. The broader perspective of evolutionary change studied by paleontologists rarely permits an examination of change within a species.

5. The silvery salamander, Ambystoma platineum, is a triploid, all-female species living in parts of the midwestern United States. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. The following website is a good starting point to learn more about this species: www.inhs.uiuc.edu/cbd/herpdist/species/am_platine.html.

6. The abundance of polyploid plants used for food facilitates further study for student assignments. Perhaps small groups or individuals can select a polyploid crop and describe its evolutionary history and/or its current method of reproduction.

7. Have your students think of analogous examples of punctuated equilibrium in our culture.

Perhaps such an example is the switch from vinyl records to compact discs, with the brief transitional form of 8 tracks (do you remember these?). Between the years 1900–2000, there were long periods of stasis (vinyl records) and a relatively short period of transition to the CDs (who knows how long they will last as MP3 files take over). Debating the validity of analogies can be instructive as students articulate the biological principles and use them to test the accuracy of the analogies. ..

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The Evolution of Biological Novelty Student Misconceptions and Concerns 1. Students are unlikely to appreciate the life history of salamanders and the similarity of a larval salamander to the axolotl form. Students might therefore best understand what happens during salamander paedomorphosis by considering more commonly understood life stages. Ask students to imagine what would result if a caterpillar reproduced and never turned into a winged adult butterfly. Then relate the caterpillar stage to the early larval form of salamanders.

2. Clear examples of evolutionary remodeling include the many variations of the pattern of bones in the vertebrate forelimb. Bat wings, bird wings, penguin flippers, the arms of apes, and the digging forelimbs of moles all show how the ancestral pattern was revised as new functions evolved. Descent with modification is a powerful explanation of such diversity.

Teaching Tips 1. Another way to think about evolutionary remodeling is to make an analogy to remodeling a home. A remodeled home retains many of the “ancestral” traits—perhaps the same plumbing and electrical system. But, where there once was a wall might now be an opening into an enlarged family room, or a window to the outside. Evolution can work like the TV show This Old House!

2. When discussing exaptations, have students consider the many new uses for common household items if they were to have them in a survival situation, stranded on an island or lost in the woods. A handkerchief, a screwdriver, and a pair of pliers might take on new functions in this different context.

3. Consider challenging your students to explain why the evolution of a group is not driven in any particular direction, or directed toward any ideal form or function. As a hint, you can ask them to describe the mechanisms by which variety arises in a species.

Earth History and Macroevolution Student Misconceptions and Concerns 1. Most of us are unable to comprehend the vast lengths of time considered by geologists.

Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60 × 60 × 24 × 365 = 31,536,000) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day).

2. Students also need to be reminded that 1 billion is 1,000 million. Many students (and too many politicians) easily confuse million and billion without realizing the scale of the error.

Teaching Tips 1. The sequence but not absolute ages are revealed by the stratifications in sedimentary rocks.

The authors make an analogy to peeling the layers of wallpaper from the walls of a very old house that has been inhabited by many owners. By the sequence we can tell which layers are older, but not the absolute ages of each layer. Cutting into a layered cake is another analogy. Although we do not know the absolute age of each layer, we know the sequence in which the layers were placed.

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2. Consider this analogy to help students understand the biological consequences of speciation as continents drifted apart. As your students left high school, and entered the workforce or continued their education, their high school social groups drifted apart. Your students, in their new circumstances, adapted and changed in different ways, separate from the members of their old social groups. A note of caution: This analogy to individual social changes is not an example of biological evolution, which occurs over generations.

3. The consequences of an asteroid impact, large or small, illustrates the role of random forces influencing evolution. Like throwing a dart at a spinning globe, where the asteroid hits and what continents and life are most greatly affected can change greatly if the impact is delayed by a few hours. An asteroid delayed by 12 hours, in what might be a journey of millions or billions of years, will land on the opposite side of Earth!

Classifying the Diversity of Life Student Misconceptions and Concerns 1. Students can become frustrated by the changing state of systematics. Perhaps some comfort can be offered by noting that this is true about many active areas of science. For example, scientists continue to learn more and revise advice regarding the causes, treatment, and prevention of heart disease and cancer.

2. Students might express concern over the need to learn scientific names, when common names already seem sufficient. Depending on where you live, find some examples of common organisms with more than one common name. Fishermen are famous for the various names they assign to the same species, depending on the geographic region where they fish. Have your students imagine the problems of using common names when communicating with someone in another language. Clearly, there are advantages to scientific names!

3. Students may struggle with many aspects of phylogenetic trees. (a) Students may not realize that each node/branch can be rotated to rearrange the groups, without changing the nature of the relationships. For example, in Figure 14.23, the position of the beaver and kangaroo can be reversed without changing any relationships represented in the phylogenetic tree. (b) The length of each branch is not meaningful and is not intended to be proportional to time. (c) The spacing between groups is not meaningful. The same phylogenetic tree squeezed onto a page or stretched wide does not denote some degree of divergence between the groups.

Teaching Tips 1. The authors note that our hierarchical classification system is analogous to sorting mail first by zip code, then by street, house number, and finally members of the household.

2. Although Linnaeus recognized a hierarchical structure in the natural world, he had no natural explanation for the occurrence of such groups. One might wonder why all life does not blend evenly from one form to another. One of Darwin’s greatest insights was to understand that these clusters reflect similarities due to shared ancestry: that life is grouped into family trees. Further, Darwin proposed a natural mechanism for the formation of new species and the generation of this diversity.

3. Homologous and analogous relationships can be confusing for students. Simple explanations and concrete examples can serve as guides to understanding each process.

Homologous relationships reflect modifications of an ancestral form for many functions.

Analogous relationships reflect modifications of many forms for one common function. ..

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4. Genetic relationships provide one strong line of evidence for the ancestral relationships of life. Fossils, anatomy, embryology, and biogeography can also be used to test these same relationships. Remind students that scientists prefer to use multiple lines of evidence to test hypotheses such as phylogenies.

5. Phylogenetic trees are tentative hypotheses. As new data are collected, the hypotheses are modified or outright rejected. Students should be cautioned to understand the tentative nature of these systems.

6. The National Center for Science Education is an organization working to support the teaching of evolution and defend it against sectarian attack. Its website, http://ncse.com, contains a great deal of useful information.

Key Terms allopatric speciation analogy binomial biological species concept clade cladistics class

convergent evolution domain evo-devo family genus geologic time scale kingdom macroevolution

order paedomorphosis phylum phylogenetic trees postzygotic barriers prezygotic barriers punctuated equilibria radiometric dating

reproductive barrier speciation species sympatric speciation systematics taxonomy three-domain system

Word Roots allo = other; patric = country (allopatric: the type of speciation in which a new species forms by geographic isolation) bi = two; nom = name (binomial: a two-part name used to identify a species) con = together (convergent evolution: the type of evolution in which unrelated organisms evolve structures with similar functions) ex = beyond (exaptation: structures that evolve in one context and later become adapted for other functions) macro = large (macroevolution: major biological changes evident in the fossil record) paedo = child; morphosis = shaping (paedomorphosis: the retention in the adult of features that were juvenile in its ancestors) post = after (postzygotic barriers: the type of barriers that prevent development of a zygote that is a hybrid between species) pre = before (prezygotic barriers: the type of barriers that prevent the fertilization of the eggs of different species) sym = together; patri = country (sympatric: the type of speciation in which a new species forms in the same geographic region)

Relevant Songs to Play in Class “I Got a Name,” Jim Croce

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Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: You could start by observing the mice in their native habitat. Do the mice naturally interbreed, or is the river a true reproductive barrier between the two groups? Observation of even one pair of interbreeding mice could negate the biological species concept definition of separate species. In the lab, experiments that artificially place the two groups in close proximity could be used to determine whether other barriers to interbreeding exist. One problem with such an effort is that the artificial habitat of the lab might compromise the experiment, since breeding habits might be altered under such conditions. Alternatively, genetic analysis of the two groups could provide an indication of whether the two gene pools are mixed or separate.

Biology and Society 12. Some issues and questions to consider: Whereas previous mass extinctions have resulted from catastrophic events, such as asteroid collisions or volcanism, this mass extinction is the result of human-caused environmental alteration. The rate of this mass extinction appears to be much greater than that of the others. Just because life bounces back, does that mean we will? Do we have any ethical responsibility to minimize our impact on other species? How long does it take diversity to recover after a mass extinction?

Additional Critical Thinking Questions The Process of Science 1. Imagine that certain fruit flies exhibit mating behavior that separates them from another group of fruit flies: one group mates and lays eggs only on apple trees, and the other group mates and lays eggs only on pear trees. How could you design an experiment to test if these are different species or still the same species?

Suggested answer: Set up an experiment in the laboratory in which members from both populations are mixed and mating frequencies are calculated. If a reproductive barrier is present, you should see more apple females mating with apple males and the same for pear females and pear males, even though they encounter each other in the experimental conditions. If speciation has truly occurred, we would expect little interbreeding. However, this experiment cannot rule out the impact of artificial conditions.

2. Cultivated American cotton plants have 52 chromosomes (2n = 52). In each cell, there are 13 pairs of large chromosomes and 13 pairs of smaller chromosomes. Old World cotton plants have 26 chromosomes (2n = 26), all large. Wild American cotton plants have 26 chromosomes (2n = 26), all small. Propose a testable hypothesis to explain how cultivated American cotton probably originated.

Suggested answer: A broad hypothesis would be that cultivated American cotton arose from a sequence of hybridization, meiotic failure, and self-fertilization.

We can divide this broad statement into at least three testable hypotheses: Hypothesis 1: The first step in the origin of cultivated American cotton was hybridization between a wild American cotton plant (with 13 pairs of small chromosomes) and an Old World cotton plant (with 13 pairs of large chromosomes). If this hypothesis is correct, we would predict that the hybrid offspring would have 13 small chromosomes and 13 large chromosomes. ..

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Hypothesis 2: The second step in the origin of cultivated American cotton was a failure of meiosis in the hybrid offspring. If this hypothesis is true, we would expect the gametes resulting from meiotic failure to each have 13 large chromosomes and 13 small chromosomes.

Hypothesis 3: The third step in the origin of cultivated American cotton was selffertilization of the gametes resulting from meiotic failure. If this hypothesis is true, we would expect the outcome of self-fertilization to be a polyploid plant with 52 chromosomes—13 pairs of large ones and 13 pairs of small ones. This is the genetic makeup of cultivated American cotton.

3. Scientists have calculated that a particular piece of rock contained about 12 grams (g) of radioactive potassium-40 when it was formed. It now contains 3 g of potassium-40. The half-life of potassium-40 is 1.3 billion years. About how old is the rock?

Suggested answer: The rock is about 2.6 billion years old. (If the half-life of potassium-40 is 1.3 billion years, there would be 6 g left after 1.3 billion years and 3 g left after another 1.3 billion years.)

Biology and Society 4. Your friend says that humans have evolved from apes. How would you respond to that statement using the information provided in this chapter?

Some issues and questions to consider: Humans and apes share a common ancestor, but we make up distinct lineages that result from an accumulation of separate mutations and adaptive evolution, that led to the human populations and the great ape populations that exist today. We certainly share common features (going back to the common ancestors) but have also evolved quite differently from the time of the split from the ancestral organism. The statement is analogous to saying that you are the children of your cousins.

Instead, you and your cousins share common ancestors—most recently your grandparents.

5. The red wolf, Canis rufus, formerly widespread in the southeastern and southcentral United States, nearly became extinct in the late 1970s. Saved by a captive breeding program under the authority of the Endangered Species Act (ESA), it has been reintroduced in areas such as the Great Smoky Mountains National Park. Recent genetic evidence indicates that the red wolf may not be a separate species, but a hybrid of the coyote, Canis latrans, and the gray wolf, Canis lupus. Though the original intent of the ESA was to protect all endangered groups—whether species, subspecies, or hybrids—the costs may be prohibitive. What criteria should be applied if we must decide which organisms to protect? Are there reasons to preserve hybrids, subspecies, or local populations of species when the species as a whole is not at risk?

Some issues and questions to consider: The rationale behind protecting all endangered groups is the desire to preserve genetic diversity. Each species, subspecies, and hybrid group may represent a unique mix of genes. Studies of the degree of genetic distinctiveness of a subspecies or hybrid group may help decision makers if cost is an issue. If the species as a whole is not at risk, it seems appropriate to determine how distinctive the gene pool of a subspecies or hybrid group is before assigning it a lower priority for saving. Questions for society in general to address are, What is the value of any particular species and its genetically distinct subgroups? In addition, how far are we willing (should we be willing) to go to preserve a genetically distinct group of organisms?

How should the costs of preserving genetic diversity compare with the costs of other public projects?

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CHAPTER

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The Evolution of Microbial Life

Why This Chapter Matters 1. Prokaryotes were the first forms of life to arise on Earth. Their history is our history.

2. Prokaryotes are found wherever there is life, greatly outnumbering the eukaryotes on Earth.

3. Prokaryotes cause some of the most deadly diseases known, recycle vital chemical nutrients, and form symbiotic relationships with most species. Without them, life on Earth would not exist.

4. The evolution of eukaryotic cells and the diversity that resulted is represented by the amazing variations in structure and function found in protists.

Chapter Objectives Biology and Society: Has Life Been Created in the Lab? 1. Explain how and why scientists are creating artificial life.

Major Episodes in the History of Life 2. Identify the sequence and timing of the major events in the evolution of early life, ending with the movement of the first life onto land.

The Origin of Life 3. Distinguish between spontaneous generation and biogenesis.

4. Describe the four stages of the hypothesis for the origin of life on Earth. Explain how natural selection would have affected these first pre-cells.

Prokaryotes 5. Describe the relative abundance of prokaryotes on Earth and the many ways they affect humans and ecosystems.

6. Describe the structure, function, and reproduction of prokaryotes.

7. Compare the types of nutritional diversity used by prokaryotes.

8. Compare the two groups of prokaryotic cells—bacteria and archaea. Describe three specific extreme environments in which members of archaea are found.

9. Describe the many ways that bacteria harm and benefit humans and ecosystems.

10. Explain how bacteria have been used as biological weapons and for bioremediation.

Protists 11. Describe the two main processes that explain how eukaryotic cells evolved.

12. Describe and compare the four main categories of protists, grouped by lifestyle. Explain how these different groups impact our lives.

Evolution Connection: The Origin of Multicellular Life 13. Explain how multicellular life evolved from unicellular life.

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Lecture Outline I. Biology and Society: Has Life Been Created in the Lab? 1. How did life first arise on Earth?

2. To gain insight, scientists have a. synthesized from scratch the entire genome of a small bacterium known as Mycoplasma mycoides and b. transplanted the artificial genome into the cells of a closely related species called Mycoplasma capricolum.

3. The newly installed genome a. took over the recipient cells, b. began cranking out M. mycoides proteins, and c. reproduced to make more cells containing the synthetic M. mycoides genome.

II. Major Episodes in the History of Life 1. Earth was formed about 4.6 billion years ago.

2. Prokaryotes a. evolved by about 3.5 billion years ago, b. began oxygen production about 2.7 billion years ago, c. lived alone for more than a billion years, and d. continue in great abundance today.

3. Single-celled eukaryotes first evolved about 2.1 billion years ago.

4. Multicellular eukaryotes first evolved at least 1.2 billion years ago.

5. All the major phyla of animals evolved by the end of the Cambrian explosion, which a. began about 540 million years ago and b. lasted about 10 million years.

6. Plants and fungi a. first colonized land about 500 million years ago and b. were followed by amphibians that evolved from fish.

7. What if we use a clock analogy to tick down all of the major events in the history of life on Earth?

III. The Origin of Life 1. We may never know for sure how life on Earth began.

A. Resolving the Biogenesis Paradox 1. All life today arises by the reproduction of preexisting life, or biogenesis.

2. If this is true, how could the first organisms arise?

3. From the time of the ancient Greeks until well into the 1800s, it was commonly believed that life regularly arises from nonliving matter, an idea called spontaneous generation.

4. Today, most biologists think it is possible that life on early Earth produced simple cells by a. chemical and b. physical processes.

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B. A Four-Stage Hypothesis for the Origin of Life 1. According to one hypothesis, the first organisms were products of chemical evolution in four stages.

2. Stage 1: Abiotic Synthesis of Organic Monomers 3. The first stage in the origin of life was the first to be extensively studied in the laboratory.

C. The Process of Science: Can Biological Monomers Form Spontaneously?

1. Observation: Modern biological macromolecules are all composed of elements that were present in abundance on early Earth.

2. Question: Could biological molecules arise spontaneously under conditions like those on early Earth?

3. Hypothesis: A closed system designed to simulate early Earth conditions could produce biologically important organic molecules from inorganic ingredients.

4. Prediction: Organic molecules would form and accumulate.

5. Experiment: An apparatus was built to mimic the early Earth atmosphere and included a. hydrogen gas (H2), methane (CH4), ammonia (NH3), and water vapor (H2O), b. sparks that were discharged into the chamber to mimic the prevalent lightning of the early Earth, and c. a condenser that cooled the atmosphere, causing water and dissolved compounds to “rain” into the miniature “sea.”

6. Results: After the apparatus had run for a week, an abundance of organic molecules essential for life had collected in the “sea,” including amino acids, the monomers of proteins.

7. These laboratory experiments a. have been repeated and extended by other scientists and b. support the idea that organic molecules could have arisen abiotically on early Earth.

8. Stage 2: Abiotic Synthesis of Polymers 9. Researchers have brought about the polymerization of monomers to form polymers, such as proteins and nucleic acids, by dripping solutions of organic monomers onto a. hot sand, b. clay, or c. rock.

10. Stage 3: Formation of Pre-Cells 11. A key step in the origin of life was the isolation of a collection of abiotically created molecules within a membrane.

12. Laboratory experiments demonstrate that pre-cells could have formed spontaneously from abiotically produced organic compounds.

13. Such pre-cells produced in the laboratory display some lifelike properties. They a. have a selectively permeable surface, b. can grow by absorbing molecules from their surroundings, and c. swell or shrink when placed in solutions of different salt concentrations.

14. Stage 4: Origin of Self-Replicating Molecules 15. Life is defined partly by the process of inheritance, which is based on self-replicating molecules. ..

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16. One hypothesis is that the first genes were short strands of RNA that replicated themselves a. without the assistance of proteins, b. perhaps using RNAs that can act as enzymes, called ribozymes.

17. From Chemical Evolution to Darwinian Evolution 18. Over millions of years a. natural selection favored the most efficient pre-cells and b. the first prokaryotic cells evolved.

IV. Prokaryotes 1. Prokaryotes lived and evolved all alone on Earth for about 2 billion years.

A. They’re Everywhere!

1. Prokaryotes a. are found wherever there is life, b. have a collective biomass that is at least ten times that of all eukaryotes, c. thrive in habitats too cold, too hot, too salty, too acidic, or too alkaline for any eukaryote, d. cause about half of all human diseases, and e. more commonly can be benign or beneficial.

2. Compared to eukaryotes, prokaryotes are a. much more abundant and b. typically much smaller.

3. Prokaryotes living in soil and at the bottom of lakes, rivers, and oceans help to decompose dead organisms and other organic waste material, returning vital chemical elements to the environment.

B. The Structure and Function of Prokaryotes 1. Prokaryotic cells a. lack a membrane-enclosed nucleus, b. lack other membrane-enclosed organelles, c. typically have cell walls exterior to their plasma membranes, but d. display an enormous range of diversity.

2. The three most common shapes of prokaryotes are a. spherical (cocci), b. rod-shaped (bacilli), and c. spiral or curved.

3. All prokaryotes are unicellular.

4. Some prokaryotes a. exist as groups of two or more cells, b. exhibit a simple division of labor among specialized cell types, or c. are very large, dwarfing most eukaryotic cells.

5. About half of all prokaryotes are mobile, and many of these travel using one or more flagella.

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6. In many natural environments, prokaryotes attach to surfaces in a highly organized colony called a biofilm, which a. may consist of one or several species of prokaryotes, b. may include protists and fungi, c. show a division of labor and defense against invaders, and d. form on almost any type of surface, including i. rocks, ii. metal, iii. plastic, and iv. organic material including teeth.

7. Most prokaryotes can reproduce a. by dividing in half by binary fission and b. at very high rates if conditions are favorable.

8. Some prokaryotes form endospores, thick-coated, protective cells that are produced within the cells when they are exposed to unfavorable conditions.

9. Prokaryotic Nutrition 10. Prokaryotes exhibit different modes of nutrition to describe how organisms obtain energy and carbon. a. Energy i. Phototrophs obtain energy from light. ii. Chemotrophs obtain energy from environmental chemicals. b. Carbon i. Autotrophs obtain carbon from carbon dioxide (CO2). ii. Heterotrophs obtain carbon from at least one organic nutrient—the sugar glucose, for instance.

11. We can group all organisms according to the four major modes of nutrition if we combine the a. energy source (phototroph versus chemotroph) and b. carbon source (autotroph versus heterotroph).

12. Dominant among multicellular organisms are a. photoautotrophs and b. chemoheterotrophs.

13. The other two modes are used only by certain prokaryotes.

C. The Two Main Branches of Prokaryotic Evolution: Bacteria and Archaea 1. By comparing diverse prokaryotes at the molecular level, biologists have identified two major branches of prokaryotic evolution: a. bacteria b. archaea (more closely related to eukaryotes).

2. Thus, life is organized into three domains: a. Bacteria, b. Archaea, and c. Eukarya.

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3. Some archaea are “extremophiles.” a. Halophiles thrive in salty environments. b. Thermophiles inhabit very hot water. c. Methanogens i. inhabit the bottoms of lakes and swamps and ii. aid digestion in cattle and deer.

D. Bacteria and Disease 1. Bacteria interact with people in many ways.

2. Bacteria That Cause Disease 3. Bacteria and other organisms that cause disease are called pathogens.

4. Most pathogenic bacteria produce poisons. a. Exotoxins are proteins bacterial cells secrete into their environment. b. Endotoxins are i. not cell secretions but instead ii. chemical components of the outer membrane of certain bacteria.

5. The best defenses against bacterial disease are a. sanitation, b. antibiotics, and c. education.

6. Lyme disease is a. caused by bacteria carried by ticks and b. treated with antibiotics, if detected early.

7. Biological Weapons 8. In October 2001, a. endospores of the bacterium that causes anthrax were mailed to members of the news media and the U.S. Senate and b. five people died from this attack.

9. Another bacterium considered to have dangerous potential as a weapon is Clostridium botulinum, producer of exotoxin botulinum, which a. blocks transmission of nerve signals that cause muscle contraction and b. is the deadliest poison on Earth.

E. The Ecological Impact of Prokaryotes 1. Pathogenic bacteria are in the minority among prokaryotes.

2. Far more common are species that are essential to our well-being, either directly or indirectly.

3. Prokaryotes and Chemical Recycling 4. Prokaryotes play essential roles in a. chemical cycles in the environment and b. the breakdown of organic wastes and dead organisms.

5. Prokaryotes and Bioremediation

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6. Bioremediation is the use of organisms to remove pollutants from a. water, b. air, and c. soil.

7. A familiar example is the use of prokaryotic decomposers in sewage treatment.

8. Certain bacteria a. can decompose petroleum and b. are useful in cleaning up oil spills.

V. Protists 1. Protists are a. eukaryotes that are not fungi, animals, or plants, b. mostly unicellular, and c. ancestral to all other eukaryotes.

A. The Origin of Eukaryotic Cells 1. Eukaryotic cells evolved by a. the infolding of the plasma membrane of a prokaryotic cell to form the endomembrane system and b. endosymbiosis, one species living inside another host species, in which free-living bacteria came to reside inside a host cell, producing mitochondria and chloroplasts.

2. Symbiosis is a more general association between organisms of two or more species.

B. The Diversity of Protists 1. The group called protists a. consists of multiple clades but b. remains a convenient term to refer to eukaryotes that are not plants, animals, or fungi.

2. Protists have a variety of ways in which they obtain their nutrition. a. Algae are autotrophs, producing their food by photosynthesis. b. Other protists are heterotrophs. i. Some protists eat bacteria or other protists. ii. Other protists are fungus-like and obtain organic molecules by absorption. iii. Parasites derive their nutrition from a living host, which is harmed by the interaction. Parasitic trypanosomes infect blood and cause sleeping sickness.

3. Protist habitats are diverse and include a. oceans, lakes, and ponds, b. damp soil and leaf litter, and c. mutually beneficial relationships such as the unicellular algae that inhabit the bodies of i. reef-building coral animals or ii. the intestinal tracts of termites.

4. Protozoans 5. Protists that live primarily by ingesting food are called protozoans.

6. Protozoans with flagella are called flagellates and a. are typically free-living, but b. some are nasty parasites. ..

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7. Amoebas are characterized by a. great flexibility in their body shape and b. the absence of permanent organelles for locomotion.

8. Most species move and feed by means of pseudopodia (singular, pseudopodium), temporary extensions of the cell.

9. Other protozoans with pseudopodia include the forams, which have shells.

10. Apicomplexans are a. named for a structure at their apex (tip) that is specialized for penetrating host cells and tissues, b. all parasitic, and c. able to cause serious human diseases, such as malaria caused by Plasmodium.

11. Another apicomplexan is Toxoplasma, a. occurring in the digestive tracts of millions of people in the United States but b. held in check by the immune system.

12. A woman newly infected with Toxoplasma during pregnancy can pass the parasite to her unborn child, who may suffer nervous system damage.

13. Ciliates are protozoans that a. are named for their use of hair-like structures called cilia to move and sweep food into their mouths, b. are mostly free-living (nonparasitic), such as the freshwater ciliate Paramecium, and c. include heterotrophs and mixotrophs.

14. Slime Molds 15. Slime molds resemble fungi in appearance and lifestyle, but the similarities are due to convergence, and slime molds are more closely related to amoebas than to fungi.

16. The two main groups of these protists are a. plasmodial slime molds and b. cellular slime molds.

17. Plasmodial slime molds a. are named for the feeding stage in their life cycle, an amoeboid mass called a plasmodium, b. are decomposers on forest floors, and c. can be large.

18. Cellular slime molds have an interesting and complex life cycle consisting of a. a feeding stage of solitary amoeboid cells, b. a slug-like colony that moves and functions as a single unit, and c. a stalk that develops into a multicellular reproductive structure.

19. Unicellular and Colonial Algae 20. Algae are a. photosynthetic protists whose chloroplasts support food chains in i. freshwater and ii. marine ecosystems.

21. Many unicellular algae are components of plankton, the communities of mostly microscopic organisms that drift or swim weakly in aquatic environments.

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22. Unicellular algae include a. dinoflagellates, with i. two beating flagella and ii. external plates made of cellulose, b. diatoms, with glassy cell walls containing silica, and c. green algae, which are i. unicellular in most freshwater lakes and ponds, ii. sometimes flagellated, such as Chlamydomonas, and iii. sometimes colonial, forming a hollow ball of flagellated cells as seen in Volvox.

23. Seaweeds 24. Seaweeds a. are large, multicellular marine algae, b. grow on or near rocky shores, c. are only similar to plants because of convergent evolution, d. are most closely related to unicellular algae, and e. are often edible.

25. Seaweeds are classified into three different groups, based partly on the types of pigments present in their chloroplasts: a. green algae, b. red algae, and c. brown algae (including kelp).

C. Evolution Connection: The Origin of Multicellular Life 1. Multicellular organisms have a. specialized cells that are dependent on each other and perform different functions, such as i. feeding, ii. waste disposal, iii. gas exchange, and iv. protection.

2. Colonial protists likely formed the evolutionary links between a. unicellular and b multicellular organisms.

3. The colonial green alga Volvox demonstrates one level of specialization and cooperation.

Chapter Guide to Teaching Resources Major Episodes in the History of Life Student Misconceptions and Concerns 1. Students often have difficulty grasping the enormity of time. Perhaps surprisingly, many students do not understand that a billion is a thousand times greater than a million.

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Exercises and examples that help students comprehend such large numbers should be considered, so that students can understand these tremendous periods for evolutionary diversification. Here are just a few examples to consider: a. If an earthquake or volcano erupts just once every thousand years or so, how often will this event occur in a million years? (One thousand times.) Note that what is rare to us becomes “common” in geologic terms. b. Have students calculate the age of a human when they reach their 1 billionth second of life. (Starting with birth, the answer is 31.688 years.) 1,000,000,000 (seconds) = 31.688 (years) × 365.25 (days in a year) × 24 (hours in a day) × 60 (minutes) × 60 (seconds). c. Then have students calculate how long it takes to live 1,000,000 seconds.

(About 11.574 days.)

Teaching Tips 1. Consider making some sort of timeline to scale in a hallway, long laboratory, or the side of the lecture hall. Mark these proportional periods: The full length of time is 4.6 billion years. The percentages below were calculated using the textbook’s approximate dates for each of these events.

0.0%—The Earth forms.

13%—The Earth’s crust solidifies.

24%—The first life appears.

41%—Photosynthetic prokaryotes start producing an oxygen-rich atmosphere.

54%—The first eukaryotes appear.

74%—The first multicellular eukaryotes appear.

89%—Plants first invade land.

2. Students may need to be reminded about the reactive properties of oxygen. Note that rust is the result of oxygen interacting with iron and could be seen in the fossil record. Oxygen is highly reactive and could interfere with life-forming chemical processes today.

The Origin of Life Student Misconceptions and Concerns 1. Students might not have considered that cells today are not “created from scratch.” Unlike the way a cake is prepared, or an automobile is constructed, life today is not known to form by the assembly of raw materials into cells. Point out that the process of piecemeal building, so common in our lives, is not a part of cellular biology.

2. Students may think that scientists have answers for all of life’s questions. Thus, they may appreciate knowing that many questions are inappropriate for science. Matters of aesthetics, morals, and political issues are often addressed by other methods of thinking.

Questions such as “Was Picasso a better artist than Rembrandt?” “How can we help homeless people?” and “Should abortion be illegal?” are examples. This might be a good time to further distinguish between the process of science and other ways of knowing.

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Teaching Tips 1. Consider pointing out the logic of spontaneous generation given the knowledge at the time.

Piles of manure and rotting flesh left in the open would apparently produce flies. At that time little was understood about eggs, sperm, and fertilization, making spontaneous generation a logical conclusion.

2. The four-stage hypothesis for the origin of life is a little like building cells “from the bottom up.” If your students do not remember details about biological molecules and basic cell structure, you may need to review these principles before addressing the stages.

3. The inherent property of bipolar molecules such as phospholipids, to naturally form double membranes or micelles, is worth discussing with your class. Because of these properties, membranes naturally heal as the hydrophobic phospholipid tails and polar heads align.

4. At some point in the presentation of the four-stage hypothesis for the origin of life, students should be encouraged to consider at what point we have life. Are self-replicating, RNA-based, membrane-bound structures alive? This discussion of the evolution of the first cells helps us better understand our definition of life.

5. Much of the remaining chapter is descriptive of the traits and habits of single-celled prokaryotes and eukaryotes. Students might benefit by developing a series of charts that allow them to quickly review the properties of various subgroups. (For example, the shapes of bacteria, the major modes of nutrition, and the various prokaryote subgroups.)

Prokaryotes Student Misconceptions and Concerns 1. Students might think of evolution as a progression, with multicellular eukaryotes somehow fundamentally better than prokaryotes. The recognition of the enduring existence of prokaryotes more than a billion years older than eukaryotes and the tremendous diversity of prokaryotic lifestyles might clarify the misperception of “evolutionary improvement.”

After all, what eukaryotes can survive in the habitats of extremophiles?

2. Some students might equate the term bacteria with prokaryotes. A discussion of the domains Archaea and Bacteria will help with this distinction.

3. Many students struggle with concepts of size and volume. For example, they may not realize that a cube twice as wide as another has a volume eight times greater. The diameter of eukaryotic cells is about ten times greater than the diameter of prokaryotic cells. Thus, the volume of eukaryotic cells can be nearly 1,000 times greater than prokaryotic cells.

4. Students may think that hand washing and the use of soap, especially antibacterial soap, leaves the washed parts free of bacteria. The tremendous numbers of bacteria that typically remain and routinely reside on and within our bodies are little appreciated.

5. Students may believe that we have already documented the diversity of life on Earth.

However, by most estimates, we have identified fewer than 10% of the suspected species of eukaryotes. The ongoing discovery of the diversity of prokaryotes humbles microbiologists working today. The diversity of prokaryotic life may very well be beyond human determination.

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Teaching Tips 1. Bacteria and archaea live within the hot springs of Yellowstone National Park. The pigments in these microbes give color to the springs. A Google Image search using the keywords “Yellowstone hot springs color” will quickly identify photographic resources revealing extremophile diversity.

2. Some modeling clay (oil-based never dries out) and toothpicks can be used to make some quick and easy visual aids to demonstrate the various shapes of these bacteria for lecture.

The construction of these diverse shapes might also make for a quick lab activity.

3. The exponential growth of bacteria is like the growth represented in the correct answer to the classic math question “Would you rather be paid a million dollars for one month’s work or start out with just a penny for the first day of the month, but have your pay doubled every remaining day of that month?” Choosing the doubling amount pays off at about $10 million after just one month!

4. The ecological impact of prokaryotes is directly relevant to students' lives, and can be of great interest to them. Consider a short Internet assignment in which each student must locate a recent article or website that addresses one aspect of this topic. (For example, exotoxins, endotoxins, bioremediation, and so on) They can then write a short summary or e-mail the website address to you for your inspection.

5. Chemoautotrophs permit ecosystems, which do not rely on sunlight for a source of metabolic energy (though Earth would quickly freeze solid without the sun!). Students may have been taught that all ecosystems are based on photosynthesis. Chemoautotrophs reveal an exception.

6. Students might enjoy an assignment to determine where and to what extent bioremediation is being used to help address the devastating results of the 2010 BP oil spill in the Gulf of Mexico.

7. The website http://water.usgs.gov/wid/html/bioremed.html is a good source for information on bioremediation.

8. Students interested in global warming might research the estimated impact of methanogens in the digestive tract of herbivores raised by humans.

9. Students may not know that Botox injections used to reduce facial wrinkles use small injections of botulinum to paralyze facial muscles. The toxin is also used therapeutically for other muscular conditions.

Protists Student Misconceptions and Concerns 1. Students may need to be reminded that most prokaryotes are about a tenth the diameter of eukaryotic cells. Thus, by the process of endosymbiosis, symbiotic bacteria could easily fit within larger eukaryotic cells.

2. Students might think of protists as “simple” organisms in comparison to our own complex multicellular bodies. However, as the authors note, within a single cell, protists must carry out all the basic functions performed by the set of specialized cells that collectively form the bodies of plants and animals.

3. Students might immediately expect that all symbiotic relationships benefit both members.

Consider noting that parasitism is a type of symbiotic relationship in which one member is harmed.

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4. Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night.

Teaching Tips 1. The reconsideration of the classification of protists further illustrates the tentative nature of science, in which no information is considered final. You may point out that new molecular tools have allowed us to understand new levels of diversity and required reconsiderations of classification schemes.

2. The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small prokaryote size of these organelles in eukaryotes.

Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons.

3. The extensive diversity of protists permits endless opportunities for students to select an example of a protist and report on it in some way. For example, students can sketch “their protist,” find web resources, and/or plot its position in a classification of protists. These short exercises in content “ownership” enable students to develop a greater depth of understanding and increase interaction with the subject.

4. Mitochondrial DNA is widely used to analyze evolutionary relationships. Challenge students to explain why mitochondrial DNA might be better than nuclear DNA to trace these relationships. (Nuclear DNA in sexually reproducing organisms reflects a mixture of the parents’ genetic material. Mitochondrial DNA is typically inherited just from the mother, and therefore only changes by the accumulation of mutations.)

5. This is a very exciting time for new scientists entering the field of renewable fuels. You may wish to share with your students how they can still get in on the “ground floor” of these emerging energy fields. Sometimes instructors need to help students imagine a place for them in the future of science.

6. The evolution of multicellularity requires the subdivision of labor in ways similar to modern human societies. Providing structure, acquiring and processing food, and facilitating movement are specialized functions of cells as well as members of society.

Key Terms algae amoebas apicomplexans Archaea bacilli Bacteria binary fission biofilm biogenesis

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bioremediation cellular slime mold ciliates cocci diatoms dinoflagellate endospore endosymbiosis endotoxins

Eukarya eukaryotes exotoxins flagellates forams green algae parasite pathogens plankton

plasmodial slime mold prokaryotes protists protozoans pseudopodia seaweeds spontaneous generation symbiosis

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Word Roots api = the tip (apicomplexans: all parasitic protists named for an apparatus at their apex that is specialized for penetrating host cells) archae = ancient (archaea: prokaryotic group most closely related to eukaryotes) bacill = a little stick (bacilli: rod-shaped prokaryotes) bi = two (binary fission: a form of asexual reproduction in which a single cell divides into two cells of about equal size) bio = life; genesis = origin (biogenesis: the principle that life gives rise to life) chemo = chemical; auto = self (chemoautotrophs: organisms that need only carbon dioxide as a carbon source and extract energy from inorganic substances) dinos = whirling (dinoflagellates: protists with two flagella that cause them to spin) endo = inner (endospores: bacterial resting cells) exo = outside (exotoxins: toxic proteins secreted by bacterial cells) flagell = a whip (flagellates: protozoa that move by means of one of more flagella) hetero = different (chemoheterotrophs: organisms that must consume organic molecules for both energy and carbon) patho = disease (pathogens: organisms that cause disease) photo = light (photoautotrophs: photosynthetic organisms, including the cyanobacteria) planktos = wandering (plankton: communities of mostly microscopic organisms that drift or swim near the water surface) protos = first; zoan = animal (protozoan: early protists that ingested food) pseudo = false; pod = foot (pseudopodia: temporary extensions of a cell used for locomotion and/or feeding) spiro = spiral (spirochetes: spiral-shaped bacteria) sym = together (endosymbiosis: the process whereby mitochondria and chloroplasts exist as associations between prokaryotic cells living within larger prokaryotic cells)

Relevant Songs to Play in Class “Got the Time,” Anthrax

“Tiny Dancer,” Elton John

“Tiny Bubbles,” Don Ho

“Germs,” Weird Al Yankovic

“More Than Words,” Extreme

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: This is not a good idea as all life depends on bacteria to perform numerous ecological functions. You could predict that eliminating all bacteria from an environment would result in a buildup of toxic wastes and dead organisms (both of which may be decomposed by bacteria), a shutdown of chemical cycling, and the consequent death of all organisms.

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12. Suggested answer: The initial atmosphere on Earth is thought to have been anaerobic, containing little or no atmospheric oxygen. Therefore, organisms requiring molecular oxygen to survive could not exist. Photosynthetic organisms, however, use carbon dioxide and water to produce oxygen and carbohydrates. It follows then that these organisms would be the source of oxygen in the atmosphere and would exist before the oxygenutilizing organisms.

Biology and Society 13. This question requires the student to perform a newspaper/Web search; depending on the reference, the answers to this question will differ. Many of the cases will be E. coli.

14. Some issues and questions to consider: What new problems might arise from an attempt to eradicate an organism used as a bioweapon? How could the world society ensure that a treaty such as Biological Weapons Convention will be effective? What costs might there be to individual rights and freedoms if a government imposes societal restrictions in an attempt to prevent a terrorist attack?

Additional Critical Thinking Questions The Process of Science 1. A technique called polymerase chain reaction (PCR) is used to manufacture multiple copies of a specific segment of DNA. This process requires DNA polymerase to catalyze the reaction. One step in the procedure requires that the mixture be heated to a high temperature. What kind of organism would be a good source of such DNA polymerase?

Explain your reasoning.

Suggested answer: Prokaryotes that are extreme thermophiles contain enzymes that are not denatured (destroyed) by high temperatures. These microbes would be a likely source of the DNA polymerase.

2. Through clever marketing and misleading information provided by the media, our society has been convinced that we need to regularly use antibacterial products. We can purchase antibacterial hand sanitizer, antibacterial kitchen utensil drawers, and even antibacterial toys for our children. Should we try to eliminate bacteria from our environment? Explain your answer.

Suggested answer: Most bacteria have very beneficial roles in the environment and do not need to be destroyed. Only a small number of bacterial species are capable of causing human disease.

By attempting to kill harmless bacteria, the selective pressure can favor resistant bacteria. We can also create “super bacteria” that are resistant to normal sterilization processes because many of the antibacterial soaps and chemicals are not 100% effective.

Biology and Society 3. A friend of yours owns a fast-food restaurant and is hesitant about continuing to use harsh chemicals to rid his sink drain of vegetable oil and animal fat deposits. Can you think of an alternative solution to his problem that might utilize living organisms? What are some of the issues that you would have to consider?

Some issues and questions to consider: One alternative would be to isolate (or genetically engineer) species of bacteria that are able to degrade vegetable oil and animal fat into harmless products. These bacteria could be incorporated into a spray solution that is

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sprayed on the insides of the drains. This solution would have to be tested on metal and plastic drains and piping to be sure that the plumbing would not be harmed. Since the bacteria would be washed down the drain, the bacteria chosen must be tested thoroughly and must be shown not to be harmful to the environment and other organisms. Finally, the local health department would likely need to approve.

4. Certain dinoflagellates have massive blooms, which cause red tides. The result is typically a massive fish kill. Some of the toxins produced by the dinoflagellates can also cause neurological problems for humans who encounter them. Should we attempt to kill the dinoflagellates before the blooms occur, or should we let nature take its course? What would be some of the advantages and potential disadvantages of each option?

Some issues and questions to consider: Attempting to kill the dinoflagellates prior to a bloom could help prevent fish kills and human complications, but the methods used to kill them might disrupt the aquatic ecosystem, making even worse problems. It is also important to understand what causes the blooms and take measures to prevent blooms from occurring.

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CHAPTER

16

Plants, Fungi, and the Move onto Land

Why This Chapter Matters 1. Humans depend on plants for thousands of products including food, building materials, fuels, and medicines.

2. Fungi are important decomposers of ecosystems and human-made materials, are parasitic to animals and plants, and are commercially important in the production of food and beverages and the manufacture of antibiotics.

3. The exploding human population and the resulting demands for space and resources are causing the extinction of plant species at an unprecedented rate.

4. The tropical rain forests may be a medicine chest of healing plants that could become extinct before we even know they exist.

Chapter Objectives Biology and Society: The Diamond of the Kitchen 1. Explain why truffles are highly desired, difficult to find, and expensive.

2. Describe the symbiotic relationship between trees and fungi.

Colonizing Land 3. Distinguish between algae and plants. Describe the functions of the following terrestrial adaptations: stomata, cuticle, lignin, vascular tissue, and gametangia.

4. Describe the process by which algae likely evolved onto land.

Plant Diversity 5. Describe the four major periods of plant evolution and the major adaptations associated with each stage.

6. Describe the life cycle and two key terrestrial adaptations of mosses.

7. Explain how ferns differ from and are similar to mosses. Explain how ancient life became today’s fossil fuels.

8. Describe the environmental conditions that favored the evolution of gymnosperms.

Describe the three additional adaptations to life on land that first appeared in gymnosperms.

9. Describe the parts and functions of a flower. Explain how flowers attract pollinators and why this is adaptive.

10. Describe the reasons for the ongoing loss of plant diversity and its likely cost to humans.

Fungi 11. Describe the feeding, structure, reproduction, ecological roles, and commercial uses of fungi.

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Evolution Connection: Mutually Beneficial Symbiosis 12. Distinguish between parasitic and mutually beneficial symbiotic relationships. Describe the relationships between fungi and plant roots to form mycorrhizae and algae and fungi to form lichens.

Lecture Outline I. Biology and Society: The Diamond of the Kitchen 1. Truffles are a. subterranean reproductive bodies of a certain fungus and b. highly prized by gourmets for their powerful scents.

2. Truffles, and many fungi, have an association with tree roots, a type of symbiosis, an interaction in which one species lives in or on another species 3. The symbiotic relationship between a truffle and a tree a. helps the plant absorb water and inorganic nutrients and b. helps the fungus by receiving sugars and other organic molecules from the plant.

II. Colonizing Land 1. Plants are terrestrial organisms that include forms that have returned to water, such as water lilies A. Terrestrial Adaptations of Plants 1. A plant is a. a multicellular eukaryote and b. a photoautotroph, making organic molecules by photosynthesis.

2. Structural Adaptations 3. In terrestrial habitats, the resources that a photosynthetic organism needs are found in two very different places a. Light and carbon dioxide are mainly available in the air. b. Water and mineral nutrients are found mainly in the soil.

4. The complex bodies of plants are specialized to take advantage of these two environments by having a. aerial leaf-bearing organs called shoots and b. subterranean organs called roots.

5. Most plants have mycorrhizae, symbiotic fungi associated with their roots, in which the fungi a. absorb water and essential minerals from the soil, b. provide these materials to the plant, and c. are nourished by sugars produced by the plant.

6. Mycorrhizae are key adaptations that made it possible for plants to live on land 7. Leaves are the main photosynthetic organs of most plants, with a. stomata, microscopic pores found on a leaf’s surface, which allow for the exchange of carbon dioxide and oxygen with the atmosphere, b. vascular tissue, a system of tube-shaped cells that i. branch throughout the plant and ii. transport vital materials, and 216

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c. a waxy layer called the cuticle surface that i. coats the leaves and other aerial parts of most plants and ii. helps the plant retain water.

8. Vascular tissue in plants is also found in the a. roots and b. shoots.

9. Two types of vascular tissue exist in plants: a. xylem transports water and minerals from roots to leaves and b. phloem distributes sugars from leaves to i. the roots and ii. other nonphotosynthetic parts of the plant.

10. Reproductive Adaptations 11. Plants produce their gametes in protective structures called gametangia, which have a jacket of protective cells surrounding a moist chamber where gametes can develop without dehydrating 12. The zygote develops into an embryo while still contained within the female parent in plants but not in algae B. The Origin of Plants from Green Algae 1. The algal ancestors of plants a. carpeted moist fringes of lakes or coastal salt marshes and b. first evolved over 500 million years ago.

2. Charophytes a. are a modern-day lineage of green algae and b. may resemble one of these early plant ancestors.

3. Plants and present-day charophytes probably evolved from a common ancestor

III. Plant Diversity 1. The history of the plant kingdom is a story of adaptation to diverse terrestrial habitats A. Highlights of Plant Evolution 1. The fossil record chronicles four major periods of plant evolution, which are also evident in the diversity of modern plants 2. (1) About 475 million years ago, plants originated from an algal ancestor giving rise to bryophytes, nonvascular plants without a. lignified walls, b. true roots, and c. true leaves. d. Bryophytes include i. mosses, ii. liverworts, and iii. hornworts.

(2) About 425 million years ago, ferns and a few other groups of vascular plants evolved a. with vascular tissue hardened with lignin but b. without seeds.

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(3) About 360 million years ago, gymnosperms evolved with seeds that consisted of an embryo packaged along with a store of food, a. within a protective covering, but b. not enclosed in any specialized chambers. c. Today, conifers i. consist mainly of cone-bearing trees such as pines and ii. are the most diverse and widespread gymnosperms.

(4) About 140 million years ago, angiosperms evolved with complex reproductive structures called flowers that bear seeds within protective chambers called ovaries.

3. The great majority of living plants a. are angiosperms, b. are represented by more than 250,000 species, and include i. fruit and vegetable crops, ii. grains and other grasses, and iii. most trees.

B. Bryophytes 1. Mosses a. are bryophytes, b. sprawl as low mats over acres of land, and c. need water to reproduce because their sperm swim to reach eggs within the female gametangium.

2. Mosses display two key terrestrial adaptations: a. a waxy cuticle that helps prevent dehydration and b. the retention of developing embryos within the mother plant’s gametangium.

3. Mosses have two distinct forms: a. the gametophyte, which produces gametes, and b. the sporophyte, which produces spores.

4. The life cycle of a moss exhibits an alternation of generations shifting between the a. gametophyte and b. sporophyte forms.

5. Among plants, mosses, and other bryophytes are unique in having the gametophyte as the larger, more obvious plant C. Ferns 1. Ferns are a. seedless vascular plants and b. by far the most diverse seedless vascular plants, with more than 12,000 known species.

2. The sperm of ferns, like those of mosses, a. have flagella and b. must swim through a film of water to fertilize eggs.

3. During the Carboniferous period, from about 360 to 300 million years ago, ferns a. were part of a great diversity of seedless plants and b. formed swampy forests over much of what is now Eurasia and North America.

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4. As they died, these forests a. fell into stagnant wetlands, b. did not decay, and c. eventually helped to form coal.

5. Fossil fuels a. formed from the remains of long-dead organisms and b. include coal, oil, and natural gas.

6. The burning of fossil fuels releases a. carbon dioxide and b. other greenhouse gases into the atmosphere, contributing to global climate change.

D. Gymnosperms 1. Near the end of the Carboniferous period, the climate turned drier and colder, favoring the evolution of gymnosperms, which can a. complete their life cycles on dry land and b. withstand long, harsh winters.

2. The descendants of early gymnosperms include the conifers, or cone-bearing plants 3. Conifers 4. Conifers a. cover much of northern Eurasia and North America, b. are usually evergreens, which retain their leaves throughout the year, and c. include the tallest, largest, and oldest organisms on Earth.

5. Terrestrial Adaptations of Seed Plants 6. Conifers and most other gymnosperms have three additional terrestrial adaptations that make survival in diverse terrestrial habitats possible: a. further reduction of the gametophyte, b. pollen, and c. seeds.

7. Seed plants have a greater development of the diploid sporophyte compared to the haploid gametophyte generation 8. A pine tree or other conifer is actually a sporophyte with tiny gametophytes living in cones 9. A second adaptation of seed plants to dry land came with the evolution of pollen 10. A pollen grain a. is actually the much-reduced male gametophyte and b. houses cells that will develop into sperm.

11. The third terrestrial adaptation was the development of the seed, consisting of a a. plant embryo and b. food supply packaged together within a protective coat.

12. Seeds a. develop from structures called ovules, located on the scales of female cones in conifers, and b. can remain dormant for long periods before they germinate, as the embryo emerges through the seed coat as a seedling.

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E. Angiosperms 1. Angiosperms a. dominate the modern landscape, b. are represented by about 250,000 species, and c. supply nearly all of our food and much of our fiber for textiles.

2. Their success is largely due to a. refinements in vascular tissue to make water transport more efficient and b. the evolution of the flower.

3. Flowers, Fruits, and the Angiosperm Life Cycle 4. Flowers help to attract pollinators that transfer pollen a. from the sperm-bearing organs of one flower b. to the egg-bearing organs of another.

5. A flower is a short stem bearing modified leaves that are attached in concentric circles at its base a. Sepals form the outer layer and are usually green. b. Next inside are petals, which are often colorful and help to attract pollinators. c. Stamens, the male reproductive structures, are below the petals. Pollen grains develop in the anther, a sac at the top of each stamen. d. Carpels are the female reproductive structure at the center of the flower. The carpel includes i. the ovary, a protective chamber containing one or more ovules in which the eggs develop, and ii. the sticky tip of the carpel, the stigma, which traps pollen.

6. Flowers come in many forms 7. Flowers are an essential element of the angiosperm life cycle 8. Although both have seeds, a. angiosperms enclose the seed within an ovary and b. gymnosperms have naked seeds.

9. Fruit a. is a ripened ovary, b. helps protect the seed, c. increases seed dispersal, and d. is a major food source for animals.

10. Angiosperms and Agriculture 11. Gymnosperms supply most of our lumber and paper 12. Angiosperms a. provide nearly all our food and b. supply fiber, medications, perfumes, and decoration.

13. Agriculture is a unique kind of evolutionary relationship between a. plants and b. animals.

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F. Plant Diversity as a Nonrenewable Resource 1. The exploding human population is a. extinguishing plant species at an unprecedented rate and b. destroying 50 million acres, an area the size of the state of Washington, every year!

2. Humans depend on plants for thousands of products including a. food, b. building materials, and c. medicines.

3. Preserving plant diversity is important to a. many ecosystems and b. humans.

4. Scientists are now rallying to a. slow the loss of plant diversity and b. encourage management practices that use forests as resources without damaging them.

IV. Fungi 1. Fungi a. recycle vital chemical elements back to the environment in forms other organisms can assimilate and b. form mycorrhizae, fungus-root associations that help plants absorb mineral and water from the soil.

2. Fungi are a. eukaryotes, b. typically multicellular, and c. more closely related to animals than plants, arising from a common ancestor about 1.5 billion years ago.

3. Fungi a. come in many shapes and sizes and b. represent more than 100,000 species.

A. Characteristics of Fungi 1. Fungi have unique a. structures and b. forms of nutrition.

2. Fungal Nutrition 3. Fungi a. are chemoheterotrophs and b. acquire their nutrients by absorption.

4. A fungus a. digests food outside its body by secreting powerful digestive enzymes to break down the food and b. absorbs the simpler food compounds.

5. Fungal Structure 6. The bodies of most fungi are constructed of threadlike filaments called hyphae.

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7. Hyphae are minute threads of cytoplasm surrounded by a. a plasma membrane and b. cell walls mainly composed of chitin.

8. Hyphae branch repeatedly, forming an interwoven network called a mycelium (plural, mycelia), the feeding structure of the fungus 9. Fungal Reproduction 10. Mushrooms a. arise from an underground mycelium and b. mainly function in reproduction.

11. Fungi reproduce by releasing haploid spores that are produced either a. sexually or b. asexually.

B. The Ecological Impact of Fungi 1. Fungi have a. an enormous ecological impact and b. many interactions with humans.

2. Fungi as Decomposers 3. Fungi and bacteria a. are the principal decomposers of ecosystems and b. keep ecosystems stocked with the inorganic nutrients necessary for plant growth.

4. Without decomposers, carbon, nitrogen, and other elements would accumulate in nonliving organic matter 5. Molds can destroy a. fruit, b. grains, c. wood, and d. human-made material.

6. Parasitic Fungi 7. Parasitic fungi absorb nutrients from the cells or body fluids of living hosts 8. Of the 100,000 known species of fungi, about 30% make their living as parasites, including a. Dutch elm disease and b. deadly ergot, which infests grain.

9. About 50 species of fungi are known to be parasitic in humans and other animals, causing a. lung and vaginal yeast infections and b. athlete’s foot.

C. The Process of Science: Did a Fungus Lead to the Salem Witch Hunt?

1. Observation: In 1692, eight young girls were accused of being witches and had symptoms consistent with ergot poisoning 2. Question: Did an ergot outbreak cause the witch hunt?

3. Hypothesis: The girls’ symptoms were the result of ergot poisoning 4. Prediction: The historical facts would be consistent with this hypothesis

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5. Results: a. Agricultural records from 1691, before the symptoms appeared, indicated a particularly warm and wet year, in which ergot thrives. b. Records from the following year, when accusations of witchcraft died down, indicate a dry year consistent with an ergot die-off. c. This correlation is consistent with the hypothesis but not conclusive.

6. Commercial Uses of Fungi 7. Fungi are commercially important. Humans eat them and use them to a. produce medicines such as penicillin, b. decompose wastes, and c. produce bread, beer, wine, and cheeses.

D. Evolution Connection: Mutually Beneficial Symbiosis 1. Relationships between species are also an evolutionary product 2. Mutually beneficial symbiotic relationships benefit both species 3. Examples of mutually beneficial symbiotic relationships involving fungi include a. mycorrhizae, the association of fungi and plant roots, and b. lichens, the association of fungi and algae.

Chapter Guide to Teaching Resources Colonizing Land Student Misconceptions and Concerns 1. Students often misunderstand evolution as a deliberate and directed process. This chapter provides good examples of how evolution actually occurs. American chestnut trees were driven nearly to extinction because they did not possess the adaptations that would have helped them to survive a blight fungus. If evolution involved acquiring needed adaptations, why then would the chestnuts suffer? As plants evolved onto land, the properties of a terrestrial environment selected among the diversity of the species that existed. For example, plants that produced leaves with more wax had the advantage of greater water retention. Plants did not evolve adaptations to address the needs of living on land. Instead, terrestrial adaptations evolved in plants that already had the traits that permitted them to invade this new environment.

2. The text identifies charophytes as the algal group most closely related to plants. Students might misinterpret this to mean that modern charophytes were the direct ancestors of plants. Instead, modern charophytes and plants share a common ancestor, but each has been evolving since the lineages diverged. This same confusion occurs when considering the evolutionary history of humans and chimps. Humans and chimps share a common ancestor. Modern humans did not evolve from modern chimps. Although such distinctions may be clear to us as instructors, beginning students with little experience can easily be confused.

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Teaching Tips 1. Consider challenging your students to suggest the new demands of emerging from water and living on land. They could work in small groups in class or outside of class and e-mail their responses to you. By asking them to consider the challenges that plants (and in the next chapter, animals) faced when they moved onto land prepares them for the discussions of the adaptations that resulted and are discussed in Chapter 16.

2. The authors make a connection between water lilies and whales, because both are aquatic organisms that evolved from terrestrial forms. Students might contemplate the changes in these organisms as they returned to the aquatic environment from which their ancestors emerged.

3. Point out to your students that in an aquatic environment, resources (such as nutrients and water) are exposed to nearly the entire plant. However, on land, structural specializations have evolved because resources are no longer evenly exposed to the plant (roots are subterranean adaptations and shoots are aerial adaptations).

4. Consider an analogy between vascular systems in plants and a major interstate highway, with traffic running in opposite directions. Highways, like vascular tissues, permit the widespread distribution of concentrated resources.

5. Have your students discuss the specific advantages of similar adaptations in the reproductive systems of plants and mammals. What are the advantages to keeping the developing embryos with the parent? (Possible answer: The embryonic environment can be carefully regulated by the parent and the parent can better protect the young from damage, disease, or predation.) What are the disadvantages to keeping the developing embryos with the parent? (Possible answer: All of the embryos are concentrated and collectively jeopardized if the parent plant is damaged or destroyed.)

Plant Diversity Student Misconceptions and Concerns 1. Students can easily confuse the animal and plant reproductive cycles. However, the unique features of alternation of generations in plants (and certain algae) make analogies and parallels challenging and potentially confusing when referencing animal life cycles. One possible relevant exercise would be to compare the timing of mitosis and meiosis in plant and animal life cycles.

2. Students often confuse global warming and the destruction of the ozone layer. This might be a good time to discuss or clarify global warming. The carbon removed from the air in the Carboniferous has been “locked up” in coal for about 300 million years. By burning fossil fuels, we are reintroducing carbon that has been “out of circulation.” Thus, there is a net gain in global carbon dioxide, which may act like glass in a car to reflect back heat (or glass in a greenhouse). Note that burning ethanol derived from corn does not directly contribute to global warming because the carbon in the ethanol was removed from the air only a year or two ago, instead of hundreds of millions of years ago (although the use of fossil fuels to raise, harvest, and process corn does contribute to global warming).

Teaching Tips 1. The authors describe four major periods of plant evolution. The remainder of the chapter sections on plants describe these periods as they evolved in major plant groups. This is consistent with good lecture advice: Tell them what you are going to tell them, tell them, then tell them what you told them (summarize).

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2. Students might enjoy the parallel between a chicken egg and the first seeds (although this is a limited analogy). Each consists of a developing embryo, enclosed in a water-resistant packet, along with a store of food.

3. The support provided by many tightly packed mosses is analogous to the collective support of the many fibers of plush carpeting. Each fiber of carpet and each individual moss plant might easily collapse without the support of its neighbor.

4. Students might wonder if humans and other animals do not also qualify as having alternation of generations. Although we do have haploid gametes, the haploid and diploid stages do not include multicellular individuals.

5. Depending on where your course is taught, coal may be an important part of the economy.

The geology of these coal deposits helps us interpret the rich history of life on Earth. If you live in a coal region, consider spending additional time on how coal was deposited, why it is an important source of energy, and how the use of fossil fuels contributes to global warming.

6. As François Jacob suggested, evolution works as a tinkerer and not like an engineer. New forms evolve by remodeling old forms. The structure of a flower represents the remodeling of leaves, a subject that you may want to explore in additional detail as an important lesson in evolution.

7. Floral shops frequently discard magnificent flowers that are just beyond their peak.

Teachers can obtain such discards for free by contacting local floral shops and sharing your educational needs. Having a variety of flowers on hand can brighten up any discussion of angiosperms.

8. Before lecturing on the examples of angiosperm and animal mutualism, let your students try to name as many as they can. They could work in small groups or do this ahead of time and bring their responses to class (or e-mail them).

9. The symbiotic relationships between angiosperms and animals are extensive but not always mutualistic. Challenge students to list all of the ways that plant reproduction benefits from animals (examples include seed dispersal in fruit and hitchhiker strategies of seeds with attachment devices).

10. You might have your class spend a minute just to list all of the plant-derived materials in your classroom—cotton material, wood for pencils, paper in many forms, and the like.

11. The tremendous volume of pollen released into the air is apparent to anyone suffering from allergies. You might wish to have your students find the pollen counts for your area, commonly given out in weather information. It might be interesting to track the pollen counts as you go through part of the semester.

12. Depending on where your course it taught, you can reference any local agricultural monoculture that replaced a much more diverse native ecosystem, perhaps many years ago.

From old-growth forest replaced with a single fast-growing species, to vast fields of corn, wheat, or soybeans that replaced native prairies, students may fail to see this loss of diversity.

Fungi Student Misconceptions and Concerns 1. The diverse ecological and medical roles of fungi are often underappreciated by students.

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2. Students often view fungi as some type of plant. However, many differences between them exist (for example, fungi are not photosynthetic and have cell walls made of chitin instead of cellulose). Emphasize these basic differences early in your lectures to clearly distinguish fungi as a separate group.

Teaching Tips 1. Consider asking your students to distinguish between fungi and animals. Both are multicellular heterotrophs lacking cellulose. Students will have to dig a little to discover that fungi have cell walls primarily composed of chitin. You might challenge them further to identify animals that also absorb their nutrients directly from their environments (for example, tapeworms).

2. The physical relationship between a fungus and its hyphae is generally analogous to a fire hydrant and the underground water pipes. Only the fire hydrant emerges above the surface of the ground.

3. The chytrid fungus is suspected in the worldwide decline of many amphibian species.

Many Internet resources are available to learn more about the impact of this fungus on amphibians. The following resources are entry points into the extensive information available about that significant threat to amphibian biodiversity.

Amphibian Ark: www.amphibianark.org/chytrid.htm The Centers for Disease Control and Prevention describe the origin of the chytrid fungus at www.cdc.gov/ncidod/EID/vol10no12/03-0804.htm.

The following website is devoted to updates on amphibian disease: www.jcu.edu.au/school/phtm/PHTM/frogs/ampdis.htm.

4. The mechanism of natural selection depends in part on the overproduction of offspring.

A single mushroom can release as many as 1 billion spores. In addition to facilitating reproduction, such overproduction also increases the likelihood of dispersal.

5. About 80% of plant diseases are from fungi. Further, human fungal diseases include athlete’s foot, ringworm, and vaginal yeast infections. If certain fungal infections are particularly problematic in your region, consider emphasizing them in your lecture.

6. Students are unlikely to appreciate the roles that fungi play in natural environments; or in causing human diseases; or the benefits of fungi to human society, including bioremediation and the production of drugs, alcoholic beverages, baked goods, or fuel. To increase student interest, consider starting your lectures on fungi by noting the many effects of fungi on human life. Also, consider outside-of-class student assignments to investigate specific roles of fungi that may be of particular interest to students with medical, agricultural, environmental, or industrial majors.

7. Wonderful coverage of lichens can be found at the aptly named www.lichen.com/ and www.sharnoffphotos.com/lichens/lichens_home_index.html.

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Key Terms absorption alternation of generations angiosperms anther bryophytes carpel charophytes conifers cuticle double fertilization endosperm

ferns flower fossil fuels fruit fungi gametangia gametophyte germinate gymnosperms hyphae lichens lignin

mosses mycelium mycorrhizae ovary ovules petals phloem plant pollen grain roots seed sepals

shoots spore sporophyte stamen stigma stomata symbiosis vascular tissue xylem

Word Roots angion = a container; sperma = seed (angiosperms: flowering plants) bryo = moss; phyte = plant (bryophytes: a group of nonvascular plants that includes the mosses) endo = inner; sperm = seed (endosperm: a source of nutrition for the developing embryo in a seed) gamet = a wife or husband (gametangia: protective structures where plants produce their gametes) gymno = naked (gymnosperms: vascular plants such as conifers with seeds not enclosed in specialized chambers) myco = fungus; rhiza = root (mycorrhizae: symbiotic root-fungus combinations) sporo = seed (sporophyte: the moss stage with diploid cells) stoma = mouth (stomata: pores in leaves for gas exchange) sym = together; bio = life (symbiosis: a relationship between two species in which one organism lives in or on another)

Relevant Songs to Play in Class “Send Me on My Way,” Rusted Root

“Mushroom Festival in Hell,” Ween

“The Dreaming Tree,” Dave Matthews Band

Answers to End-of-Chapter Questions The Process of Science 13. Suggested answer: Mosses are haploid plants (the dominant stage in the moss life cycle is the gametophyte, which is haploid). The diploid (sporophyte) generation is dominant in most other plants. Mutations are more likely to show up in haploid organisms because they only have one set of genes. Recessive mutations may not be expressed in a diploid organism. Some factors to consider in designing your experiment: What are the advantages/disadvantages of performing the experiment in the laboratory? In the field? What variables would be important to control?

How many potted plants should you use? At what distances from the radiation source would you place them? What would serve as a control group for the experiment? What age of plants should you use? What is the mutation rate of mosses under natural conditions? ..

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14. Suggested answer: The mycelium of an individual fungus can be massive. The hyphae branch out quickly in response to a food source and may cover a very large area. One way to confirm that distant hyphae belong to the same organism is to perform a DNA profiling experiment (as described in Chapter 12): gather samples of the hyphae from various locations and then compare the DNA fingerprints. If they match, this supports the hypothesis that you have found one giant fungus.

Biology and Society 15. Suggested answers: Population growth is a major factor—more people inhabit Earth and the population growth rate is often highest in developing nations that are home to rain forests. Forests are cut and cleared often for timber products, cattle grazing, and even just for fuel used for cooking.

Some issues and questions to consider: Are there products that can be found only in the rain forest that necessitate destruction of the forest? How much of this destruction is financially motivated? Once a country exhausts its resources, does it have a right to influence another country? Who should be responsible for the preservation of rain forests? How can we motivate people to be concerned with conservation? Do indigenous peoples have more rights than outsiders when it comes to harvesting products from the tropical rain forest they call home? How can you balance the rights and needs of local peoples with more global concerns?

16. Some issues and questions to consider: National forests are considered to be the “Land of Many Uses.” How do you balance the need for recreational activities such as hiking and snowmobiling with resource extraction such as mining and logging? What are the consequences of these activities in the forest, such as hiking and snowmobiling?

Logging? Mining? How do you balance reasonable regulations while still protecting the forest? Who should enforce these regulations? Should forests be protected solely for recreational activities? Who should be allowed to profit from the natural resources in national forests?

Additional Critical Thinking Questions The Process of Science 1. Suggest some ways to test the hypothesis that a particular angiosperm species is pollinated exclusively by beetles.

Suggested answer: The answer to this would come through field observations and controlled experiments. The experiments would need to be performed using plants isolated from any insects to see if they are able to pollinate without assistance. These plants would then have to be tested with different insect species that live in the same area as the plants in nature to see how the rate of pollination changes. The experiment would need to answer the following questions: Can the plant be self-pollinated? What other animals might serve as pollinators?

2. Can you think of a strategy to use lichens as monitors for air quality in an urban area?

Suggested answer: One possibility might be to have lichens growing on posts at certain locations in the city and suburban areas. Lichen health can be monitored regularly at these sites to determine any unhealthy areas or trends. Would different species of lichens (ones that grow on rocks versus ones that grow on trees) be better suited to monitoring air quality?

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3. Many fungi produce antibiotics, such as penicillin, that are valuable in medicine. Of what value might the antibiotics be to the fungi? Similarly, fungi often produce compounds with unpleasant tastes and odors as they digest their food. What might be the value of these chemicals to the fungi? How might the production of antibiotics and odors have evolved?

Suggested answer: Many types of bacteria break down organic materials and would therefore compete with fungi. Antibiotics probably kill bacteria that compete with fungi for food. Similarly, bad tastes and odors deter animals that eat or compete with fungi. They are valuable warnings to animals that might eat spoiled food on which the fungi are growing. Those fungi that produce antibiotics and bad-smelling and bad-tasting chemicals would survive and reproduce better than fungi unable to inhibit competitors. Animals that could recognize the smells and tastes also would survive and reproduce better than their competitors. Thus, natural selection would favor fungi that produce the chemicals and, to some extent, the competitors deterred by them.

Biology and Society 4. Nonvascular plants and seedless vascular plants, such as mosses and ferns, respectively, are extremely common and several are economically and ecologically very important (for example, energy from peat and coal). However, essentially none of these groups is of agricultural importance. Why? Can you think of attributes that seedless plants lack that may explain why so many seed plants are of agricultural significance to society? What attributes do seedless plants have that limit their agricultural use?

Some issues and questions to consider: In nonvascular plants, the lack of vascular tissue can prevent growth against gravity (upward), and they require water for fertilization to occur. Seedless vascular plants can grow upward against gravity but still require water for fertilization. Seed plants, on the other hand, have vascular tissue that transports water and nutrients, and seed plants do not require water for fertilization. Cultivating seed plants is easier since dry seeds can be stored and transported for later planting. Seeds and fruits also store nutrients, making them valuable food sources. The stems and leaves of some seed plants are also useful as food. Many of the crops we consume are actually the fruits; humans rarely consume just the leafy portion of a plant. Most of the nutrients are in the fruits and seeds.

5. American chestnut trees once made up more than 25% of the hardwood forests of the eastern United States. These trees were wiped out by a fungus accidentally introduced on imported Asian chestnuts, which themselves are not affected. More recently, a fungus (Discula) has killed large numbers of dogwood trees from New York to Georgia. Some experts suspect the parasite was accidentally introduced from elsewhere. Why are plants particularly vulnerable to fungi imported from other regions? What kinds of human activities might contribute to the spread of plant diseases? Do you think the introduction of a plant pathogen such as chestnut blight is more likely or less likely to occur in the future?

Why? Some issues and questions to consider: Plants are more vulnerable to fungi imported from other regions because they have not had the chance to evolve resistance. Human activities that contribute to the spread of disease are construction (materials imported to new areas for building) and the import of exotic plant species. The introduction of a foreign plant pathogen such as chestnut blight is more probable in the future as the global economy increases. Should the import of exotic plants and animals be further regulated or stopped?

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CHAPTER

17

The Evolution of Animals

Why This Chapter Matters 1. The lives of humans and other animals are intimately interwoven as we rely on animals as sources of food, understand animals as vectors of human disease, appreciate their roles in ecosystems, and enjoy each other in companionship.

2. Understanding the evolutionary history of animals helps us understand our evolutionary history and our place in the living world.

Chapter Objectives Biology and Society: The Discovery of the Hobbit People 1. Describe the fossil discoveries on the Indonesian island of Flores and relate the findings to modern humans.

The Origins of Animal Diversity 2. Define what it means to be an animal and describe common aspects of animal development.

3. Describe the significance of the Cambrian explosion.

4. Distinguish between the nine major animal phyla according to the presence of tissues, type of body symmetry, presence of a body cavity, type of digestive tract, and presence of segmentation.

Major Invertebrate Phyla 5. Describe the body structure and feeding strategies of sponges, cnidarians, molluscs, and flatworms.

6. Describe the general structure of annelids and nematodes. Compare the lifestyles and feeding habits of earthworms, polychaetes, leeches, and nematodes.

7. Describe the general structure of arthropods, and discuss the advantages and disadvantages of an exoskeleton. Distinguish between arachnids, crustaceans, millipedes, centipedes, and insects.

8. Describe the general structure of echinoderms and explain the significance of the water vascular system.

Vertebrate Evolution and Diversity 9. Describe the four defining characteristics of the phylum Chordata.

10. Distinguish between the following groups: invertebrate chordates, jawless vertebrates, cartilaginous fishes, ray-finned fishes, and lobe-finned fishes. Describe the significance of jaws and a swim bladder.

11. Describe several aquatic and terrestrial adaptations of amphibians.

12. Describe the adaptations of reptiles to life on land.

13. Describe three adaptations for flight found in birds.

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14. Describe the characteristics common to all mammals. Distinguish between monotremes, marsupials, and eutherian mammals, and provide examples of each.

The Human Ancestry 15. Describe the primate adaptations for life in trees. Compare the three main groups of primates, noting examples of each.

16. Compare Old World monkeys and New World monkeys.

17. Explain why it is incorrect (a) to consider chimpanzees as our ancestors, (b) to think of human evolution as a ladder, and (c) to think that human traits evolved together.

18. Describe the traits of each of the following species and the relationships between them: Australopithecus afarensis, Homo habilis, Homo erectus, Homo neanderthalensis, and Homo sapiens, and the hobbit people of Flores.

19. Describe the evolution and impact of our species as we spread across the world.

Evolution Connection: Are We Still Evolving?

20. Describe examples of modern human evolution.

Lecture Outline I. Biology and Society: The Discovery of the Hobbit People 1. In 2003, anthropologists discovered bones on the Indonesian island of Flores, dating back about 18,000 years, of people just over three feet tall, and with heads one-third the size of modern humans 2. Since the initial discovery, researchers have unearthed the bones of a dozen or so more of these miniature humans 3. Some scientists think that these bones represent a previously unknown human species, named Homo floresiensis 4. Other scientists suggest that the bones are from diseased Homo sapiens

II. The Origins of Animal Diversity 1. Animal life began in Precambrian seas with the evolution of multicellular creatures that ate other organisms A. What Is an Animal?

1. Animals are a. eukaryotic, b. multicellular, c. heterotrophic organisms that obtain nutrients by ingestion, and d. able to digest their food within their bodies.

2. Animal cells lack the cell walls that provide strong support in the bodies of plants and fungi 3. Most animals have a. muscle cells and b. nerve cells that control the muscles.

4. Most animals a. are diploid, b. reproduce sexually, and c. proceed through a series of typically similar developmental stages.

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B. Early Animals and the Cambrian Explosion 1. Scientists hypothesize that animals evolved from a colonial flagellated protist 2. The oldest animal fossils found are 550–575 million years old 3. The molecular data suggest a much earlier origin for animals 4. Animal diversification appears to have accelerated rapidly from 525 to 535 million years ago, during the Cambrian period 5. Because so many animal body plans and new phyla appear in the fossils from such an evolutionarily short time span, biologists call this episode the Cambrian explosion 6. The Cambrian explosion may have been ignited by a. increasingly complex predator-prey relationships and/or b. an increase in atmospheric oxygen.

7. The genetic framework for complex bodies, a set of “master control” genes, was already in place C. Animal Phylogeny 1. Biologists categorize animals by a. “body plan,” general features of body structure and, b. more recently, genetic data.

2. One major branch point distinguishes sponges from all other animals because, unlike more complex animals, sponges lack true tissues 3. A second major evolutionary split is based on body symmetry a. Radial symmetry refers to animals that are identical all around a central axis. b. Bilateral symmetry exists where there is only one way to split the animal into equal halves.

4. Animals also vary according to the presence and type of body cavity, a fluid-filled space separating the digestive tract from the outer body wall 5. There are differences in how the body cavity develops a. If the body cavity is not completely lined by tissue derived from mesoderm, it is called a pseudocoelom. b. A true coelom is completely lined by tissue derived from mesoderm.

III. Major Invertebrate Phyla 1. Invertebrates a. are animals without backbones and b. represent 95% of the animal kingdom.

A. Sponges 1. Sponges represent multiple phyla 2. Sponges a. are stationary animals, b. lack true tissues, and c. probably evolved very early from colonial protists.

3. The body of a sponge resembles a sac perforated with holes 4. Choanocyte cells draw water through the walls of the sponge where food is collected

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B. Cnidarians 1. Cnidarians (phylum Cnidaria) are characterized by a. the presence of body tissues, b. radial symmetry, and c. tentacles with stinging cells.

2. The basic body plan of a cnidarian is a sac with a gastrovascular cavity, a central digestive compartment with only one opening 3. The body plan has two variations: a. the stationary polyp and b. the floating medusa.

4. Cnidarians are carnivores that use tentacles, armed with cnidocytes (“stinging cells”), a. for defense and b. to capture prey.

C. Molluscs 1. Molluscs (phylum Mollusca) are a. represented by soft-bodied animals and b. usually protected by a hard shell.

2. Many molluscs feed by using a file-like organ called a radula to scrape up food 3. The body of a mollusc has three main parts: a. a muscular foot used for movement, b. a visceral mass containing most of the internal organs, and c. a mantle, a fold of tissue that secretes the shell if present.

4. There are three major groups of molluscs a. Gastropods i. include snails which ii. are protected by a single, spiraled shell, iii. have no shell at all, as with slugs and sea slugs. b. Bivalves i. include clams, oysters, mussels, and scallops and ii. have a shell divided into two halves hinged together. c. Cephalopods i. include squids and octopus, ii. typically lack an external shell, and iii. are built for speed and agility.

D. Flatworms 1. Flatworms (phylum Platyhelminthes) are the simplest bilateral animals 2. Flatworms include forms that are a. parasites or b. free-living in marine, freshwater, or damp habitats.

3. The gastrovascular cavity of flatworms a. is highly branched and b. provides an extensive surface area for absorption of nutrients.

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E. Annelids 1. Annelids (phylum Annelida) have body segmentation, a subdivision of the body along its length into a series of repeated parts 2. The three main groups of annelids are a. earthworms, which eat their way through soil, b. polychaetes, marine worms with segmental appendages for movement and gas exchange, and c. leeches, typically free-living carnivores but with some bloodsucking forms.

3. The body of annelids includes a. a coelom and b. a complete digestive tract with i. two openings, a mouth and anus, and ii. one-way movement of food.

F. Roundworms 1. Roundworms (phylum Nematoda) are a. cylindrical in shape, tapered at both ends, and b. the most numerous and widespread of all animals.

2. Roundworms (also called nematodes) are a. important decomposers and b. dangerous parasites in plants, humans, and other animals.

G. Arthropods 1. Arthropods (phylum Arthropoda) are named for their jointed appendages 2. There are over 1 million arthropod species identified, mostly insects 3. Arthropods are a very diverse and successful group, occurring in nearly all habitats in the biosphere 4. There are four main groups of arthropods: a. arachnids, b. crustaceans, c. millipedes and centipedes, and d. insects.

5. General Characteristics of Arthropods 6. Arthropods are segmented animals with a. specialized segments and b. appendages for an efficient division of labor among body regions.

7. The body of arthropods is completely covered by an exoskeleton, an external skeleton that provides a. protection and b. points of attachment for the muscles that move appendages.

8. Arachnids 9. Arachnids a. usually live on land, b. usually have four pairs of walking legs and a specialized pair of feeding appendages, and c. include spiders, scorpions, ticks, and mites. ..

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10. Crustaceans 11. Crustaceans a. are nearly all aquatic, b. have multiple pairs of specialized appendages, and c. include crabs, lobsters, crayfish, shrimp, and barnacles.

12. Millipedes and Centipedes 13. Millipedes and centipedes have similar segments over most of the body 14. Millipedes a. eat decaying plant matter and b. have two pairs of short legs per body segment.

15. Centipedes a. are terrestrial carnivores with poison claws and b. have one pair of short legs per body segment.

16. Insect Anatomy 17. Insects typically have a three-part body consisting of a. head, b. thorax, and c. abdomen.

18. The insect head usually bears a. a pair of sensory antennae and b. a pair of eyes.

19. The mouthparts are adapted for particular kinds of eating 20. Flight is one key to the great success of insects 21. Insect Diversity 22. Insects outnumber all other forms of life combined 23. Insects live in a. almost every terrestrial habitat, b. fresh water, and c. the air.

24. Many insects undergo metamorphosis in their development 25. Young insects may a. appear to be smaller forms of the adult or b. change from a larval form to something much different as an adult.

H. Echinoderms 1. Echinoderms (phylum Echinodermata) a. lack body segments, b. typically show radial symmetry as adults but bilateral symmetry as larvae, c. have an endoskeleton, and d. have a water vascular system that facilitates movement and gas exchange.

2. Echinoderms are a very diverse group

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IV. Vertebrate Evolution and Diversity 1. Vertebrates have unique endoskeletons composed of a. a cranium (skull) and b. a backbone made of a series of bones called vertebrae.

A. Characteristics of Chordates 1. Chordates (phylum Chordata) all share four key features that appear in the embryo and sometimes the adult: a. a dorsal, hollow nerve cord, b. a notochord, c. pharyngeal slits, and d. a post-anal tail.

2. Another chordate characteristic is body segmentation, apparent in the a. backbone of vertebrates and b. segmental muscles of all chordates.

3. Chordates consists of three groups of invertebrates: a. lancelets are bladelike animals without a cranium, b. tunicates, or sea squirts, also lack a cranium, and c. hagfishes are eel-like forms that have a cranium.

4. All other chordates are vertebrates 5. An overview of chordate and vertebrate evolution B. Fishes 1. The first vertebrates were aquatic and probably evolved during the early Cambrian period, about 542 million years ago. They a. lacked jaws and b. are represented today by lampreys.

2. Hagfish a. also lack jaws, b. have a cranium, but c. are not vertebrates.

3. The two major groups of living fishes are the a. cartilaginous fishes (sharks and rays), with a flexible skeleton made of cartilage, and b. bony fishes, with a skeleton reinforced by hard calcium salts.

4. Bony fishes, include a. ray-finned fishes and b. lobe-finned fishes.

5. Cartilaginous and bony fishes have a lateral line system that detects minor vibrations in the water 6. To provide lift off the bottom, a. cartilaginous fish must swim but b. bony fish have swim bladders, gas-filled sacs that help them be buoyant.

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C. Amphibians 1. Amphibians a. exhibit a mixture of aquatic and terrestrial adaptations, b. usually need water to reproduce, and c. typically undergo metamorphosis from an aquatic larva to a terrestrial adult.

2. Amphibians a. were the first vertebrates to colonize land and b. descended from fishes that had i. lungs, ii. fins with muscles, and iii. skeletal supports strong enough to enable some movement on land.

3. Terrestrial vertebrates are collectively called tetrapods, which means “four feet.”

4. Tetrapods include a. amphibians, b. reptiles, and c. mammals.

D. Reptiles 1. Reptiles (including birds) and mammals are amniotes, producing amniotic eggs, which a. are fluid-filled, b. have waterproof shells, and c. enclose the developing embryo.

2. Reptiles include a. snakes, b. lizards, c. turtles, d. crocodiles, e. alligators, and f. birds.

3. Reptile adaptations to living on land include a. an amniotic egg and b. scaled waterproof skin.

4. Nonbird Reptiles 5. Nonbird reptiles are ectotherms, sometimes referred to as “cold-blooded,” which means that they obtain body heat from the environment 6. A nonbird reptile can survive on less than 10% of the calories required by a bird or mammal of equivalent size 7. Reptiles diversified extensively during the Mesozoic era 8. Dinosaurs were a. the most diverse reptile group and b. the largest animals ever to live on land.

9. Birds

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10. Recent genetic and fossil evidence shows that during the great reptilian radiation of the Mesozoic era, birds evolved from a lineage of small, two-legged dinosaurs called theropods 11. Birds have many adaptations that make them lighter in flight: a. honeycombed bones, b. one instead of two ovaries, and c. a beak instead of teeth.

12. Unlike other reptiles, birds are endotherms, maintaining a warmer and steady body temperature 13. Bird wings adapted for flight are airfoils, powered by breast muscles anchored to a keel-like breastbone E. Mammals 1. The first mammals a. arose about 200 million years ago and b. were probably small, nocturnal insect-eaters.

2. Most mammals are terrestrial, although dolphins, porpoises, and whales are totally aquatic 3. Mammals have two unique characteristics: a. hair and b. mammary glands that produce milk, which nourishes the young.

4. There are three major groups of mammals: a. monotremes, egg-laying mammals, b. marsupials, pouched mammals with a placenta, and c. eutherians, also called placental mammals.

5. Eutherian placentas provide more intimate and long-lasting association between the mother and her developing young than do marsupial placentas

V. The Human Ancestry 1. Humans are primates, the mammalian group that also includes a. lorises, b. pottos, c. lemurs, d. tarsiers, e. monkeys, and f. apes.

A. The Evolution of Primates 1. Primates evolved from insect-eating mammals during the late Cretaceous period, about 65 million years ago 2. Primates are distinguished by characteristics that were shaped by the demands of living in trees. These characteristics include a. limber shoulder joints, b. eyes in front of the face, c. excellent eye-hand coordination, and d. extensive parental care.

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3. Taxonomists divide the primates into three main groups 4. The first group of primates includes a. lorises, b. pottos, and c. lemurs.

5. Tarsiers form the second group 6. The third group, anthropoids, includes a. monkeys, b. apes, the ape relatives of humans, c. and humans.

B. The Emergence of Humankind 1. Humans and chimpanzees have shared a common African ancestry for all but the last 5–7 million years 2. Some Common Misconceptions 3. Chimpanzees and humans represent two divergent branches of the anthropoid tree that each evolved from a common, less specialized ancestor 4. Our ancestors were not chimpanzees or any other modern apes 5. Human evolution is not a ladder with a series of steps leading directly from an ancestral anthropoid to Homo sapiens a. This is often illustrated as a parade of fossil hominins (members of the human family) becoming progressively more modern as they march across the page. b. Instead, human evolution is more like a multibranched bush than a ladder.

6. At times in hominins history, several different human species coexisted 7. Different human features evolved at different rates 8. At separate times during human evolution, upright posture and an enlarged brain evolved 9. Australopithecus and the Antiquity of Bipedalism 10. Present-day humans and chimpanzees clearly differ in two major physical features.

Humans a. are bipedal and b. have much larger brains.

11. Bipedalism evolved first a. Before there was the genus Homo, several hominin species of the genus Australopithecus walked the African savanna. b. Scientists are now certain that bipedalism is a very old trait.

12. Homo habilis and the Evolution of Inventive Minds 13. Homo habilis, “handy-man,” a. had a larger brain, intermediate in size between Australopithecus and modern humans, b. walked upright, and c. made stone tools that enhanced hunting, gathering, and scavenging on the African savanna.

14. Homo erectus and the Global Dispersal of Humanity

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15. Homo erectus was the first species to extend humanity’s range from Africa to other continents 16. The global dispersal began about 1.8 million years ago 17. Homo erectus a. was taller than H. habilis and b. had a larger brain.

C. The Process of Science: Who Were the Hobbit People?

1. Observation: The hominin fossils on the island of Flores did not belong to any known species 2. Question: Where does this hominin fit in our evolutionary history?

3. Hypothesis: The hobbits evolved from an isolated population of Homo erectus 4. Prediction: Key traits of the new species, such as its skull characteristics and body proportions, would resemble those of a miniature Homo erectus 5. Experiment: Detailed measurements and other observations of the new fossils were compared with data from Homo erectus fossils 6. Results: The initial results supported the hypothesis 7. Other analyses including additional specimens suggest alternate hypotheses: a. Homo floresiensis is most closely related to Homo habilis or b. the hobbits are not a species at all, but Homo sapiens with a disorder that caused bone malformations.

D. Homo neanderthalensis 1. Homo erectus gave rise to a. regionally diverse descendents in Europe and Asia and b. Homo neanderthalensis, commonly called Neanderthals.

2. Neanderthals a. and modern humans last shared a common ancestor about 500,000 years ago and b. may have interbred with some Homo sapiens.

3. The Origin and Dispersal of Homo sapiens 4. The oldest known fossils of our own species, Homo sapiens, a. were discovered in Ethiopia and b. date from 160,000 to 195,000 years ago.

5. DNA studies strongly suggest that all living humans can trace their ancestry back to a single African Homo sapiens lineage that began 160,000 to 200,000 years ago 6. Fossil evidence suggests that our species emerged from Africa in one or more waves 7. The oldest fossils of H. sapiens outside of Africa are 50,000 years old 8. The oldest fossils of humans in the New World are uncertain, but are at least 15,000 years old 9. Certain uniquely human traits have allowed for the development of human societies a. The primate brain continues to grow after birth and the period of growth is longer for a human than for any other primate. b. The extended period of human development lengthens the time for parents to care for their offspring and pass along culture.

10. Culture is the social transmission of accumulated knowledge, customs, beliefs, and art over generations ..

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11. Culture is primarily transmitted by language 12. Nothing has had a greater impact on life on Earth than Homo sapiens a. Cultural evolution made modern Homo sapiens a new force in the history of life. b. Humans are the most numerous and widespread of all large animals and bring environmental change faster than many species can adapt.

E. Evolution Connection: Are We Still Evolving?

1. The human body has not changed much in the past 100,000 years 2. But as humans wandered far from their site of origin and settled in diverse environments, populations encountered different selective forces a. Certain populations evolved sickle hemoglobin as an adaptation to the deadly disease malaria. b. The loss of skin pigmentation in humans who migrated north from Africa is thought to be an adaptation to low levels of ultraviolet light in northern latitudes. c. Tibetans living at altitudes up to 14,000 feet have evolved changes in response to this challenging environment. d. Despite evolutionary tweaks such as these, we remain a single species.

Chapter Guide to Teaching Resources The Origins of Animal Diversity Student Misconceptions and Concerns 1. When asked to think about animals in general, students are typically biased to think of vertebrate examples. As an exercise to generate thought and attention, consider starting your lectures on animal diversity (at the very beginning of the first class on that subject) by asking students to “write down the name of the first type of animal that comes to mind.

Don’t give it any thought, just what first comes to mind, and then pass it in.” Depending on the size of your class, either tabulate their responses quickly or have students raise their hands depending upon what they indicated. In general, fewer than 5% (often fewer than 1%) of my students have indicated an invertebrate. This exercise makes the point that what we tend to think of, when we think of animals, is vertebrates. Many of us have had a dog, cat, or other vertebrate for a pet. Yet, more than 95% of all known species of animals are invertebrates. The challenge to the students is to expand their mental image and expectations of what it means to be an animal. The content in Chapter 17 should facilitate that understanding.

2. Students struggle to think through the requirements of invertebrates, and to consider them as animals with basic needs. It is intellectually challenging to see the similarities between an earthworm and a bird or a tick and a cat. The common features of animals addressed at the start of Chapter 17 can be expanded to include the needs for oxygen, nourishing food, a tolerable environment, and a suitable habitat to reproduce, applied to animals representing all of the major phyla. Illustrating these common demands can help to build the intellectual foundations that can be so difficult to fully comprehend.

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Teaching Tips 1. Depending on what chapters you have included to this point in your course, you might consider carefully examining the defining traits common to all animals. Consider challenging your students to identify at least one characteristic of each of the other kingdoms that is distinctly different from animals.

2. You might wish to share the now somewhat famous quote of Lewis Wolpert, who in 1986 said, “It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.” The development and arrangement of the basic embryonic layers (ectoderm forming skin and nervous system, mesoderm forming muscle and bone, and endoderm forming the digestive tract) establishes the basic body plan.

3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (No, to both questions.)

4. Before addressing the subject of animal symmetry, you might wish to have your students speculate about the adaptive advantages of radial or bilateral symmetry found in animals.

This sort of comparison raises an opportunity to make some larger points about biology.

There is no “one” best animal. Each form, each adaptation, each body plan has advantages and disadvantages. The value of adaptations is relative to the organism’s environment and most adaptations represent a compromise.

5. The website of the University of California Museum of Paleontology is an excellent resource in support of evolution and the history of life. The following portion of that website specifically addresses the Cambrian period: www.ucmp.berkeley.edu/cambrian/camb.html.

Major Invertebrate Phyla Student Misconceptions and Concerns 1. Students typically expect that an animal will have a head. The subject of a head might have already been introduced when discussing body plans. As you proceed through the animal phyla, have students consider how sponges and cnidarians meet their basic needs without the benefit of a well-defined head.

2. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods.

Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point.

Determine how many students represent 1% of the class. Then have the entire class stand.

Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction).

Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded.

Even higher percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.) ..

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Teaching Tips 1. Imagine a country cabin with a roaring fire in a fireplace. The windows are partially opened to permit air to rush into the house to feed the fire. This flow of air through the windows, through the home, to the fireplace, and then out the chimney is analogous to the flow of water through a sponge. Side note: Many sponges, especially commercial bath sponges, have outer body walls that are highly folded. Simpler vase sponges, with straighter walls, are good examples to show students when discussing this basic water flow pattern.

2. Students may be challenged to fully appreciate why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.

3. Just about any glass bottle with a narrow neck makes a good model of the cnidarian body plan. The narrowed neck of the body represents the constricted region of a cnidarian that regulates what enters and leaves the gastrovascular cavity.

4. The gastrovascular cavity of cnidarians and flatworms is the functional equivalent of two systems in our bodies. Ask students to explain how nutrients they consume at a meal nourish the cells in their toes. Nutrients absorbed by our gut are transported throughout our body by the circulatory system. Extensions of the gastrovascular cavity permit nutrient distribution in these cnidarians and flatworms.

5. If students have been stung by a jellyfish, it was a toxin produced by the cnidocytes that caused a reaction. (Nematocysts are the firing part of a cnidocyte cell. The toxin is delivered by the firing of the nematocysts. A new cnidocyte must take the place of one that has fired its nematocyst, since cnidocytes cannot “reload.”)

6. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, they may also include portions of the intestines.

7. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the paired shells. For a startling demonstration, discuss the anatomy of a specimen and then enjoy it for lunch.

8. When discussing cephalopods, the subject of animal intelligence may be noted. Defining and identifying animal intelligence is not a simple task. Consider discussing the correlation of intelligence and predation. Why might these two traits be linked? What other characteristics correlate with intelligence (perhaps sophistication of communication)?

9. A planarian, indicated in Figure 17.14, ingests food in the middle of its body. Challenge students to think of other animals that have a mouth located distantly from the head. The discussion that will follow this challenge will likely include defining features of a head.

Such challenges as this invoke critical analysis of animal body plans, an important exercise for this chapter.

10. The undercooking of meat contributes to the spread of parasitic diseases. If you addressed the denaturation of proteins in Chapter 3, here is a chance to reinforce the points about the effects of heat. Proteins denature and discolor when heated (pink meat turns brown). This same process denatures proteins in parasites and can kill them (although some parasites can survive relatively high temperatures). If any portion of a steak is still pink, the meat has not been cooked enough to denature the meat or parasitic proteins.

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11. Annelids and nematodes have the advantage of a digestive tract with openings at both ends. This permits the efficiency and specialization of the digestive tract for one-way flow of ingested materials. Assembly lines enjoy this same advantage, but in the reverse process of construction, using a sort of “disassembly line.” These worms (and all animals with a mouth separate from the anus) “disassemble” food as it moves through the digestive tract.

12. Leeches remain an important tool in modern medicine. Consider presenting some examples of the latest use of leeches in medicine to the class, or asking your students to research and discuss them. Such short asides will often liven up your class.

13. Conceptually, and very generally speaking, the exoskeleton of an arthropod is like the hard outside of an M&M. The exoskeleton prevents physical damage to the internal anatomy and prevents desiccation. The outside of an M&M prevents damage to the chocolate and keeps the chocolate from melting or drying out.

14. Many students assume that all insects possess six legs and two pairs of wings. As common examples of variation on this theme, challenge students with images of beetles (in which the outer wings, called elytra, are hardened) and flies (in which one pair of wings is reduced to a pair of structures called halteres).

15. Beetles have a long history in human culture, used in textiles, ornamentation, and jewelry.

A quick image search of the Internet will reveal many examples. In particular, note the significance of scarab beetles in ancient Egypt.

16. The life history of dung beetles is a fun and amusing insect story for lecture, revealing the important role of these animals in recycling animal waste. Details of their interesting life cycle can be obtained from many resources, including those resulting from an Internet search for “dung beetle life history.”

17. The bodies of adult echinoderms reveal degrees of radial symmetry, which may cause students to wonder why echinoderms are not grouped with cnidarians. As discussed in the text, the bilateral symmetry of embryonic echinoderms demonstrates the acquisition of radial symmetry from a bilaterally symmetrical ancestor. Thus, echinoderms are more closely associated with other bilaterally symmetrical organisms.

18. Radial symmetry, such as that seen in many adult echinoderms, enables an organism to respond well to resources and threats in any direction. You cannot sneak up behind their back. This ability is especially adaptive in sedentary or relatively sedentary organisms, such as sea urchins, sea stars, and cnidarians. Ask your students if these same advantages also occur in radially symmetrical plants.

19. If you can obtain a model or image of a 1-month-old human embryo, you can demonstrate our four main chordate characteristics. A figure of a human embryo, comparing human and dog embryos of similar stages, was prepared by Charles Darwin and included in the first chapter of his book, The Descent of Man.

Vertebrate Evolution and Diversity Student Misconceptions and Concerns 1. The classification of life has been undergoing some major changes, with the addition of domains and the rearrangement of vertebrate groups. Birds are now commonly classified as reptiles, an association likely not seen previously in older K–12 textbooks. Students may be surprised by this association. Better classification tools, new techniques, and the attempt to classify organisms only into monophyletic groups have required these reconsiderations. ..

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2. Students might think of vertebrate groups as sharply defined, lacking appreciation for the transitional organisms that illuminate aspects of the rich evolutionary history of vertebrates. Recent discoveries such as the 375-million-year-old fossil fish Tiktaalik reveal important traits that are intermediate between ancient fishes and modern amphibians.

Discussion of this important transitional species, as well as similar species such as Archaeopteryx and modern monotremes, will reveal the blurry boundary lines between our classifications of vertebrate groups.

Teaching Tips 1. The movement of lampreys from Lake Ontario to the other Great Lakes was historically limited by Niagara Falls. However, the creation of canals to bypass the falls created a channel for lamprey invasion. Lampreys are just one example of the tremendous problem of invasive (alien) species.

2. Lampreys possess vertebrae, but hagfishes do not. Thus, only lampreys are now classified as vertebrates, a distinction that may not have been made in textbooks used by students before they arrived at college.

3. Eel-skin wallets and purses are typically made from the skin of hagfish. It is possible that one or more of your students has such an item.

4. The wide, flat bodies of rays provide an obvious exception to the general rule that cartilaginous fishes have streamlined bodies. Their ventral mouths and flattened form are well adapted to a life on the ocean bottom.

5. Unlike bony fishes, sharks lack a swim bladder. To lift off the bottom, they swim using their stiff pectoral fins and tail for uplift (along with some buoyant materials in their body cavity).

6. The menacing perception of sharks may be due in part to their particular method of maneuvering in water. Shark fins do not rotate to brake their forward movements. Cruising sharks that swim near an object of interest are not necessarily out to intimidate their prey (although it may have this effect). They may simply be curious, but unable to remain motionless while they investigate their environment.

7. Of all of the vertebrate clades alive today, ray-finned fishes are the most abundant. More than 27,000 species of ray-finned fishes have been identified.

8. Our knowledge about the basic development of vertebrates was significantly advanced by the early study of amphibian embryos. With clear outer layers, the detailed anatomy of many developing amphibians may be observed without disturbing the organism.

Furthermore, their size permitted the identification of basic systems without requiring magnification.

9. Adult salamanders are the only adult tetrapods that can completely regenerate a lost limb.

Although some reptiles can regenerate portions of their tails, no other tetrapod can replace part or all of a limb. Even more amazingly, salamanders that suffer the partial loss of a limb regenerate only the missing sections. Research into the mechanisms of regeneration inform our understanding of limb development and bring hope that medical science may one day be able to achieve the same thing in humans.

10. One of the most widely studied laboratory amphibians over the past 200 years has been the axolotl, a Mexican salamander that retains juvenile characteristics, including gills that persist into the adult state. These animals do not normally undergo metamorphosis, reproducing instead in their strictly aquatic form. Many images of these neotenic/paedomorphic axolotls can be found by performing a simple Internet image search for “axolotl.”

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11. The transition to a life on land required some major changes. You might ask your students to discuss the challenges of moving from an aquatic to terrestrial lifestyle. These include adaptations to breathing air, additional skeletal support (when the buoyancy of water is lost), loss of a lateral line system, adaptations to hearing in air, mechanisms to reduce water loss through the skin, and so on. Reptiles were the first group to be independent of standing water.

12. The way amphibians and reptiles move on land reveals the ancestral derivation of their anatomy. As an alligator swings its body from side to side, moving its legs forward, the lateral undulations of its vertebral column resemble those of a fish. In contrast, the movements of a dolphin in water reveal its more recent terrestrial ancestry. It moves its vertebral column vertically so that its back undulates in the same direction, just like a land mammal such as a horse.

13. Reptiles diversified in the Mesozoic in much the same way that mammals have diversified today. To make this point, choose some well-known dinosaurs and compare their habitats to modern mammals that live in a similar ecological niche. (Triceratops was a grazer, much like a modern bison; a duck-billed hadrosaur shares much the same diet as a hippopotamus today; Tyrannosaurus rex may have been an aggressive hunter like a modern tiger.)

14. In the last few years, the debate about the evolution of birds has been punctuated by exciting new fossil discoveries including many from China. Your students should be able to find images and details about these recent discoveries on the Internet.

15. Feathers perform several functions, typically in the same bird. They insulate, they provide species-specific coloration for identification by members of the same species, and they form aerodynamic surfaces. As you list these diverse functions, note that all of these functions may not have arisen simultaneously. Thus, feathers may have first evolved as identifying traits or as an important source of insulation, long before their role in flight.

16. The intermediate nature of Archaeopteryx can be demonstrated to your students. Have your students compare an Archaeopteryx fossil to the skeleton of a modern chicken. Good photographs of both organisms can be sufficient. Have them note both the shared and unique characteristics of the two organisms.

17. The marsupial distribution on Earth is a fine example of biogeography. The geographic isolation of Australia has allowed these animals to evolve, independent of much of the eutherian evolution, resulting in greater diversification of marsupials. As suggested for the dinosaurs, students can be encouraged to make parallels between the lifestyles of Australian marsupials and eutherian mammals, which occupy similar ecological niches elsewhere in the world.

The Human Ancestry Student Misconceptions and Concerns 1. At the start of the chapter section “The Emergence of Humankind,” the authors directly address three common misconceptions about human evolution. One of these is the depiction of human evolution as a “march of progress” image, a series of apes giving way to increasingly modern-looking and upright humans in a linear progression. Such images are common and can be found easily by searching “human evolution” on a Google image search. The human family tree has many branches, with multiple species existing simultaneously for long periods (more than a million years). Furthermore, representing the ..

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diversity of hominin evolution as a narrow progression from past to present is misleading.

It would be the equivalent of depicting any one student’s family history as a direct lineage of grandparent to parent to student, ignoring all siblings and cousins.

2. Students will need to be reminded that modern apes and humans share ancestry. Humans are not descendants of modern chimps. This basic observation may need to be repeated, to remind students that evolution is a branching family tree united by common descent.

3. Students and biologists in general often expect evolutionary intermediates to have characteristics that are an average of ancestors and descendants. They may expect intermediate forms to have intermediate traits. The concept of mosaic evolution, in which intermediates demonstrate a mixture of primitive and derived traits, more accurately depicts the history of life. Human ancestors did not walk partially upright with mid-sized brains. Instead, upright posture evolved before larger brains, revealing a “mosaic” of traits.

4. Students may continue to struggle with false Lamarckian concepts of evolution. They should be reminded that organisms do not acquire characteristics because of want or need.

Instead, naturally occurring genetic variations are selected for or against depending on a population’s interactions with its environment. Many students need to be reminded about the process of natural selection wherever it applies.

5. Some students raise objections about evolution because they believe it is incompatible with their religious philosophy. Some students see humans as an exception to biological rules. How you handle these philosophical objections depends upon the greater context of your course in the curriculum and the specific political and social circumstances of your institution. Reminding students about the rules and philosophy of science may help to clarify the particular perspective of biology and science.

Teaching Tips 1. You may wish to discuss with your class the human versions of the primate traits addressed at the beginning of this chapter section. For example, do we have a loosely connected shoulder, good dexterity, eyes with overlapping fields of vision, and extensive periods of parental care?

2. Students are often unaware of a second type of chimp, the bonobo. An excellent source of information about this underappreciated species can be found at http://bonobo.org/.

3. Your students may enjoy a conversation to identify traits unique to humans. To what degree are tool-marking and symbolic language only human traits? What traits are found only in humans?

4. Figure 17.39 is an excellent way to introduce the history of human evolution. The vertical bars represent the known history of each species based on the discovery of fossils. However, the relationships between the species are not represented, because of uncertainty. The ongoing efforts to work through human ancestral relationships reveals the process of science, forming tentative hypotheses that are refined as more evidence and insight are added.

5. Students may wish to debate whether we are more intelligent than our cave-dwelling ancestors. What is the distinction between knowledge and intelligence? If your course permits it, these could be some interesting discussions.

6. Students may wonder if people living today with larger brains are indeed more intelligent than other smaller-brained people. Although this relationship may generally be true between species, there is no clear evidence that it is valid within a species.

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7. Consider asking your class to speculate on the adaptive advantages of speech, language, and music in early humans. The resulting discussion may help students practice the language of evolution and natural selection.

8. There are many excellent Internet sites addressing aspects of human evolution. The Leakey Foundation website lists a variety of these resources at http://leakeyfoundation.org/education/helpful-links/.

Key Terms amniotes amniotic egg amphibians animals annelids anthropoids arachnids arthropods bilateral symmetry birds bivalves blastula body cavity body segmentation bony fishes cartilaginous fishes centipedes cephalopods chordates

cnidarians insects coelom invertebrates complete digestive tract lancelets crustaceans larva culture lateral line system dorsal, hollow nerve leeches cord lobe-finned fishes earthworms mammals echinoderms mantle ectotherms marsupials endoskeleton medusa endotherms metamorphosis eutherians millipedes exoskeleton molluscs flatworms monotremes gastropods nematodes gastrovascular cavity notochord gastrula operculum hominins pharyngeal slits

placenta placental mammals polychaetes polyp post-anal tail primates pseudocoelom radial symmetry radula ray-finned fishes reptiles roundworms sponges swim bladder tetrapods tunicates vertebrates water vascular system

Word Roots amphi = double; bio = life (amphibians: vertebrates that live life in and out of the water) annel = ring (annelids: segmented worms) anthrop = man; oid = like (anthropoid: monkeys, apes, and humans) arachn = spider (arachnids: spiders, scorpions, mites, and ticks) arthro = joint; pod = foot (Arthropoda: the phylum of animals with jointed legs) bi = double; valva = leaf of a folding door (bivalves: molluscs with two hinged shells) centi = one hundred; ped = foot (centipedes: arthropods with many legs, one pair per body segment) ceph(al) = head (cephalopods: molluscs that include octopus and squid) echino = spiny; derm = skin (Echinodermata: the phylum of sea stars, which have spiny skin) ecto = outside; therm = temperature (ectotherms: animals that absorb heat instead of producing it internally) endo = inside (endothermic: animals that produce heat internally) exo = outside (exoskeleton: an external skeleton such as that found in all arthropods) ..

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gaster = belly (gastropods: molluscs with their gut near their muscular foot) homin = man (hominins: members of the human family) marsupi = bag or pouch (marsupials: the pouched mammals) meta = change; morph = form (metamorphosis: a change in animal form during a lifetime) milli = one thousand (millipedes: arthropods with many legs, two pairs per body segment) mollusc = soft (Mollusca: the phylum of soft-bodied animals usually surrounded by hard shells) mono = one (monotremes: mammals that lay eggs) noto = the back; chord = string (notochord: a flexible, longitudinal rod characteristic of chordate animals) platy = flat; helminthes = a worm (Platyhelminthes: the phylum of flatworms) por = pore; fer = bearer (Porifera: the phylum of sponges) post = behind (post-anal tail: the type of tail found in chordate animals) pseudo = false (pseudocoelom: a body cavity that is not completely lined by tissue derived from mesoderm) tetra = four (tetrapods: the group of terrestrial vertebrates with four legs)

Relevant Songs to Play in Class “Ants Marching,” Dave Matthews Band

“The Mollusk,” Ween

“Under the Sea,” from Disney’s The Little Mermaid

“SpongeBob SquarePants Theme,” Nickelodeon

“Animal,” Pearl Jam

“Mammal,” They Might Be Giants

“Rock You Like a Hurricane,” Scorpions

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: Important characteristics include symmetry, the presence and type of body cavity, segmentation, type of digestive tract, type of skeleton, and appendages.

12. The answer to this question would be based completely on the results of the student’s interview.

13. Suggested answer: Bipedalism would have allowed early hominins to see farther and run faster in the more open savanna environment, enabling them to find food and escape predators more easily. Bipedalism would have freed the hands to carry objects and use tools. Some anthropologists believe that tool users with larger brains would have been favored by natural selection.

Biology and Society 14. Some issues and questions to consider: How does the decline of the reefs relate to agriculture?

Deforestation? Overfishing? Rapid population growth? What value are the reefs to the local people? What is their value as a world biological resource? What activities would be more sustainable that could generate income for poor countries? What might be the consequences if the reefs disappear? What is likely to make the situation worse? What is likely to improve the 250

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situation? In what ways might developed countries contribute to this problem? In what ways might developed countries be able to help the local people preserve the reefs? How might developed countries benefit from helping?

15. Technology has played a key role in our ability to rapidly and dramatically alter our environment. The widespread availability of electrical energy and carbon-based fuels has also increased our ability to do work. Students might consider how modern cities and the places where people live have changed the qualities of the environments where we live. Are there certain regions where human-caused environmental changes are happening at a more rapid rate, where few changes have occurred, or where many changes have already occurred? Do third-world countries that are cutting down their forests for fuel and grazing have similar impacts on industrialized nations that use those resources?

Additional Critical Thinking Questions The Process of Science 1. How would you describe a phylogenetic tree to a nonscientist? What is the significance of placing related groups on a phylogenetic tree? How does this type of classification help scientists?

Suggested answer: Each junction point represents the common ancestor to each new lineage. The organisms of each branch have evolved distinct characteristics that differentiate them from the common ancestor. This approximates the history of evolution.

Classification of this type can show an evolutionary scenario and indicate organisms that are closely related or distantly related regardless of phenotypic differences. Analyses of evolutionary trees can also be useful to determine the evolutionary history of groups of animals.

2. What types of genetic evidence might be useful in resolving the relationship between Neanderthals and modern humans?

Suggested answer: Mitochondrial DNA is maternally inherited so it is restricted to maternal lineages. This provides valuable information about evolutionary relationships.

Y-linked markers could provide data from paternal lineages. In addition, other types of genetic data could include chromosome rearrangements and linkage analysis, identification of pseudogenes and their locations, or data on transposon insertions, which have also proven to be very valuable molecular markers. Hopefully, all of these types of data and more will soon be available from Neanderthal DNA. 3. Anthropologists are interested in locating areas in Africa where fossils 4–8 million years old might be found. Why? Suggested answer: Most anthropologists think that humans and apes diverged from a common apelike ancestor 5–7 million years ago. Primate fossils 4–8 million years old might help us understand how and where hominins first evolved.

Biology and Society 4. Many people argue about whether or not it is important to save animal diversity. Should human hardship be factored into the equation? Set up your own personal debate, and come up with several reasons why maintaining animal diversity is important and then some scenarios of when you think human survival/benefit might be more important.

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Some issues and questions to consider: Some positive reasons for maintaining diversity may include the need for a diverse gene pool for natural selection, maintaining the balance of the ecosystem, and the idea of humans as caretakers. Some negative reasons may revolve around the human need for jobs, food, and other natural resources. How does the short-term need for jobs compare to the long-term benefit of maintaining diversity? What are the direct and indirect benefits of maintaining diversity such as pollinators for our food crops and sources of cures for new diseases? What are the direct and indirect costs of losing diversity?

5. Which primate would be the best for medical studies of drugs to be used on humans? Why? Does this mean that primates should be used more extensively as subjects for drug testing?

Some issues and questions to consider: Phylogenetic analysis reveals that chimpanzees are the primates most closely related to humans. This means that humans and chimps shared a common ancestor more recently in the past than they do with any other species. In fact, humans and chimps are only on average about 1–2% different at the nucleotide level.

Since chimps are most similar to humans, they would be the best subjects to use as surrogates for medical experimentation. However, chimps are intelligent, can communicate through sign language, and have a complex social structure that is also very similar to that seen in humans. For these reasons, many feel that it is unethical to use chimps or even other primates for certain types of medical studies. It should be noted that humans also share many important features with other mammals such as mice and rabbits.

Such species are also useful surrogates and serve as model organisms for many kinds of studies. Although it is important to remember that all animals can suffer, it is also important to weigh the benefits of such studies to humans.

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CHAPTER

18

An Introduction to Ecology and the Biosphere

Why This Chapter Matters 1. Our biosphere is the sum of all ecosystems.

2. Understanding the diversity of ecosystems, their composition, and their interactions enables us to better appreciate the natural world in which we live.

3. Human interactions in the natural world routinely disrupt ecosystems. We cannot understand our impact without first understanding the natural properties of these systems.

Chapter Objectives Biology and Society: Penguins and Polar Bears in Peril 1. Describe the global climate changes already documented over the past century.

An Overview of Ecology 2. Define ecology and explain how ecologists learn about the structure and processes of our natural world.

3. Distinguish between biotic and abiotic factors.

4. Define the biosphere and the four levels of ecology.

Living in Earth’s Diverse Environments 5. Explain why the biosphere is patchy. List and describe the major abiotic factors affecting the distribution of life in the biosphere.

6. Define and describe examples of the three main types of responses that enable plants or animals to adjust to changes in their environments.

Biomes 7. Define a biome.

8. Compare the photic, aphotic, and benthic zones of a lake or large pond.

9. Compare the properties of a stream or river at its source and at the place where it empties into a lake or the sea. Explain how human activities impact the properties of rivers and streams.

10. Define a wetland and describe their values to natural ecosystems and humans.

11. Compare the characteristics of the pelagic realm, coral reefs, intertidal zones, and estuaries. Explain what is special about hydrothermal vent communities.

12. Describe the threats to marine ecosystems.

13. Explain how climate affects terrestrial biome distribution.

14. Distinguish between the types of terrestrial biomes.

15. Explain how the biosphere is linked by the global water cycle.

16. Explain how humans have impacted the world’s biomes and describe the goals of sustainability.

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Global Climate Change 17. Explain how greenhouse gases affect global climates.

18. Explain why CO2 levels may be increasing in the global atmosphere.

19. Explain how global climate change affects the distribution and interactions of species.

20. Explain how you can decrease your carbon footprint.

Evolution Connection: Climate Change as an Agent of Natural Selection 21. Explain why organisms with low genetic diversity and long life spans might suffer the most in a rapidly changing climate.

Lecture Outline I. Biology and Society: Penguins and Polar Bears in Peril 1. The scientific debate is over 2. The great majority of scientists now agree that the global climate is changing 3. Average global temperatures have risen 0.8°C (about 1.4°F) over the past century, mostly over the last 30 years 4. Precipitation patterns have also changed, bringing a. longer and more intense drought to some regions and b. flooding to other areas.

5. Overwhelming evidence indicates that human enterprises are responsible for the changes that are occurring 6. Our response to this crisis will determine whether circumstances improve or worsen

II. An Overview of Ecology 1. Ecology is the scientific study of the interactions between organisms and their environments 2. Humans have always had an interest in other organisms and their environments 3. Extraordinary insight can be gained from a discovery-based approach of a. watching nature and b. recording its structure and processes.

A. Ecology and Environmentalism 1. Technological innovations have enabled people to colonize almost every environment on Earth 2. Earth’s resources a. affect our survival and b. have been greatly affected by our activities.

3. Environmental problems a. can be understood by the science of ecology and b. require decisions based on values and ethics.

4. On a personal level, each of us makes daily choices that affect our ecological impact

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B. A Hierarchy of Interactions 1. Many different factors can potentially affect an organism’s interaction with the environment a. Biotic factors are i. all of the organisms in the area and ii. the living component of the environment. b. Abiotic factors i. are the environment’s nonliving component and ii. include chemical and physical factors, such as temperature, light, water, minerals, and air.

2. An organism’s habitat a. is the specific environment it lives in and b. includes the biotic and abiotic factors of its surroundings.

3. Ecology can be divided into four increasingly comprehensive levels: a. organismal ecology, b. population ecology, c. community ecology, and d. ecosystem ecology.

4. An organism is an individual living thing 5. Organismal ecology is concerned with evolutionary adaptations that enable individual organisms to meet the challenges posed by their abiotic environments 6. Population ecology a. addresses populations, groups of individuals of the same species living in a particular geographic area and b. concentrates mainly on factors that affect i. population density and ii. growth.

7. Community ecology a. is concerned with communities, all the organisms that inhabit a particular area and b. focuses on how interactions between species affect a community’s i. structure and ii. organization.

8. Ecosystem ecology a. is concerned with ecosystems, all the abiotic factors in addition to the community of species in a certain area and b. focuses on energy flow and the cycling of chemicals among the various abiotic and biotic factors.

9. The biosphere is a. the global ecosystem, b. the sum of all the planet’s ecosystems, or c. all of life and where it lives.

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III. Living in Earth’s Diverse Environments 1. The distribution of life varies on a a. global scale and b. local scale.

A. Abiotic Factors of the Biosphere 1. Patterns in the distribution of life mainly reflect differences in the abiotic factors of the environment 2. Energy Source 3. All organisms require a usable source of energy to live 4. Solar energy from sunlight a. is captured by chlorophyll during the process of photosynthesis and b. powers most ecosystems.

5. Hydrothermal vents a. occur a mile or more below the ocean’s surface and b. are ecosystems powered by chemoautotrophic bacteria that derive energy from the oxidation of inorganic chemicals such as hydrogen sulfide.

6. Bacteria with similar metabolic talents support communities of cave-dwelling organisms 7. Temperature 8. Temperature affects metabolism a. Few organisms can maintain a sufficiently active metabolism at temperatures close to 0ºC. b. Temperatures above 45ºC destroy the enzymes of most organisms.

9. Most organisms function best within a specific range of environmental temperatures 10. Water 11. Water is essential to all life 12. For terrestrial organisms, the main water problem is drying out 13. Aquatic organisms a. are surrounded by water and b. face problems of water balance if their own solute concentration does not match that of their surroundings.

14. Inorganic Nutrients 15. The distribution and abundance of plants are often determined by the a. availability of inorganic nutrients such as nitrogen and phosphorus and b. the structure, pH, and nutrient content of the soil.

16. In many aquatic ecosystems, the growth of algae and photosynthetic bacteria is often limited by levels of a. nitrogen and b. phosphorus.

17. Other Aquatic Factors

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18. Aquatic but not terrestrial ecosystems are more limited by a. the levels of dissolved oxygen, b. salinity, c. currents, and d. tides.

19. Other Terrestrial Factors 20. Terrestrial but not aquatic ecosystems are more limited by a. wind, b. storms, or c. fire.

B. The Evolutionary Adaptations of Organisms 1. The ability of organisms to live in Earth’s diverse environments demonstrates the close relationship between the fields of a. ecology and b. evolutionary biology.

2. Evolutionary adaptation via natural selection results from the interactions between a. organisms and b. their environments.

C. Adjusting to Environmental Variability 1. The abiotic factors in a habitat may vary a. from year to year, b. seasonally, or c. over the course of a day.

2. Birds may adjust to cold by a. migrating to warmer regions (a behavioral response), b. growing heavier feathers (an anatomical response), or c. fluffing up their feathers to trap more heat (a physiological response).

3. These responses, which occur during the lifetime of an individual, do not qualify as evolution, which is change in a population over time 4. Physiological Responses 5. Acclimation is a. gradual, b. reversible, and c. a physiological adjustment to an environmental change.

6. The ability to acclimate is generally related to the range of environmental conditions a species naturally experiences 7. Among vertebrates, a. birds and mammals can tolerate the greatest temperature extremes because they are endotherms, while b. ectothermic reptiles can only tolerate a more limited range of temperatures.

8. Anatomical Responses 9. Many organisms respond to environmental challenges with some type of change in a. body shape and b. structure. ..

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10. Reversible change, such as a heavier fur coat in response to cold, is an example of acclimation 11. Environmental variation can irreversibly affect a. growth and b. development.

12. Behavioral Responses 13. In contrast to plants, most animals can respond to an unfavorable change in the environment by moving to a new location a. Ectotherms may shuttle between sun and shade. b. Migratory birds travel great distances in response to changing seasons. c. Humans have an especially rich range of behavioral responses.

IV. Biomes 1. A biome is a. a major terrestrial or aquatic life zone, b. characterized by i. vegetation type in terrestrial biomes or ii. the physical environment in aquatic biomes.

2. Aquatic biomes a. occupy roughly 75% of Earth’s surface and b. are determined by their i. salinity and ii. other physical factors.

3. Freshwater biomes a. have a salt concentration of less than 1% and b. include lakes, streams, rivers, and wetlands.

4. Marine biomes a. typically have a salt concentration around 3% and b. include oceans, intertidal zones, coral reefs, and estuaries.

A. Freshwater Biomes 1. Freshwater biomes a. cover less than 1% of Earth, b. contain a mere 0.01% of its water, c. harbor about 6% of all described species, and d. are used for i. drinking water, ii. crop irrigation, iii. sanitation, and iv. industry.

2. Freshwater biomes fall into two broad groups: a. standing water, which includes lakes and ponds, and b. flowing water, such as rivers and streams.

3. Lakes and Ponds

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4. Standing bodies of water range from small ponds to large lakes, such as North America’s Great Lakes 5. In lakes and large ponds, the communities of plants, algae, and animals are distributed according to the a. depth of water and b. distance from shore.

6. The photic zone, named because light is available for photosynthesis, includes a. the shallow water near shore and b. the upper layer of water away from shore.

7. The aphotic zone a. is deeper and b. has light levels too low to support photosynthesis.

8. The benthic realm is a. at the bottom of all aquatic biomes, b. made up of sand and organic and inorganic sediments, and c. occupied by communities of organisms that are collectively called benthos.

9. The amount of phytoplankton growth in a lake or pond is typically regulated by the nutrients a. nitrogen and b. phosphorus.

10. Rivers and Streams 11. Rivers and streams a. are bodies of water flowing in one direction and b. generally support quite different communities of organisms than lakes and ponds.

12. Near the source of a stream, the water is usually a. clear, b. cold, c. swift, and d. low in nutrients.

13. Downstream, the water is usually a. murkier, b. warmer, c. slower, and d. higher in nutrients.

14. Many streams and rivers have been affected by pollution from human activities and dams to a. control floods, b. provide reservoirs for drinking water, or c. generate hydroelectric power.

15. Wetlands 16. A wetland is a transitional biome between a. an aquatic ecosystem and b. a terrestrial one. ..

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17. Wetlands a. support the growth of aquatic plants and b. are rich in species diversity.

B. Marine Biomes 1. Marine biomes are diverse, ranging from vivid coral reefs to perpetually dark realms in the deepest regions 2. As in freshwater biomes, the seafloor is known as the benthic realm 3. The pelagic realm includes all of the open water of the oceans 4. In shallow areas such as the submerged parts of continents, called continental shelves, the photic zone includes pelagic and benthic regions 5. In these sunlit areas, photosynthesis by phytoplankton and multicellular algae provides energy for a diverse community of animals 6. The pelagic photic zone includes a. zooplankton (free-floating animals, including many microscopic ones), b. fishes, and c. marine mammals.

7. The coral reef biome occurs a. in the photic zone of warm tropical waters, b. in scattered locations around the globe.

8. The photic zone extends down a maximum of 200 m in the ocean 9. The region between 200 and 1,000 m is a. dimly lit, sometimes called the twilight zone, and b. dominated by a fascinating variety of small fish and crustaceans.

10. Below 1,000 m, the ocean is completely dark 11. The intertidal zone is where a. the ocean meets land, b. the shore is pounded by waves during high tide, and c. the bottom is exposed to the sun and drying winds during low tide.

12. Estuaries a. are a transition area between a river and the ocean, b. have a saltiness ranging from nearly that of fresh water to that of the ocean, and c. are among the most productive areas on Earth.

13. Estuaries are threatened by a. landfills, b. nutrient pollution, c. contamination by pathogens or toxic chemicals, such as the massive Deepwater Horizon oil spill in the Gulf of Mexico in 2010, and d. alteration of freshwater inflow.

C. How Climate Affects Terrestrial Biome Distribution 1. Terrestrial biomes are primarily determined by climate, especially a. temperature and b. rainfall.

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2. Earth’s global climate patterns are largely the result of a. the input of radiant energy from the sun and b. the planet’s movement in space.

3. Heated by the direct rays of the sun, air at the equator a. rises, b. then cools, forming clouds, and c. drops rain.

4. This largely explains why rain forests are concentrated in the tropics, the region from the Tropic of Cancer to the Tropic of Capricorn 5. Temperate zones generally have milder climates than the tropics or the polar regions.

They occur in latitudes between a. the tropics and the Arctic Circle in the north and b. the tropics and the Antarctic Circle in the south.

6. Climate is also affected by a. proximity to large bodies of water and b. the presence of landforms such as mountain ranges.

7. Mountains affect climate in two major ways a. First, air temperature drops as elevation increases. b. This results in several biomes moving up a tall mountain. c. Second, mountains can i. block the flow of cool, moist air from a coast and ii. cause radically different climates on opposite sides of a mountain range.

D. Terrestrial Biomes 1. Terrestrial ecosystems are grouped into biomes primarily on the basis of their vegetation type 2. A climograph is a visual representation of the differences in a. precipitation and b. temperature ranges that characterize terrestrial biomes.

3. Tropical Forest 4. Tropical forests occur in equatorial areas, where a. the temperature is warm, and b. days are 11–12 hours long year-round.

5. Savanna 6. Savannas a. are dominated by grasses and scattered trees, b. are warm year-round, and c. experience rainfall of 30–50 cm (roughly 12–20 inches per year) with dramatic seasonal variation.

7. Desert 8. Deserts a. are the driest of all biomes, b. are characterized by low and unpredictable rainfall of less than 30 cm (about 12 inches) a year, and c. may be very hot or very cold. ..

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9. Chaparral 10. Chaparral has a climate that results from cool ocean currents circulating offshore and producing a. mild, rainy winters and b. hot, dry summers.

11. Temperate Grassland 12. Temperate grasslands a. are mostly treeless, b. have 25–75 cm (10–30 inches) of rain per year, c. experience frequent droughts and fires, and d. are characterized by grazers including bison and pronghorn in North America.

13. Temperate Broadleaf Forest 14. Temperate broadleaf forest a. occurs throughout midlatitudes where there is sufficient moisture to support the growth of large trees, ranging from 75 to 150 cm (30 to 60 inches.), and b. includes dense stands of deciduous trees in the Northern Hemisphere.

15. Deciduous trees drop their leaves before winter, when a. temperatures are too low for effective photosynthesis and b. water lost by evaporation is not easily replaced from frozen soil.

16. Coniferous Forest 17. Coniferous forests a. are dominated by cone-bearing evergreen trees and b. include the northern coniferous forest, or taiga, the largest terrestrial biome on Earth.

18. Temperate rain forests a. are found along coastal North America from Alaska to Oregon and b. are also coniferous forests.

19. Tundra 20. Tundra a. covers expansive areas of the Arctic between the taiga and polar ice and b. is characterized by i. permafrost (permanently frozen subsoil), ii. bitterly cold temperatures, and iii. high winds.

21. Polar Ice 22. Polar ice covers the land a. at high latitudes north of the arctic tundra in the Northern Hemisphere and b. in Antarctica in the Southern Hemisphere.

23. Only a small portion of these landmasses is free of ice or snow, even during the summer E. The Water Cycle 1. All parts of the biosphere are linked by the global water cycle 2. Human activities that affect the global water cycle include a. destruction of forests and b. pumping large amounts of groundwater to the surface for irrigation.

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J. Human Impact on Biomes 1. Sustainability is the goal of developing, managing, and conserving Earth’s resources in ways that meet the needs of people today without compromising the ability of future generations to meet their needs 2. Forests 3. Satellite photos of a small area in Brazil show how thoroughly a landscape can be altered in a short amount of time 4. Every year, more and more forested land is cleared for agriculture 5. Fresh Water 6. The impact of human activities on freshwater ecosystems may pose an even greater threat to life on Earth, including ourselves, than the damage to terrestrial ecosystems 7. Las Vegas, the population center of Clark County, Nevada, is one example of a city whose water resources are increasingly stressed by drought and overuse 8. The water level in Lake Mead has a. dropped drastically and b. parched cities and farms farther downstream, which are pleading for more water.

V. Global Climate Change 1. Global climate patterns are changing because of rising concentration in the atmosphere of a. carbon dioxide (CO2) and b. certain other gases.

A. The Greenhouse Effect and Global Warming 1. Greenhouse gases a. include CO2, water vapor, and methane, b. are transparent to solar radiation, c. absorb or reflect heat, and d. contribute to increases in global temperatures in what is often called the greenhouse effect.

2. The largest increases are in a. the northernmost regions of the Northern Hemisphere and b. parts of Antarctica.

B. The Accumulation of Greenhouse Gases 1. The vast majority of scientists are confident that human activities have caused the rising concentrations of greenhouse gases 2. Overall, the uptake of CO2 by photosynthesis roughly equals the release of CO2 by cellular respiration 3. However, a. extensive deforestation has significantly decreased the incorporation of CO2 into organic material and b. CO2 is flooding into the atmosphere from the burning of fossil fuels and wood.

C. The Process of Science: How Does Climate Change Affect Species Distribution?

1. Observations: a. The average temperature in Europe has risen 0.8ºC. b. Butterflies are sensitive to temperature change. ..

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2. Question: Have the ranges of butterflies changed in response to the temperature changes?

3. Hypothesis: Butterfly range boundaries are shifting in line with the warming trend 4. Prediction: a. Butterfly species will establish new populations to the north of their former ranges. b. Butterfly populations at the southern edges of their ranges will become extinct.

5. Experiment: Historical data on the ranges of 35 species of butterflies in Europe were analyzed 6. Results: a. More than 60% of the species have pushed their northern range boundaries poleward over the last century, some by as much as 150 miles. b. The southern boundaries have simultaneously contracted for some species, but not for others.

D. Effects of Climate Change on Ecosystems 1. In many plants and animals, life cycle events are triggered by a. warming temperatures or b. day length.

2. As global temperatures warm, and day length remains steady, natural interactions may become out of sync a. The winter white fur of snowshoe hares may be conspicuous against a greening landscape. b. Plants may bloom before pollinators have emerged.

3. The combined effects of climate change on forest ecosystems in western North America have spawned catastrophic wildfire seasons 4. Warmer weather helps bark beetles a. bore into drought-stressed conifers and b. reproduce twice a year instead of just once.

E. Looking to Our Future 1. Emissions of greenhouse gases continue to rise 2. In the United States, for example, total emissions increased more than 13% from 1990 to 2008 3. At this rate, further climate change is inevitable 4. The amount of greenhouse gas emitted as the result of the actions of a single individual is that person’s carbon footprint 5. We can reduce our carbon footprints by a. reducing our use of electricity, b. driving less, and c. recycling.

6. In addition, eating locally grown fresh foods may lower the greenhouse gas emissions that result from food processing and transportation F. Evolution Connection: Climate Change as an Agent of Natural Selection 1. Can evolutionary adaptations counteract the negative effects of climate change on organisms?

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2. The species most likely to adapt have a. high genetic variability and b. short life spans.

Chapter Guide to Teaching Resources An Overview of Ecology Student Misconceptions and Concerns 1. Students may confuse the uses of the terms ecology and environmentalism. The science of ecology and the environmental concerns that often emerge are related but separate fields.

Teaching Tips 1. In the first textbook chapter, the authors introduce levels of biological organization extending from an atom to the biosphere (see Figure 1.2). This might be a good review for your students and help to place these ecology chapters in context.

2. As a focusing exercise, consider challenging your students to make lists of abiotic and biotic components. You might suggest a particular region to consider (a nearby park or other natural area of local interest). They may work in small groups in class for a few minutes or turn the lists in as a short class assignment (perhaps via e-mail).

3. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing the following websites for basic ideas on what individuals can do to start to make a difference. http://www.dep.state.pa.us/earthdaycentral/96/business/FS1977.htm www.eco-pros.com/waysyoucanhelp.htm

Living in Earth’s Diverse Environments Student Misconceptions and Concerns 1. Many students confuse acclimations, changes that occur during an individual’s lifetime, with evolutionary change in a species. The similarity in the terms only adds to the confusion. You may wish to remind your students that individuals cannot evolve.

2. The authors describe the general ability of animals to engage in behavioral responses to their environment and the more limited ability of plants to do likewise. Students might not have considered the different mechanisms that plants, fungi, and animals employ to redistribute themselves in ecosystems.

Teaching Tips 1. Consider challenging your students to explain why organisms are typically limited to living in only certain parts of the biosphere. A species range may be limited by adaptations to particular environmental conditions. The same adaptations that permit survival under certain conditions may reduce survival rates under other conditions. Such trade-offs between specialization and generalization are a normal part of biology. If you want to emphasize the point with an analogy, you might note that choosing a particular major in college increases the student’s skills in that field, but comes at the cost of detailed study in other fields. ..

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2. As you address the many types of abiotic factors, try to relate aspects of your local climate to the geography of your region. See if the local television weather forecasts reflect local features so your students may consider these factors when learning about a local weather forecast.

3. Consider this opportunity to teach students a new way to learn. The aquatic conditions that provide the highest dissolved oxygen content are cold temperature, freshwater, and turbulent conditions. By imagining a pool of water at the bottom of a waterfall, supplied by water from melting snow, the students can picture all of these conditions. Creating integrative mental imagery to associate factors to be learned can be a creative way to reduce mental efforts.

4. Consider a brief review of the reasons why we have days, seasons, years, and phases of the moon. Many students still have fundamental misunderstandings about these cycles. You might begin with simple multiple choice questions to probe their understandings of the mechanisms of seasons and phases of the moon.

5. The Internet has many resources that allow students to view recent satellite weather images of Earth. These are great ways to demonstrate the prevailing wind patterns, precipitation patterns, and the like. For example, in the United States most storms move from west to east. Use this assignment over several days or weeks to follow patterns, trends, and note freak weather events.

Biomes Student Misconceptions and Concerns 1. Before addressing specific biomes, consider discussing some specific details about global weather patterns with references to the major factors that influence your local weather.

Depending on where you live, students may not understand the influences of mountains, large bodies of water, and latitude on weather.

2. Students may expect that similar biomes have similar species, a common misperception.

As the text notes, the similarities in organisms between widely separated but similar biomes is much more likely due to convergent evolution.

Teaching Tips 1. Before lecturing about rivers and streams, ask students to speculate how the qualities of a stream change from its source to the point where it joins a larger body of water many kilometers downstream. In particular, how does water temperature, water clarity, water speed, and the types of fish compare as the water flows away from its source?

2. The removal and deposition of sediment in a river or stream reveals the importance of the speed of water. Near the outer edge of a curve, a river or stream will erode the bank.

However, when the river slows or along the slower inside of curves, sediment tends to deposit. The result is the winding nature of mature rivers. A satellite image of the Mississippi River reveals the extensive curvature of this old system and many oxbow lakes that result when adjacent curves connect and generally straighten the flow.

3. Throughout the text, the sun has been generally considered as the primary energy input to ecosystems. Hydrothermal vent communities are a clear exception. Some students might enjoy additional details about the nature of these ecosystems and the roles they might have played in the early evolution of life on Earth. One source of good Internet information about hydrothermal vent communities is found at www.csa.com/discoveryguides/vent/websites.php.

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4. The turnover of lakes and ponds in the fall often results in noticeable changes. Fish kills and distinct changes in the colors and smells of the water may have been noticed by students in your course (depending on your particular location). If you are addressing this subject in the fall or early winter, you might have students watch for this phenomenon.

5. Many websites introduce the diversity of biomes with varying degrees of detail and imagery. Many related sites are targeted toward pre-college students. The following site lists links related to biomes: www.aresearchguide.com/biomes.html.

6. Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Helping students learn how to organize information may still be needed at the beginning levels of college.

7. Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent on these natural disturbances? Exploring the role of disturbances in ecosystems may provide hope to students who may be saddened by human impacts on biomes.

8. In the 1960s and early 1970s, movies about the American West were produced in portions of Europe. Relying on similar biomes in Europe and North America, these “spaghetti westerns” were made to look as if they were filmed in the American West. A Google search of “spaghetti westerns” will produce links to websites devoted to this genre of film.

9. A discussion of the movements of water through your local community might help students relate to the concept of global water cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community or campus and the possible routes of exit. Students may not realize that it is possible that the outflow of water from one community leads to the inflow of water in a community downstream.

10. Consider exploring with your students the many ways that the Gulf of Mexico was impacted by the BP 2010 spill and the natural mechanisms in this biome that are helping it to recover.

Global Climate Change Student Misconceptions and Concerns 1. The thinning of the ozone layer is a related but separate issue from global warming.

Students often confuse these issues and think of them as somehow the same problem.

2. The general tendency to discount one’s impact on global issues and concerns can be difficult. How can one person matter? Consider addressing this perspective and involving your class in a related discussion to consider including the concept of a person’s carbon footprint.

Teaching Tips 1. Many students do not realize that greenhouses get very warm when exposed to strong sunlight. (Most of them have probably never even been inside a greenhouse.) However, most students understand that a closed car gets warmer when sitting in the sun (thus the need for the various windshield sun reflectors). The glass in the car functions like the glass in a greenhouse.

2. Identify local issues that are related to the topics addressed in this chapter. What can be done in and around your campus to make meaningful changes? ..

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3. One of many carbon footprint calculators can be found at the website for the Nature Conservancy: www.nature.org/greenliving/carboncalculator/.

4. Consider challenging your students to find at least one scholarly article online that documents the impact of climate change on at least one species. They could e-mail the link to you as their assignment.

5. Additional details on the greenhouse effect can be found in many places and at the following websites.

NASA’s: http://gcmd.nasa.gov/Resources/pointers/glob_warm.html The National Climatic Data Center: www.ncdc.noaa.gov/oa/climate/globalwarming.html 6. In 2007, former U.S. Vice President Al Gore and the Intergovernmental Panel on Climate Change (IPCC) received the Nobel Peace Prize “for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change.” The full statement of the Nobel Prize committee can be found at http://nobelprize.org/nobel_prizes/peace/laureates/2007/.

7. Students are unlikely to enter your course with a prior understanding of the diverse impacts of global climate change on ecosystems and individual species. Concepts such as the increased spread of disease vectors, the shifting of natural ranges and breeding seasons, and the spread of invasive species will likely be new to them, and taking it all in can be overwhelming. However, an awareness of the impact of global climate change can also be motivating. Consider ending your class sessions by discussing positive actions that students can take to make a difference. A few websites that provide related suggestions follow. www.liveneutral.com www.green-e.org www.stopglobalwarming.org www.sierraclub.org/energy/

Key Terms abiotic factors acclimation aphotic zone benthic realm biome biosphere biotic factors carbon footprint chaparral community community ecology

coniferous forests coral reef deserts ecology ecosystem ecosystem ecology estuary greenhouse effect greenhouse gases habitat intertidal zone

organismal ecology pelagic realm permafrost photic zone phytoplankton polar ice population population ecology savannas sustainability taiga

temperate broadleaf forests temperate grasslands temperate rain forests temperate zones tropical forests tropics tundra wetland zooplankton

Word Roots a = without; bio = life (abiotic factors: the nonliving chemical and physical factors in an environment) benth = the depths of the seas (benthic realm: a seafloor or the bottom of a freshwater pond, lake, river, or stream) 268

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bio = life; sphere = a ball (biosphere: the sum of all of Earth’s ecosystems) eco = house (ecology: the scientific study of the interactions between organisms and their environments) estuar = the sea (estuary: the area where a freshwater stream or river merges with the ocean) inter = between (intertidal zone: the type of zone where land meets the sea) pelag = the sea (pelagic realm: all of the open-water areas of an ocean, excluding the intertidal zone) perman = remaining (permafrost: a permanently frozen stratum below the arctic tundra) photo = light (photic zone: the region of an aquatic ecosystem where light penetrates and photosynthesis occurs) phyto = a plant; plankto = drift or wander (phytoplankton: algae and photosynthetic bacteria that drift passively in aquatic environments) zo = animal (zooplankton: animals that drift in aquatic environments)

Relevant Songs to Play in Class “Mercy Mercy Me (The Ecology),” Marvin Gaye

“One Thing Leads to Another,” The Fixx “Big Yellow Taxi,” Joni Mitchell

“The Trees,” Rush

Answers to End-of-Chapter Questions The Process of Science 12. Suggested answer: Various populations could be exposed to varying water temperatures under well-controlled laboratory conditions. The population density would be monitored to track population sizes. The results could be used to determine the optimal temperature for the population to survive. Temperature would be the independent variable; population size would be the dependent variable. Light and food source would be held constant.

13. Suggested answer: Evidence presented in this chapter and in many reliable sources describes documented changes in global temperature, precipitation patterns, the distribution of organisms, and levels of atmospheric carbon dioxide. Although correlations do not necessarily indicate cause and effect, our knowledge of the natural role of greenhouse gases in our atmosphere identifies a mechanism for global climate change and enables intelligent predictions of future consequences. The textbook identifies the many human activities that have and that continue to affect global levels of greenhouse gases.

Natural causes of climate change such as increases in solar output and increases in CO2 concentrations can also be ruled out. As a result, the correlation between man’s activities and global climate change become much stronger because there are no good alternative hypothesis (theories) explaining the observed changes to the planet.

Biology and Society 14. Some issues and questions to consider: What reasons are there for protecting areas like this? Is a public refuge or preserve the only way to protect species and habitats? Is there some way to protect organisms without confiscating land? Do the public’s interests in protecting species and ecosystems take precedence over property rights? Would the prairie have been better off without the publicity? Should the public be able to condemn land to ..

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protect it? Should there be state or federal laws to protect endangered plants on private land? Should there be laws to protect endangered habitats, like this patch of prairie?

Should the farmer have been compensated so that he would not want to plow the field?

15. Some issues and questions to consider: Are there some agricultural practices that have less of an environmental impact than others? Can genetic engineering produce plants that require less environmental impact? What agricultural practices are most likely to produce sustainable uses of the land? How will agriculture need to change in response to regional shifts in temperature and precipitation? Environmentally friendly, sustainable practices are used today, but are not yet in widespread use.

16. Students may use the carbon footprint calculator found at the website for the Nature Conservancy, at www.nature.org/initiatives/climatechange/calculator/. The chapter discusses many ways for students to decrease their carbon footprint.

17. Some issues and questions to consider: What obligations do developers have when adding housing and industry to a region? Should these developers secure adequate resources before being allowed to build? How do we prioritize the needs of existing industries and populations compared to new expansion into a region? How do we prioritize the need for limited resources that affect conservation, natural ecosystems, and commercial interests?

As noted in the chapter, the competing needs for water as populations increase in the southwestern United States, and as precipitation drops in these regions, are already testing these questions. Students may investigate how these regions have dealt with these issues and continue to struggle as the problems become more severe.

Additional Critical Thinking Questions The Process of Science 1. Should humans be concerned with the extinction of “pests” like mosquitoes? Why or why not?

Suggested answer: The elimination of the mosquito could have a large environmental impact by eliminating a food source for other animals. Other members of the community in which mosquitoes live, like bats, depend on their existence. The extinction of any animal will disrupt a community. What would be the economic impact to third-world countries if mosquito-borne illnesses such as malaria were eliminated? Would this contribute to additional population growth or just economic growth?

Biology and Society 2. How can we balance the need for fire in an ecosystem with the existence of human housing?

Some issues and questions to consider: Controlled fires can be set in situations where housing could be threatened. Setting controlled fires reduces the chances that an uncontrolled fire will rage through a developed area. Houses can also be built in areas that can be buffered from fire, usually by clear-cutting or other fire barriers.

3. In most communities, storm drains send the collected water into streams, bypassing the wastewater treatment sites. How could washing your car and fertilizing your lawn affect the streams receiving the runoff?

Some issues and questions to consider: Excess phosphates can lead to algal blooms. The algae can use up the oxygen in the water and result in large fish kills. Everyone needs to be aware that runoff can have a direct effect on the wildlife in their ponds and streams.

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CHAPTER

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Population Ecology

Why This Chapter Matters 1. The human population explosion is now Earth’s most significant biological phenomenon.

2. The current mass extinction of species is related to the exploding human population.

3. To understand human population growth, we must understand the principles of ecology that apply to all species.

Chapter Objectives Biology and Society: Invasion of the Lionfish 1. Describe the spread and consequences of introduced lionfish in the Atlantic region.

Explain why people should not introduce pets into the wild.

An Overview of Population Ecology 2. Define the terms population, population ecology, and population density.

3. Explain how life tables are used to track mortality and survivorship in populations.

4. Compare Type I, Type II, and Type III survivorship curves.

5. Compare the characteristics of species that show opportunistic or equilibrial life histories.

Describe examples of each.

Population Growth Models 6. Compare the exponential growth model to the logistic growth model. Describe examples of each.

7. Distinguish between density-dependent and density-independent factors.

8. Explain why the hare and lynx populations cycle in a boom-and-bust pattern.

Applications of Population Ecology 9. Explain how population ecology can help guide efforts to save populations close to extinction. Distinguish between endangered species and threatened species.

10. Explain how population ecology can be used to provide the highest sustainable yields from harvests of natural populations.

11. Define invasive species and explain why they are a major ecological and financial problem.

12. Explain how biological controls are used to manage introduced species and the risks of adopting this strategy.

13. Describe the goals of integrated pest management and its advantages over the widespread use of pesticides.

Human Population Growth 14. Describe the growth of the human population over the last 2,000 years.

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16. Explain how the ecological footprint of a nation indicates the country’s impact on the world’s resources.

Evolution Connection: Humans as an Invasive Species 17. Explain how and why the North American population of mammals has changed in the last 15,000 years.

Lecture Outline I. Biology and Society: Invasion of the Lionfish 1. Lionfish are favorites of saltwater aquarium enthusiasts. But lionfish a. have venomous spines, b. are merciless predators, and c. grow quickly from 2 to 18 inches.

2. Apparently some lionfish owners released their lionfish into the waters along the southeastern coast of Florida. Now lionfish populations have spread a. up the East Coast of the United States, b. throughout the Atlantic and Gulf of Mexico, and c. into the Caribbean region.

3. To slow the lionfish invasion, the National Oceanic and Atmospheric Administration (NOAA) has launched an “Eat Lionfish” campaign to encourage human predation on the tasty fish 4. Lionfish are just one example of many non-native species a. spread intentionally or accidentally by humans and b. leaving environmental havoc and radically changed environments in their wake.

II. An Overview of Population Ecology 1. A population is a group of individuals of a single species that occupy the same general area 2. Population ecology focuses on the factors that influence a population’s a. density, b. structure, c. size, and d. growth rate.

3. Population ecology is used to study a. how to develop sustainable fisheries, b. how to control pests and pathogens, and c. human population growth.

A. Population Density 1. Population density is the number of individuals of a species per unit of area or volume. Examples include the number of a. largemouth bass per cubic kilometer (km3) of a lake, b. oak trees per square kilometer (km2) in a forest, and c. nematodes per cubic meter (m3) in a forest’s soil.

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2. How do we measure population density? a. In most cases, it is impractical or impossible to count all individuals in a population. b. In some cases, population densities are estimated by indirect indicators, such as i. number of bird nests or ii. rodent burrows.

B. Population Age Structure 1. The age structure of a population is the distribution of individuals in different age-groups 2. The age structure of a population provides insight into a. the history of a population’s survival, b. reproductive success, and/or c. how the population relates to environmental factors.

C. Life Tables and Survivorship Curves 1. Life tables a. track survivorship (the chance of an individual in a given population surviving to various ages) and b. help to determine the most vulnerable stages of the life cycle.

2. Survivorship curves a. plot the number of individuals still alive at each age in the maximum life span and b. are classified based upon the rate of mortality over the life span of an organism.

D. Life History Traits as Evolutionary Adaptations 1. An organism’s life history is the set of traits that affect the organism’s schedule of a. reproduction and b. survival.

2. Key life history traits include the a. age at first reproduction, b. frequency of reproduction, c. number of offspring, and d. amount of parental care given.

3. Life history traits a. evolve and b. represent a compromise of the competing needs for i. time, ii. energy, and iii. nutrients.

4. Organisms with an opportunistic life history a. take immediate advantage of favorable conditions and b. typically exhibit a type III survivorship curve.

5. Organisms with an equilibrial life history a. develop and reach sexual maturity slowly, b. produce few, well-cared-for offspring,

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c. are typically larger-bodied and longer-lived, and d. typically exhibit a type I survivorship curve.

III. Population Growth Models 1. Population size fluctuates as new individuals a. are born, b. immigrate into an area, c. emigrate away, and d. die.

A. The Exponential Population Growth Model: The Ideal of an Unlimited Environment 1. Exponential population growth describes the expansion of a population in an ideal and unlimited environment 2. Exponential growth explains how a. a few dozen rabbits can multiply into millions and b. in certain circumstances following disasters, organisms that have opportunistic life history patterns can rapidly recolonize a habitat.

B. The Logistic Population Growth Model: The Reality of a Limited Environment 1. Limiting factors a. are environmental factors that hold population growth in check and b. restrict the number of individuals that can occupy a habitat.

2. The carrying capacity is the maximum population size that a particular environment can sustain 3. Logistic population growth occurs when the growth rate decreases as the population size approaches carrying capacity 4. The carrying capacity for a population varies, depending on the a. species and b. resources available in the habitat.

5. Organisms exhibiting equilibrial life history patterns occur in environments where the population size is at or near carrying capacity 6. The logistic model and the exponential model are theoretical ideals of population growth.

7. No natural population fits either one perfectly C. Regulation of Population Growth 1. Density-Dependent Factors 2. The logistic model is a description of intraspecific competition, competition between individuals of the same species for the same limited resources 3. A density-dependent factor is a population-limiting factor whose effects intensify as the population increases in density 4. Intraspecific competition is competition between individuals of the same species for the same limited resources 5. As population size increases, a. competition becomes more intense and b. birth rates decline.

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6. Density-dependent factors may include a. accumulation of toxic wastes, b. limited food supply, and c. limited territory.

7. Density-Independent Factors 8. Density-independent factors a. are population-limiting factors whose intensity is unrelated to population density and b. include abiotic factors such as i. fires, ii. floods, and iii. storms.

9. In many natural populations, abiotic factors may limit or reduce population size before other limiting factors become important 10. Over the long term, most populations are probably regulated by a mixture of a. density-independent factors and b. density-dependent factors.

11. Population Cycles 12. Some populations have regular boom-and-bust cycles characterized by a. periods of rapid, exponential growth followed by b. steep population declines.

13. A well studied example of boom-and-bust cycles are cycles of a. snowshoe hares and b. one of the hares’ predators, the lynx.

14. The cause of these hare and lynx cycles may be a. winter food shortages for the hares, b. overexploitation of hares by lynx and other predators, and c. a combination of both of these mechanisms.

IV. Applications of Population Ecology 1. Population ecology is used to a. increase populations of organisms we wish to harvest, b. decrease populations of pests, and c. save populations of organisms threatened with extinction.

A. Conservation of Endangered Species 1. The U.S. Endangered Species Act defines a. an endangered species as one that is in danger of extinction throughout all or a significant portion of its range and b. a threatened species as one that is likely to become endangered in the foreseeable future.

2. A major factor in population decline is a. habitat destruction or b. habitat modification.

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3. The red-cockaded woodpecker a. requires longleaf pine forests with clear flight paths between trees, b. suffered from fire suppression, increasing the height of the vegetation on the forest floor, and c. recovered from near-extinction to sustainable populations due to controlled burning and other management methods.

B. Sustainable Resource Management 1. According to the logistic growth model, the fastest growth rate occurs when a population size is at roughly half the carrying capacity 2. Theoretically, populations should be harvested down to this level, assuming that growth rate and carrying capacity are stable over time 3. In the northern Atlantic cod fishery, a. estimates of cod stocks were too high, and b. the practice of discarding young cod (not of legal size) at sea caused a higher mortality rate than was predicted.

4. The fishery collapsed in 1992 and has not recovered C. Invasive Species 1. An invasive species a. is a non-native species that has spread far beyond the original point of introduction and b. causes environmental or economic damage by colonizing and dominating suitable habitats.

2. In the United States, invasive species cost about $137 billion a year 3. Invasive species typically exhibit an opportunistic life history pattern 4. Cheatgrass a. is an invasive species in the western United States, b. currently covers more than 60 million acres of rangeland formerly dominated by native grasses and sagebrush, c. produces seeds earlier and in greater abundance than native species, and d. forms highly flammable brush, creating fires that native plants cannot tolerate.

5. Burmese pythons a. are another invasive species, b. were set loose in South Florida, either deliberately or accidentally, and c. are now abundant in South Florida, eating native species of i. birds, ii. mammals, iii. reptiles, and iv. amphibians.

D. Biological Control of Pests 1. Invasive species may benefit from the absence of a. pathogens, b. predators, or c. herbivores.

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2. Biological control is a. the intentional release of a natural enemy to attack a pest population and b. used to manage an invasive species.

3. Leaf beetles have been used to control St. John’s wort, a perennial European weed that invaded the western United States in the 1930s 4. Mongooses a. were introduced to the Hawaiian Islands to control rat populations, but b. soon became an invasive species themselves as they ate native amphibians, reptiles, birds, and domestic poultry.

E. The Process of Science: Can Biological Control Defeat Kudzu?

1. Kudzu a. is an invasive Asian vine, b. covers about 12,000 square miles of the southeastern United States, and c. has a range limited by cold winters.

2. Many strategies to control kudzu have been considered with little success 3. A fungal pathogen called Myrothecium verrucaria appears to be a promising candidate for biological control 4. Observation: The fungus Myrothecium verrucaria causes severe disease in other weeds belonging to the same family as kudzu 5. Question: Will the application of fungal spores of M. verrucaria control an established stand of kudzu in a natural setting?

6. Hypothesis: M. verrucaria treatment that was effective in small outdoor plantings would also be most effective in a natural setting 7. Prediction: The greatest kudzu mortality would result from the treatment that sprayed the highest concentration of spores in combination with a wetting agent 8. Results: The hypothesis was supported by the data, as indicated in the following table F. Integrated Pest Management 1. Agricultural operations create their own highly managed ecosystems that a. have genetically similar individuals (a monoculture), b. are planted in close proximity to each other, and c. function as a “banquet” for i. plant-eating animals, ii. pathogenic bacteria, and iii. viruses.

2. Like invasive species, most crop pests a. have an opportunistic life history pattern and b. can cause extensive crop damage.

3. Pesticides may a. result in pesticide-resistant pests, b. kill the pest and their natural predators, and c. kill pollinators.

4. Integrated pest management (IPM) a. tolerates a low level of pests instead of total eradication, b. produces a sustainable control of agricultural pests, and ..

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c. uses a combination of i. biological methods, ii. chemical methods, and iii. cultural methods.

5. IPM methods include a. using pest-resistant varieties of crops, b. using mixed-species plantings, and c. rotating crops to deprive the pest of a dependable food source.

V. Human Population Growth A. The History of Human Population Growth 1. From 2,000 to 500 years ago (in 1500), a. mortality was high, b. births and deaths were about equal, and c. the world population held steady at about 300 million.

2. Worldwide population growth rates reflect a mosaic of the changes occurring in different countries a. In the most developed nations, the overall growth rates are near zero. b. In the developing world, i. death rates have dropped and ii. high birth rates persist.

B. Age Structures 1. Age structures help predict a population’s future growth 2. The following figure shows the estimated and projected age structures of Mexico’s population in a. 1985, b. 2010, and c. 2035.

3. Population momentum is the continuation of population growth as girls in the prereproductive age group reach their reproductive years 4. Age structure diagrams may also indicate social conditions. An expanding population needs a. schools, b. employment, and c. infrastructure.

5. Trends in the age structure of the United States from 1985 to 2035 reveal important patterns C. Our Ecological Footprint 1. An ecological footprint is an estimate of the amount of land required to provide the raw materials an individual or a nation consumes, including a. food, b. fuel, c. water,

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d. housing, and e. waste disposal.

2. The ecological footprint of the United States a. is 9 hectares per person and b. represents almost twice what the U.S. land and resources can support.

3. The ecological impact of affluent nations is a problem of a. overconsumption and b. overpopulation.

4. Compared to a family in rural India, Americans have an abundance of possessions 5. There is a huge disparity between resource consumption in more developed and less developed nations D. Evolution Connection: Humans as an Invasive Species 1. Pronghorn antelope a. roamed the open plains and shrub deserts of North America millions of years ago, b. have a top speed of 97 km/h (60 mph), and c. are the fastest mammal on the continent.

2. Pronghorn speed is likely an adaptation to outrun American cheetahs, which went extinct about 10,000 years ago 3. About 10,000 years ago, a. changes in the biotic and abiotic environments happened too rapidly for an evolutionary response and b. many large North American mammals, in addition to American cheetahs, went extinct, including i. lions, ii. saber-toothed cats, and iii. towering short-faced bears.

4. Although still hotly disputed, many scientists think that the extinction at the end of the ice age about 10,000 years ago was in part the result of the human invasion of North America, with humans serving as the damaging invasive species 5. Like other invasive species, humans may change the environment a. at an accelerating pace and b. too rapidly for other species to evolve and survive.

Chapter Guide to Teaching Resources An Overview of Population Ecology Student Misconceptions and Concerns 1. Students might imagine that the opportunistic life history is risky and might not be successful over time. Plants such as the agave (century plant) risk all of their reproductive effort on a single life-ending event. However, this reproductive strategy has evolved over time because it has been successful (but like investments, past success does not guarantee future success).

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2. Many nonmajors have trouble thinking about the evolution of systems. One analogy that can be developed, especially for economically minded students, makes parallels to the “evolution” of businesses. Consider the introduction and expansion of McDonald’s restaurants in the United States over the last 50 years. When McDonald’s restaurants were just starting out, they experienced little competition with access to many customers. The population of McDonald’s grew exponentially (or so it seemed!) with few densitydependent factors. Today in the United States, McDonald’s restaurants experience competition with each other and many other fast-food restaurants such as Burger King and Taco Bell. The population of McDonald’s restaurants in the United States has somewhat leveled off because of this competition for customers, a density-dependent factor. A graph of the growth of McDonald’s restaurants in the United States would likely resemble the lazy S shape.

Teaching Tips 1. Consider comparing opportunistic and equilibrial life histories in a table with the following top headings: Type of Survivorship Curve, Age of Maturity, Number of Offspring, Use of Parental Care, Stability of the Population, Is the Population Density Dependent, and Examples.

2. Your class might get some practice analyzing life histories by describing additional examples. Challenge your students to classify the type of survivorship curve that would be expected. Frogs and fish typically produce hundreds of eggs, leading to Type III survivorship curves. Elephants and whales typically produce few offspring in life histories that more likely represent Type I survivorship curves. Mice and other small mammals are capable of producing litters of 10 or more offspring a year, over a several-year period.

These mammals have life histories that may be intermediate, leading to Type II survivorship curves.

3. The following Centers for Disease Control and Prevention website provides information and life tables for people living in the United States: www.cdc.gov/nchs/products/life_tables.htm.

4. Compromise is a key principle of biology. No adaptation can be perfect, and no reproductive strategy can maximize all types of effort. As the text notes, an organism cannot have a great number of offspring and invest great amounts of parental care in each one. Resources, including time, are limited. Have students imagine how different their lives would have been if they had been born as one of a set of quadruplets—or if they themselves were faced with the task of rearing four children at once!

Population Growth Models Student Misconceptions and Concerns 1. Students with limited biology backgrounds may unrealistically expect simplistic explanations. When we consider the factors that limit population size, we learn to appreciate the complex nature of biology. As noted in the text, population growth models are approximations and density-dependent and density-independent factors are usually both involved.

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Teaching Tips 1. Exponential growth of a population is like compounded interest on a bank account. The growth of the account is initially small, but as the interest earns interest, the growth expands. For example, $1,000 invested at 7% interest is worth about $30,000 in 50 years.

Consider a short assignment to have students calculate the value of a simple interestbearing investment over a set period of years, similar to the example just noted.

2. It is typically easier to understand a concept when the examples are familiar. Consider the biology of your region and identify a species that is likely to be well known by your students. Perhaps this will be a squirrel population on your campus. Challenge your class to imagine the changes in this squirrel population if (a) a strong storm toppled half the trees on campus or (b) a large group of dogs moved onto campus for a few weeks.

3. Consider challenging your class to explain why the lynx and hare cycle does not result in the elimination of one or both of the species. Why don’t we see hares hunted to extinction?

Students may not have considered the difficulty in finding prey when prey populations are low. This challenge permits a recovery of the hare population, which in turn supports the recovery of the lynx population.

Applications of Population Ecology Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $137 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public.

2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book, Silent Spring, or passages from it, might be a good assignment for your class.

Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences.

2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations.

Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species.

3. The U.S. Department of Agriculture sponsors the National Invasive Species Information Center, which has a website at www.invasivespeciesinfo.gov/.

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4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of overharvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Human Population Growth Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip 4 below for a list of websites where your students can calculate their ecological footprint.

2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these websites for basic ideas on what individuals can do to start to make a difference. www.calacademy.org/exhibits/california_hotspot/what_you_can_do.htm www.dep.state.pa.us/earthdaycentral/96/business/FS1977.htm www.nwzaa.org/project-pages/green6.html

Teaching Tips 1. The U.S. government’s Census Bureau sponsors a U.S. and world population clock at www.census.gov/main/www/popclock.html for the most recent estimates of U.S. and world human populations.

2. Medicare and Social Security will be increasingly impacted as the U.S. population ages.

By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes.

3. The United States has an ecological footprint greater than the land area of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures: a. 1 football field with end zones is 57,600 square feet (360 × 160 feet) b. 1 acre = 43,560 sq. feet c. 2.47 acres = 1 hectare = 107,639 square feet d. 1.87 football fields in 1 hectare = 107,639 (1 hectare) sq. feet / 57,600 sq. feet (football field with end zones) e. 17.6 football fields = 9.4 hectare × 1.87 football fields = average ecological footprint of each U.S. citizen.

4. Many Web resources are available for students to calculate their ecological footprint.

A few of them are noted below: www.earthday.net/footprint/ www.footprintnetwork.org/ www.ecologyfund.com/ecology/res_bestfoot.html www.myfootprint.org/en/visitor_information/ 282

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Key Terms age structure biological control carrying capacity density-dependent factor density-independent factor ecological footprint

endangered species equilibrial life history exponential population growth intraspecific competition invasive species life history

life table limiting factors logistic population growth opportunistic life history population population density

population ecology population momentum survivorship curve threatened species

Word Roots co = together (coevolution: the evolution of two species in response to each other) eco = house (ecosystem: an ecological system) equ = same (equilibrial life history: the type of life history pattern of reaching sexual maturity slowly and producing few offspring but caring for the young) intra = within (intraspecific competition: competition within a species)

Relevant Songs to Play in Class “Mercy Mercy Me (The Ecology),” Marvin Gaye

“One Thing Leads to Another,” The Fixx “Big Yellow Taxi,” Joni Mitchell

“The Trees,” Rush

Answers to End-of-Chapter Questions The Process of Science 10. Suggested answer: Common plants that are similar to kudzu could be tested with applications of Myrothecium verrucarria under well-controlled laboratory conditions using water and variations of the wetting agents indicated in Figure 19.18. If results suggest further study, small-scale field tests may be conducted to test Myrothecium verrucarria in a natural setting. The effects of Myrothecium verrucarria on other organisms in the environment should also be carefully monitored.

11. Suggested answer: Several hypotheses are reasonable. Human interactions and/or global climate change may have resulted in the spread of disease, loss of essential habitat, or shortages of food. Some populations may have been hunted to near extinction.

Biology and Society 12. Suggested answer: Organisms with equilibrial life histories cannot recover quickly from population declines and are disproportionately hurt by the loss of offspring. Type I survivorship curves are characteristic of large animals with equilibrial life histories.

13. Suggested answer: Ecological impacts are a consequence of population size and the ecological footprint of each member of the population. Fast growth of populations of individuals with small ecological footprints can have less of an impact than moderate growth of populations with individuals who have larger ecological footprints.

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Additional Critical Thinking Questions The Process of Science 1. Using the theories of population ecology, justify the establishment of fishing limits that are based on the number and the size of the fish.

Suggested answer: Fishing limits prevent a community from being hunted to extinction but encourage the thinning of the population so it does not overcrowd its environment. By removing the optimal amount of fish, the population can remain at a higher growth rate, maximizing the harvest. The weight limit for fish ensures that fishermen do not eliminate the next breeding generation of fish, thereby driving the fish to extinction. Also by placing a weight limit or size limit on fish, larger individuals are not selected for, resulting in a population with smaller individuals.

2. The average human life span has been increasing for decades. What are some of the leading factors contributing to this increase in the mean life span for humans?

Suggested answer: Advances in health care, nutrition, and sanitation enable humans to maximize their life spans. The greatest influence on the average human life span is the decrease in infant mortality, which can be attributed to many of the same advances as previously mentioned.

Biology and Society 3. Many exotic species have been introduced to a new environment unintentionally. Many people are unaware of the dangers of introducing “just one or two” new organisms.

Explain why the introduction of exotic species can cause major problems.

Suggested answer: Introduced species can prey on native species or outcompete the native species. These introduced species may carry invisible parasites that can do major damage to native species. Once introduced species take hold, it may be nearly impossible to remove them.

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CHAPTER

20

Communities and Ecosystems

Why This Chapter Matters 1. Humans have an unusually destructive impact on the environment, typically reducing species diversity.

2. Human activities also disrupt biogeochemical cycles.

3. Yet, humans have a fascination with the natural world. We are naturally curious about our world and wish to preserve it.

4. This chapter helps us understand the nature of the problems and our efforts to save what we value.

Chapter Objectives Biology and Society: Why Biodiversity Matters 1. Define biodiversity and explain why it matters.

The Loss of Biodiversity 2. Describe the three levels of biological diversity.

3. Describe the four main factors responsible for the loss of biodiversity.

Community Ecology 4. Define a community, an ecological niche, and the competitive exclusion principle, noting examples of each.

5. Distinguish between parasitic and mutualistic relationships and describe examples of each.

6. Describe examples of predator adaptations, plant defenses against herbivores, and animal defenses against predators.

7. Define cryptic coloration and warning coloration and describe examples of each.

8. Define and list examples of producers, primary consumers, secondary consumers, tertiary consumers, quaternary consumers, detritivores, and decomposers in an ecosystem.

9. Distinguish between a food chain and a food web.

10. Explain how biological magnification concentrates toxins in the highest trophic levels.

11. Explain how species richness and relative abundance contribute to species diversity.

12. Describe the function of a keystone species in a community.

13. Explain how predation can help maintain species diversity.

14. Describe the types and effects of disturbances in communities.

15. Distinguish between primary and secondary succession.

Ecosystem Ecology 16. Compare the processes of energy flow and chemical cycling as they relate to ecosystem dynamics.

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18. Describe the composition of the levels of an energy pyramid. Explain why energy pyramids usually do not have more than five levels.

19. Explain why it takes about the same amount of photosynthetic productivity to produce 10 kilograms of corn as 1 kilogram of bacon.

20.

Describe the biogeochemical cycles of carbon, nitrogen, water, and phosphorus.

21. Explain how human activities have disrupted the carbon, nitrogen, phosphorus, and water cycles.

Conservation and Restoration Biology 22. Explain the importance of biodiversity hot spots to the conservation of biological diversity.

23. Describe the nature of the issues confronting modern conservation biology.

24. Explain how edges and movement corridors impact species.

25. Explain how habitat fragmentation affects biodiversity.

26. Describe the goals and some of the methods of restoration ecology.

27. Describe the goals of sustainable development.

Evolution Connection: Can Biophilia Save Biodiversity?

28. Describe the concept and significance of biophilia.

Lecture Outline I. Biology and Society: Why Biodiversity Matters 1. The expanding human population threatens a. biodiversity and b. the loss of natural ecosystems.

2. Healthy ecosystems a. purify air and water, b. decompose wastes, and c. recycle nutrients.

3. Wetlands a. buffer coastal populations against hurricanes, b. reduce the impact of flooding rivers, and c. filter pollutants.

4. It is estimated that the average annual value of ecosystem services each year in the United States is more than $33 trillion

II. The Loss of Biodiversity 1. Biological diversity, or biodiversity, includes a. genetic diversity, b. species diversity, and c. ecosystem diversity.

A. Genetic Diversity 1. The genetic diversity within populations of a species is the raw material that makes microevolution and adaptation to the environment possible

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2. Genetic resources for that species are lost if a. local populations are lost and/or b. the number of individuals in a species declines.

B. Species Diversity 1. Ecologists believe that we are pushing species toward extinction at an alarming rate 2. The present rate of species loss may a. be 100 times higher than at any time in the past 100,000 years and b. result in the loss of half of all living plant and animal species by the end of this century.

3. Two recent victims of human-caused extinctions are a. Chinese river dolphins and b. golden toads.

C. Ecosystem Diversity 1. The local extinction of one species can have a negative effect on the entire ecosystem 2. The disappearance of natural ecosystems results in the loss of ecosystem services, functions performed by an ecosystem that directly or indirectly benefit people, including a. air and water purification, b. climate regulation, and c. erosion control.

3. Coral reefs are rich in species diversity, yet a. an estimated 20% of the world’s coral reefs have been destroyed by human activities and b. a 2011 study found that 75% of the remaining reefs are threatened, climbing to 90% by 2030 if current abuse continues.

D. Causes of Declining Biodiversity 1. Ecologists have identified four main factors responsible for the loss of biodiversity: a. habitat destruction and fragmentation, b. invasive species, c. overexploitation, and d. pollution.

2. Habitat Destruction 3. Biodiversity is threatened by the destruction and fragmentation of habitats by a. agriculture, b. urban development, c. forestry, and d. mining.

4. Invasive Species 5. Invasive species have a. competed with native species, b. preyed upon native species, and c. parasitized native species.

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8. Overharvesting has greatly affected populations of a. tigers, b. the American bison, and c. Galápagos tortoises.

9. Pollution 10. Air or water pollution is a contributing factor in declining populations of hundreds of species a. Acid precipitation is a threat to ecosystems. b. The global water cycle can transport pollutants from terrestrial to aquatic ecosystems hundreds of miles away.

III. Community Ecology 1. An organism’s biotic environment includes a. other individuals in its own population and b. populations of other species living in the same area.

2. An assemblage of species living close enough together for potential interaction is called a community A. Interspecific Interactions 1. Interspecific interactions are interactions between species 2. Interspecific interactions can be classified according to the effect on the populations concerned a. –/– interactions occur when two populations in a community compete for a common resource. b. +/+ interactions are mutually beneficial, such as between plants and their pollinators. c. +/– interactions occur when one population benefits and the other is harmed, such as in predation.

3. Interspecific Competition (–/–) 4. In interspecific (between-species) competition, the population growth of a species may be limited a. by the population densities of competing species and b. by the density of its own population.

5. An ecological niche is an organism’s total use of the a. abiotic and b. biotic resources in its environment.

6. The competitive exclusion principle states that if two species have an ecological niche that is too similar, the two species cannot coexist in the same place 7. Mutualism (+/+) 8. In mutualism, both species benefit from an interaction 9. One example is the root-fungus associations known as mycorrhizae 10. Another example is the mutualistic relationship of coral animals and the unicellular algae that live inside their cells a. The coral gains energy from the sugars produced by the algae.

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b. The algae gain i. a secure shelter, ii. access to light, iii. carbon dioxide, and iv. ammonia, a valuable source of nitrogen.

11. Predation (+/–) 12. Predation refers to an interaction in which one species (the predator) kills and eats another (the prey) 13. Numerous adaptations for predator avoidance have evolved in prey populations through natural selection 14. Cryptic coloration is a. camouflage and b. a way for prey to hide from predators.

15. A warning coloration is a. a brightly colored pattern and b. a way to warn predators that an animal has an effective chemical defense.

16. Mimicry is a form of defense in which one species looks like another species 17. Some insects have elaborate disguises that make them resemble a. twigs, b. leaves, c. bird droppings, and d. predators.

18. Herbivory (+/–) 19. Herbivory is the consumption of plant parts or algae by an animal 20. Plants have evolved numerous defenses against herbivory, including a. spines, b. thorns, and c. chemical toxins.

21. Parasites and Pathogens (+/–) 22. Plants and animals can be victims of a. parasites, animals that live in or on a host from which they obtain nutrients, or b. pathogens, disease-causing i. bacteria, ii. viruses, iii. fungi, and iv. protists.

B. Trophic Structure 1. Trophic structure is the feeding relationships among the various species in a community 2. A community’s trophic structure determines the passage of energy and nutrients from plants and other photosynthetic organisms a. to herbivores b. and then to predators. ..

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3. The sequence of food transfer between trophic levels is called a food chain 4. The trophic level that supports all other trophic levels consists of autotrophs, which ecologists call producers 5. All organisms in trophic levels above the producers are heterotrophs, or consumers 6. Primary consumers are called herbivores, which eat plants 7. Above the level of primary consumers are carnivores, which eat the consumers from the level below a. Secondary consumers eat primary consumers. b. Tertiary consumers eat secondary consumers. c. Quaternary consumers eat tertiary consumers.

8. Some consumers derive their energy from detritus, the dead material left by all trophic levels 9. Different organisms consume detritus a. Scavengers, such as crows and vultures, feast on carcasses. b. Detritivores, such as earthworms and millipedes, primarily consume decaying organic material. c. Decomposers, mainly prokaryotes and fungi, secrete enzymes that digest molecules in organic material and convert organic materials into inorganic forms.

10. Biological Magnification 11. Toxins become concentrated as they pass through a food chain in a process called biological magnification 12. Food Webs 13. Few ecosystems are as simple as an unbranched food chain 14. The feeding relationships in a community are usually woven into elaborate food webs 15. Omnivores eat a. producers and b. consumers.

C. Species Diversity in Communities 1. Species diversity of a community, the variety of species that make up the community, consists of a. species richness, the number of different species in the community, and b. relative abundance of the different species, the proportional representation of a species in a community.

2. The next figure shows that the relative abundance of one species in woodland A is much higher than the other three species 3. A keystone species is a species whose impact on its community is much larger than its total mass or abundance indicates 4. Experiments in the 1960s a. were among the first to provide evidence of the keystone species effect and b. demonstrated that a sea star functioned as a keystone species in intertidal zones of the Washington coast.

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D. Disturbances in Communities 1. Disturbances are episodes that damage biological communities, at least temporarily, by a. destroying organisms and b. altering the availability of resources such as mineral nutrients and water.

2. Examples of disturbances include a. storms, b. fires, c. floods, d. droughts, and e. human activities.

3. Disturbances may cause a. the emergence of a previously unknown disease or b. opportunities for other organisms to grow.

E. Ecological Succession 1. Disturbances may cause a gradual replacement by other species in a process called ecological succession 2. Primary succession begins a. in a virtually lifeless area with no soil, b. in places such as i. the rubble left by a retreating glacier or ii. lava flows.

3. Secondary succession occurs where a disturbance has a. destroyed an existing community but b. left the soil intact.

4. Examples of secondary succession are areas recovering from a. floods or b. fires.

IV. Ecosystem Ecology 1. An ecosystem includes a. the community of species in a given area and b. all the abiotic factors, such as i. energy, ii. soil characteristics, and iii. water.

2. A simple terrarium is a community that interacts with abiotic factors a. Energy flow is the passage of energy through the components of the ecosystem. b. Chemical cycling is the use and reuse of chemical elements such as carbon and nitrogen within the ecosystem.

3. Energy flows through and ultimately out of ecosystems 4. Chemicals are recycled within and between ecosystems.

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A. Energy Flow in Ecosystems 1. All organisms require energy for a. growth, b. maintenance, c. reproduction, and, d. in many species, locomotion.

2. Primary Production and the Energy Budgets of Ecosystems 3. Each day, Earth receives about 1019 kcal of solar energy, the energy equivalent of about 100 million atomic bombs 4. Most of this energy is absorbed, scattered, or reflected by the atmosphere or by Earth’s surface 5. About 1% is converted to chemical energy by photosynthesis 6. The amount, or mass, of living organic material in an ecosystem is the biomass 7. The rate at which an ecosystem’s producers convert solar energy to the chemical energy stored in biomass a. is primary production and b. yields about 165 billion tons of biomass per year.

8. Different ecosystems vary considerably in their primary production 9. Ecological Pyramids 10. When energy flows as organic matter through the trophic levels of an ecosystem, much of it is lost at each link in the food chain 11. Consider the example of a caterpillar 12. A pyramid of production illustrates the cumulative loss of energy with each transfer in a food chain 13. The energy level available to the next higher level a. ranges from 5 to 20% and b. is illustrated here as 10%.

14. The energy available to top-level consumers is small compared to the energy available to lower-level consumers 15. This explains why a. top-level consumers require more geographic area and b. most food chains are limited to three to five levels.

16. Ecosystem Energetics and Human Resource Use 17. The dynamics of energy flow apply to the human population as much as to other organisms 18. The human population has less energy available to it when we eat higher trophic levels than when we eat as primary consumers B. Chemical Cycling in Ecosystems 1. Life depends on the recycling of chemicals a. Nutrients are acquired and waste products are released by living organisms. b. At death, decomposers return the complex molecules of an organism to the environment. c. The pool of inorganic nutrients is used by plants and other producers to build new organic matter.

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2. The General Scheme of Chemical Cycling 3. Biogeochemical cycles involve a. biotic components and b. abiotic components from an abiotic reservoir where a chemical accumulates or is stockpiled outside of living organisms.

4. Biogeochemical cycles can be a. local or b. global.

5. Three important biogeochemical cycles are a. carbon, b. phosphorus, and c. nitrogen.

6. The Carbon Cycle 7. Carbon, the major ingredient of all organic molecules, a. has an atmospheric reservoir and b. cycles globally.

8. The cycling of carbon between the biotic and abiotic worlds is accomplished mainly by the reciprocal metabolic processes of a. photosynthesis and b. cellular respiration.

9. The Phosphorus Cycle 10. Organisms require phosphorus as an ingredient of a. nucleic acids, b. phospholipids, and c. ATP. 11. Phosphorus is also required as a mineral component of vertebrate bones and teeth 12. The phosphorus cycle does not have an atmospheric component 13. The Nitrogen Cycle 14. Nitrogen is a. an ingredient of proteins and nucleic acids and b. essential to the structure and functioning of all organisms.

15. Nitrogen has two abiotic reservoirs: a. the atmosphere and b. the soil.

16. The process of nitrogen fixation converts gaseous N2 to nitrogen compounds that plants can assimilate 17. Most of the nitrogen available in natural ecosystems comes from biological fixation performed by two types of nitrogen-fixing bacteria a. Some bacteria live symbiotically in the roots of certain species of plants, supplying their hosts with a direct source of usable nitrogen. b. Free-living nitrogen-fixing bacteria in soil or water convert N2 to ammonia, which then picks up another H+ to become ammonium (NH4+).

18. Nutrient Pollution

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19. The growth of algae and cyanobacteria in aquatic ecosystems is limited by low nutrient levels, especially a. phosphorus and b. nitrogen.

20. Nutrient pollution occurs when human activities add excess amounts of these chemicals to aquatic ecosystems 21. Nitrogen runoff from Midwestern farm fields has been linked to an annual summer “dead zone” in the Gulf of Mexico

V. Conservation and Restoration Biology 1. Ecologists have discovered many environmental problems caused by human enterprises 2. Ecological research is the foundation for a. finding solutions to these problems and b. reversing the negative consequences of ecosystem alteration.

3. Conservation biology is a goal-oriented science that seeks to understand and counter the loss of biodiversity 4. Restoration ecology uses ecological principles to develop methods of returning degraded areas to their natural state A. Biodiversity “Hot Spots” 1. Conservation efforts are often focused on biodiversity hot spots, relatively small areas that have a. a large number of endangered and threatened species and b. an exceptional concentration of endemic species, those that are found nowhere else.

B. Conservation at the Ecosystem Level 1. Conservation biology increasingly aims at sustaining the biodiversity of entire a. communities, b. ecosystems, and c. landscapes, i. regional assemblages of interacting ecosystems, ii. such as an area with forest, adjacent fields, wetlands, streams, and streamside habitats.

2. Landscape ecology is the application of ecological principles to the study of land-use patterns 3. Edges between ecosystems a. are prominent features of landscapes, whether natural or altered by people, and b. have their own sets of physical conditions, such as i. soil type and ii. surface features.

4. A movement corridor is a narrow strip or series of small clumps of suitable habitat that connects otherwise isolated patches 5. Corridors a. can promote dispersal and help sustain populations and b. are especially important to species that migrate between different habitats seasonally.

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C. The Process of Science: How Does Tropical Forest Fragmentation Affect Biodiversity?

1. Observation: Forests are becoming fragmented when cleared for agriculture 2. Question: How does fragmentation of tropical forests affect species diversity within the fragments?

3. Hypothesis: Species diversity declines with the size of the forest fragment 4. Prediction: Predators will only be found in the largest areas 5. Results: Fragmentation of forests into smaller pieces does lead to a decline in species diversity D. Restoring Ecosystems 1. Bioremediation uses living organisms to detoxify polluted ecosystems 2. Researchers are investigating the use of plants to remove toxic substances from contaminated soil 3. The Kissimmee River was straightened into a canal between 1962 and 1971, draining the floodplain 4. The Kissimmee River restoration project is reversing the engineering of the river by a. removing water control structures such as dams and reservoirs and b. filling in about 35 km of the canal.

5. The first phase of the project was completed in 2004 E. The Goal of Sustainable Development 1. As the world population grows and becomes more affluent, the demand increases for the provisioning services of ecosystems, such as a. food, b. wood, and c. water.

2. The goal of sustainable development is to acquire the ecological information necessary for the responsible a. development, b. management, and c. conservation of Earth’s resources.

3. Sustainable development depends on a. continued research, b. the application of ecological knowledge, and c. the connection of the life sciences with i. social sciences, ii. economics, and iii. humanities.

4. Sustainable development aims to a. conserve biodiversity and b. improve the human condition.

F. Evolution Connection: Can Biophilia Save Biodiversity?

1. Edward O. Wilson uses the term biophilia to describe the human desire to affiliate with other life in its many forms

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2. Most biologists have a. embraced the concept of biophilia and b. turned their passion for nature into careers.

3. If biophilia is evolutionarily embedded in our genomes, then there is hope that we can become better custodians of the biosphere

Chapter Guide to Teaching Resources The Loss of Biodiversity Student Misconceptions and Concerns 1. The importance of biodiversity may not be obvious to many students. Yet, as this chapter notes, biodiversity is inherently valuable on many levels. Consider challenging your class to explain why biodiversity matters, as an introduction to the subject.

2. Frustration can overwhelm students who are alarmed by the many problems addressed in this chapter. One way to address this is to provide meaningful ways for students to respond to this information (for example, changes in personal choices and informed voting).

Several related websites are noted in the Teaching Tips below.

Teaching Tips 1. Consider referencing some of the following websites for basic ideas on what individuals can do to help address the loss of biodiversity: Conservation International: www.conservation.org/act/simplesteps/Pages/simplesteps.aspx www.biodiversityhotspots.org/ The Biodiversity Economics Site: www.biodiversityeconomics.org/index.html Biodiversity Support Program: www.worldwildlife.org/bsp/ 2. The bottleneck effect, not directly referenced in this chapter, is an important aspect of the loss of diversity within a species. Genetic bottlenecks are discussed in Chapter 13.

3. You might wish to note the mission of the Nature Conservancy, an organization devoted to the purchase and protection of land across the world. The Nature Conservancy’s website is www.nature.org/.

Community Ecology Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.

2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined.

3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis.

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4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has been (a) burned, (b) struck by high winds and/or lightning, or (c) temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage.

Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, and the like, that students could visit and return from with new insights.

2. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction.

3. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil.

4. Rattlesnakes are a good example of a highly specialized predator. Since they are unable to move fast enough to catch their prey, rattlesnakes typically ambush them, a process facilitated by their camouflaged bodies. Rattlesnakes often feed during the cooler parts of the day, using heat-detecting facial pits to identify prey before injecting them with fastacting venom. The prey is immediately released (perhaps to avoid damage to the snake from struggling prey), but is disabled by the venom within seconds. The rattlesnake then uses a variety of senses to track the prey the short distance to where it has collapsed.

5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution.

6. Students who are business-oriented may also enjoy this analogy. Many corporate leaders describe the best business deals as mutualistic, fostering a win-win relationship. For example, perhaps a new company creates a marketable product from another company’s wastes.

7. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems.

8. Many keystone species have been identified in ecosystems, including sea otters, elephants, wolves in Yellowstone National Park, freshwater bass, and Pisaster, a sea star noted in

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Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve?

9. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process.

10. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies?

How can such systems evolve if the model is killed in the learning experience?

Ecosystem Ecology Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding on these explanations in the book.

2. The environmental impact of eating farm animals is little appreciated by most students.

This chapter section helps explain the basis of the increased costs associated with a diet that includes meat.

3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle.

Teaching Tips 1. Although reading the children’s book, The Salamander Room may not be best for a college class, the lessons of this book may help to frame the problems of understanding the diverse and interrelated processes occurring in an ecosystem. Perhaps some of your students will know this book. In it, a boy tries to provide for his new pet salamander. Eventually, the boy’s room becomes a natural setting, to include all of the natural processes in the salamander’s ecosystem. Figure 20.25 references a terrarium and illustrates some of the basic processes occurring in these model systems.

2. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs.

3. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel-burning process.

4. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The systems will not work without a steady input.

NASA, however, must rely on some closed systems for its spacecraft. Students might enjoy investigating the recycling of gases and fluids in these NASA systems.

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5. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high-protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high-protein vegetarian options: www.vegsoc.org/page.aspx?pid=781.

6. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth.

7. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input.

8. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit.

9. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Fewer pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations, characteristic of each type of plant.

Conservation and Restoration Biology Student Misconceptions and Concerns 1. Although likely sympathetic to the conservation of species, students often do not understand the complexity of the issues. This final chapter section helps to describe some of the recent efforts and challenges of sustainable development. A class discussion about the challenges of conservation might help students realize that there are no simple solutions.

Teaching Tips 1. In some ways, highways are types of movement corridors between populations of people living in cities.

2. Sometimes students would like to learn more about conservation but are not aware of professional organizations that study these issues. The Society for Conservation Biology has a web address of www.conbio.org/.

3. If a short field trip is possible, you might wish to take students into a wooded area to generally compare the diversity of life at the edge and deep within the woods. Even the edge of some campus ecosystems might be worthwhile.

4. Consider having your students update the progress of the Kissimmee River Restoration Project.

5. The IUCN Red List of threatened and endangered species can be accessed at www.iucnredlist.org/.

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Key Terms abiotic reservoir biodiversity biodiversity hot spot biogeochemical cycles biological magnification biomass biophilia bioremediation carnivores chemical cycling community competitive exclusion principle conservation biology consumers

cryptic coloration decomposers detritivores detritus disturbances ecological niche ecological succession ecosystem ecosystem services endemic species energy flow food chain food webs herbivores herbivory host

interspecific competition interspecific interactions keystone species landscape landscape ecology movement corridor mutualism nitrogen fixation omnivores parasite predation primary consumers primary production primary succession

producers pyramid of production quaternary consumers relative abundance restoration ecology scavenger secondary consumers secondary succession species diversity species richness sustainable development tertiary consumers trophic structure warning coloration

Word Roots a = without; bio = life (abiotic reservoir: the part of an ecosystem where chemicals accumulate or are stockpiled outside of living organisms) bio = life; geo = the Earth (biogeochemical cycles: the various chemical cycles occurring in an ecosystem) crypt = hidden (cryptic coloration: another name for camouflage) detrit = wear off (detritivores: decomposers in an ecosystem) eco = house (ecology: the scientific study of the interactions between organisms and their environments) herb = grass; vor = eat (herbivore: an animal that eats mostly plants and algae) inter = between (interspecific competition: competition between species) intra = within (intraspecific competition: the reliance of individuals of the same species on the same limited resources) mutu = reciprocal (mutualism: a symbiosis that benefits both partners) omni = all (omnivore: an animal that eats plants and animals) para = near; sit = food (parasite: an organism that benefits at the expense of another) phili = love (biophilia: the human desire to affiliate with other life in its many forms) quatr = by fours (quaternary consumer: an organism that eats tertiary consumers) sym = together; bio = life (symbiotic relationship: an interspecific relationship in which one species lives in or on another species) terti = the third (tertiary consumer: a consumer that eats secondary consumers) troph = food (trophic structure: the feeding relationships among the various species making up a community)

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Relevant Songs to Play in Class “Mercy Mercy Me (The Ecology),” Marvin Gaye

“One Thing Leads to Another,” The Fixx “Big Yellow Taxi,” Joni Mitchell

“The Trees,” Rush

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: The results suggest that kangaroo rats are a keystone species in this ecosystem, in much the same way that the text describes the impact of the sea star Pisaster in an intertidal zone of the Washington coast.

12. Suggested answer: Photoautotrophs (either plants or algae) would be required to convert the energy in sunlight to sugars to provide a source of energy. Photosynthetic plants would also provide a source of oxygen for any animal life on the station. To be efficient, a variety of plants would be required so that people living on the station would obtain a balanced diet. Small insects would be necessary to serve as pollinators to the plants so they would produce fruits. Bacteria and fungi would be necessary as decomposers.

13. Suggested answer: These birds might be affected by pesticides while in their wintering grounds in Central and South America, where such chemicals may still be in use. To determine whether pesticides are affecting the birds, feathers grown while the birds were on their wintering grounds could be pulled and analyzed for the presence of pesticides such as DDT. If the DDT is present in their feathers, then you would check their eggs to determine whether their eggs are more fragile. If pesticides are not present in the wintering grounds, then another hypothesis should be proposed such as the loss of critical habitat.

Biology and Society 14. Some issues and questions to consider: How do population growth, competition for resources, pollution, and reduction in biodiversity relate to sustainability? How do poverty, economic growth and development, and political issues relate to sustainability? Why might developed and developing nations take different views of a sustainable society? What would life be like in a sustainable society? Have any steps toward a sustainable society been taken in your community? Can population growth be slowed, or will the population continue to grow at a very rapid rate? What are the consequences of a rapidly growing population? What are the social and economic factors that prevent the reduction in population growth?

15. Some issues and questions to consider: The BDFFP investigates the consequences of the very same threats to its own existence. Progress toward sustainable development requires an understanding of the consequences of our actions.

Additional Critical Thinking Questions The Process of Science 1. Why is it important to maintain biodiversity in every ecosystem?

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role in an ecosystem. In addition, we depend on other species for food, clothing, shelter, oxygen, soil fertility, and pharmaceuticals. The problems that affect other species may also affect humans.

2. An oil tanker runs aground in a rocky bay, and a local environmental group wants to assess the damage that the spilled oil caused to the bay’s marine life. No previous survey of the organisms in this area has ever been done. Two members of the environmental group collect intertidal organisms in both the oil-affected bay and a neighboring bay roughly similar to it. The group then hires a biologist to classify and count the organisms from both bays. Her report states that several important molluscs have significantly lower populations in the oil-affected bay than in the other bay. Concluding that the oil spill killed off the molluscs, the environmental group hires a lawyer and sues the oil company for criminal damage to the local environment. A judge throws the case out for lack of solid evidence. Which of the following arguments do you suppose the oil company’s attorney used? Explain your choice. a. No effort was made to determine why the animals were damaged by the oil spill, and a proposed effect without a proposed mechanism has no scientific credibility. b. No amount of data can prove a hypothesis. Instead of trying to do so, the group or the biologist should have designed the experiment to falsify the hypothesis that the oil was having an effect. c. The oil-free bay was not a true control because it may be slightly different from the contaminated bay. d. The group’s conclusion was hasty because it was based only on some of the species present.

Suggested answer: Choice c is the most convincing. Without samples prior to the oil spill, there is no reason to believe that the oil spill killed off the molluscs. The two bays may have had different mollusc populations before the spill.

Biology and Society 3. You may have heard that human activities cause the extinction of one species about every hour. Such estimates vary widely because we do not know precisely how many species exist or how fast their habitat is being destroyed. You can make your own estimate of the rate of extinction. Start with the number of species thought to exist. To keep things simple, ignore extinction in the temperate latitudes and focus on the 80% of plants and animals that live in the tropical rain forest. Assume that destruction of the forest continues at a rate of 1% per year, so the forest will be gone in 100 years. Assume (optimistically) that half the rain forest species will survive in preserves, forest remnants, and zoos. How many species will disappear in the next century? How many species is that per year? Per day?

Recent studies of the rain forest canopy have led some experts, such as Terry Erwin of the Smithsonian Institution, to suggest that there might be as many as 30 million species on Earth. How does starting with this figure change your estimates?

Suggested answer: Current counts indicate there are about 1.5 million identified species of organisms. Assume 80% of all living things—not just plants and animals—live in tropical rain forests. This means there are 1.2 million species identified there. If half the species survive, this means 0.6 million species will be extinct in 100 years, or 6,000 per year. If we divide these 6,000 by the 365 days in a year, about 16 species will disappear per day, or almost one per hour. If there are 30 million species on Earth, 24 million live in the tropics, and 12 million will disappear in the next century. This is 120,000 per year, 329 per day, or 14 per hour.

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CHAPTER

21

Unifying Concepts of Animal Structure and Function

Why This Chapter Matters 1. Unifying principles of structure and function apply across the animal kingdom.

2. Human anatomy and physiology address the same fundamental challenges faced by other animals: nutrition, gas exchange, osmoregulation, thermoregulation, and other aspects of homeostasis.

3. Understanding evolutionary adaptations in the animal kingdom provides insight into the structure and function of human systems.

Chapter Objectives Biology and Society: An Avoidable Tragedy 1. Explain how a person keeps from overheating when exercising strenuously. Explain how these functions fail when heat exhaustion or heat stroke occur.

The Structural Organization of Animals 2. Define and compare anatomy and physiology. Explain why the two are usually studied together.

3. Define a tissue and describe the four main categories of animal tissues, noting examples of each.

4. Describe the relationships among tissues, organs, and organ systems.

Exchanges with the External Environment 5. Explain why every organism is an open system.

6. Explain how an animal’s size and shape affect how it exchanges energy and materials with its surrounding environment.

Regulating the Internal Environment 7. Define homeostasis and illustrate with an example.

8. Define and compare negative and positive feedback. Give examples of each within the human body.

9. Define thermoregulation and describe adaptations, in humans and other animals, which aid in thermoregulation.

10. Define and compare endotherms and ectotherms.

11. Describe the causes and functions of fever.

12. Define the process of osmoregulation. Distinguish between osmoconformers and osmoregulators.

13. Describe the functions of the kidneys. Explain how the structure of the human kidney contributes to the process of osmoregulation.

14. Relate the anatomy of the human urinary system to its functions.

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15. Describe the causes, consequences, and treatment of kidney failure.

Evolution Connection: Adaptations for Thermoregulation 16. Explain how animals conserve heat or cool themselves in the process of thermoregulation.

Lecture Outline I. Biology and Society: An Avoidable Tragedy 1. Our bodies are kept in a narrow temperature range 2. When we exercise, our bodies are cooled by a. evaporation of sweat on the skin and b. expansion of blood vessels near the skin surface.

3. Extreme conditions can lead to a. loss of consciousness in heat exhaustion, b. even higher body temperatures, which can disrupt the brain’s control center, and c. heat stroke, a life-threatening emergency.

II. The Structural Organization of Animals 1. Life is characterized by a hierarchy of organization 2. In animals, a. individual cells are grouped into tissues, b. tissues combine to form organs, c. organs are organized into organ systems, and d. organ systems make up the entire organism.

A. Form Fits Function 1. Analyzing a biological structure gives us clues about a. what it does and b. how it works.

2. Biologists distinguish anatomy from physiology a. Anatomy is the study of the structure of an organism’s parts. b. Physiology is the study of the function of those parts.

B. Tissues 1. The cell is the basic unit of all living organisms 2. In almost all animals, including humans, cells are grouped into tissues a. A tissue is an integrated group of similar cells that performs a specific function. b. Animals have four main categories of tissue.

3. Epithelial Tissue 4. Epithelial tissue, also known as epithelium, a. covers the surface of the body and b. lines organs and cavities within the body.

5. Cells of epithelial tissues a. are fused together, b. form a protective barrier, and c. fall off and are continuously renewed.

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6. Connective Tissue 7. Connective tissues have a sparse population of cells in an extracellular matrix consisting of a web of protein fibers within a uniform foundation that may be liquid, jellylike, or solid 8. The structure of connective tissue is correlated with its functions: a. to bind and b. support other tissues.

9. Loose connective tissue a. is the most widespread connective tissue, b. binds epithelia to underlying tissues, and c. holds organs in place.

10. Adipose tissue a. stores fat, b. stockpiles energy, and c. pads and insulates the body.

11. Blood a. is a connective tissue and b. contains red and white blood cells suspended in a liquid called plasma.

12. Fibrous connective tissue a. has a dense matrix of collagen and b. forms tendons and ligaments.

13. Cartilage a. is strong but flexible, b. has no blood vessels, so it heals very slowly, c. functions as a flexible, boneless skeleton, and d. forms the shock-absorbing pads that cushion the ends of bones including the vertebrae of the spinal column.

14. Bone a. is a rigid connective tissue and b. has a matrix of collagen fibers hardened with deposits of calcium salts.

15. Muscle Tissue 16. Muscle tissue a. is the most abundant tissue in most animals, b. consists of bundles of long, thin, cylindrical cells called muscle fibers, and c. has specialized proteins arranged into a structure that contracts when stimulated by a signal from a nerve.

17. Skeletal muscle is a. attached to bones by tendons, b. responsible for voluntary movements, and c. striated because the contractile proteins form a banded pattern.

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18. Cardiac muscle is a. found only in heart tissue, b. composed of cells that are branched and striated, c. involuntary, and d. responsible for the contraction of the heart.

19. Smooth muscle is a. named for its lack of obvious stripes, b. found in the walls of various organs such as intestines and blood vessels, and c. involuntary.

20. Nervous Tissue 21. Nervous tissue a. makes communication of sensory information possible, b. is found in your brain and spinal cord, and c. consists of a network of neurons.

22. The basic unit of nervous tissue is the neuron, or nerve cell C. Organs and Organ Systems 1. An organ consists of two or more tissues packaged into one working unit that performs a specific function 2. Examples include the heart, liver, stomach, brain, and small intestines 3. Organ systems are teams of organs that a. work together and b. perform vital body functions.

III. Exchanges with the External Environment 1. Every organism is an open system, continuously exchanging chemicals and energy with its surroundings to survive 2. An animal’s size and shape affect its exchanges with its surrounding environment 3. All living cells must be bathed in a watery solution so that exchange of materials can occur 4. The entire surface area of a single-celled amoeba is in contact with its watery environment 5. A hydra has a body wall only two cell layers thick 6. Both layers of cells are bathed in pond water, enabling exchange with the environment 7. Animals with complex body forms face the same basic problems. Every cell must a. be bathed in fluid and b. have access to resources from the outside environment.

8. Complex animals have evolved extensively folded or branched internal surfaces that maximize surface area for exchange with the immediate environment 9. Lungs a. have a very large total surface area and b. exchange oxygen and carbon dioxide with the air you breathe.

10. Animals use three organ systems to exchange materials with the external environment: a. digestive, b. respiratory, and c. urinary.

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11. The circulatory system a. connects to nearly every organ system, b. transports needed materials from the environment to the body’s tissues, and c. carries waste away.

IV. Regulating the Internal Environment 1. Animals adjust to a changing environment A. Homeostasis 1. Homeostasis is the body’s ability to stay relatively unchanged even when the world around it changes 2. The internal environment of vertebrates includes the interstitial fluid that a. fills the spaces between cells and b. exchanges nutrients and wastes with microscopic blood vessels.

B. Negative and Positive Feedback 1. Most mechanisms of homeostasis depend on a principle called negative feedback, a. in which the results of a process inhibit that same process, b. such as a thermostat that turns off a heater when room temperature rises to the set point.

2. Less common is positive feedback, a. in which the results of a process intensify that same process, b. such as uterine contractions during childbirth.

C. Thermoregulation 1. Thermoregulation is the maintenance of internal body temperature a. Endotherms i. such as mammals and birds ii. derive the majority of their body heat from their metabolism. b. Ectotherms i. such as most invertebrates, fishes, amphibians, and nonbird reptiles ii. obtain body heat primarily by absorbing it from their surroundings.

2. Humans have homeostatic mechanisms that aid in thermoregulation, which a. cool or b. heat the body.

3. Fever a. is an abnormally high internal body temperature and b. usually indicates an ongoing fight against infection.

D. The Process of Science: How Does a Python Warm Her Eggs?

1. Observation: A female Burmese python incubating eggs a. wraps her body around them, b. raises her body temperature, and c. frequently contracts the muscles in her coils.

2. Hypothesis: The muscle contractions elevate the snake’s body temperature 3. Experiment: A python and her eggs were monitored to measure a. the python’s muscle contractions and b. her oxygen uptake.

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4. Results: The python’s oxygen consumption increased a. when the temperature in the chamber decreased and b. as she increased the rate of muscle contraction.

E. Osmoregulation 1. Living cells depend on a precise balance of a. water and b. solutes (dissolved substances).

2. Osmoregulation is the control of the gain or loss of a. water and b. dissolved solutes, such as the ions of NaCl and other salts.

3. Osmoconformers a. have internal and external environments with similar solute concentrations and b. include most marine invertebrates.

4. Osmoregulators a. actively regulate their water loss or gain and b. include freshwater animals, most marine vertebrates, and all land animals.

F. Homeostasis in the Urinary System 1. The human urinary system a. plays a central role in homeostasis, b. forms and excretes waste-carrying urine, and c. regulates the amount of water and solutes in body fluids.

2. In humans, the two kidneys a. are the main processing centers and b. contain many fine tubes called tubules and an intricate network of capillaries.

3. As blood circulates through the kidneys, a. a fraction of it is filtered and b. plasma enters the kidney tubules, forming filtrate.

4. Filtrate contains a. valuable substances that need to be reclaimed (such as water and glucose) and b. substances to be eliminated, such as urea.

5. The human urinary system includes a. the circulatory system, b. the kidneys, c. nephrons, the functional units within the kidneys, and d. the urinary bladder, where urine is stored.

6. Nephrons a. carry out the functions of the urinary system, b. consist of a tubule and its associated blood vessels, and c. number more than a million in a kidney.

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7. Nephrons perform four key functions a. Filtration, forcing water and other small molecules from the blood to form filtrate b. Reabsorption of water and valuable solutes back into the blood c. Secretion of certain substances, such as ions and drugs, into the filtrate d. Excretion of urine from the kidneys to the outside 8. Hormonal control of the nephrons allows the body to control its internal concentration of a. water and b. dissolved molecules.

9. Kidney failure can be caused by a. injury, b. illness, or c. prolonged use of pain relievers (including over-the-counter medicines such as aspirin), alcohol, or other drugs.

10. One option for treatment of kidney failure is dialysis, filtration of blood by a machine that mimics the action of a nephron G. Evolution Connection: Adaptations for Thermoregulation 1. Animals regulate their body temperatures using adaptations that are a. anatomical, b. physiological, and/or c. behavioral.

2. A major anatomical adaptation in mammals and birds is insulation, consisting of a. hair (fur), b. feathers, or c. fat layers.

3. Some adaptations are physiological, such as a. changes in metabolic rate, b. shivering, or c. panting and sweating.

Chapter Guide to Teaching Resources The Structural Organization of Animals Student Misconceptions and Concerns 1. Students often find it challenging to gain a proper understanding of the evolution of form and function relationships. Such relationships appear to have been “constructed” to meet a purpose, a consequence of deliberate planning and design. Ask students to explain why we have lungs, and they may answer something along the line of “because we need to breathe,” or “because we need oxygen.” Need, however, does not cause evolution. Natural selection involves editing rather than creating diversity. A better answer might be “Because lung-like structures conveyed an advantage in gas exchange in our ancestors.”

2. Relationships between form and function are found all around us. For some of us, noticing the connections is easy. However, many students have spent little time considering why any particular structure has its characteristic shape. Practice with examples helps to build a better understanding of these important relationships. ..

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3. Students exploring form and function relationships should be cautioned to avoid confusing properties of an adaptation with its biological role(s). What a particular form can do may be quite different from how it is used by an organism. For example, the long canine tooth of a saber-toothed cat might make a great letter opener, but these teeth were not used by these cats for that function (biological role)!

Teaching Tips 1. When relating the principle of form and function, ask students to consider their own teeth as examples. Ask them to use their tongues to feel their teeth and relate their shape to the human diet.

2. The elastic cartilage in the human ear is a wonderful example of form and function in a tissue. Elastic fibers are abundant in the extracellular matrix, increasing the flexibility of this cartilage. Have students bend their own ears to feel the effects.

3. All muscle cells are only able to contract. None can actively relengthen. Challenge your students to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.)

4. Consider an exercise to challenge students to explore the long-term consequences of sunlight on human skin. Changes in elasticity and pigmentation of the skin might help students understand the cost of a lifetime of sun exposure.

5. Extracellular substances, such as collagen fibers, are the source of the main functional properties of many connective tissues such as tendons, ligaments, cartilage, and bone.

6. Simple squamous cells have a shape that is generally similar to a fried egg: flattened, with a bump in the middle representing the nucleus or yolk.

7. Students might enjoy this simple observation when discussing neurons. As we consider the structure and functions of neurons, we are using our own neurons to think about them. Our neurons become self-aware!

Exchanges with the External Environment Student Misconceptions and Concerns 1. It can be difficult for students to think of their own bodies in such simple terms as surfaces and tubes. Perceiving the digestive tract as one continuous tube, in which food that passes through never technically enters the body, is one such challenge. Illustrate these fundamental principles first using simple animals as examples. Then apply these principles to humans as a final test of comprehension.

2. If students have not previously examined the diversity of animals, consider a brief overview of the fundamental body plans before explaining how these fundamental principles of form and function generally apply to the animal kingdom.

Teaching Tips 1. Students often fail to consider the overall significance of body size. Consider asking your students to think about the impact of being small. Do they recall ever having trouble emerging from a swimming pool because of the adhesive properties of water? Yet, small insects that land on a pond’s surface may find these forces to be lethal, preventing these organisms from breaking away from the water’s surface! In addition, are your students frequently prevented from leaving their homes because of high winds, simply unable to 310

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walk around outside? The movements of small insects are often prevented by winds that would do little more than toss around our hair! Many campers know that mosquitoes and flies are less of a pest on days when there is a good breeze.

2. The consequences of large size in organisms require transport and exchange systems extending to the deepest inner regions. Whether we think of a whale, a giant redwood, or the United States, these principles apply. By analogy, the railway and highway systems of the United States transport essential products from ocean ports to the deepest interior regions, where warehouses and other transport systems deliver the goods to stores for purchase.

A person living near the ocean may obtain food directly, by fishing in the ocean. A person living in the Midwest may purchase ocean fish at a store or at a restaurant!

3. Organisms and individual cells need sufficient surface exchange and transport systems to support their surface to volume ratios. Cell size is limited, in part, by the ability of a cell to exchange materials efficiently with its surface. Thus, adaptations that increase surface area can permit cells to reach larger sizes.

4. You might note how sponges are well adapted to maximize their surface area exposed to water.

Their highly porous system dramatically increases the region engaged in water filtration.

5. The stratified squamous epithelium on most outside surfaces of our body resists abrasions in part because it is keratinized. However, the nonkeratinized epithelial tissues that line our body cavities, such as the mouth, pharynx, esophagus, and anus, are also resistant to abrasion as a result of its mucus coatings, which provide friction-reducing lubrication. Students may not realize that the same type of tissue performs similar functions in very different parts of the body.

Regulating the Internal Environment Student Misconceptions and Concerns 1. The concept of homeostasis may be new to many students, who have never considered how organisms maintain their structure and physiology. Analogies to other systems that engage in self-regulation (noted in the text and below) can help.

2. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively refilling the closet with what you wish to store.

Teaching Tips 1. Challenge your students to think of other examples of negative and positive feedback.

Students from diverse disciplines may think of many new examples, including mechanisms in an automobile.

2. The terms warm-blooded and cold-blooded are less precise than endotherm and ectotherm.

Encourage students to discuss why endotherm and ectotherm are preferred.

3. Ask your students to explain the adaptive advantages of endothermy and ectothermy. You might prompt the discussion by noting that endotherms consume about 10 times as many calories as ectotherms of equivalent body mass. What might be the advantages worth this additional “cost” for endotherms?

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4. Heat generation resulting from aerobic metabolism is analogous to heat generation in the engine of an automobile. In both cases, the heat is a by-product of the process. In the winter, this excess heat helps keep the body and an automobile warm. In the summer, both the body and the automobile’s engine must work to keep from overheating.

5. Have students list the many factors that affect heat gain and loss during times of physical activity. These include (a) the age of the person—younger people tend to have higher metabolic rates, (b) the level of physical activity—aerobic metabolism increases to generate ATP to move muscles, (c) proper hydration to permit adequate sweating, (d) the color of the person’s clothing, (e) the intensity of sunlight, (f) higher humidity levels—which decrease evaporative cooling, (g) intensity of wind—which promotes evaporative cooling, and (h) the physical condition of the person.

6. Ask students to explain how blood vessel constriction at the body surface, shivering, and a general increase in metabolism help a person to keep warm in a cold environment.

7. Tylenol (acetaminophen) is often used to reduce fevers. Discuss with your students the advantages and disadvantages of using drugs to lower a fever.

8. Students might better understand the problems faced by freshwater fish if you relate it to what occurs when they soak their hands in water. Students will likely recall that their skin wrinkles when soaked in water. Some may have noticed that their hands wrinkle even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water).

Oils on our skin reduce the influx of water. Thus soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers.

9. A moderately full human urinary bladder holds about 500 mL (or 1 pint) of fluid. The maximum capacity of the bladder may reach double that volume, although when overdistended, it can burst!

10. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider sharing this issue with your class. Many state and federal organ donation organizations can be located by a quick Internet search. The National Kidney Foundation site (www.kidney.org/) includes information on kidney donation.

Key Terms adipose tissue anatomy blood bone cardiac muscle cartilage connective tissue dialysis ectotherms endotherms epithelial tissue epithelium

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excretion extracellular matrix fever fibrous connective tissue filtrate filtration homeostasis interstitial fluid loose connective tissue muscle tissue negative feedback

nephron nervous tissue neuron open system organ organ systems osmoconformers osmoregulation osmoregulators physiology positive feedback reabsorption

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secretion skeletal muscle smooth muscle thermoregulation tissue tubules ureter urethra urinary bladder urine

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Word Roots ecto = outside; therm = heat (ectotherms: animals that obtain body heat primarily by absorbing it from their surroundings) endo = inside (endotherms: organisms whose bodies are warmed by heat generated by metabolism; this heat is used to maintain a body temperature higher than that of the external environment) epi = upon or over (epithelium: tissues that cover the surfaces of the body) extra = outside (extracellular matrix: a web of protein fibers embedded in a liquid or solid between cells) fibro = a fiber (fibrous connective tissue: a dense tissue with large numbers of collagenous fibers organized into parallel bundles) homeo = same; stasis = standing (homeostasis: the steady-state physiological condition of the body) inter = between (interstitial fluid: the fluid that fills the space between cells) nephro = the kidney (nephron: the functional unit of a kidney) neuro = a nerve (neuron: a nerve cell)

Relevant Songs to Play in Class “Under the Sea,” from Disney’s The Little Mermaid

“The Mollusk,” Ween

“Animal,” Pearl Jam

“SpongeBob SquarePants Theme,” Nickelodeon

“Rock You Like a Hurricane,” Scorpions

“Mammal,” They Might Be Giants

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: In the morning the environmental temperature is lower. The animals face east for sunlight and group together to conserve heat. During the day the temperatures become warmer, so the animals can disperse for better protection from extreme heat. Many different experiments could test the hypotheses that these caterpillars change their behavior to thermoregulate. Artificially heating a different side of the tent in the morning or repositioning the tent in the tree could test the directionality of the caterpillars in the morning. Artificially heating or cooling the tent could test for the association of the hanging behavior and temperature. Or a controlled experiment could be performed where several “tents” were collected and brought into a lab where direction of sunlight and temperature can be tightly controlled.

Biology and Society 12. Some issues and questions to consider: Could drug use endanger the safety of the employee or others? Is drug testing relevant to jobs where safety is not a factor? Is drug testing an invasion of privacy, interfering in the private life of an employee? Is an employer justified in banning drug use off the job if it does not affect safety or ability to do the job? Do the same criteria apply to employers requiring the test? Could an employer use a drug test to regulate other employee behavior that is legal, such as smoking? Should bus drivers, airline pilots, and controllers of other forms of public transportation be held to a higher standard? Would these higher standards apply to authorities who oversee the public’s needs and interests (police officers, medical personnel, firefighters)? What about the problems with false-positives? What about prescription drugs that would show up in a drug test? Do all drugs have the same negative effects on the body? ..

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13. Some issues and questions to consider: What would happen to people who cannot afford to pay for an organ? What would the cost of these organs be? Would this allow those with more money to get better health care? Who would regulate the cost? Who would negotiate the “deals”? Would people donate purely for financial motivation, with no concern for their health? Does this increase the need to invest in cloning technologies so that damaged organs could be regenerated relatively cheaply? Should individuals who abuse their bodies by taking large quantities of drugs be allowed to receive organ transplants?

Additional Critical Thinking Questions The Process of Science 1. Why do intestines, kidneys, and lungs all have such large surface areas and such a large number of capillaries?

Suggested answer: Intestines, kidneys, and lungs all have a very large surface area and extensive networks of capillaries because each must function to exchange materials between the inside and outside of the body. Nutrients pass from the intestines to the circulatory system; waste products pass from the circulatory system to the kidneys; and oxygen passes from the lungs into the circulatory system. All of these processes occur by diffusion. The larger the surface area, the higher the rate of diffusion. The microvilli of the intestines, the convoluted tubules of the kidneys, and the alveoli of the lungs all significantly increase surface area and thus the rate of diffusion. This is important because these organs must meet the needs of all the other tissues of the body in a relatively small space. It is also important to note that these large surfaces occur internally, not externally, which prevents excessive water loss due to evaporation.

2. Athletes are told to refrain from drinking alcohol and to drink a lot of water before a marathon or they may collapse. Consider the hormones that might be affected by alcohol and explain why the athlete might collapse.

Suggested answer: Antidiuretic hormone (ADH) is released when body fluids become too concentrated. It acts on the nephrons of the kidneys, promoting the reabsorption of water from the filtrate. Alcohol inhibits the release of ADH and, as a result, the reabsorption of water into the blood is inhibited. This, plus inadequate water intake, will cause blood volume and blood pressure to drop. This can result in fainting as the brain and other tissues are deprived of adequate blood flow.

3. You are studying the body temperature of a large, active lizard. Your hypothesis is that the lizard has homeostatic mechanisms that maintain its temperature within a narrow range.

You decide to test your hypothesis by comparing the lizard’s body temperature in a range of surrounding air temperatures with the body temperatures of a turtle and a rat in the same air temperatures. (The body temperatures of rats and most other mammals are steady, whereas the body temperatures of turtles generally fluctuate with the temperature [°C] of their surroundings.) You obtain the following results in your first test:

Time 6 A.M. Noon 6 P.M. Midnight 6 A.M. 314

Air Temperature 22 31 27 23 21

Turtle Temperature 21 29 26 22 21

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Lizard Temperature 27 30 29 27 26 ..

Rat Temperature 36 37 37 37 37

Do these data support your hypothesis? How does the lizard’s temperature-regulating ability compare with the turtle’s and with the rat’s?

Suggested answer: The lizard does not have a steady body temperature, but it does maintain a markedly more stable temperature and a higher temperature than the turtle. While the air is varying over a 10°C range (21–31°C), the turtle varies over an 8°C range (21–29°), and the lizard varies over only a 4°C range (26–30°C). On the other hand, the lizard’s temperature regulation is not nearly as narrow as that of the rat, whose temperature range is 1°C (36–37°C). Temperature-regulating ability is determined by temperature fluctuation and the ability of an animal to maintain a difference between its body temperature and the temperature of the environment. Lizards have behavioral modifications to maintain a higher body temperature so that they can actively hunt for prey.

Biology and Society 4. Medical researchers are investigating the possibilities of artificial substitutes for various human tissues. Examples are a liquid that could serve as artificial blood and a fabric that could temporarily serve as artificial skin for victims of serious burns. In what situations might artificial blood or skin be useful? What characteristics would these substitutes need to function effectively in the body? Why do real tissues work better? Why not use real blood if they work better? Can you think of other artificial tissues that might be useful?

What problems do you anticipate in developing and applying them?

Some issues and questions to consider: Artificial blood and skin would be useful wherever human blood and skin grafts are not available or practical. Artificial blood would need to consist of a liquid with salts and proteins, and ideally would transport substances (particularly oxygen) and provide immunity. Artificial skin would need to protect underlying tissues and organs. A reason for using artificial materials is that they are nonliving and could be available at any time and people in need would not have to wait for the real product. Real tissues work better because they have all the necessary characteristics, but they are not always available.

Real tissues from another human may also be rejected by the patient’s immune system. Other artificial tissues that would be useful include artificial bone, cartilage, muscle, and nervous tissue, but it would be difficult to replicate the complex functions of these tissues.

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CHAPTER

22

Nutrition and Digestion

Why This Chapter Matters 1. Understanding the basic structures and functions of the human digestive tract is important to maintaining good health and understanding disorders and disease.

2. Ignorance of nutritional requirements can lead to vitamin and mineral deficiencies even in affluent people.

3. Obesity and eating disorders are serious health threats in our society.

Chapter Objectives Biology and Society: The “Secret” to Shedding Pounds 1. Explain why there are really no tricks to losing weight.

Overview of Animal Nutrition 2. Define and distinguish between herbivores, carnivores, and omnivores.

3. Define and distinguish between ingestion, digestion, absorption, and elimination.

4. Explain why the digestive dismantling of large food molecules is necessary.

5. Distinguish between mechanical and chemical digestion.

6. Explain how animals digest their food without digesting their own cells and tissues.

7. Compare the structure and functions of a gastrovascular cavity and digestive tube.

A Tour of the Human Digestive System 8. Describe the main components of the human digestive tract and the associated digestive glands.

9. Describe the functions of the molecules in saliva and the roles of the tongue and teeth in digestion.

10. Explain how swallowing occurs and how food is directed away from the trachea.

11. Relate the structure of the stomach to its functions. Describe the functions of the components of gastric juice. Finally, explain the causes of heartburn and why the stomach does not digest itself.

12. Describe the most common cause of stomach ulcers and the primary forms of treatment.

13. Explain how gastric bypass is performed and why it is effective in promoting weight loss.

14. Describe the different types of chemical digestion that occur in the small intestine.

Explain how the structure of the small intestine promotes nutrient absorption.

15. Describe the structure and functions of the large intestine and rectum. Note the causes of constipation and diarrhea.

Human Nutritional Requirements 16. Distinguish between calories and kilocalories.

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18. Define essential amino acids and explain the complexities associated with a vegetarian diet.

19. Define vitamins and minerals and explain why they are important in the diet.

20. Describe the types of information found on food labels.

Nutritional Disorders 21. Define and distinguish between malnutrition and obesity.

22. Describe the causes, symptoms, and treatments of bulimia and anorexia nervosa.

Evolution Connection: Fat and Sugar Cravings 23. Explain how fat cravings in humans might have evolved.

Lecture Outline I. Biology and Society: The “Secret” to Shedding Pounds 1. About 50 million Americans go on a diet each year a. Weight loss is a growing industry. b. Yet only about 5% of dieters are able to reach their goal weight and maintain it for the long term.

2. More than a third of American adults are obese (very overweight) 3. Obesity is estimated to contribute to 300,000 deaths per year in the United States 4. The United Nations World Health Organization recognizes obesity as a major global health problem 5. There really is no trick to managing your weight a. Add up the calories from the food you eat. b. Subtract the calories that your body burns. c. If you take in more than you burn, you will gain weight. d. If you burn more than you take in, you will lose weight.

II. Overview of Animal Nutrition 1. Food provides the raw materials that animals, including people, need to a. build tissue and b. fuel cellular work.

A. Animal Diets 1. Herbivores mainly feed on plants or algae 2. Carnivores mainly eat other animals 3. Omnivores eat a. animals and b. plants or algae.

B. The Four Stages of Food Processing 1. Ingestion is another word for eating 2. Digestion is the breakdown of food into molecules small enough for the body to absorb 3. Absorption is the uptake of the small nutrient molecules by cells lining the digestive tract 4. Elimination is the disposal of undigested materials left over from food 5. Digestion: A Closer Look

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6. The dismantling of food molecules is necessary because food molecules are a. too large to cross the membranes of animal cells and b. different from molecules that make up an animal’s body.

7. Mechanical digestion a. begins the process and b. involves physical processes like chewing.

8. Chemical digestion is the chemical breakdown of food by digestive enzymes 9. Chemical digestion proceeds via hydrolysis, chemical reactions that break down polymers into monomers using water in the process 10. Like most biological reactions, digestion also requires enzymes C. Digestive Compartments 1. How do animals digest their food without digesting themselves?

2. In animals, chemical digestion is contained safely within some kind of compartment 3. As a cell engulfs food by phagocytosis, a. a food vacuole forms, b. which then fuses with a lysosome filled with digestive enzymes, and c. as food is digested, small food molecules pass through the vacuole membrane into the cytoplasm, which nourishes the cell.

4. Food vacuoles are the simplest of all digestive compartments 5. Sponges are the only animals that digest food solely within their cells 6. Gastrovascular cavities a. are digestive compartments surrounded by cells and b. have only a single opening.

7. A digestive tube, or alimentary canal, has two separate openings: a. a mouth and b. an anus.

8. Food moves through specialized regions of a digestive tube that a. digest and b. absorb nutrients in a stepwise fashion.

III. A Tour of the Human Digestive System A. System Map 1. The human digestive system consists of a. a digestive tube, the alimentary canal (or gut), and b. accessory organs that secrete digestive chemicals.

B. The Mouth 1. The mouth, or oral cavity, functions in a. ingestion and b. the preliminary steps of digestion.

2. Chemical digestion begins in the mouth with the secretion of saliva from salivary glands 3. The muscular tongue a. tastes, b. shapes food into a ball, and c. pushes the food to the back of the mouth for swallowing. ..

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C. The Pharynx 1. The pharynx a. connects the mouth to the esophagus and b. opens to the trachea, which leads to the lungs.

2. During swallowing, a reflex a. moves the opening of the trachea upward and b. tips the epiglottis to close the trachea entrance.

D. The Esophagus 1. The esophagus a. is a muscular tube, b. connects the pharynx to the stomach, and c. moves food down by peristalsis, alternating waves of muscular contraction and relaxation.

E. The Stomach 1. The stomach a. can store food for several hours and b. churns food into a thick soup called chyme.

2. Fluid in the stomach contains gastric juice, made of a. strong acid, b. digestive enzymes, c. mucus, and d. the enzyme pepsin, which digests proteins.

3. Stomach Ailments 4. Heartburn is caused by backflow of chyme into the esophagus 5. Gastric ulcers are a. erosions of the stomach lining and b. often caused by the bacterium Helicobacter pylori.

6. Weight Loss Surgeries 7. The most common weight loss surgery in the United States is gastric bypass a. Staples are used to reduce the stomach to about the size of a chicken egg. b. The first 18 inches of the small intestine are bypassed by attaching the downstream intestine directly to the reduced stomach pouch.

8. As a result, a. patients quickly feel full when eating and b. the body’s ability to absorb food is reduced.

F. The Small Intestine 1. The small intestine is a. the longest part of the alimentary canal and b. the major organ for chemical digestion and absorption of nutrients into the bloodstream.

2. Chemical Digestion in the Small Intestine 3. Most chemical digestion occurs in the duodenum, the first part of the small intestine

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4. In the duodenum, chyme from the stomach mixes with a. pancreatic juice, b. bile, and c. a digestive juice secreted by the intestinal lining.

5. The pancreas secretes juice that a. neutralizes stomach acids in the duodenum and b. aids in digestion.

6. The liver secretes bile, which a. is stored in the gallbladder and b. helps digest fats.

7. Absorption of Nutrients 8. In the duodenum, nutrients are a. completely digested and b. ready to be absorbed.

9. Nutrients only enter the body if they are absorbed into the walls of the digestive tract 10. Villi and microvilli on the surface of the small intestine increase a. the surface area and b. capacity for absorption.

G. The Large Intestine 1. The large intestine is a. shorter, but wider, than the small intestine and b. about 1.5 meters in length.

2. At the junction of the small and large intestine is a small, finger-like extension called the appendix a. The appendix contains white blood cells that make minor contributions to the immune system. b. Appendicitis is a bacterial infection of the appendix.

3. The colon a. forms the main portion of the large intestine, b. absorbs water from the alimentary canal, and c. produces feces, the waste product of food.

4. The rectum a. forms the last 15 cm (6 inches) of the large intestine and b. stores feces until elimination.

5. The anus a. consists of two sphincters and b. regulates the opening of the rectum.

6. Food processing takes place along the alimentary canal

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A. Food as Fuel 1. Cells use cellular respiration to a. extract energy stored in food molecules and b. generate molecules of ATP to do work.

2. Calories 3. Calories are a measure of the energy a. stored in your food and b. used in daily activities.

4. A calorie is the amount of energy required to raise the temperature of one gram of water by 1º C 5. A kilocalorie (kcal) is a. 1,000 calories, b. the unit listed on food labels, and c. often called Calories with an uppercase C. 6. Metabolic Rate 7. The rate of energy consumption by the body is the metabolic rate 8. A person’s metabolic rate consists of a. the basal metabolic rate (BMR), the amount of energy it takes to maintain body functions, and b. energy needed for activities.

B. Food as Building Material 1. Building blocks from the breakdown of organic molecules are used to a. repair tissues and b. maintain tissues.

2. Essential nutrients a. are substances needed by the body but b. cannot be made in the body from other molecules.

3. Essential Amino Acids 4. In humans, eight essential amino acids a. must be obtained from the diet and b. are in different proportions in different foods.

5. All eight essential amino acids can be consumed by eating a. meat, eggs, or milk or b. a variety of plants, typically grains and legumes such as beans, peanuts, and peas.

6. Vitamins 7. Vitamins a. are organic molecules, b. are required in the diet in very small amounts, and c. usually assist enzymes in catalyzing metabolic reactions.

8. Too much or too little of most vitamins can cause harm 9. Minerals 10. Minerals are inorganic substances required in the diet 11. Too much or too little of most minerals can cause harm 322

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12. Essential Fatty Acids 13. Our cells make fats and other lipids by combining fatty acids and other molecules 14. Essential fatty acids must be obtained in the diet C. Decoding Food Labels 1. On food labels, the FDA requires a. the list of ingredients and b. key nutrition facts.

V. Nutritional Disorders 1. Dietary problems can cause severe health problems A. Malnutrition 1. Malnutrition refers to health problems caused by an a. improper or b. insufficient diet.

2. Protein deficiency a. causes the most human suffering and b. is concentrated where there is a great gap between food supply and population size.

3. Eating Disorders 4. Eating disorders a. affect millions of Americans, b. are more common in women than men, and c. result in malnutrition.

5. Anorexia nervosa is self-starvation, even when a person is underweight 6. Bulimia involves a. binge eating, b. purging through induced vomiting, c. abuse of laxatives, and/or d. excessive exercise.

B. Obesity 1. Obesity a. is a too-high body mass index (BMI), b. is the nutritional disorder of greatest concern, c. affects about one-third of all Americans, and d. increases the risk of heart attack, diabetes, and other diseases.

C. The Process of Science: Can a Gene Make You Fat? 1. Observation: A mutation in a particular gene in mice leads to a significant increase in body fat 2. Question: How does a small change in DNA cause such a large change in the body?

3. Hypothesis: The mutant mice become overweight because their obese gene fails to produce a protein called leptin 4. Experiment: Mutant and normal mice were injected with leptin or a saline control 5. Results: Mutant mice that received leptin ended the study weighing about half as much as mutant mice that received the saline control

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6. More than 100 genes are known to contribute to weight maintenance in humans 7. Genetics only partially explains why weight control can be difficult D. Evolution Connection: Fat and Sugar Cravings 1. Most Americans a. crave fatty and/or sweet foods and b. eat too many high-calorie foods.

2. A feast-or-famine existence in our ancestors may have favored individuals who gorged themselves on the rare occasions when rich, fatty foods were available

Chapter Guide to Teaching Resources Overview of Animal Nutrition Student Misconceptions and Concerns 1. Students are likely familiar with the basics of the digestive system and the different types of animal diets. However, they are less likely to understand the distinctions between chemical and mechanical digestion and the specific roles of enzymes. An extra effort may be needed to differentiate between these important components of the digestive process.

Teaching Tips 1. Consider discussing the form and function relationships between diet and teeth. The sharp, slicing teeth of a cat are well adapted to eating meat. The blunt molars of cattle and horses reveal a structure well suited for crushing vegetable matter. Human teeth reveal the compromises necessary for a diverse diet. If skeletal materials are not available, photographs can easily substitute.

2. If your class size permits, consider demonstrating the process of chemical digestion in the human mouth by distributing crackers to students. As students hold chewed crackers in their mouths, they will likely notice a sweet taste developing. The students taste sugars produced by the chemical breakdown of starch by amylase, a digestive enzyme found in human saliva.

3. Challenge your students to explain why digestive tubes are more efficient than gastrovascular cavities (such as those found in cnidarians). Point out the advantages of stepwise specializations of the digestive tract that are permitted by the one-way flow of materials through a digestive tube with openings on both ends (mouth and anus). As the authors note, one-way digestive tracts are types of “disassembly” lines.

A Tour of the Human Digestive System Student Misconceptions and Concerns 1. Students may confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The cartilage in the walls of the trachea keeps the tube open as air is sucked through it. The esophagus, however, relies on rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function.

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2. Students may confuse pain in the intestines with pain in the stomach. The looping nature of the colon causes fecal material to pass near the stomach on its way down the digestive tract. This may cause “stomach” pains before the need to defecate, or more painful contractions of the intestines associated with diarrhea. Young children might therefore confuse the need to defecate with an upset stomach.

3. The liver is often said to filter the blood. However, unlike a coffee or air filter, the liver does not trap particles. Instead, chemicals are broken down by the liver into less toxic forms.

Teaching Tips 1. The role of saliva in adhering food particles together into a bolus and lubricating the bolus for easy passage can be demonstrated by eating crackers or pretzels. Students can be challenged to see how many pretzels/crackers they can chew and swallow in a short period, without the use of any beverages. The main factor limiting the speed of this consumption is the ability to produce sufficient saliva.

2. If you have not already discussed the functional significance of the structure of human teeth, consider the following exercise. Challenge your students to explain why the teeth in their mouths have different shapes. Help them to understand the form and function relationships of sharp incisors (best suited for cutting and biting) and the flatter, blunter surfaces of molars (more effective at smashing and grinding).

3. Students often invert the “y” and “n” of pharynx. Consider emphasizing the “inks” sound in this word. This mistake is nearly as common as the mispronunciation of “nuclear” as “nucular”!

4. Slurping a beverage, by inhaling while sipping, runs the risk of aspirating fluid into the trachea. Such simple behaviors can be most illustrative to students who have not carefully analyzed such phenomena.

5. Consider demonstrating the process of peristalsis by moving a ball through a tube sock by squeezing behind the ball. Balls with smooth surfaces work best (such as racquetballs or golf balls).

6. Ask your students to identify structures and processes of the human digestive tract that promote one-way flow. Peristalsis in the esophagus, stomach, and intestines plus the sphincters along the esophagus and stomach encourage one-way flow. Of course, during vomiting, an exception occurs when forceful contractions of the abdominal cavity force the stomach contents back up the digestive tract when the upper (cardiac) sphincter opens.

7. The efficiency of peristalsis in the esophagus is so good that liquid water can be propelled along the esophagus against the forces of gravity. If someone wants to take a little risk, have a person fill his or her mouth with water and then bend over at the waist, such that the mouth is lower than the stomach. The person can then swallow, staying bent over for 20–30 seconds. Without lifting up, the person can demonstrate that the mouth is now empty. (Some students might recognize this as a potential cure of hiccups.) It is possible that some water in the pharynx will leak back out the nasal passageway. Thus, this demonstration is best using water and not carbonated beverages and with tissues available!

8. A person who continues to vomit after emptying the stomach might eventually bring up a small amount of bitter-tasting green fluid. This is likely to be small amounts of bile brought up from the small intestine.

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9. If a person’s gallbladder is removed, they will continue to produce bile; however, they will no longer have the capacity to release large amounts of bile after the ingestion of a particularly fatty meal.

10. One of the important roles of stomach acids is to kill pathogens (mostly bacteria) that we ingest with our meals. Although it is best to wash our hands before we eat, stomach acids serve as a backup system.

11. The finding that most human ulcers result from Helicobacter pylori infections represented a significant shift in medical understanding, and led to the 2005 Nobel Prize in Medicine being awarded to Drs. Robin Warren and Barry Marshall. This new explanation helps to illustrate the tentative nature of scientific knowledge, and the importance of the willingness to reject a hypothesis if another offers a better explanation.

12. The anticipation of a meal may result in an increase in the peristaltic activity of an empty stomach. The movement of gas pockets in the stomach and intestines may lead to the rumbling/gurgling sounds of hunger.

13. Students might wonder why they might need to take another dose of aspirin or other drug every 4 hours. What happened to the first dosage? The liver (or kidneys) is often involved in the destruction (or elimination) of medicines. Thus, as time passes, the drug is depleted in the bloodstream.

14. The same process of emulsification that helps break down fats in the small intestine also helps keep oil permanently mixed with vinegar in some commercial salad dressings.

15. Bacteria in the large intestine ferment otherwise indigestible carbohydrates, releasing methane, carbon dioxide, and other gases. Most adult humans produce about 500 mL of this gas (flatulus) each day. A diet particularly rich in certain carbohydrate-rich foods (such as beans) can greatly increase the quantity of flatulus that is produced.

16. In a 2009 report, the United Nations estimated that worldwide, approximately 1.5 million children (under the age of 5) die each year from diarrhea. The United Nations report notes that the total annual deaths from diarrhea exceed the combined deaths caused by AIDS, malaria, and measles.

Human Nutritional Requirements Student Misconceptions and Concerns 1. Advertising frequently leads to false expectations that there are simple shortcuts to dieting.

Consider emphasizing the importance of a well-balanced diet and exercise.

2. College students frequently experiment with their diet, given new choices and greater freedom in determining their meals. The chapter details on nutritional requirements are worth additional emphasis in lecture.

3. Students may struggle with the concept that a pound of fat contains more than twice the calories of a pound of sugar. It might seem that a pound of food would potentially add on a pound of weight. Other students may have never understood the concept of Calories in the diet, simply following general guidelines of avoiding fatty foods. Further, fiber and water have no caloric value but add to the weight of food. Consider class discussions that explore student misconceptions about Calories, body weight, and healthy diets.

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Teaching Tips 1. The heat lost during cellular respiration is like the extra heat produced by our automobile engines. This extra heat in our bodies and in our automobiles is useful during a cold winter, but a burden during a hot summer day.

2. Three of the four main types of organic molecules are sources of Calories. Students can examine a nutrition label on a package of food to identify these three groups (carbohydrates, fats, and proteins). Challenge students to think of the fourth category of organic molecule that is not a source of dietary Calories (nucleotides, which include ATP, DNA, and RNA).

3. A gram of fat stores more than twice the energy of a gram of a polysaccharide such as starch. You might elaborate with a simple calculation to demonstrate how a person’s body weight would vary if the energy stored in body fat were stored instead in carbohydrates. If a 100-kg man carried 25% body fat, he would have 25 kg of fat in his body. Fat stores about 2.25 times more energy per gram than carbohydrate. What would be the man’s weight if he stored the energy in the fat in the form of carbohydrate? (Answer: 2.25  25 = 56.25 kg of carbohydrate + 75 kg = 131.25 kg total body weight, an increase of 31.25%.)

4. Students are often surprised to learn that the mineral iron in our diets is the same iron we use as a building material. You might wish to point out that like rust forming by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Furthermore, the familiar “metal” taste we experience when we have a cut in our mouth is due to the presence of iron in our blood.

5. You might demonstrate the iron in fortified breakfast cereals by crushing some of the cereal in front of the class and dragging a magnet across the crumbs. Iron particles should be seen clinging to the magnet.

6. Basal metabolic rates change throughout a lifetime and typically decline with age. The high caloric needs of a growing child decrease in adulthood. College students might already be experiencing increased weight gain due in part to the reduced caloric needs of adulthood. Few students appreciate these fundamental changes in caloric demands.

7. Physical activity, often still high in active college students, tends to decline throughout life. Few students appreciate the need to maintain physical activity throughout adulthood or the need to further reduce caloric intake.

8. One of the challenges zookeepers face is to determine the essential nutrients required in the diets of exotic animals. Without an appreciation of the natural diet of a rare animal, certain dietary requirements may remain undetected, resulting in malnourishment.

9. Students who take vitamins might recall that fat-soluble vitamins are often taken as gel capsules (such as vitamin E), whereas water-soluble vitamins are taken in crushable pill form.

10. Research suggests that physical activity remains an important aspect of health, independent of body weight. Certain studies have concluded that sedentary people of normal body weight might be less healthy than very physically active people who are overweight.

11. Margarine commonly comes in liquid squeeze containers, in tubs, and in sticks. These forms reflect increasing amounts of hydrogenation, gradually increasing in firmness from a liquid, to a firmer spread, to a solid stick of margarine. As noted in the text, recent studies have suggested that unsaturated oils become increasingly unhealthy as they are hydrogenated. Public attention to hydrogenation and the health risks of the trans fats that result are causing many people to cut their consumption of trans fats.

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12. The American Cancer Society website (www.cancer.org) has extensive information on the relationship between diet and cancer. Search within their website for “Common Questions About Diet and Cancer.”

Nutritional Disorders Student Misconceptions and Concerns 1. Bulimia Anorexia Nervosa Association is an excellent resource for information on these disorders. The association’s website is www.bana.ca/.

Teaching Tips 1. Consider an assignment in which all students keep track for one complete (and hopefully typical) day the number of grams of fat, carbohydrates, and proteins that they consume.

Students should compare the relative amounts of each group. They might be surprised at the relatively high amount of protein in their diets.

2. According to the U.S. Department of Agriculture, U.S. consumption of added fats and oils is among the highest in the world.

3. According to the U.S. Department of Agriculture, the average citizen of the United States consumes more than 5 gallons of ice cream each year.

Key Terms absorption chyme alimentary canal colon anorexia nervosa digestion anus digestive tract appendix duodenum basal metabolic rate elimination (BMR) esophagus bile essential amino acids body mass index (BMI) essential fatty acids bulimia essential nutrients calorie feces carnivores gallbladder

gastric juice gastrovascular cavity herbivores ingestion kilocalorie large intestine liver malnutrition metabolic rate minerals mouth obesity

omnivores oral cavity pancreas pepsin peristalsis pharynx rectum salivary glands small intestine stomach tongue vitamins

Word Roots an = without; orex = appetite (anorexia: an eating disorder characterized by self-starvation due to an intense fear of gaining weight) bulim = hunger (bulimia: a pattern of binge eating followed by purging through induced vomiting) carni = flesh; vora = eat (carnivores: animals that eat other animals) gastro = stomach; vascula = a little vessel (gastrovascular cavities: compartments with a single opening through which food enters and undigested food is expelled) herb = grass (herbivore: a heterotrophic animal that eats plants) kilo = a thousand (kilocalorie: a thousand Calories) mal = bad (malnutrition: a deficiency in one or more of the essential nutrients)

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omni = all (omnivore: a heterotrophic animal that consumes both meat and plant material) peri = around; stalsis = a constriction (peristalsis: rhythmic waves of contraction of smooth muscle that push food along the digestive tract)

Relevant Songs to Play in Class “Do You Want Fries with That?,” Tim McGraw

“Eat It,” Weird Al Yankovic

“The Middle,” Jimmy Eat World

“Eat You Alive,” Limp Bizkit

“Lick It Up,” Kiss

Answers to End-of-Chapter Questions The Process of Science 13. Suggested answer: 60 Calories from fat, 72 Calories from carbohydrates, and 8 Calories from protein.

14. Suggested answer: Nutrition will likely be a significant problem. There could be problems relating to the extremely small size of the stomach and perhaps some issues concerning complete digestion of food due to issues with the digestive enzymes.

Biology and Society 15. Some issues and questions to consider: Most students will probably indicate that the makers of these supplements should be held accountable for the false claims. It is variable as to how they will propose a solution to the problem. Most will agree that the situation would improve if the FDA stepped in. The downsides of getting the FDA involved might include a significant increase in the cost of the products and the need for prescriptions.

16. Some issues and questions to consider: Is obesity a disease? Is this surgery medically important and necessary? Is it a reliable approach or an experimental procedure? What are the long-term benefits, costs, and risks of the surgery and weight loss?

Additional Critical Thinking Questions The Process of Science 1. If you talk and eat at the same time, you run the risk of choking and coughing violently, and blocking your airway with food. We often describe this situation by saying the “food went down the wrong way.” What is the biological explanation for the situation that this phrase describes?

Suggested answer: As the food passes through the pharynx, it could theoretically move toward the front into the trachea rather than toward the back into the esophagus, which is where it should go. The swallowing reflex ensures that food passes into the esophagus.

However, talking and eating at the same time interferes with this reflex. Food passing into the trachea stimulates choking and coughing, and could block this air passageway to the lungs. The Heimlich maneuver attempts to dislodge food stuck in the trachea.

2. Gallstones are insoluble deposits that block the duct between the gallbladder and the duodenum. Describe what kinds of foods people with gallstones may have problems digesting and why (aside from the pain they might experience in doing so).

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Suggested answer: People with gallstones may have problems digesting fats. Normally, as food enters the duodenum, the gallbladder releases bile, which is necessary for the fatdigesting enzymes produced by the pancreas to function.

3. Some essential mineral nutrients, such as selenium and molybdenum, are required in the human diet in minuscule amounts, thousandths of a milligram per day. What kinds of experiments would you have to carry out to show that one of these minerals is required by humans? Why might this be difficult?

Suggested answer: To show that a mineral is essential, you could feed experimental subjects a diet without the mineral and look for ill effects. One problem with this is that it might harm the subjects. In addition, it is very difficult to remove all traces of a mineral from the diet. Slight contamination or cheating by subjects might supply sufficient amounts. An additional problem is that animal subjects might not have the same needs as humans.

Biology and Society 4. Individuals who eliminate fat from their diet and eat foods high in recently developed fat substitutes often suffer from certain vitamin deficiencies even though these vitamins are ingested. Which vitamin deficiencies would be most likely to occur? Explain the reason for your answer. Should warning labels be placed on foods with fat substitutes?

Some issues and questions to consider: A deficiency of the fat-soluble vitamins (D, E, A, and K) would most likely be seen. These vitamins require fat to be absorbed. Without sufficient fat intake, they will not be absorbed despite adequate intake of the vitamins.

Should food manufacturers be expected to warn people about all possible outcomes of eating their product? What kinds of side effects should be included in the warnings?

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CHAPTER

23

Circulation and Respiration

Why This Chapter Matters 1. Every animal must acquire oxygen from and release carbon dioxide to its environment.

2. Most organisms are too large or too complex to rely only on diffusion through the body surfaces for these exchanges.

3. Elaborate respiratory and circulatory systems have evolved with adaptations specific to the particular characteristics of each group.

4. The leading cause of human death in the United States is cardiovascular disease.

5. Choosing not to smoke is the single most important lifestyle choice that affects long-term health.

Chapter Objectives Biology and Society: Avoiding “The Wall” 1. Explain what limits the speed and stamina of most endurance athletes.

Unifying Concepts of Animal Circulation 2. Explain why most animals require a circulatory system.

3. Describe the three main components of circulatory systems. Compare the structures of open and closed circulatory systems.

The Human Cardiovascular System 4. Compare the structures and functions of the human pulmonary and systemic circuits.

5. Describe the path of blood as it makes one full circuit through the body, including the heart.

6. Explain how heart rate is regulated and detected by an EKG (ECG).

7. Relate the structure of blood vessels to their functions. Define blood pressure, pulse, and hypertension.

8. Explain how blood is returned to the heart.

9. Describe the components of blood and their functions.

10. Explain why it is better to “live high and train low” for some athletes.

11. Define stem cells and leukemia. Explain how stem cells can be used to fight leukemia.

12. Explain how the cardiovascular system contributes to homeostasis.

13. Describe the causes and frequency of cardiovascular disease.

Unifying Concepts of Animal Respiration 14. Explain how the circulatory and respiratory systems cooperate to facilitate gas exchange.

15. Describe four types of respiratory surfaces and the types of animals that use them.

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The Human Respiratory System 16. Describe the three phases of gas exchange in humans.

17. Trace the path of a breath of air as it travels to and from the deepest portions of the lungs.

18. Describe the process of breathing and explain how it is controlled.

19. Describe the functions of hemoglobin. Explain how a shortage of iron, the presence of carbon monoxide, and smoking interfere with oxygen transport.

20. Explain how cigarette smoking affects public health.

Evolution Connection: Evolving Endurance 21. Explain how Tibetans are adapted to living at very high altitudes.

Lecture Outline I. Biology and Society: Avoiding “The Wall” 1. What does it take to be an elite endurance athlete?

2. To be a marathoner or a long-distance swimmer or runner, you must have world-class a. circulatory and b. respiratory systems.

3. For an endurance athlete to perform work over an extended period, muscle cells a. require a steady supply of oxygen and b. must be able to rid themselves of carbon dioxide waste.

4. What limits the speed and stamina of most endurance athletes is the ability of their heart and lungs to deliver oxygen at a steady rate 5. Properly functioning circulatory and respiratory systems are essential to all of us 6. The two systems are such close partners that they are explored together in this chapter

II. Unifying Concepts of Animal Circulation 1. Every organism must exchange materials with its environment, relying upon a. diffusion, the spontaneous movement of molecules from an area of higher concentration to an area of lower concentration, and b. a circulatory system, which facilitates the exchange of materials for all but the simplest animals.

A. Open and Closed Circulatory Systems 1. Circulatory systems typically consist of a a. central pump, b. vascular system, and c. circulating fluid.

2. In an open circulatory system, a. the heart pumps blood into large open-ended vessels and b. fluid circulates freely among cells.

3. Open circulatory systems are found in many invertebrates, including a. arthropods and b. most molluscs.

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4. In a closed circulatory system, blood a. stays within a set of tubes and b. is distinct from the interstitial fluid, the fluid that fills the spaces around cells.

5. Closed circulatory systems are found in a. many invertebrates, including earthworms and octopuses, and b. vertebrates.

6. The cardiovascular system of vertebrates consists of the a. heart and b. blood vessels.

7. In the heart, a. the atrium receives blood and b. the ventricle pumps blood away from the heart.

8. Blood is confined to three main types of blood vessels: a. Arteries carry blood away from the heart into smaller arterioles as they approach the organs. b. Capillaries are the site of exchange between blood and interstitial fluid. c. Venules collect blood from the capillaries and converge to form veins, which return blood back to the heart.

III. The Human Cardiovascular System 1. In the human cardiovascular system, a. the central pump is the heart, b. the vascular system is the blood vessels, and c. the circulating fluid is the blood.

A. The Path of Blood 1. Humans and other terrestrial vertebrates have a double circulation system consisting of a. a pulmonary circuit between the heart and lungs and b. a systemic circuit between the heart and the rest of the body.

2. One complete trip through the human cardiovascular system a. takes about one minute and b. requires two passes through the heart.

B. How the Heart Works 1. The human heart a. is a muscular organ about the size of a fist, b. is located under the breastbone, and c. has four chambers.

2. The path of blood flow through the human heart functions as two pumps moving blood between a. the heart and lungs and b. the heart and the rest of the body.

3. The Cardiac Cycle

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4. The heart relaxes and contracts throughout our lives a. Diastole is the relaxation phase of the heart cycle. b. Systole is the contraction phase.

5. A heart murmur is a sound that may indicate a defect in one or more of the heart valves 6. The Pacemaker and the Control of Heart Rate 7. The pacemaker, or SA (sinoatrial) node, a. sets the tempo of the heartbeat and b. is composed of specialized muscle tissue in the wall of the right atrium.

8. Impulses from the pacemaker spread quickly through the walls of both atria, prompting the atria to contract at the same time 9. The AV (atrioventricular) node a. is a relay point that delays the signal and b. sends impulses to the ventricles.

10. The impulses sent by the pacemaker can be a. detected by electrodes placed on the skin and b. recorded as an electrocardiogram (ECG or EKG).

11. In certain kinds of heart disease, the heart fails to maintain a normal rhythm 12. The remedy for this failure of the electrical control of the heart is an artificial pacemaker, a small electronic device surgically implanted near the SA node C. Blood Vessels 1. If the heart is the body’s “pump,” then the “plumbing” is the system of arteries, veins, and capillaries a. Arteries carry blood away from the heart. b. Veins carry blood toward the heart. c. Capillaries allow for exchange between the bloodstream and tissue cells.

2. All blood vessels are lined by a thin layer of tightly packed epithelial cells 3. Structural differences in the walls of the different kinds of blood vessels correlate with their different functions 4. Blood Flow through Arteries 5. The force that blood exerts against the walls of blood vessels is blood pressure a. Blood pressure pushes blood from the heart to the capillary beds. b. A pulse is the rhythmic stretching of the arteries caused by the pressure of blood forced into the arteries during systole.

6. Optimal blood pressure for adults is a. below 120 systolic and b. below 80 diastolic.

7. High blood pressure, or hypertension, is persistent a. systolic blood pressure higher than 140 and/or b. diastolic blood pressure higher than 90.

8. Blood Flow through Capillary Beds 9. At any given time, only about 5–10% of the capillaries have a steady flow of blood

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10. Blood flow through capillaries may be diverted from one part of the body to another, depending on need 11. The walls of capillaries are thin and leaky a. At the arterial end of the capillary, blood pressure pushes fluid rich in oxygen, nutrients, and other substances into the interstitial fluid. b. At the venous end of the capillary, CO2 and other wastes diffuse from tissue cells into the interstitial fluid, and then into the capillary bloodstream.

12. Blood Return through Veins 13. Blood returns to the heart a. after chemicals are exchanged between the blood and body cells and b. at a pressure that has nearly dropped to zero.

14. Blood moves back toward the heart because of a. surrounding skeletal muscles that compress the veins and b. one-way valves that permit blood flow only toward the heart.

D. Blood 1. An adult human has about 5 L (11 pints) of blood 2. By volume, blood is a. a little less than half cells and b. a little more than half plasma, consisting of about i. 90% water and ii. 10% dissolved salts, proteins, and other molecules.

3. Suspended in plasma are three types of cellular elements: a. red blood cells, b. white blood cells, and c. platelets.

4. Red Blood Cells and Oxygen Transport 5. Red blood cells (erythrocytes) a. are the most numerous type of blood cell and b. are shaped like discs with indentations in the middle.

6. Each red blood cell contains approximately 250 million molecules of hemoglobin, an iron-containing protein that transports oxygen 7. Carbohydrate-containing molecules on the surface of red blood cells determine the blood type 8. Each red blood cell contains large amounts of the protein hemoglobin, which a. contains iron and b. transports oxygen throughout the body.

9. Anemia may result from a. an abnormally low amount of hemoglobin or b. a low number of red blood cells.

10. The hormone erythropoietin (EPO) boosts production of red blood cells E. The Process of Science: Live High, Train Low? 1. Observation: It is difficult to train at low altitude (near sea level) and then compete at high altitude ..

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2. Question: Will athletes who train at high altitude increase their performance when at lower altitudes?

3. Hypothesis: Living at high altitudes will boost red blood cell production, which can improve stamina during competition at lower altitudes 4. Experiment: a. Five elite athletes lived for 18 days in rooms that were gradually adjusted to simulate an altitude of 3,000 meters (nearly 2 miles). b. Six elite athletes lived for 18 days at an altitude of 1,200 meters. c. All athletes trained at 1,200 meters.

5. Results: a. At the start of the study, both groups were similar in their aerobic capacity, a measure of the body’s ability to take in and use oxygen. b. By the end of the training regimen 18 days later, the group living at higher altitude had a higher aerobic capacity that partially persisted two weeks later.

6. White Blood Cells and Defense 7. White blood cells (leukocytes) a. fight infections, b. are larger than red blood cells, c. lack hemoglobin, and d. are much less abundant than red blood cells (about 700 times fewer).

8. Platelets and Blood Clotting 9. Blood contains two components that aid in clotting: a. platelets, bits of cytoplasm pinched off from larger cells in the bone marrow, and b. clotting factors released from platelets that convert fibrinogen, a protein found in plasma, into a threadlike protein called fibrin.

10. In the inherited disease hemophilia, excessive and sometimes fatal bleeding can occur from even minor cuts and bruises 11. Hemophilia is caused by a genetic mutation in one of several genes that code for clotting factors 12. Stem Cells and the Treatment of Leukemia 13. Leukemia a. is cancer of white blood cells and b. may require treatment using i. radiation, ii. chemotherapy, and/or iii. bone marrow transplantation.

F. Cardiovascular Disease 1. The cardiovascular system contributes to homeostasis by a. exchanging nutrients and wastes with the interstitial fluid, b. controlling the composition of blood by moving it through the lungs, liver, and kidneys, c. helping to regulate temperature by moving blood to or away from the skin, d. distributing hormones, and e. defending against foreign invaders.

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2. Cardiovascular disease a. includes all diseases affecting the heart and blood vessels, b. accounts for 40% of all deaths in the United States, and c. kills more than 1 million people each year.

3. Coronary arteries a. supply the heart muscle and b. can narrow or close, contributing to a heart attack.

4. Atherosclerosis a. is a chronic cardiovascular disease and b. results from fatty deposits called plaque that develop in the inner walls of arteries, clogging the passages through which blood can flow.

5. Cardiovascular disease a. involves inherited factors but b. can be reduced by i. not smoking, ii. exercising regularly, and iii. eating a heart-healthy diet.

IV. Unifying Concepts of Animal Respiration A. The Structure and Function of Respiratory Surfaces 1. Animals can get oxygen from a. the atmosphere, which contains about 21% oxygen, and b. bodies of water, which contain about 3–5% oxygen.

2. Gas exchange occurs at the respiratory surface, which must be a. large enough to take up oxygen for every cell in the body and b. adapted to the lifestyle of the organism.

3. Moist skin is used as a respiratory surface in earthworms 4. In aquatic environments, the main respiratory surfaces are a. skin and b. extensions of the body surface called gills.

5. In most land-dwelling animals, the respiratory surfaces are a. folded into the body and b. open to the air only through narrow tubes.

6. Insects breathe using a tracheal system, an extensive network of internal tubes called tracheae that a. branch throughout the body and b. extend to nearly every cell.

7. Lungs a. are located in only one part of the body and b. are the most common respiratory surface of snails, some spiders, and terrestrial vertebrates.

8. The circulatory system transports gases between the respiratory surface and the rest of the body

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V. The Human Respiratory System 1. The human respiratory system has three phases of gas exchange: a. breathing, the ventilation of the lungs by alternate inhalation and exhalation, b. transport of oxygen from the lungs to the rest of the body via the circulatory system, and c. diffusion of oxygen from the blood and release of CO2 into the blood by cells of the body.

A. The Structure and Function of the Human Respiratory System 1. Air moves sequentially from the mouth and nose to a. the pharynx, where digestive and respiratory systems meet, b. the larynx (voice box) and trachea (windpipe), c. the bronchi (one bronchus to each lung), d. the bronchioles, the smallest branches of the tubes within the lungs, and e. the alveoli, the air sacs where gas exchange primarily occurs.

2. Muscles in the voice box can stretch vocal cords within the larynx 3. During exhalation, outgoing air can produce vocal sounds as air passes by the stretched vocal cords B. Taking a Breath 1. Breathing is the alternating process of a. inhalation and b. exhalation.

2. During inhalation, the chest is expanded by the a. upward movement of the ribs and b. downward movement of the diaphragm.

3. Air moves into the lungs by negative pressure breathing, as the air pressure in the lungs is lowered by the expansion of the chest 4. Breathing can be controlled a. consciously, as you deliberately take a breath, or b. unconsciously.

5. Breathing control centers in the brain stem a. automatically control breathing most of the time and b. regulate breathing rate in response to CO2 levels in the blood.

C. The Role of Hemoglobin in Gas Transport 1. The human respiratory system a. takes in O2, b. expels CO2, but c. relies on the circulatory system to shuttle these gases between the lungs and the body’s cells.

2. However, there is one problem with this simple gas delivery system a. Problem: Oxygen does not readily dissolve in blood. b. Solution: Oxygen is carried in hemoglobin molecules within red blood cells.

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3. A shortage of iron a. causes a decrease in the rate of hemoglobin synthesis and b. can lead to anemia.

D. How Smoking Affects the Lungs 1. Breathing exposes your respiratory tissues to potentially damaging chemicals, including one of the worst pollutants, tobacco smoke 2. Tobacco smoke a. damages the cells that line the bronchi and trachea and b. interferes with the normal cleansing mechanism of the respiratory system, allowing more toxin-laden smoke particles to reach and damage the lungs’ delicate alveoli.

3. Smoking a. kills half of all people who smoke, about 440,000 Americans every year, b. causes 90% of all lung cancer (one of the deadliest forms of cancer), and c. causes more deaths than the combined total of i. all accidents, ii. alcohol and other drug abuse, iii. HIV, and iv. murders.

4. The lifestyle choice with the greatest impact on your long-term health is choosing not to smoke E. Evolution Connection: Evolving Endurance 1. Conditioning can boost athletic performance by improving the ability of the circulatory and respiratory systems to deliver oxygen to muscles 2. Tibetans a. live and work at altitudes above 13,000 feet and b. have evolved in response to this environmental stress.

3. Tibetans have genes that a. are rare in low-dwelling Chinese groups and b. contribute to the functioning of the circulatory and respiratory systems.

Chapter Guide to Teaching Resources Unifying Concepts of Animal Circulation Student Misconceptions and Concerns 1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions), the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.

2. Students might not realize that closed circulatory systems are capable of greater pressures, when fluids remain confined to limited spaces.

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Teaching Tips 1. The following analogy about a home might help students distinguish between open and closed circulatory systems. Airflow through a home with a blower furnace is an open system, in which the furnace blower propels air through ducts that open into rooms. Air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system, in which water, under high pressure, is contained in pipes. The analogy is not perfect, because in part, water pipes eventually open up into sinks and toilets, before draining into the sewage system.

2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries and large animals have deep regions that are not near a surface or edge. Therefore, large countries such as the United States, Canada, and Mexico require an internal system of roads and railways to move the many goods from seaports (the edges/surfaces) to regions deep within the countries. These roads and railways work in partnership with ports in the same way that blood vessels (and blood) cooperate with a respiratory surface.

3. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.

4. The three-chambered heart of amphibians and turtles should not be seen as a necessary “intermediate” stage in some predestined evolution of a four-chambered heart. Instead, the three-chambered heart conveys advantages not permitted by the complete subdivision of the ventricle. In amphibians and turtles, the circuit to the lungs can be bypassed when diving underwater. When breathing is not possible, blood can be rerouted past the lungs.

Thus, a loss in efficiency conveys the advantage of flexibility. This fundamental principle, in which efficiency and flexibility are traded against each other, is illustrated in many systems in living organisms.

The Human Cardiovascular System Student Misconceptions and Concerns 1. Students often develop an incorrect mental model of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on their inside surface. However, in atherosclerosis, the blood vessels narrow through an accumulation of materials within the walls themselves. In the pipe analogy, atherosclerosis is a pipe with thicker walls, which shrink the size of the lumen.

2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities.

3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart does not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need.

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4. Students often struggle to explain how blood is propelled up their legs to return to their hearts. Frequently, students will suggest that the heart itself must provide sufficient force to move blood completely around the body. However, such pressures would destroy delicate capillaries. Other student hypotheses might include attributing a negative, siphoning effect to the heart. (Although the heart can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thinking and motivate them to learn the answer. After explaining the role of skeletal muscles and one-way valves in veins, you might also note that it has been suggested that students will be more alert in class and even perform better on tests if they wiggle their legs. Challenge students to explain why this might work and why locking their knees when standing might have the opposite effect. (And enjoy watching some of your students deliberately wiggling their legs on the next exam!)

Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body.

Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences.

2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students.

3. Students often benefit from a quick connection between abstract ideas and a “concrete” example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by 4 will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander.

4. Having students take their own pulses also provides an opportunity to stimulate further curiosity. You may want to assign students to measure and record the variation in their pulse rates during the day’s different activities, perhaps (a) upon arrival to a class, (b) after 20 minutes of sitting in the class, (c) before and after drinking coffee, or (d) prior to and during exercise.

5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen-poor blood, the pulmonary artery transports low-oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or toward the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant.

6. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries. If these muscles contract, they narrow the arteries and increase pressure.

7. Veins on the back of our hands can reveal many of the principles of venous blood flow. If students keep their hands down below their hearts for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. ..

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8. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand,” students might better understand the propulsive forces moving venous blood back to the heart.

9. Students might wonder why they are discouraged from swimming soon after eating a meal.

As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway.

10. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers “glow” red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies.

11. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at http://www.heart.org/HEARTORG/ and using the keyword “aspirin” will generate many current and related articles.

12. Strokes can result from the blockage of or rupture of a blood vessel in the brain. Thus, clot-busting drugs may either help resolve a brain clot or lead to disastrous bleeding.

13. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

14. Discuss the relationship between the structure and functions of erythrocytes. The absence of a nucleus allows red blood cells to carry a greater amount of hemoglobin. But why is an erythrocyte dented in the middle? Wouldn’t it seem more likely to be shaped like a hockey puck with greater volume and less wasted space? The indentation in the center of an erythrocyte might increase its flexibility, permitting easier passage through small capillaries. Encourage students to contribute other ideas on the adaptive advantages of this unique shape (including a higher surface-to-volume ratio).

15. Just for fun, you might have your students pause for exactly 5 seconds and then note that during that period of time they each replaced 10 million red blood cells!

16. Levels of anemia are often higher in college women. Consider mentioning this in class and noting the many sources of iron available to women (the American Heart Association website cited above may be useful).

17. One function of the circulatory system that is rarely discussed is the transport of heat.

Blood vessels near the surface of the body expand when the body is overheated, releasing some of this excess heat to the environment. Conversely, during periods of exposure to cold, blood is shunted away from the skin to conserve heat. The increased blood flow to a region of sunburn feels warm because of the transport of heat by blood.

18. If your class is large in size, you may have at least one student who is a hemophiliac, or who has a close family member with hemophilia. If the student is willing, consider having him or her share some of the details of the routine necessary to manage hemophilia.

Generating empathy for the challenges of various ailments can be an important part of an education.

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Unifying Concepts of Animal Respiration Student Misconceptions and Concerns 1. As the authors note, it is important to distinguish between the uses of the word respiration in the context of the whole organism (breathing) versus in the context of cells (cellular respiration).

2. Respiratory structures such as gills, lungs, and insect tracheal systems are highly branched, reflecting an adaptation to increase the surface area and ultimately the surface-to-volume ratio of the animal. Students might not realize the common principles of adaptations to increase surface-to-volume ratios in the highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients).

Teaching Tips 1. Salamanders in the family Plethodontidae are unusual terrestrial vertebrates that include many species that survive mainly on land as adults, yet have no lungs. The adults acquire all of their oxygen through their skin. Consider discussing with your class how this is possible. Their relatively small size, slow metabolic rates, preference for cool environments, and minimal physical activity all permit the lack of lungs.

2. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. This appears to be true of the first tetrapods such as the new fossil fish–amphibian Tiktaalik.

3. You might mention to your class that most animals use tracheal systems. After all, insects are by far the dominant type of animal on Earth (at least 70% of all known species).

Therefore, what insects do is automatically the most common animal adaptation!

4. In a very general sense, the tracheal system of insects is like the ductwork distributing outside air into the individual offices of a high-rise building. (But unlike a tracheal system, the air is removed from the building by another system.)

5. Challenge your class to explain why fish gills do not work well in air. First, respiratory surfaces need to remain moist. Second, the surface area of the gills is greatly reduced as the filaments adhere to each other out of water. You can visually demonstrate this point by simply lifting your hand and spreading your fingers apart, noting the spaced arrangement of gills in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area.

The Human Respiratory System Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation!

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2. Many students still struggle with diffusion as the main mechanism for gas transport.

Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up?

3. Students might misunderstand how the cilia lining our respiratory passages work. Cilia do not filter the air like a comb. Instead, cilia are covered by a layer of mucus. Dust particles adhere to sticky mucus, which is then swept up the respiratory tract by the cilia. If students clear their throats, they will identify the fate of this mucus. We swallow after clearing our throats!

4. Students often confuse the structures and functions of the trachea and esophagus. To help them distinguish, point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to propel food toward the stomach. If the esophagus had stiff walls, it would not be able to perform this function.

5. Some basic models of the human diaphragm your students might have experienced do not properly represent the anatomy of the diaphragm. When relaxed, the diaphragm arches upward toward the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily.

Teaching Tips 1. Some of your students may have been taught to breathe deeply by actively extending their stomach outward. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity).

2. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood.

3. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lowerpitched sounds occur.

4. Students often appreciate explanations that help them understand their own experiences.

When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, facilitating their movement up and out of our respiratory systems. Although students might have heard this advice, they might not have fully understood the mechanisms. (Sipping hot tea or soup also helps to hydrate these mucus surfaces.)

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Key Terms alveoli anemia arteries arterioles atherosclerosis atrium AV (atrioventricular) node blood pressure breathing bronchi bronchioles capillaries cardiac cycle cardiovascular disease cardiovascular system

circulatory system closed circulatory system coronary arteries diaphragm diastole diffusion double circulation system electrocardiogram (ECG or EKG) erythrocytes fibrin fibrinogen gills heart

heart attack pulmonary circuit heart murmur pulse heart rate red blood cells hemoglobin respiratory surface hypertension respiratory system larynx SA (sinoatrial) node leukemia systemic circuit leukocytes systole lungs trachea negative pressure tracheal system breathing veins open circulatory system ventricle pacemaker venules pharynx vocal cords plasma white blood cells platelets

Word Roots alveoli = a cavity (alveoli: one of the dead-end, multilobed air sacs that constitute the gas exchange surface of the lungs) atrio = a vestibule; ventriculo = ventricle (atrioventricular node: a region of specialized muscle tissue between the right atrium and right ventricle; it generates electrical impulses that primarily cause the ventricles to contract) cardi = heart; vascula = a little vessel (cardiovascular system: the closed circulatory system characteristic of vertebrates) erythro = red; cyte = cell (erythrocyte: a red blood cell) fibrino = a fiber; gen = produce (fibrinogen: the inactive form of the plasma protein that is converted to the active form fibrin, which aggregates into threads that form the framework of a blood clot) hyper = above, excessive; tens = stretched (hypertension: high blood pressure) leuk = white; emia = blood (leukemia: cancer of leukocytes)

Relevant Songs to Play in Class “Irish Blood, English Heart,” Morrissey

“Hot Blooded,” Foreigner

“Sunday Bloody Sunday,” U2 “Heart-Shaped Box,” Nirvana

“(All I Need Is) The Air That I Breathe,” The Hollies

“Blood,” My Chemical Romance

“In the Air Tonight,” Phil Collins

“The Bloodmobile,” They Might Be Giants

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Answers to End-of-Chapter Questions The Process of Science 12. Suggested answer: It is likely that at least some dinosaurs had a four-chambered heart with two ventricles. A four-chambered heart with two dedicated large ventricles would allow blood to move at a higher pressure. With just a single ventricle, the higher pressure needed to reach the brain might not be possible. Phylogenetic analyses would also be helpful.

Recent studies indicate that birds and crocodiles are more closely related to each other and dinosaurs than to other extant reptiles that have a three-chambered heart. This evidence also supports the theory that dinosaurs had a four-chambered heart 13. Suggested answer: Hyperventilation causes an increase in oxygen levels and a decrease in carbon dioxide levels. When carbon dioxide levels are very low, you can actually stop breathing until carbon dioxide levels build back up. This could be very dangerous.

Biology and Society 14. Some issues and questions to consider: Is it ethical to have a child to save the life of another? Is it ethical to conceive a child as a means to an end—to produce a tissue or organ? Was this the only reason that the parents chose to have another child? Would they love the second child any less than the first child? Is this a less acceptable reason than most reasons parents have for bearing children? Do parents need a reason for conceiving a child? Do doctors find this acceptable? If they do, why do we seldom hear about it, and why did this story make the front page? Do parents have the right to make decisions like this for their young children? How will the donor (and recipient) feel about this when the donor is old enough to know what happened? How do you think you would feel if you were the second child and first learned about this as a young adult?

15. Some issues and questions to consider: What are the risks of blood doping? What are other methods used by athletes to increase their performance? Where would you draw the limit to performance-enhancing drugs such as human growth hormone, steroids, creatine, or even caffeine?

Additional Critical Thinking Questions The Process of Science 1. A friend of yours said, “You can never kill yourself by holding your breath.” Explain what she meant.

Suggested answer: If you hold your breath, the carbon dioxide generated by cellular metabolism builds up in your blood (because you are not exhaling). The carbon dioxide will react with water in your blood, resulting in the formation of carbonic acid and therefore decreasing the pH of your blood. When the breathing control center in your medulla senses this pH drop, you will involuntarily resume breathing.

2. The term fibrillation refers to an irregular, ineffective heartbeat. Why would ventricular fibrillation be a far more serious condition than atrial fibrillation in a human?

Suggested answer: The two atria function mainly as receiving chambers, receiving blood returning to the heart from the lungs and rest of the body. The ventricles are the main

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pumping chambers. Their thick walls pump blood to the lungs and the rest of the body.

When ventricle function is impaired and contraction is irregular, the body tissues will be deprived of their blood supply. Therefore, faulty ventricular function is far more serious.

3. Juan has a disease in which damaged kidneys allow some of his normal plasma proteins to be removed from the blood. How might this condition affect the osmotic pressure of blood in capillaries, compared to the surrounding interstitial fluid? One of the symptoms of this kidney malfunction is an accumulation of excess interstitial fluid, which causes Juan’s arms and legs to swell. Can you explain why this occurs?

Suggested answer: Proteins are important solutes in blood, accounting for much of the osmotic pressure that draws fluid into the blood. If protein concentration is reduced, the inward pull of osmotic pressure will fail to balance the outward push of blood pressure.

The net pressure at the arterial end of a capillary forces fluid out into the interstitial fluid.

Net pressure at the venous end is not great enough to draw fluid back in.

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CHAPTER

24

The Body’s Defenses

Why This Chapter Matters 1. More than 50 million lives have been lost to outbreaks of influenza and HIV in just the past century.

2. Nearly everything in our world teems with microbes. Many of these are capable of significant harm to a defenseless organism.

3. Understanding how we fight infections, how we can enhance our ability to fight disease, and how our immune system turns against us improves our chances of survival.

Chapter Objectives Biology and Society: The Elusive Search for an AIDS Vaccine 1. Explain why vaccines are important in the fight against harmful viruses.

Innate Defenses 2. Describe and compare the external and internal innate defenses that protect us from microbes and other substances that could invade and harm the body.

3. Describe the inflammatory response, the role of histamine, and the effects of drugs such as aspirin and ibuprofen.

4. Explain how lymph is formed.

5. Describe the general structure and functions of the lymphatic system.

Adaptive Defenses 6. Explain how T and B cells are formed and how each functions.

7. Distinguish between an antigen and an antibody.

8. Relate the shape of an antibody to its functions.

9. Explain how antibodies are used in research and the treatment of disease.

10. Describe the process of clonal selection. Explain how effector cells and antibodies are produced.

11. Compare the primary immune response and the secondary immune response.

12. Explain how vaccination can prevent disease.

13. Explain how helper T cells and cytotoxic T cells participate in immune responses.

Immune Disorders 14. Define an allergen, an allergy, and anaphylactic shock. Describe the two steps of an allergic reaction.

15. Explain how an individual’s immune system distinguishes self from nonself.

16. Explain why autoimmune diseases occur and describe four examples.

17. Explain why immunodeficiency diseases occur and describe three examples.

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18. Describe the widespread nature of HIV and AIDS. Explain the meaning of the name acquired immunodeficiency syndrome. Explain why most people with AIDS die from another infectious agent or from cancer.

Evolution Connection: HIV Evolution 19. Explain why the treatment of HIV remains very difficult.

Lecture Outline I. Biology and Society: The Elusive Search for an AIDS Vaccine 1. A vaccine is a harmless version or piece of a disease-causing microbe 2. Vaccinations against HIV, the virus that causes AIDS, have not been successful

II. Innate Defenses 1. The immune system is the body’s defense against infectious disease 2. Our bodies defend us against pathogens, disease-causing a. viruses and b. microorganisms.

3. The human body contains two lines of defense: a. external barriers and b. internal defenses.

4. Both are innate defenses, fully ready to respond before an invader has been encountered 5. Adaptive defenses are a. a third line of defense b. activated by exposure to specific invaders.

A. External Innate Defenses 1. The body has physical barriers including a. a tough outer skin layer generally impenetrable to viruses and bacteria, b. mucous membranes covered with sticky mucus, c. wax in the ear canal, which traps particles before they can get deep inside, d. secretions (such as tears, sweat, and saliva) with antimicrobial chemicals, and e. strong stomach acids that kill most pathogens ingested with food.

B. Internal Innate Defenses 1. To fight pathogens within the body, an animal’s immune system must a. detect foreign particles and cells and b. distinguish nonself from self.

2. This second line of defense includes a. white blood cells and b. defensive proteins.

3. Two types of white blood cells contribute to internal innate defenses: a. phagocytic cells, which engulf i. foreign cells or molecules and ii. debris from dead cells, and

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b. natural killer (NK) cells, which i. recognize virus-infected cells and ii. release chemicals that kill diseased cells.

4. The defensive proteins that aid in internal innate defenses work indirectly and directly a. Interferons indirectly help healthy cells resist damage. b. Complement proteins attack pathogens directly.

5. The Inflammatory Response 6. Another example of an internal innate defense is the inflammatory response, a coordinated set of nonspecific defenses in response to injury or infection 7. Damaged cells release chemicals that a. increase blood flow to the damaged area and b. turn the wound red and warm.

8. Anti-inflammatory drugs, such as aspirin and ibuprofen, a. dampen the normal inflammatory response and b. reduce swelling and fever.

C. The Lymphatic System 1. The lymphatic system consists of a. a branching network of vessels, b. numerous lymph nodes, and c. several other organs.

2. Lymphatic vessels carry lymph, a fluid that is similar to interstitial fluid surrounding body cells 3. The lymphatic system a. returns tissue fluid to the circulatory system and b. fights infection.

III. Adaptive Defenses 1. Adaptive defenses a. are the third line of defense, b. are activated after exposure to specific pathogens, and c. depend upon lymphocytes that recognize and respond to specific invading pathogens.

2. There are two types of lymphocytes: a. B cells, which mature in the bone marrow, and b. T cells, which mature in the thymus, a gland in the chest.

3. B cells and T cells eventually make their way to a. lymph nodes and b. other lymphatic organs.

4. Antigens a. are molecules on the surfaces of viruses or foreign cells and b. elicit a response from a lymphocyte.

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A. Recognizing the Invaders 1. B and T cells develop antigen receptors on their surfaces a. All the antigen receptors on a particular cell recognize a single specific antigen. b. The great diversity of B cells and T cells produces enough different antigen receptors to bind to just about every possible antigen.

2. When a particular B cell binds to its particular antigen, it gives rise to other short-lived cells, which secrete a receptor-like molecule called an antibody 3. Antibodies a. are Y-shaped molecules, b. enable the immune system to react to just about any kind of antigen, and c. combine with an antigen to form an antigen-antibody complex.

4. Antibodies are used to a. treat disorders of the immune system, b. treat certain cases of aggressive cancer, and c. detect pregnancy in home testing kits.

B. The Process of Science: How was HIV First Linked to AIDS? 1. Observation: The spread of AIDS among sexual partners, intravenous drug users, and blood transplant recipients strongly suggested that some infectious agent caused AIDS 2. Question: What pathogen causes AIDS? 3. Hypothesis: A newly discovered virus causes AIDS 4. Prediction: The blood of people with AIDS would contain antibodies to this new virus 5. Experiment: Researchers used one kind of antibody to test for another 6. Results a. Almost every patient with AIDS had antibodies to the new virus. b. None of the controls had antibodies to the new virus.

C. Responding to the Invaders 1. B cells and T cells carry out a coordinated attack along with the innate defenses 2. Clonal Selection: Multiplying Lymphocytes 3. Clonal selection a. generates B cells and T cells appropriate to the invading antigen and b. is the mechanism that underlies the immune system’s specificity and memory of antigens.

4. Effector cells a. are short-lived and b. have an immediate effect against an antigen.

5. The primary immune response a. is the first response to exposure of lymphocytes to an antigen and b. takes several days to produce effector cells via clonal selection.

6. B cells a. produce a peak amount of antibodies about two weeks after first exposure and b. secrete their antibodies into the blood and lymph.

7. Immunological Memory

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8. Clonal selection also produces memory cells, which a. are long-lived, lasting decades, b. respond to subsequent exposures to a previously encountered antigen, and c. give rise to i. effector cells and ii. more memory cells.

9. In the secondary immune response, memory cells a. bind to the antigen and b. initiate a faster and strong response.

10. Thus, in adaptive defenses, but not innate defenses, exposure to a particular antigen enhances future responses to the same antigen 11. Vaccination 12. Vaccination confronts the immune system with a vaccine, which includes a harmless version of a disease-causing microbe or one of its parts 13. A vaccine stimulates the immune system to mount defenses against the actual pathogen possessing the same antigens 14. In the United States, vaccinations have virtually eliminated a. polio, b. mumps, and c. smallpox.

15. B Cells and the Humoral Immune Response 16. The humoral immune response a. is the secretion of free-floating antibodies into the blood and lymph and b. is caused by B cells.

17. T Cells and the Cell-Mediated Immune Response 18. The cell-mediated immune response a. reacts to pathogens that have already entered body cells and b. involves two main kinds of T cells: i. helper T cells and ii. cytotoxic T cells.

19. Helper T cells a. stimulate the activity of cytotoxic T cells, b. help activate B cells, and c. grow and divide to produce i. more activated helper T cells and ii. memory T cells.

20. Cytotoxic T cells a. are the only T cells that kill infected cells and b. identify and find infected body cells through a receptor to a self-nonself complex.

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21. Cytotoxic T cells synthesize and discharge a. proteins such as perforin, which makes holes in the infected cell’s plasma membrane, and b. other proteins that trigger a process that results in the death of the infected cell by lysis (bursting).

IV. Immune Disorders 1. If the interplay of immune cells goes awry, problems can arise that range from mild irritations to deadly diseases A. Allergies 1. Allergies are exaggerated sensitivities to harmless antigens in the environment 2. Allergens are antigens that cause allergies 3. The symptoms of an allergy result from a two-stage reaction 4. Anaphylactic shock a. is an especially dangerous type of allergic reaction and b. can be counteracted with injections of the hormone epinephrine.

B. Autoimmune Diseases 1. The immune system a. normally reacts only against foreign (nonself) substances but b. may attack i. our own tissues and ii. tissues transplanted into our bodies.

2. When the immune system improperly turns against the body's own molecules, it can lead to serious autoimmune diseases such as a. lupus, b. insulin-dependent diabetes, c. multiple sclerosis, and d. rheumatoid arthritis.

C. Immunodeficiency Diseases 1. Immunodeficiency diseases a. result when one or more of the components of the immune system are lacking and b. leave affected people more susceptible to infections.

2. Immunodeficiencies may arise a. through inborn conditions such as severe combined immunodeficiency (SCID), b. from acquired illness such as Hodgkin’s disease, a type of cancer, or c. from radiation or drug therapies used against many cancers.

D. AIDS 1. AIDS (acquired immunodeficiency syndrome) a. has killed more than 30 million people worldwide and b. infects millions of new people each year.

2. HIV, the virus that causes AIDS, a. currently infects more than 33 million people worldwide, b. attacks helper T cells, and c. severely impairs humoral and cell-mediated immunity.

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3. Lives can be saved by a. reducing promiscuity and b. properly using condoms.

E. Evolution Connection: HIV Evolution 1. HIV has one of the fastest rates of mutation of any pathogen ever studied 2. The evolution of drug-resistant HIV strains is the main obstacle to eradicating AIDS 3. Drug-resistant HIV strains a. are now being documented in newly infected patients and b. exhibit how the virus readily adapts through natural selection.

Chapter Guide to Teaching Resources Innate Defenses Student Misconceptions and Concerns 1. Depending on their backgrounds, students may not be aware of the lymphatic system.

A quick review of its general structure and the movements and functions of lymph might be a helpful part of an introduction.

2. The concepts of innate and adaptive defenses are sometimes difficult distinctions to students new to the subject. Some analogies, such as the following, might help. Clothing can be considered a general defense against physical harm, excessive sunlight, and some minor chemical damage. Firefighters and their equipment often function like an adaptive defense, responding after a problem has arisen in an attempt to limit damage.

Teaching Tips 1. The inflammatory response is a good topic to hook students into this chapter on immunology. The inflammatory response is a reaction that is immediately apparent, with characteristics that can cause alarm. Students are typically more interested in subjects that have obvious relevance and that address threats to their health.

2. During a medical examination, a physician might feel for tenderness in the throat and axillary (armpit) regions. Students are unlikely to appreciate the significance of this part of the exam. Such relevancy can add meaning to your class discussions and generate additional interest in the subject.

3. In an interesting article on the effectiveness of common hygiene methods, “Hygiene of the Skin: When Is Clean Too Clean?” Elaine Larson reviews the relationship between skin hygiene and infection. It can be found at the CDC website at www.cdc.gov/ncidod/eid/vol7no2/larson.htm.

4. Students might be interested in learning that interferons are now mass-produced using recombinant DNA technology. Clinical studies are under way to explore their use in treating viral infections and cancer.

5. Excessive iron in the human body can promote bacterial infections and other diseases.

Searching the keywords “iron supplements bacteria” on the CDC website www.cdc.gov/ leads to many articles on this subject.

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Adaptive Defenses Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.)

Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions.

Teaching Tips 1. Current research is investigating ways to use recombinant DNA technology to make genetic modifications to plants to produce vaccines. A Google search of “plant edible vaccine” reveals many research articles on this subject. If you do not know about Google’s search engine dedicated to research sites, called Google Scholar, consider adding it to your options at http://scholar.google.com/.

2. The authors suggest that the specific nature of the binding between an antigen and an antibody is like the relationship between a lock and a key. You might further this analogy by noting that the tremendous diversity of antibodies is like having a set of keys for virtually every possible type of lock.

3. Monoclonal antibodies are widely used in research for tagging specific molecules. Some cancers are treated with tumor-specific antibodies coupled with toxins to attack and destroy tumor cells.

4. Our own learning experiences provide an analogy to the greater swiftness and intensity of a secondary immune response. When first presented with a problem, we may struggle to determine how best to respond. However, with that first experience behind us, we expect to respond more quickly and effectively when we meet that challenge again. Although in each circumstance we benefit from a certain type of memory (experiential in one case, chemical in the other), their mechanisms are quite different. Consider noting these similarities and differences in your class discussion of primary and secondary immune responses.

5. Consider challenging your class to explain the adaptive advantages of the Y shape of an antibody. Why, instead, is an antibody not just a single heavy chain and light chain?

(Many biologists think that the Y shape permits the binding together of two antigens or antigen-presenting surfaces, permitting a chain reaction or form of clumping.)

6. Your students might enjoy developing some sort of fight analogy to the attack by a cytotoxic T cell. The two cells “in battle” become interlocked, the infected cell develops “puncture wounds,” and a fatal poison is absorbed into these “wounds.”

7. The recognition by a helper T cell of a self protein and a foreign antigen in combination is like the two-key system used by banks to access safe-deposit boxes.

8. The Centers for Disease Control and Prevention has extensive information about AIDS and other public health threats at www.cdc.gov/hiv.

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Immune Disorders Student Misconceptions and Concerns 1. Student interest in diseases and allergies can be useful motivation for this final chapter section. However, interest in a medical subject without the necessary background to understand advice often leads to confusion. Consider “probing” for misunderstandings about allergies by asking students about allergy causes and treatments before discussing this final portion of the chapter. Because personal medical information is private, consider an anonymous survey of your students to learn who suffers from allergies, what are the allergens, and how they are treated.

2. Students may have a feeling that anything “natural” is somehow good. In addition to the many natural poisons found in animals and plants, our allergic responses to pollen, molds, and other environmental allergens reminds us that “natural” is not always healthy.

3. Students often do not understand the disproportionate distribution of HIV infections and AIDS in our world. Consider an Internet assignment, asking students to identify the regions of the world most affected by HIV and AIDS. 4. Despite efforts to educate the general public, many misconceptions about AIDS persist.

A list of 18 common misconceptions can be found at the website www.gng.org/currents/teachers/hiv101/misconceptions.html.

Teaching Tips 1. Allergic contact dermatitis occurs when an allergen triggers an immune response on the skin. A rash from exposure to poison ivy is an example.

2. Antihistamines are drugs that interfere with the action of histamine. They provide temporary relief from the symptoms of allergic reactions. Consider asking students if taking antihistamines when suffering from poison ivy might help.

3. The quickly evolving HIV virus is like an enemy that keeps changing uniforms.

4. Although the triggers of autoimmune diseases are not well understood, it does appear that autoimmune diseases are not communicable, and cannot be caught through exposure to others with the disease. Family histories of autoimmune diseases do suggest some degree of heritability, at least of predisposition. Thus, some family members may share degrees of a common autoimmune disease.

5. Students may enter your course knowing that the best types of tissue transplants are from a closely matched donor. However, what does it mean to have a tissue “match”? Few students can explain the specific reasons behind the need for tissue matching, or how such matching is done. Challenge your students to explain why we try to ensure a match between the tissues of a donor and a recipient. By posing such general questions, instructors can raise interest in the specific details of the answers.

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Key Terms adaptive defenses allergens allergies antibody antigen autoimmune diseases B cells cell-mediated immune response clonal selection

complement proteins cytotoxic T cells effector cells helper T cells histamine humoral immune response immune system immunodeficiency diseases

inflammatory response phagocytic cells innate defenses primary immune interferons response lymph secondary immune lymph nodes response lymphatic system T cells lymphocytes vaccination memory cells vaccine natural killer (NK) cells pathogens

Word Roots anti = against; gen = produce (antigen: a foreign macromolecule that does not belong to the host organism and that elicits an immune response) auto = self (autoimmune diseases: when the immune system turns against the body’s own molecules) cyto = cell; toxic = poison (cytotoxic T cells: T cells that kill other cells) humor = fluid (humoral immune response: the immunity conferred by B cells, which secrete antibodies into blood) immuno = safe (immune system: the system that protects the body by recognizing and attacking pathogens and cancer cells) lymph = fluid (lymph: a fluid, similar to interstitial fluid) mono = one (monoclonal antibodies: the antibodies produced by a single clone of cells) patho = disease; gen = produce (pathogen: disease-causing viruses and microorganisms)

Relevant Songs to Play in Class “Disease,” Matchbox Twenty

“The HIV Song,” Ween

“The Boy in the Bubble,” Paul Simon

“Catch My Disease,” Ben Lee

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: Before you start any tests, you might look for cases in which the selfnonself hypothesis does not explain observed phenomena or cases that have been interpreted as exceptions to the self-nonself concept. Why might this be a useful approach?

Promoters of the “damage” hypothesis argue that immune system failures, such as autoimmune diseases, indicate that the self-nonself hypothesis is flawed. Why do you suppose they make this argument? One case being studied in detail is the immune system in newborn mammals. According to the self-nonself hypothesis, a newborn’s immune system is incapable of recognizing foreign antigens, and this ability develops during a critical period soon after birth. (You could read about this in a more advanced general biology textbook or an immunology book.) However, new evidence suggests that the neonatal immune system can respond to at least some foreign antigens. Does this evidence 358

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support the damage hypothesis? How so? To test the damage hypothesis, you might try to identify specific danger signals that trigger immune responses. Several research groups are currently focusing on such signals. A possible question is: Could damaged tissue cells signal the antigen-presenting cells (APCs) of the immune system, making the APCs in turn cause changes in T cells? Perhaps the signal is a protein that leaks from a damaged cell.

On the other hand, perhaps it is simply the loss of physical contact of an APC with a tissue cell that dies suddenly. Can you think of other possibilities? The idea that a body defense system would evolve in response to actual danger—that is, a threat to survival and the perpetuation of genes—is consistent with evolutionary theory. Natural selection would tend to favor those individuals with such a defense system and not favor individuals lacking such a system. Why would natural selection favor individuals whose body defense system distinguishes self from nonself? Could the ability to distinguish self from nonself molecules increase evolutionary fitness?

12. Suggested answer: The primary response to antigens X and Y have the same general shape. In the secondary immune response to antigen X, the activated memory cells multiply quickly, producing a large new clone of lymphocytes, which in turn can produce larger amounts of antibodies.

Biology and Society 13. Some issues and questions to consider: There is no correct answer to this question.

Possible directions include the idea that if the donor felt strongly about the process, that a person’s wishes should be respected. The opposite position would be that the next of kin should be able to approve or deny the procedure. Other possible considerations would be appropriate, including positions based on religious beliefs or other strongly held values.

Are doctors less likely to try as hard to save a person if he or she is a donor? (This was actually an investigation on the TV show 60 Minutes.)

Additional Critical Thinking Questions The Process of Science 1. Mr. Smith was admitted to the emergency room after stepping on a sharp garden rake. The physician recommended that he receive immunization against tetanus. Upon questioning, it was learned that Mr. Smith had never been vaccinated against tetanus as a child. Based on this information, the physician gave him passive immunization: antibodies against the tetanus toxin. Explain why this was the preferred treatment at this time rather than the tetanus vaccine.

Suggested answer: Because Mr. Smith had never been immunized against tetanus toxin, he had never formed memory cells. This means that he had never mounted a primary immune response. Therefore, if he were only given the vaccine at this time, he would not produce antibodies quickly enough to protect him right away from the tetanus toxin. As a result, he might not have adequate protection. Passive immunity, although temporary, provides an immediate source of antibodies.

2. When you have strep throat (a sore throat caused by Streptococcus bacteria), the lymph nodes in your neck often enlarge. Does this have a purpose? Explain.

Suggested answer: Lymph nodes contain lymphocytes and macrophages. Lymph circulating through the lymph nodes may contain bacteria picked up at the infection site.

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Biology and Society 3. A group of parents in your community became very concerned about vaccine-associated complications. They were contemplating forming a group to protest mandatory childhood vaccination programs. They knew that you had just completed a biology course and asked you to join them at their next meeting and give your opinion. Discuss some of the issues that you would talk about.

Some issues and questions to consider: Although some vaccines can cause side effects and, rarely, severe complications, the risk of contracting the deadly diseases that they protect against, such as polio, whooping cough, and hepatitis B, is much greater than the chance of suffering a serious complication. Where could you get authoritative information on this issue? What are the risks to the child and the community if they do not receive vaccinations? If more people decline vaccinations, then the community is at risk because vaccinations do not confer 100% immunity.

4. Concern is increasing over the rising rate of HIV infection among teenagers. Schools in some large cities have instituted programs to make condoms available to students, along with counseling about safer sex. These plans have divided school boards and communities.

Some citizens and church groups are opposed to giving condoms to students because it might appear to encourage sexual activity. By contrast, many school and public health officials view the situation as a health issue rather than a moral issue. The heart of the controversy seems to be whether the schools should take such a direct role in this part of student life. What are the reasons for and against distribution of condoms? What do you think the school’s role should be?

Some issues and questions to consider: How important is it to protect students from AIDS? Is this a function of schools? Do schools serve similar purposes? Should parents or citizens and church groups—on either side of the issue—have a say in this, or is it a matter between the school and the student? Does the distribution of condoms condone or sanction sexual activity or promiscuity? Is a school legally liable if a school-issued condom fails to protect a student? Are there alternative measures, such as education, that might be as effective for slowing the spread of AIDS? Does separation of church and state indicate that churches shouldn’t have a say? Recent studies indicate the importance of sex education in reducing the spread of sexually transmitted diseases and rates of teen pregnancy. These same studies have also shown that abstinence-only programs and no sex education actually result in higher rates of teen pregnancy and sexually transmitted diseases. Based on this data, how do you feel about certain groups who want to oppose these measures?

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CHAPTER

25

Hormones

Why This Chapter Matters 1. The abuse of steroids by athletes is a significant problem in society.

2. The endocrine system is the primary mechanism for internal chemical regulation of the body.

3. Hormones reach all parts of the body, controlling whole-body activities such as growth, metabolic rate, maturation, and reproduction.

4. Diabetes mellitus is just one serious hormonal disease that affects about 8% of Americans.

Chapter Objectives Biology and Society: Sluggers and Steroids 1. Describe the doubts and concerns related to the recent major league baseball home run records.

Hormones: An Overview 2. Define an endocrine system, endocrine glands, a hormone, and target cells.

3. Compare the ways that water-soluble and lipid-soluble hormones trigger changes in target cells.

The Human Endocrine System 4. Describe the different types and functions of vertebrate endocrine glands and the hormones they produce.

5. Describe the functions of and interrelationships between the hypothalamus and the anterior and posterior pituitary glands. Compare the two types of hormones that the hypothalamus uses to control the anterior pituitary.

6. Describe the functions of follicle-stimulating hormone, luteinizing hormone, growth hormone, and endorphins.

7. Describe the functions of the thyroid gland. Describe the symptoms of hypothyroidism, hyperthyroidism, and a goiter.

8. Explain how the thyroid and parathyroid glands maintain calcium homeostasis.

9. Explain how insulin and glucagon manage blood glucose levels. Describe the frequency, causes, symptoms, and treatments of type 1 and type 2 diabetes.

10. Compare the functions of the hormones released by the adrenal medulla and the adrenal cortex.

11. Describe the benefits and risks of using glucocorticoid drugs to address pain and inflammation.

12. Describe the three major categories of sex hormones and explain their general functions.

13. Explain how the abuse of steroids may be related to violent mood swings.

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Lecture Outline I. Biology and Society: Sluggers and Steroids 1. The 1998 major league home run records reflect another chapter in baseball’s shameful “steroids era.”

2. The abuse of anabolic steroids by athletes increases muscle mass and brings greater power to a batter’s swing

II. Hormones: An Overview 1. Hormones are produced by most plants and animals 2. Animal hormones a. are made and secreted mainly by endocrine glands, b. are usually carried by the circulatory system, and c. communicate regulatory messages to specific sites in the body.

3. The endocrine system a. consists of all hormone-secreting cells and b. is the body’s main system for internal chemical regulation.

4. Endocrine cells secrete into the bloodstream hormones that a. can affect many cells in many different body organs but b. only affect target cells, cells that have receptors for that specific hormone.

5. There are two general mechanisms by which hormones trigger changes in target cells: a. Water-soluble hormones trigger responses without ever entering their target cells. b. Lipid-soluble hormones trigger responses after entering the target cell.

III. The Human Endocrine System 1. The human endocrine system consists of about a dozen major glands that may have a. only endocrine functions or b. endocrine and non-endocrine functions.

2. The major endocrine glands in humans are spread about the human body 3. Hormones have a wide range of a. target cells and b. effects.

A. The Hypothalamus and Pituitary Gland 1. The hypothalamus a. is part of the brain, b. is the main control center of the endocrine system, and c. receives information from nerves about i. the internal condition of the body and ii. the external environment.

2. The pituitary gland a. is a pea-sized structure that hangs below the hypothalamus, b. responds to signals from the hypothalamus, and c. secretes hormones that influence numerous body functions.

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3. The pituitary gland consists of two parts: a. The posterior pituitary i. is an extension of the hypothalamus, ii. stores hormones, and iii. secretes hormones made in the hypothalamus. b. The anterior pituitary i. synthesizes its own hormones, such as FSH and LH, and ii. secretes hormones directly into the blood.

4. The hypothalamus operates through the posterior pituitary to direct the activities of the kidneys a. The hypothalamus makes antidiuretic hormone (ADH) which is stored and released by the posterior pituitary. b. ADH helps kidney cells reabsorb water, preventing dehydration by decreasing urine volume.

5. The anterior lobe of the pituitary also secretes human growth hormone (HGH), which a. promotes development and enlargement of all parts of the body and b. can lead to i. dwarfism, if too little GH is produced, or ii. gigantism, if too much GH is produced.

6. Endorphins a. are produced by the anterior pituitary and b. act as natural painkillers.

B. The Thyroid and Parathyroid Glands 1. The thyroid gland a. is located in the neck just under the larynx and b. produces the hormones thyroxine and triiodothyronine, which increase i. oxygen consumption and ii. metabolic rate in all the cells of your body.

2. Hypothyroidism a. results from too little thyroid hormone in the blood and b. can result from i. dietary deficiencies of iodine or ii. a defective thyroid gland.

3. Hyperthyroidism (Graves disease) a. results from too much thyroid hormone in the blood and b. can lead to i. overheating, ii. profuse sweating, iii. high blood pressure, and iv. protruding eyeballs.

4. The parathyroid glands a. are four disk-shaped glands embedded within the thyroid and b. produce parathyroid hormone, which raises calcium levels in the blood. ..

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5. Calcitonin a. is produced by the thyroid gland and b. lowers calcium levels in the blood.

6. Calcitonin and parathyroid hormone are antagonistic hormones, because they have opposite effects on calcium levels in the blood C. The Pancreas 1. The pancreas produces two antagonistic hormones that play important roles in managing the body’s energy supplies: a. insulin which reduces blood sugar levels and b. glucagon which increases blood sugar levels.

2. Diabetes mellitus is a serious hormonal disease in which body cells are unable to absorb glucose from the blood either because a. there is not enough insulin produced (type 1, or insulin-dependent diabetes) or b. the target cells do not respond normally to insulin (type 2, or non-insulin-dependent diabetes).

3. Diabetes affects about 8% of all Americans 4. More than 90% of those affected have type 2 diabetes, which is associated with being a. overweight and b. underactive.

5. People with diabetes use glucose meters to measure the amount of glucose in the blood D. The Adrenal Glands 1. The adrenal glands are paired structures resting atop each kidney 2. Each adrenal gland consists of two glands: a. the central adrenal medulla and b. the outer adrenal cortex.

3. The adrenal medulla secretes epinephrine and norepinephrine, hormones that a. enable a rapid, short-term response to stress and b. produce the “fight-or-flight” response.

4. Stressful stimuli activate nerve cells in the hypothalamus that send signals to stimulate the adrenal medulla to secrete a. epinephrine and b. norepinephrine.

5. The adrenal cortex a. is also stimulated by the hypothalamus and b. secretes corticosteroid hormones (including glucocorticoids) that provide a slower, longer-lasting response to stress.

E. The Gonads 1. The gonads secrete sex hormones that a. affect growth and development and b. regulate i. reproductive cycles and ii. sexual behavior.

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2. Males and females have the same three types of sex hormones: a. estrogens, b. progestins, and c. androgens.

3. Estrogens a. maintain the female reproductive system and b. promote the development of specific female features, such as breasts and wider hips.

4. Progestins, such as progesterone, are primarily involved in preparing the uterus to support a developing embryo 5. Androgens, mainly testosterone, stimulate the development and maintenance of the male reproductive system F. The Process of Science: Do ‘Roids Cause Rage?

1. Observation: Doctors observed an apparent link between abuse of anabolic steroids and violent mood swings 2. Question: Could scientists measure a relationship between steroids and mood in the lab?

3. Hypothesis: The administration of increasing doses of steroids to volunteers would produce measurable changes in behavior 4. Prediction: Scientists could document mood swings resulting from anabolic steroid injection 5. Experiment: Twenty male volunteers between the ages of 18 and 42 who had no history of drug abuse or psychiatric problems were given a. a placebo drug with no steroids for days 1–3, b. a low dose of steroids for days 4–6, c. a high dose of steroids for days 7–9, and then d. a placebo for days 10–12.

6. Results: The experiment revealed a significant increase in ratings for hostility, anger, and violent feelings during the high-dose period G. Evolution Connection: Steroids and Male Aggression 1. Testosterone and other androgens a. promote the development and maintenance of the human male reproductive system and b. play a similar role in all vertebrates.

2. In addition to determining the male sexual condition, in many vertebrates, androgens a. are responsible for male vocalizations and b. promote aggressive behavior.

3. The different roles for androgens among vertebrates illustrate two central aspects of life resulting from Darwinian evolution: a. the unity of life (a consistent effect on the development of the male gonads) and b. the diversity of life (the variety of secondary effects).

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Chapter Guide to Teaching Resources Hormones: An Overview Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies on a good understanding of cell membranes and basic cellular chemistry.

If these subjects have not been addressed previously or recently in your course, consider a brief refresher before distinguishing between these mechanisms.

2. Students might not appreciate the diverse ways to coordinate activities in our world.

Endocrine glands send out hormones in the body similar to the way that radio stations and satellites broadcast signals over the Earth. Only certain cells with the right receptors are affected by a specific hormone, just as only a radio tuned to a particular station’s frequency (like target cells) will receive a specific radio signal. The nervous system provides direct connections between the sender and receiver, much more like a land-based telephone call. These analogies might help establish the basic mechanisms of the endocrine system and avoid early confusion.

Teaching Tips 1. The nervous and endocrine systems coordinate and regulate most other systems of the body.

You might consider comparing the speed and duration of each system’s response. The nervous system generally responds faster but for shorter duration than the endocrine system.

2. Consider this analogy to compare the two mechanisms by which hormones trigger changes in target cells. Imagine that a house is like a cell. Ringing the doorbell and having someone answer it is like using a signal transduction pathway. Pushing the doorbell, like a hormone binding to plasma membrane receptors, causes an internal change. The second mechanism, using steroid hormones, is like walking up to the house, opening the door, and walking inside to speak to a friend. Here the signal (the person) passes through the surface and interacts deep within the home to directly communicate a message.

The Human Endocrine System Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate endocrine organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information.

2. A central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension.

Teaching Tips 1. Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat.

However, additional research is necessary to fully appreciate the benefits and potential risks of human growth hormone injections in the elderly.

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2. The abuse of growth hormones and steroids is of great concern in the world of professional and amateur sports. The following website of the National Institute of Health provides additional details at www.drugabuse.gov/ResearchReports/Steroids/AnabolicSteroids.html.

3. Morphine and other opiates bind to the same cell receptors that naturally bind endorphins, producing powerful pain-killing effects.

4. Students might not have carefully considered the benefits of pain. Consider emphasizing the adaptive nature of pain to your class. The authors note the risks of stopping pain in an injured part of the body. Given this, challenge students to next explain why endorphins might have evolved.

5. Hypothyroidism produces symptoms that are like turning down the temperature in a home during a cold winter. When thyroid levels are low, cells produce ATP and heat at a slower rate, and the person feels colder and is more lethargic than others in the same room. This reminds students that aerobic respiration produces heat and ATP. Hyperthyroidism is just the opposite, with an overproduction of heat as the consequence.

6. The use of calcitonin and parathyroid hormone to hold blood calcium levels steady is similar to the use of a furnace and air conditioner in a home to keep temperatures steady.

The same analogy can be applied to the contrasting functions of insulin and glucagon.

7. Scientists are exploring the use of pancreatic cell transplants into patients with type 1 diabetes as a new source of insulin. Pancreatic cells may be derived from donors and/or modified from other cells using stem cell technology. One website devoted to this subject is http://diabetes.niddk.nih.gov/dm/pubs/pancreaticislet/.

8. The effects of the “fight-or-flight” response will likely last many minutes after the initial events that triggered the response. Telling a person experiencing this response to calm down is unlikely to help. Instead, removing the person from the stimulus (if possible), engaging in mild exercise such as walking, and allowing many minutes of time will more likely reverse the condition.

9. There seems to be no equivalent of menopause in males. Although men experience a steady decline in testosterone production as they age, they can retain the ability to father offspring through at least 80 years of age.

10. The North American Menopause Society is a scientific nonprofit organization that may be a useful reference for related questions. They can be reached at www.menopause.org/.

11. In humans, differences in the concentrations of sex hormones decrease between the sexes in late adulthood. Differences in secondary sexual characteristics such as muscle tone and hair growth may diminish as a natural part of aging. Students with interests in geriatrics may enjoy assignments or extra credit to investigate this topic.

Key Terms adrenal cortex adrenal glands adrenal medulla androgens antagonistic hormones anterior pituitary calcitonin corticosteroids

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diabetes mellitus endocrine glands endocrine system endorphins epinephrine estrogens glucagon glucocorticoids

gonads human growth hormone (HGH) hormones hypothalamus insulin norepinephrine pancreas

parathyroid glands parathyroid hormone (PTH) pituitary gland posterior pituitary progestins target cell thyroid gland

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Word Roots andro = male; gen = produce (androgens: the principal male steroid hormones, such as testosterone, that stimulate the development and maintenance of the male reproductive system and secondary sex characteristics) endo = within (endorphins: the body’s natural painkillers) epi = above, over (epinephrine: a hormone produced as a response to stress; also called adrenaline) gluco = sweet (glucagon: a hormone that increases blood sugar levels) hyper = excessive (hyperthyroidism: the excessive production of thyroid hormones) hypo = below (hypothalamus: the master control center of the endocrine system, located just below the thalamus in the brain) mellit = honey (diabetes mellitus: a hormonal disease in which cells cannot obtain glucose from blood, resulting in high glucose levels in blood and urine) para = beside (parathyroid glands: important endocrine glands located next to the thyroid gland) pro = before; lact = milk (prolactin: a hormone produced by the anterior pituitary gland; it stimulates milk synthesis in mammals)

Relevant Song to Play in Class “Strong Enough,” Sheryl Crow

Answers to End-of-Chapter Questions The Process of Science 12. a. No. Blood sugar level goes too low. Diabetes would tend to make the blood sugar level go too high after a meal. b. No. Insulin is working, as seen by the homeostatic blood sugar response to feeding. c. Correct. Without glucagon, exercise and fasting lower blood sugar.

The cells cannot mobilize any sugar reserves, and their blood sugar level drops. Insulin (which lowers blood sugar) has no effect. d. No. If this were true, blood sugar level would increase too much after a meal.

Biology and Society 13. Some issues and questions to consider: Why are parents concerned about their children’s height? Just because the hormone is available, does this mean that parents should request its use? What is the role of the physician in this situation? Would this kind of use be worth the risk? Is a child able to make an informed decision? How might the child feel in later years if the hormone has unintended side effects? In what ways would usage by an older adult be different? What are the pros and cons of adult use of HGH? At what age would it help the most or the least? Should athletes be allowed to use HGH if it can enhance their performance? How can people be prevented from misusing a legal drug? How are the distribution and use of these kinds of medications regulated?

14. Valid differences of opinion should be expected. Some students might say that parents need to be responsible for their children’s diet and exercise, but will acknowledge that this is more difficult today than it was 30 years ago. They might mention the elimination of physical education classes at school, the rise of fast-food restaurants, and that for many families, both parents work outside the home, making it more difficult to find time to cook 368

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nutritious meals and exercise. Other students might disagree and decide that the parents made the choice to feed their children fast food every day. They may also mention that fast-food restaurants frequently post nutrition information about their menu, so the information is available for parents to use. There are also socioeconomic reasons as well.

The government heavily subsidizes the corn industry—as a result, processed foods with lots of sugar and low nutritional value are often cheaper than more nutritious fruits and vegetables. How would this affect a parent’s choice of foods to buy? What else can be done as a society to reduce the obesity epidemic?

Additional Critical Thinking Questions The Process of Science 1. If all cells in the body contain the same DNA, why do some tissues have receptors for certain hormones, whereas others do not?

Suggested answer: Cells within an individual differ in their hormone receptors for the same reason they differ in any other respect, and that is differential gene expression. The different receptors are produced by the activation of certain genes in certain cells. This allows the cells to become even more differentiated as development proceeds.

2. Why do amine hormones generally require membrane receptors, whereas steroid hormones generally do not?

Suggested answer: Steroid hormones are generally relatively small, uncharged, and hydrophobic. Such molecules can pass through the hydrophobic core of the plasma membrane relatively easily. Amine hormones may be relatively large and usually contain amino acids that are charged and hydrophilic. Such molecules cannot easily pass through the hydrophobic core of the phospholipid bilayer. Therefore, membrane receptors are required outside the plasma membrane for signal transduction to occur inside the cell.

Biology and Society 3. Why is the incidence of type 2 diabetes so high compared to most other inheritable diseases? Why hasn’t this deleterious allele been eliminated by natural selection?

Some issues and questions to consider: Type 2 diabetes is typically a late-onset disease.

Therefore, it does not significantly affect the reproductive success of most individuals with the disease—so there is little reproductive selection against this trait, and selection will be largely ineffective in eliminating this allele. In addition, treatments are available that reduce the impact of the disease, thus allowing suboptimal genotypes to be passed to future generations. It is also possible that lifestyle and dietary choices associated with increased disease frequency may be a relatively recent development and evolution has not yet had time to reduce the frequency of what have become deleterious alleles. It should be noted that the selective value of an allele is always determined within an environmental context.

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CHAPTER

26

Reproduction and Development

Why This Chapter Matters 1. All forms of life are products of reproduction.

2. Understanding the basic structures and functions of the human reproductive system is important to maintaining good health and understanding disorders and disease.

3. Sexually transmitted diseases can threaten fertility, lead to lifelong disease, and be fatal.

Chapter Objectives Biology and Society: Life after Death 1. Describe an example where society’s laws have not caught up to new reproductive technologies.

Unifying Concepts of Animal Reproduction 2. Describe the different forms of asexual reproduction. Explain the advantages and disadvantages of asexual reproduction.

3. Explain how hermaphrodites reproduce.

4. Distinguish between external and internal fertilization.

5. Describe the circumstances in which sexual reproduction is generally more adaptive than asexual reproduction.

Human Reproduction 6. Compare the structures and functions of the female and male human reproductive systems.

7. Describe and compare the processes and products of oogenesis and spermatogenesis.

8. Describe the events of the female reproductive cycle.

Reproductive Health 9. Compare the most common methods of contraception. Note the effectiveness of each.

10. Describe the major types of sexually transmitted diseases and the organisms that cause them. Explain why all sexually active people should be tested regularly for sexually transmitted diseases.

Human Development 11. Describe the events of fertilization. Explain how the structure of sperm matches its functions.

12. Describe the stages of development from the zygote to the gastrula. Explain the significance of the three layers produced in gastrulation.

13. Explain why induction and programmed cell death are significant parts of development.

14. Describe the structure of the embryo and its relationship to the uterus during and soon after implantation. Include the functions of the amnion, yolk sac, allantois, and chorion.

15. Describe the developmental changes that occur in each of the three trimesters of pregnancy.

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17. Describe the main events of the three stages of labor.

Reproductive Technologies 18. Describe the common causes and treatments of infertility. Distinguish between infertility and impotency.

19. Describe the process of in vitro fertilization.

20. Describe some of the problems created by modern reproductive technologies.

Evolution Connection: The “Grandmother Hypothesis” 21. Explain how natural selection may have favored females who undergo menopause.

Lecture Outline I. Biology and Society: Life after Death 1. Infertility a. is the inability to conceive after at least one year of trying and b. affects one in seven American couples.

2. An infertile couple in New Jersey were using reproductive technologies to try to become pregnant 3. But during those efforts, the husband suddenly died of a heart attack 4. Within 6 hours of the death of her husband, the woman requested that a sample of her late husband’s sperm be removed 5. That sperm was used to fertilize the wife’s eggs and produce a child who is alive today 6. However, laws remain unclear regarding the rights of the child to death benefits

II. Unifying Concepts of Animal Reproduction 1. Reproduction is the creation of new individuals from existing ones A. Asexual Reproduction 1. Asexual reproduction a. is reproduction without sex and b. creates offspring that are genetically identical to the parent.

2. Budding a. is a type of asexual reproduction and b. produces offspring by the outgrowth and eventual splitting off of a new individual from the parent.

3. During the asexual process of fission, a parent separates into two or more offspring of about equal size 4. Fragmentation is the breaking of a parent body into several pieces 5. Regeneration a. typically follows fragmentation and b. is the regrowth of lost body parts.

6. Asexual reproduction a. eliminates the need to find a mate, b. allows a population to perpetuate itself if its individual members are isolated from one another, and c. permits organisms to multiply quickly without spending time or energy producing sperm and eggs.

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7. However, asexual reproduction produces genetically identical offspring, which limits a population’s chances of surviving periods of environmental change B. Sexual Reproduction 1. Sexual reproduction involves the a. fusion of two haploid sex cells called gametes (sperm and egg) and b. formation of a zygote.

2. Sexual reproduction increases the a. genetic variability among offspring and b. chances that some of the varying offspring will survive and reproduce.

3. Some animals can reproduce a. sexually and b. asexually.

4. In some species, each individual is a hermaphrodite, with a. male and b. female reproductive systems.

5. Some hermaphrodites can fertilize their own eggs, while other species require a partner 6. The mechanics of fertilization play an important part in sexual reproduction 7. Many aquatic animals a. use external fertilization and b. discharge their gametes into the water.

8. In nearly all terrestrial animals, males deposit sperm directly into the female body

III. Human Reproduction 1. Both sexes of humans have a. a pair of gonads that produce gametes, b. ducts to store and deliver the gametes, and c. structures that allow mating.

A. Male Reproductive Anatomy 1. The penis a. contains erectile tissue that fills with blood and b. becomes erect during sexual arousal.

2. A prepuce, or foreskin, a. covers the glans and b. may be removed surgically in a procedure known as circumcision.

3. The male gonads, the testes, a. are enclosed in a sac called the scrotum and b. produce sperm.

4. A testis and scrotum together are called a testicle 5. By keeping the sperm-forming cells away from the body, the scrotum keeps the testes cool enough for sperm to develop normally 6. During ejaculation, sperm leave the epididymis and travel through a duct called the vas deferens, and

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7. The seminal vesicles and prostate gland add fluid that a. nourishes the sperm and b. provides protection from the natural acidity of the vagina.

8. Semen consists of these glandular fluids and sperm 9. The urethra conveys through the penis, at different times, both a. semen and b. urine.

B. Female Reproductive Anatomy 1. The outer features of the female reproductive tract are collectively called the vulva and consist of a. the vagina, or birth canal, b. the labia majora, fatty ridges that protect the entire genital region, c. the labia minora, inner folds bordering the openings, d. the hymen, partially covering the vaginal opening, and e. the clitoris, which becomes erect upon sexual arousal.

2. The ovaries a. are the sites of gamete production and b. contain follicles consisting of a single egg surrounded by cells that nourish and protect it.

3. The follicles also produce estrogen, the female sex hormone 4. During ovulation, an immature egg a. is ejected from a follicle and b. enters the oviduct, where fertilization typically occurs.

5. The remains of the follicle grow to form a solid mass, the corpus luteum, which secretes hormones during the reproductive cycle 6. The uterus is a. the actual site of pregnancy and b. lined by a thick blood-rich layer of tissue, the endometrium, where an embryo implants and grows.

7. A developing human is called a. an embryo for the first nine weeks and b. a fetus from the 9th week until birth.

8. The cervix a. is the narrow neck at the bottom of the pear-shaped uterus and b. opens into the vagina.

9. Annual Pap smears a. sample cervical cells and b. can detect cervical cancer early, when treatment is more likely to be successful C. Gametogenesis 1. Gametogenesis a. uses meiosis and b. produces haploid cells called gametes.

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2. Humans have a. diploid cells with 46 chromosomes and b. haploid gametes with 23 chromosomes.

3. Spermatogenesis 4. Spermatogenesis a. is the formation of sperm cells and b. occurs in seminiferous tubules inside the testes.

5. Primary spermatocytes a. are diploid cells, b. undergo meiosis I, and c. produce secondary spermatocytes.

6. Secondary spermatocytes undergo meiosis II, each with the haploid number of chromosomes 7. Thus, spermatogenesis produces a total of four haploid cells from each primary spermatocyte D. Oogenesis 1. Oogenesis is the development of eggs within the ovaries 2. A primary oocyte a. is a diploid cell that pauses during prophase of meiosis I and b. can be triggered to develop further by the hormone FSH to produce i. a secondary oocyte and ii. a small polar body with almost no cytoplasm.

3. Meiosis II produces a. a mature ovum and b. another polar body.

4. Both oogenesis and spermatogenesis produce haploid gametes, but there are several important differences a. Human males create new sperm every day, from puberty through old age. b. Human females create primary oocytes only during fetal development. c. Spermatogenesis produces four gametes from each diploid parent cell, but oogenesis produces only one gamete from each diploid parent cell. d. Sperm are small and motile, while eggs are large and nonmotile.

E. The Female Reproductive Cycle 1. Human females have a reproductive cycle, a recurring series of events that a. produces gametes, b. makes eggs available for fertilization, and c. prepares the body for pregnancy.

2. The female reproductive cycle is actually two cycles in one: a. the ovarian cycle controls the growth and release of an egg and b. the menstrual cycle prepares the uterus for possible implantation of an embryo.

3. Hormonal messages coordinate the ovarian and menstrual cycles 4. Menstruation is a. uterine bleeding b. caused by the breakdown of the endometrium. ..

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IV. Reproductive Health 1. Two issues of human reproductive health are a. contraception, the deliberate prevention of pregnancy, and b. sexually transmitted diseases (STDs).

A. Contraception 1. Contraception comes in many forms with varying degrees of effectiveness 2. Complete abstinence (avoiding intercourse) is the only totally effective method of contraception 3. Sterilization surgery prevents sperm from reaching an egg and is very reliable a. The oviducts are cut and often tied off in a tubal ligation. b. The vas deferens are cut, preventing sperm from reaching the urethra, in a vasectomy.

4. Temporary abstinence a. is also called the rhythm method or natural family planning and b. depends on refraining from intercourse during the days around ovulation.

5. Barrier methods prevent sperm from meeting an egg. These include a. diaphragms, dome-shaped rubber caps that cover the cervix, and b. condoms, sheaths usually made of latex, that fit i. over the penis or ii. within the vagina.

6. Barrier devices are usually used with spermicides, sperm-killing chemicals 7. Birth control hormones include a. oral contraceptives, or birth control pills, b. morning-after pills (MAPs), which are about 75% effective at preventing pregnancy when taken within three days of intercourse, and c. RU-486, which can induce an abortion.

B. Sexually Transmitted Diseases 1. Sexually transmitted diseases (STDs) are a. contagious diseases and b. spread by sexual contact.

2. Viral STDs a. cannot be cured but can be controlled by medications and b. include i. AIDS, ii. genital herpes, and iii. genital warts.

3. STDs caused by bacteria, protozoans, and fungi are generally curable with drugs 4. Chlamydia a. is the most common bacterial STD in the United States, b. poses a public health challenge because it is frequently “silent,” producing no visible symptoms, c. may lead to pelvic inflammatory disease (PID) and infertility, and d. can be easily treated with a single dose of an antibiotic.

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V. Human Development 1. Embryonic development begins with fertilization, the union of sperm and egg to form a zygote A. Fertilization 1. Sexual intercourse releases hundreds of millions of sperm into the vagina, but a. only a few thousand sperm survive the trip to the egg and b. only one will fertilize it.

2. The shape of a human sperm is streamlined, which helps it swim through fluids in the a. vagina, b. uterus, and c. oviduct.

3. Fertilization by a sperm involves many steps B. Basic Concepts of Embryonic Development 1. The key to development is that each stage of development takes place in a highly organized fashion 2. Development begins with cleavage, a series of rapid cell divisions that results in a multicellular ball 3. Cleavage continues as the embryo moves down the oviduct toward the uterus 4. A blastocyst a. forms about 6–7 days after fertilization and b. consists of a fluid-filled hollow ball with i. about 100 cells and ii. a small clump of inner cells called the inner cell mass, which eventually forms the fetus.

5. About 9 days after conception, the embryo a. undergoes gastrulation, an organized migration of cells, and b. changes to a gastrula stage with three main tissue layers that establish the basic body plan: i. ectoderm, the outer layer that forms the nervous system and skin, ii. mesoderm, the middle layer that forms the heart, kidneys, and muscles, and iii. endoderm, the innermost layer that becomes the lining of the digestive tract.

6. Tissues and organs take shape in a developing embryo as a result of many different changes in the cells 7. In the process called induction, one group of cells influences the development of an adjacent group of cells 8. Programmed cell death a. selectively kills cells to reshape the embryo and b. is used to form fingers and toes.

C. Pregnancy and Early Development 1. Pregnancy, or gestation, a. is the carrying of developing young within the female reproductive tract and b. is measured as 40 weeks from the start of the last menstrual cycle in humans.

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2. The early stages of human development begin in the oviduct with a. fertilization and b. cleavage.

3. About 1 week after conception, a. the embryo has become a blastocyst, b. the blastocyst contains an inner cell mass made of stem cells, which have the potential to give rise to every type of cell in the body, c. the blastocyst implants in the uterine wall, and d. the outer embryonic cell layer, the trophoblast, starts to form part of the placenta, the organ that i. provides nourishment and oxygen to the embryo and ii. helps dispose of metabolic waste.

4. About a month after conception, four life-supporting pieces of equipment have formed: a. the amnion, a fluid-filled sac that encloses and protects the embryo, b. the yolk sac, which produces the first blood cells and first gamete-producing cells in the gonads, c. the allantois, which helps form the umbilical cord, and d. the chorion, which contributes to the placenta.

5. The placenta a. develops fingerlike chorionic villi that absorb nutrients and oxygen from the mother’s blood and pass these substances to the embryo and b. allows protective antibodies to pass from the mother to the fetus.

D. The Stages of Pregnancy 1. Pregnancy is divided into three trimesters of about 3 months each E. The First Trimester 1. About 5 weeks after fertilization, the embryo has developed a. a brain and spinal cord, b. four stumpy limb buds, and c. a short tail.

2. About 9 weeks after fertilization, a. the embryo is called a fetus, b. the embryo has all of its organs and major body parts, and c. the embryo’s limb buds have become tiny arms and legs with fingers and toes.

3. By the end of the first trimester, the sex of the fetus can be determined by an ultrasound 4. The Second Trimester 5. At about 14 weeks of development, the fetus a. is about 6 cm (2.4 inches) long and b. starts to look distinctly human.

6. At 20 weeks, the fetus a. is about 19 cm (7.6 inches) long, b. weighs about half a kilogram (1 lb), and c. has the face of an infant.

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8. The third trimester a. is a time of rapid growth and b. includes many important physical changes.

9. At birth, a typical baby a. is about 50 cm (20 inches) long and b. weighs 3–4 kg (6–8 lb).

F. Childbirth 1. The birth of a child is brought about by a series of strong, rhythmic contractions of the uterus called labor 2. Hormones such as oxytocin, a powerful stimulant of the smooth muscle walls in the uterus, play a key role in inducing labor 3. Labor involves three stages: a. dilation, the longest stage of labor, which increases the opening of the cervix, b. expulsion, which results in the delivery of the child, and c. delivery of the placenta usually within 15 minutes after the birth of the baby.

VII. Reproductive Technologies 1. Reproductive technologies can help solve problems related to the inability to conceive a child A. Infertility 1. Infertility is a. the inability to have children after one year of trying, b. most often due to problems in the man, such as underproduction of sperm or poor sperm quality, and c. sometimes caused by impotence (erectile dysfunction), the inability to maintain an erection.

2. Female infertility can result from a. lack of eggs, b. failure to ovulate, or c. blocked oviducts.

3. There are technologies available to help treat the many forms of infertility B. In Vitro Fertilization 1. In vitro fertilization (IVF) begins with the administration of drugs that promote the development of multiple eggs followed by the, a. surgical removal of the eggs, b. collection of sperm, c. fertilization of the eggs with sperm in a petri dish, and d. injection of the resulting embryos into a uterus.

C. The Process of Science: Can Viable Embryos Be Identified?

1. Observation: Embryonic cells can be removed from the outer layer of a preimplantation blastocyst without any harm 2. Hypothesis: An analysis of gene activity within such cells could provide useful information about the chances of a successful pregnancy from each embryo 3. Prediction: Gene expression would differ between successful and unsuccessful embryos ..

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4. Experiment: Genetic samples from embryos implanted in women were analyzed to identify genetic differences between successful embryos and those that did not develop fully 5. Results: A large number of differences were found between embryos that developed and those that did not. The results may help fertility researchers identify which embryos are most likely to develop when determining which embryos to implant D. The Ethics of IVF 1. IVF a. offers choices that nature does not and b. raises many moral and legal issues.

E. Evolution Connection: The “Grandmother Hypothesis” 1. Around age 50, human females undergo menopause, the cessation of ovulation and menstruation 2. How might menopause be adaptive?

3. Menopause might increase a woman’s fitness by allowing her to invest more time and energy in her children and grandchildren instead of having more children

Chapter Guide to Teaching Resources Unifying Concepts of Animal Reproduction Student Misconceptions and Concerns 1. Many students expect that hermaphroditic animals fertilize themselves. Although this may be common in some animals, exchanging gametes between hermaphrodites also occurs, as noted in the text.

2. Students do not often understand the costs and benefits of asexual and sexual reproduction.

Consider discussing the advantages and disadvantages of each of these forms of reproduction. Encourage students to focus on the compromises involved in any adaptation.

There is simply no one “best” way for all animals to reproduce.

Teaching Tips 1. Aphid life cycles usually alternate between asexual and sexual reproductive strategies during a single year. Consider challenging your class to explain why aphids (and other animals) do this. In general, sexual reproduction is most common in times of stress, and may be related to overpopulation or environmental change in which diversity may be favored.

2. Many salamander species use spermatophores to transfer sperm from the male to the female. Spermatophores are reproductive structures produced by males during courtship.

Sperm is deposited atop a gelatinous base, which is, in turn, attached to the substrate. The female moves over the spermatophore, removes some of the sperm from the cap, and stores the sperm in her reproductive tract until the time of egg deposition. Thus, sperm transfer is external but fertilization is internal. Many terrestrial salamander species use spermatophores, thus serving as one of the exceptions to the general rule that terrestrial animals reproduce by depositing sperm directly into the female’s body.

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Human Reproduction Student Misconceptions and Concerns 1. Student background knowledge of human reproductive biology is likely quite uneven.

What is well understood by some students is new to others. Further, the embarrassment frequently associated with related topics makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much.

2. Student embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions.

Teaching Tips 1. Endometriosis is an inflammatory condition in which the endometrium spreads beyond the uterus. It can lead to painful menstrual cycles and infertility. The Endometriosis Association website at www.endometriosisassn.org/ is a good resource for additional information.

2. Men in your class will be well aware of physiological changes in the scrotum associated with thermoregulation. When a man enters into cool water, the scrotum is pulled tight and the testes are held close to the body. During a warm shower or bath, the scrotum relaxes and the testes are held far away from the body. Women in your class may be much less aware of this common phenomenon.

3. In class, on a quiz, or on an exam, ask students to explain why polar bodies are produced at all, and why they have so little cytoplasm. Challenge them to explain why polar bodies are not produced in spermatogenesis. (In general, oogenesis conserves cytoplasm while reducing the genetic composition of the forming ovum.)

4. Testicular cancer is the most common form of cancer in men between 15 and 35 years of age. Students can find information about testicular cancer and how to perform a self-exam at the website for the American Cancer Society at www.cancer.org.

5. Students might wonder why a woman’s body goes through menstrual cycles. Why not just sustain the endometrium continuously? One hypothesis suggests that because the uterus is a good environment in which bacteria can grow, menstrual cycles are a way to “flush” the system and discourage microbial growth.

6. Many home pregnancy tests rely upon antibodies to HCG. 7. The Sexuality Information and Education Council of the United States (SIECUS) is a national, nonprofit organization, which affirms that sexuality is a natural and healthy part of living. Its website, at www.siecus.org, is an excellent source of information related to this chapter.

Reproductive Health Student Misconceptions and Concerns 1. Students often mistakenly equate contraception with prevention of sexually transmitted diseases. As you review the forms of birth control, consider pointing out the strategies that provide little or no protection against STDs. The pill, for example, does nothing to prevent disease transmission. Consider noting that methods that greatly reduce the transmission of disease (condoms used with spermicides) are also effective forms of birth control.

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2. Students often expect that drugs are available to cure most or all STDs. However, viral infections should be considered lifelong diseases. HIV, herpes, and HPV are examples of such STD viruses.

Teaching Tips 1. Although people infected with sexually transmitted diseases might have no apparent symptoms, they may still be capable of infecting partners. This important point is worth repeating to young college audiences who may be overly optimistic about the health of their partners.

2. Chlamydia is the most frequently reported bacterial STD in the United States (Source: CDC fact sheet at www.cdc.gov/std/chlamydia/STDFact-Chlamydia.htm).

Human Development Student Misconceptions and Concerns 1. Students often think that fetal blood and mother’s blood run together, one into the other.

Few students typically have a good understanding of the relationship of fetal and maternal blood in the placenta.

2. The extraembryonic membranes surrounding a human embryo are also not well understood by college students outside of the health sciences. These extraembryonic membranes can be viewed as analogous to the life-support systems used by astronauts.

Teaching Tips 1. Gastrulation establishes the basic body plan by positioning the future systems of the body in relationship to each other. This essential element of gastrulation is a crucial event that is a prerequisite for later developmental events (and thus is the basis of the quote directly below).

2. You might wish to reflect on the somewhat famous quote of Lewis Wolpert, who in 1986 said, “It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.” The development and arrangement of the basic embryonic layers (ectoderm: skin and nervous system; mesoderm: muscle and bone; and endoderm: digestive tract) establishes the basic body plan.

3. Ectopic pregnancies occur when an embryo implants anywhere other than the uterus. Most frequently, ectopic pregnancies occur in the oviducts. However, the structure of the oviduct cannot accommodate the growth of a fetus. Surgical removal of the ectopic pregnancy, resulting in an abortion, is thus required for the sake of the mother’s health. In the ongoing political and ethical debate about abortion, this circumstance is often noted as an acceptable exception, “to save the life of the mother.”

4. Programmed cell death in the formation of human hands is like carving. One begins with more “material” than is necessary and removes what is not needed to reveal the final shape.

5. All vertebrates develop in a fluid environment. Fish and amphibians typically lay their eggs in water. Amniotes (reptiles, birds, and mammals) are defined by the presence of an amniotic sac, a self-contained aquatic system that surrounds the embryo with water inside the egg. The evolution of the amniotic egg removed the need to reproduce near water, freeing amniotes to reproduce underground, in deserts, and in trees!

6. Morning sickness typically occurs during the first trimester and subsides during the second. However, a great deal of variation in the timing and degree of symptoms is known.

Unfortunately, the precise cause of morning sickness remains unknown.

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7. Most human babies weigh 3–4 kilograms (kg) at birth. Birth weights much larger or smaller than this are associated with increased mortality. This is an example of stabilizing selection, discussed in Chapter 13.

8. When discussing the dilation of the cervix as part of labor, it might be useful to note that cigarettes are 90–100 mm long. Thus, a fully dilated cervix is about as wide as a cigarette is long.

9. The descriptions of basic development address questions that students may have never thought to ask. How do we get so many cells (trillions!) in our adult bodies? How do basic tissues, organs, and organ systems form? What mechanisms permit the coordinated development of the body? Before beginning this chapter, consider challenging your students with some of these fundamental questions: How did you get a heart, a brain, and ears? What determined when you were ready to be born? How did you get nutrients and oxygen before you could eat or breathe?

10. The many benefits of breast-feeding are noted at the website of the U.S. Dept. of Health and Human Services, which can be found at www.womenshealth.gov/breastfeeding/.

Reproductive Technologies Student Misconceptions and Concerns 1. Students frequently confuse the terms infertility and impotency. Care should be used to distinguish these terms.

2. Few students understand that many STDs can lead to infertility. For example, chlamydia is the most frequently reported bacterial sexually transmitted disease, according to the CDC. Infertility is a common consequence of chlamydial infections.

Teaching Tips 1. Cardiovascular disease is often the cause of impotency (erectile dysfunction). Smoking, poor diet, and lack of exercise can therefore contribute to sexual problems.

2. The fate of surplus frozen embryos produced by in vitro fertilization is often debated.

Some have suggested that they be used as sources of stem cells. Others regard this as a form of unacceptable abortion. Students might enjoy researching and discussing the issues related to these embryos.

Key Terms asexual reproduction birth control pills budding cervix chlamydia chorion chorionic villi cleavage clitoris condoms contraception corpus luteum diaphragm ..

egg ejaculation embryo endometrium fertilization fetus fission follicles gametes gametogenesis gastrula gastrulation genital herpes

gestation gonads hermaphrodite hymen impotence in vitro fertilization (IVF) induction infertility labia majora labia minora labor menstrual cycle

menstruation morning-after pills (MAPs) natural family planning oogenesis ovarian cycle ovaries oviduct ovulation penis placenta prepuce primary oocyte

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primary spermatocytes programmed cell death prostate gland reproduction reproductive cycle rhythm method scrotum secondary oocyte

secondary spermatocytes semen seminal vesicles seminiferous tubules sexual reproduction sexually transmitted diseases (STDs) sperm

spermatogenesis spermicides stem cells testes testicle trimesters trophoblast tubal ligation umbilical cord

urethra uterus vagina vas deferens vasectomy vulva zygote

Word Roots a = without (asexual reproduction: reproduction without sex) contra = against (contraception: the prevention of pregnancy) ectomy = cut out (vasectomy: the cutting of each vas deferens to prevent sperm from entering the urethra) fertil = fruitful (fertilization: the union of haploid gametes to produce a diploid zygote) gastro = stomach, belly (gastrulation: the formation of a gastrula from a blastula) in = without (infertility: the inability to reproduce sexually) labi = lip; major = larger (labia majora: a pair of thick, fatty ridges that enclose and protect the labia minora and vestibule) oo = egg; genesis = producing (oogenesis: the process in the ovary that results in the production of female gametes) ovi = egg (oviduct: the tube that carriers an egg from the ovary) tri = three (trimester: a three-month period) tropho = nourish; blast = bud (trophoblast: the outer epithelium of the blastocyst, which forms the fetal part of the placenta)

Relevant Songs to Play in Class “Miserable Bastard” (from the album Zygote), John Popper

“I Want Your Sex,” George Michael

“Reproduction,” Grease 2 Soundtrack

“Let’s Talk About Sex,” Salt N Pepa

“Two Kinds of Seagulls,” Tom Chapin

Answers to End-of-Chapter Questions The Process of Science 12. Suggested answer: If some sperm can live 5 days, then there is a risk of pregnancy up to 5 days prior to ovulation (day 9), meaning that if the sperm are already present at ovulation, fertilization can occur. If the egg can survive up to 48 hours, there is a risk up to 2 days after ovulation (day 16) if sperm are present. Overall, this produces a potential 7-day fertility window.

13. Suggested answer: One of the first things to test would be temperature. At warmer temperatures, the sperm do not function properly. It would also be appropriate to test sperm numbers and shape. Men typically release 200,000,000 to 300,000,000 sperm per 384

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fertilization attempt. If the numbers were less, or the number of malformed sperm was unusually high, it could account for the problem. Finally, an analysis of the semen might determine if there were problems with the secretions from the seminal vesicles or prostate that may be causing the problem.

Biology and Society 14. Some issues and questions to consider: If it is technologically possible to save a baby, does that mean we have to do it? What would bring “the greatest good to the greatest number” of babies? If we diverted resources away from premature babies, would such resources really be used for prenatal care? Who pays for the treatment of premature babies? For prenatal care?

15. Some people will believe that using a surrogate mother is not acceptable under any circumstances and that other options, such as adoption, should be considered. Others may agree that surrogacy is an option but that the surrogate mother should be carefully selected and screened (for example, a family member who is not seeking financial gain). For those who believe that contracted surrogates are an option for infertile couples, their opinion on custody issues may be dependent on whether the surrogate mother was the donor of the egg. In any case, decisions on custody are extremely difficult to decide and many states are attempting to prevent the use of contracted surrogates. Should a couple have the right to sue a surrogate who breached a contract and decided to keep the baby or undertook activities such as drug use that would harm the baby?

16. Some issues and questions to consider: What characteristics might parents prefer? If parents had the right to choose embryos based on these characteristics, what are some possible benefits? What are potential pitfalls? Could an imbalance in the population result by favoring one sex over another? Is it okay to keep an embryo disease-free, but choose one with certain genes for hair or eye color? Intelligence? (Providing we learn the genetic basis of these traits.)

Additional Critical Thinking Questions The Process of Science 1. Why are egg cells usually much larger than sperm cells?

Suggested answer: Eggs are usually much larger than sperm because the developing embryo must have access to sufficient resources to allow it to develop to the point where it can obtain more nutrients from its environment. For example, in humans it can take 2 days to a week for the fertilized embryo to implant in the wall of the uterus. During this time, many cell divisions take place. If the egg were as small as the sperm, the embryo could never develop to the point where it could implant and begin to obtain nutrients from the mother.

The same is true of many other plants and animals. For this reason, at least one gamete is usually relatively large and immobile—usually the female. The other gamete—usually the male—is small and mobile. The sexual dichotomy ensures fertilization and sufficient nutrients for the developing embryo. Also, the egg typically is the source of mitochondria and other cellular organelles.

2. As a frog embryo develops, the neural tube forms from ectoderm along what will be the frog’s back, directly above the notochord. To study this process, a researcher carefully extracted a bit of notochord tissue and inserted it underneath the ectoderm, where the belly

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of the frog would normally develop. What can the researcher hope to learn from this experiment? Predict the possible outcomes. What experimental control would you suggest?

Suggested answer: The researcher might find out whether chemicals from the notochord stimulate the nearby ectoderm to become the neural tube, a process called induction.

Transplanted notochord tissue might cause ectoderm anywhere in the embryo to become neural tissue. Control: Transplant non-notochord tissue under the ectoderm of the belly area.

3. Variation in the length of the human menstrual cycle results mainly from individual differences in the preovulatory phase. The relatively uniform life span of the corpus luteum keeps the length of the postovulatory phase close to 14 days. A certain woman usually has 34-day cycles. If she last began menstruating on January 29 and it is now February 14, what is her reproductive status? Choose the best answer, and briefly explain why you chose it. a. Her endometrium has reached its peak development. b. An ovarian follicle has just started to grow. c. Unprotected intercourse now has a good chance of resulting in pregnancy. d. The LH concentration in her blood has surged upward, stopping menstruation.

Suggested answers: a. No. The endometrium reaches its peak development after ovulation. b. No. If menstruation started on January 29, it probably stopped around February 2, and the follicle started to grow then. By February 14, the follicle is very well developed. c. Correct. If the woman has 34-day cycles and we can assume that the postovulatory phase is 14 days, she has 20 days in her preovulatory phase. She started menstruating 17 days ago, so on February 14 it is probably 3 days before ovulation. Estrogen is rising rapidly, the follicle is about to ovulate, and (if recent data on the life span of sperm in the female reproductive tract are reliable) intercourse now could result in fertilization just after ovulation, in 3 days. d. No. Menstruation stopped about 5 days after it started, and the LH peak in the middle of the cycle has nothing to do with stopping it.

Biology and Society 4. New techniques for sorting sperm, combined with in vitro fertilization, make it possible for a couple to choose their baby’s sex. Would you want to do this if you had the chance?

Why or why not? What potential problems can you foresee if this procedure becomes widely available?

Some issues and questions to consider: Why might some people choose to have a girl?

A boy? Are these reasons important enough to go through the process of in vitro fertilization? Do you think more people would want to have a boy or a girl? Could an imbalance in the population result? What could be some problems to society with an imbalance of males or females? What problems could result if the procedure produced a baby of the opposite sex from what was planned?

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CHAPTER

27

Nervous, Sensory, and Locomotor Systems

14 This Chapter Matters Why 1. Nervous systems form a communication and coordination network in an animal’s body.

How we perceive, understand, and respond to our world are functions of this system.

2. The health and proper function of our senses greatly affects our ability to interact with our world.

3. The musculoskeletal system enables us to interact with our environment.

Chapter Objectives Biology and Society: The Seismic Sense of Elephants 1. Explain how echolocation, electroreception, and magnetoreception are used by animals with these systems.

An Overview of Animal Nervous Systems 2. Describe the structural and functional subdivisions of the nervous system.

3. Describe the structure and functions of neurons.

4. Define a resting potential and explain how it is generated.

5. Describe the changes that are associated with an action potential.

6. Explain how an action potential propagates itself along a neuron.

7. Compare the structures and locations of electrical and chemical synapses.

8. Describe the types of inputs a single neuron can receive and note the nature of the neuron’s response.

9. Describe the types and functions of human neurotransmitters.

10. Explain how drugs can alter chemical synapses.

The Human Nervous System: A Closer Look 11. Describe the general structure and functions of the brain and spinal cord.

12. Describe the functions of meninges and cerebrospinal fluid.

13. Compare the functions of the motor and autonomic divisions of the peripheral nervous system.

14. Compare the functions of the parasympathetic and sympathetic divisions of the peripheral nervous system.

15. Describe the three main regions of the human brain and note their parts and functions.

16. Note the detailed structures and functions of the cerebral cortex.

17. Describe the characteristics of major depression, bipolar disorder, and Alzheimer’s disease.

The Senses 18. Define sensory transduction, a receptor potential, and sensory adaptation. Illustrate each with examples.

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19. Describe the five general categories of sensory receptors found in animals. Note examples of each.

20. Describe the parts of the human eye and their functions.

21. Compare the structures, functions, distributions, and densities of rods and cones.

22. Explain the causes and symptoms of glaucoma, farsightedness, nearsightedness, and astigmatism.

23. List in order the structures of the ear involved in hearing. Describe the possible causes of hearing loss.

Locomotor Systems 24. Distinguish between the axial and appendicular skeletons. Describe three types of joints and provide examples of each.

25. Describe the complex structure of a bone, noting the major tissues that contribute to bones and their functions.

26. Describe the most common skeletal disorders. Explain why bones break and how we can help them heal.

27. Describe the structure and arrangement of the filaments found in a muscle cell.

28. Explain, in detail, how a muscle cell contracts.

29. Describe the structure and function of motor units.

30. Explain how a motor neuron signals a muscle fiber to contract.

31. Describe an example of a person using his or her sensory receptors, central nervous system, skeleton, and muscles to perform an activity.

Evolution Connection: Seeing UV 32. Explain how UV detection appears to have evolved in birds.

Lecture Outline I. Biology and Society: The Seismic Sense of Elephants 1. Many animals perceive the world in ways we cannot 2. Bats generate ultrasonic sounds in echolocation to a. detect echoes and b. determine the size, shape, location, speed, and direction of objects in the environment.

3. Many fish can detect prey by electroreception, detecting changes in electric fields 4. Many animals, including birds, fishes, turtles, and bees, navigate using magnetoreception, the ability to detect Earth’s magnetic fields 5. Elephants can communicate using low-rumbling infrasounds too low to be heard by human ears

II. An Overview of Animal Nervous Systems 1. The nervous system forms a communication and coordination network throughout an animal’s body 2. Neurons are nerve cells that carry electrical signals from one part of the body to another

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A. Organization of Nervous Systems 1. The nervous system of most animals has two main divisions a. The central nervous system (CNS) is made up of the brain and spinal cord (in vertebrates). b. The peripheral nervous system (PNS) is made up of mostly nerves that carry signals into and out of the CNS. 2. A nerve is a communication line made from cable-like bundles of neuron fibers tightly wrapped in connective tissue 3. The three interconnected functions of the nervous system are carried out by three types of neurons a. Sensory neurons function in sensory input, sending signals from sensory receptors to the CNS. b. Interneurons integrate sensory signals and formulate appropriate responses. c. Motor neurons function in motor output, the process of sending signals from integration centers to effector cells.

4. Effector cells perform the body’s responses to motor output B. Neurons 1. Neurons a. are the functional units of the nervous system, b. vary widely in shape, and c. share some common features.

2. The cell body houses a. the nucleus and b. other organelles.

3. Two types of extensions project from the cell body: a. dendrites i. receive incoming messages from other cells and ii. convey the information toward the cell body, and b. axons transmit signals toward another neuron or toward an effector cell.

4. Supporting cells a. outnumber neurons by as many as 50 to 1 and b. protect, insulate, and reinforce the neurons.

5. The myelin sheath a. forms an insulating material around an axon and b. helps speed electrical transmission along an axon.

6. An axon ends in a cluster of branches, each with a bulb-like synaptic terminal that relays signals to a. another neuron or b. an effector cell.

C. Sending a Signal through a Neuron 1. A resting neuron has potential energy that can be put to work to send nerve signals from one part of the body to another 2. This difference in charge (voltage) across the plasma membrane of a resting neuron is the resting potential ..

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3. The Action Potential 4. A stimulus is any factor that causes a nerve signal to be generated 5. A stimulus of sufficient strength can trigger an action potential, a nerve signal that carries information along a neuron 6. If the stimulus is strong enough, a sufficient number of channels open to reach the threshold, the minimum change in a membrane’s voltage that must occur to trigger the action potential 7. Propagation of the Signal 8. An action potential is a localized electrical event 9. To function as a long-distance signal, this local event must be passed along the neuron 10. Action potential propagation is like a “domino effect” along a neuron 11. Action potentials are a. all-or-none events and b. the same no matter how strong or weak the stimulus that triggers them.

D. Passing a Signal from a Neuron to a Receiving Cell 1. A synapse is a relay point a. between two neurons or b. between a neuron and an effector cell.

2. Synapses come in two varieties: a. electrical and b. chemical.

3. Chemical synapses a. have a narrow gap, the synaptic cleft, separating a synaptic terminal of the sending neuron from the receiving cell and b. rely on neurotransmitters, chemicals that carry information from one nerve cell to another kind of cell.

4. Chemical synapses can process extremely complex information 5. A neuron may receive input from hundreds of other neurons via thousands of synaptic terminals 6. Neurotransmitters 7. A variety of small molecules can act as neurotransmitters, including amines and peptides a. Amines i. are derived from amino acids and ii. affect sleep, mood, attention, and learning. b. Peptides i. are short chains of amino acids and ii. include endorphins, which decrease our perception of pain.

8. Drugs and the Brain 9. Many drugs, such as caffeine, nicotine, and alcohol, act at synapses by increasing or decreasing the normal effect of neurotransmitters 10. Prescription drugs used to treat psychological disorders alter the effects of neurotransmitters

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III. The Human Nervous System: A Closer Look 1. Although there is remarkable uniformity in the way nerve cells function, there is great variety in how nervous systems as a whole are organized 2. Vertebrate nervous systems are diverse in a. structure and b. level of sophistication.

A. The Central Nervous System 1. Vertebrate central nervous systems a. integrate information coming from the senses, b. transmit signals that produce responses, and c. consist of the i. brain, the master control center of the nervous system, and ii. spinal cord, a jellylike bundle of nerve fibers inside the spine.

2. The brain and spinal cord a. contain spaces and b. are filled with cerebrospinal fluid, a liquid that i. cushions the CNS and ii. helps supply the CNS with nutrients, hormones, and white blood cells.

3. Also protecting the brain and spinal cord are layers of connective tissues called meninges B. The Peripheral Nervous System 1. The vertebrate peripheral nervous system is divided into two functional components, the a. motor system and b. autonomic nervous system.

2. The motor system a. carries signals to and from skeletal muscles and b. mainly responds to external stimuli.

3. The autonomic nervous system a. regulates the internal environment and b. controls i. smooth and cardiac muscles and ii. organs and glands of the digestive, cardiovascular, excretory, and

endocrine systems.

4. The autonomic nervous system contains two sets of neurons with opposing effects on most organs a. The parasympathetic division primes the body for digesting food and resting. b. The sympathetic division prepares the body for intense, energy-consuming activities.

C. The Human Brain 1. The human brain is more powerful than the most sophisticated computer and consists of a. up to 100 billion intricately organized neurons and b. many more supporting cells.

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2. The brain is divided structurally into three regions, the a. hindbrain, b. midbrain, and c. forebrain 3. The brainstem a. consists of the hindbrain (medulla oblongata and pons) and the midbrain and b. serves as a sensory filter, selecting which information to pass on.

4. The cerebellum, another part of the hindbrain, is a planning center for body movements 5. The forebrain contains the most sophisticated integrating centers in the brain a. The thalamus relays information to the cerebral cortex. b. The hypothalamus has many regulatory functions.

6. The Cerebral Cortex 7. The cerebrum a. is the largest and most complex part of the brain and b. consists of the right and left cerebral hemispheres.

8. The corpus callosum connects the cerebral hemispheres, enabling them to process information together 9. The cerebral cortex a. is a highly folded layer of tissue that forms the surface of the cerebrum, b. accounts for over 80% of the total brain mass, c. contains about 10 billion neurons, and d. helps produce our most distinctive human traits.

10. The right and left cerebral hemispheres have four lobes, each named for a nearby skull bone 11. Higher mental activities occur in association areas of the brain 12. Brain Trauma 13. Evidence from brain surgery indicates that patterns of lateralization are not fixed 14. Neurologists sometimes gain insight into how the brain works from people who have suffered brain trauma 15. In 1848, a railroad accident involving a man named Phineas Gage a. propelled a three-foot-long spike through his head and b. caused significant changes in his personality.

16. Neurological Disorders 17. Neurological disorders can also affect brain function a. Major depression may be associated with extreme and persistent sadness and loss of interest in pleasurable activities. b. Bipolar disorder, or manic-depressive disorder, involves extreme mood swings. c. Alzheimer’s disease is a form of mental deterioration, or dementia, characterized by i. confusion, ii. memory loss, and iii. a variety of other symptoms.

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IV. The Senses 1. Sensory structures a. gather information and b. pass it on to the CNS. A. Sensory Input 1. Sensory input is the process of using receptors to a. sense the environment and b. send information about it to the CNS to be integrated and acted upon.

2. Sensory transduction is the conversion of a stimulus signal to an electrical signal by a sensory receptor cell 3. Sensory Transduction 4. Receptor potentials a. are changes in membrane potentials caused by sensory stimuli and b. vary in intensity, depending on the strength of the stimulus.

5. Sensory adaptation a. causes some sensory receptors to be less sensitive when they are stimulated repeatedly and b. keeps the body from continuously reacting to normal background stimuli.

6. Types of Sensory Receptors 7. Sensory receptors can be grouped into five categories, which work in various combinations to produce the five human senses 8. A section of human skin reveals why the surface of our body is sensitive to such a variety of stimuli 9. Pain receptors sense stimuli that may indicate tissue damage 10. Thermoreceptors detect heat or cold 11. Mechanoreceptors are stimulated by various forms of mechanical energy 12. Chemoreceptors respond to chemicals in the external environment or body fluids 13. Electromagnetic receptors respond to electricity, magnetism, or light (photoreceptors) B. Vision 1. Human eyes are able to a. detect a multitude of colors, b. form images of faraway objects, and c. respond to minute amounts of light energy.

2. Structure of the Human Eye 3. The human eye consists of a. a tough outer covering, the sclera, b. a transparent cornea in front of the lens, c. an iris with a center opening, the pupil, and d. the retina, at the back of the eyeball, where photoreceptors respond to light.

4. The optic nerve connects the retina to the brain 5. Two fluid-filled chambers make up the bulk of the eye a. The large chamber behind the lens is filled with jellylike vitreous humor. b. The much smaller chamber in front of the lens contains a thinner fluid called the aqueous humor. ..

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6. Function of the Human Eye 7. The cornea lets light into the eye and helps focus light 8. The iris a. regulates the size of the pupil and b. lets light shine onto the lens.

9. The lens of the eye changes shape and focuses light onto the retina 10. Photoreceptors 11. The human retina contains two types of photoreceptors a. Rods i. are extremely sensitive to light, ii. perceive only shades of gray, and iii. are distributed at the outer edges of the retina. b. Cones i. are less sensitive to light, ii. can distinguish color, and iii. are distributed at the retina’s center of focus.

12. Rods and cones a. detect light using an array of disks containing light-absorbing pigments and b. convert a stimulus to an electrical signal.

13. Other retinal neurons a. integrate these receptor potentials and b. generate action potentials that travel along the optic nerve to the brain.

14. Vision Problems and Corrections 15. The most common visual problems are a. nearsightedness, the inability to focus well on distant objects, b. farsightedness, the inability to focus well on near objects, and c. astigmatism, blurred vision caused by a misshapen lens or cornea.

C. Hearing 1. The Structure of the Human Ear 2. The ear is composed of a. the outer ear, b. the middle ear, and c. the inner ear.

3. The outer ear a. consists of the flap-like pinna and the auditory canal, b. collects sound waves, and c. passes sound waves to the eardrum, a sheet of tissue that separates the outer ear from the middle ear.

4. In the middle ear, the vibrating eardrum passes the sound waves to three small bones that relay the sound to the inner ear 5. The Eustachian tube a. conducts air between the middle ear and back of the throat and b. allows air pressure to stay equal on either side of the eardrum.

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6. The inner ear consists of fluid-filled channels in the bones of the skull 7. One of the channels, the cochlea, is a long coiled tube 8. The cochlea contains the organ of Corti, which a. is the actual hearing organ and b. includes hair cells, the receptor cells of the ear.

9. Function of the Human Ear 10. When we hear, sound waves are a. collected by the pinna and the auditory canal, b. channeled to the eardrum, making it vibrate, c. passed through the middle ear bones, and d. transmitted to the cochlea.

11. The waves generated in the cochlear fluid move hair cells of the organ of Corti against an overlying membrane, triggering receptor potentials and sending nerve signals to the brain 12. Louder sounds cause a. greater movement of the hair cells and b. more action potentials.

13. Hearing Problems 14. Deafness, the loss of hearing, can be caused by a. middle ear infections, b. injury, such as a ruptured eardrum, c. stiffening of the middle-ear bones (a common age-related problem), or d. overexposure to loud noises.

V. Locomotor Systems 1. Movement a. is one of the most distinctive features of animals and b. relies upon an interplay of organ systems 2. The nervous system issues commands to the muscular system 3. The muscular system exerts the forces that make animals move by acting on the skeletal system A. The Skeletal System 1. The skeletal system provides a. anchoring, b. support, and c. protection of internal organs.

2. Organization of the Human Skeleton 3. All vertebrates have an endoskeleton, situated among soft tissues, and consisting of a. bones, hard supporting elements, and b. cartilage at points of flexibility.

4. The axial skeleton a. supports the axis of the body and b. includes the skull, vertebral column, and ribs.

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5. The appendicular skeleton is made up of the bones of the a. limbs, b. shoulders, and c. pelvis.

6. The bones of the skeleton are held together at movable joints by strong fibrous tissues called ligaments 7. Much of the versatility of our skeleton comes from three types of movable joints: a. ball-and-socket joints in the shoulder and hip, b. hinge joints that permit movement in a single plane, and c. pivot joints that allow rotation.

8. The Structure of Bones 9. Bones a. are covered with a sheet of fibrous connective tissue, b. have cartilage at their ends that cushions the joints, and c. are supported by blood vessels.

10. The central cavity of a long bone contains yellow bone marrow, which is mostly stored fat 11. The end of a long bone contains red bone marrow, a specialized tissue that produces blood cells 12. Skeletal Diseases and Injuries 13. The human skeleton is a. quite strong and provides reliable support, but b. susceptible to disease and injury.

14. Arthritis a. is an inflammation of the joints and b. affects one out of every seven people in the United States.

15. Rheumatoid arthritis a. is an autoimmune disease, b. usually begins between ages 40 and 50, and c. affects more women than men.

16. Osteoporosis a. makes bones thinner and more porous and b. is most common in women after menopause.

17. Bones are rigid but not inflexible 18. If a force exceeds a bone’s capacity to bend, the result is a broken bone, or fracture 19. The treatment of a fracture involves a. putting the bone back into its natural shape and b. immobilizing it until the body’s natural bone-building cells can repair the fracture.

B. The Muscular System 1. The muscular system is made of all the skeletal muscles in the body 2. Skeletal muscles a. are attached to the skeleton and b. produce body movement by interacting with the skeleton.

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3. Tendons connect muscles to bones 4. Antagonistic pairs of muscles produce opposite movements 5. The Cellular Basis of Muscle Contraction 6. Skeletal muscle is made up of a hierarchy of smaller and smaller parallel strands 7. Each skeletal muscle cell, or fiber, a. contains bundles of myofibrils and b. is called striated, because the myofibrils exhibit alternating light and dark bands when viewed with a light microscope.

8. A sarcomere is a. the region between two dark, narrow lines in the myofibril and b. the functional unit of muscle contraction.

9. A myofibril is composed of regular arrangements of two kinds of filaments a. Thin filaments are made mostly of the protein actin. b. Thick filaments are made mostly of the protein myosin.

10. A sarcomere contracts (shortens) when its thin filaments slide past its thick filaments 11. In the sliding-filament model, the key events are the binding between a. parts (called heads) of the myosin molecules in the thick filaments and b. specific sites on actin molecules in the thin filaments.

12. Contraction requires energy supplied by ATP 13. Motor Neurons: Control of Muscle Contraction 14. Motor neurons a. are part of the central nervous system, b. release neurotransmitters that cause muscle fibers to contract, and c. can branch to a number of muscle fibers.

15. A motor unit consists of a. a neuron and b. all the muscle fibers it controls.

16. Motor units may consist of a. just one muscle fiber or b. up to several hundred muscle fibers.

17. The strength of a muscle contraction depends on the number of motor units activated C. The Process of Science: How Do New Senses Arise?

1. Observation: Two species of electric fish use special ion channel proteins in muscle cells to generate electric fields 2. Question: Did different ion channel proteins evolve in these two species?

3. Hypothesis: Ion channel genes of the two electric species had mutated in unique ways 4. Experiment: The DNA sequence of the genes in the two electric fish was determined and compared to a closely related but nonelectric South American fish 5. Results: A single ion channel gene duplicated in the common ancestor, into forms a and b a. The a form mutated differently in the two electric fish species. b. The b form retained its muscle functions in electric and non electric fishes.

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D. Stimulus and Response: Putting It All Together 1. An animal’s nervous system connects sensations derived from environmental stimuli to responses carried out by its muscles E. Evolution Connection: Seeing UV 1. Many birds can see ultraviolet light, which seems to be important in a. social communication and b. food gathering.

2. Researchers have discovered that a single amino acid change in the pigment protein rhodopsin converted it to a UV-detecting form 3. This is another example of a large-scale change that can be traced to a small change: a single mutation

Chapter Guide to Teaching Resources An Overview of Animal Nervous Systems Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges of ions, and natural electrical attractions may be unfamiliar assumptions. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).

2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees.” Regularly relate the three fundamental functions of the nervous system—sensory input, integration, and motor output—to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure.

3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table, for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will enable easy reference to check an action of a drug.

Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation.

2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog–like item and bring along three hot dog buns.

3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick, clear demonstration. As noted in the text, potential electrical energy can be stored in a battery.

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4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments.

5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium.

6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency.

7. Students may better comprehend the idea of the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person can reach a “threshold” where he or she is stimulated enough to get up and turn it off.

8. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus?

9. The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry).

10. Drugs that block a receptor act like someone who has parked in your parking space. Your vehicle cannot “bind” to your “receptor.”

11. Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage.

12. An analogy to the diverse signal input to a neuron might be helpful, if not amusing.

A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience.

13. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide one’s medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell illegal drugs on the street?

14. Students may have heard about “chemical imbalances” in the brain, but not known specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

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The Human Nervous System: A Closer Look Student Misconceptions and Concerns 1. Popular media often suggests that certain people are “left-brained,” whereas others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is this clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity.

2. Students may think of the human brain as completely unique. Yet, the anatomical components of the human brain mirror the basic components found in many other vertebrates. These similarities are so extensive that sheep brains are often studied in biology laboratories to better understand human anatomy.

3. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion.

4. Students often think of the motor system as “voluntary” and directed by conscious thoughts. You might point out to your students that they are not likely concentrating on contracting the various muscles needed to maintain their posture as they sit in class.

Teaching Tips 1. Tables such as 27.1, which provide summaries of structures and functions, can relieve lectures from the repetition of tedious detail. Instead, more class time can be spent on more interesting and meaningful aspects of the topic. Such tables also facilitate the creation of matching questions on exams!

2. Challenge your students to explain what we mean by a “head” in an animal. Why are heads concentrated on one end of the body? Why is the mouth usually, but not always, associated with the head? (The opening to the digestive tract of a planarian is in the middle of the body.) An analogy might be made to an airplane, whose pilot sits inside the cockpit at the front of the plane, gathering and processing information about where the plane is headed.

Why are all six of our major senses (taste, smell, sight, touch, sound, and balance) all centered in our heads?

3. Students often are surprised to learn that their brain is hollow, although some students may know that the central nervous system is surrounded by cerebrospinal fluid. The basic development of the brain and spinal cord arise from an embryonic tube.

4. Students often remember the functions of the autonomic nervous system better by thinking of them as “automatic.”

5. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses cannot be quickly reversed. You might want to encourage students to think of how long it usually takes for them or others to calm down after having become extremely nervous or upset. Time and separation from the source of stress are usually required. For example, those who take a long walk to calm down often find, in the mild exercise and the retreat from the situation, an emotional comfort that also makes biological sense.

6. Students may remember the functions of the sympathetic division as “sympathetic” to our problems. For example, the sympathetic nervous system may react to stressful situations by preparing us to fight or to run (although we often choose to do neither).

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7. As students learn about the structure and function of the cerebral cortex, they are actually using these sets of cells to think about these cells. As student understanding grows, these sets of cells become increasingly aware of their own properties, in a process that is like looking in a mirror!

8. Sleep seems to be involved in learning and memory. Study strategies that involve cramming large amounts of information into the memory in a short period of time may not permit enough sleep and review for deeper understanding. Students who engage in such practices may easily be confused on an exam. The strategy of processing smaller amounts of information over a longer period of time, allowing for rest and frequent review, is likely to result in the retention of a better-integrated body of information.

9. Moving information from short-term memory to long-term memory requires frequent rehearsal. Using note cards to create questions and answers based upon the information for an exam is one form of rehearsal that can be very effective when studying basic information. This chapter helps students understand the underlying physiological basis of many successful study techniques.

10. The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website www.census.gov/main/www/popclock.html. At the time of the writing of this book, the U.S. population was nearly 315 million people.

11. The frequent occurrence of the neurological disorders discussed in this chapter makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class.

12. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure.

The Senses Student Misconceptions and Concerns 1. We tend to think the world is that which we perceive. These modules on the sensory systems provide hints of the world that other organisms detect. From sounds and wavelengths above and below our spectrum to concentrations of scents beyond our detection, other organisms may perceive the world very differently from us. Consider encouraging your students to imagine the world as other organisms perceive it and thereby gain insight into their existence.

2. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. For example, digital cameras and DVD recordings rely on electronic storage and signal conversions to store and generate sounds and images.

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3. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.)

Teaching Tips 1. The natural tendency to wonder about our world seems sadly to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences.

Perhaps you might have your class ask questions about their sensory experiences on 3 × 5 cards, which you can selectively answer later, and as time permits. The following tips include some examples.

2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain.

3. You might want to ask your students to consider the uneven distribution of sensory receptors in the human body. Sensory receptors may be concentrated in regions where environmental inputs are focused, such as the eyes and ears, or spread more generally, such as skin or the walls of the digestive tract.

4. Students can better understand sensory adaptation by thinking about events in their lives.

Perhaps they notice a distinct smell in the hallways and laboratories of the science facilities at your school. However, after a few minutes, we tend not to notice the smells as much. These experiences illustrate sensory adaptation.

5. Bits of cellular debris can drift within the vitreous humor and temporarily distort our image. These bits are commonly called “floaters.”

6. Some students might recognize the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure of a sphere.

7. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because tears drain into our nose.

8. Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots: the more dots to paint the picture, the clearer the image.

9. Cataracts, a clouding of the lens of the eye, are a common vision problem. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce exposure to UV light.

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cells. This pigment prevents reflected light from interfering with the detection of new light.

Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by this pigment layer, and instead reflects off of red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red-colored blood, and make the pupils appear red.

11. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods.

Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax.

12. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class.

13. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. Your students may not understand the concept of triangulation.

14. The lumping together of hearing and balance in the five senses learned in elementary school may result in a decreased appreciation for the sense of balance. Yet, hearing and balance are clearly separate senses. (Hearing-impaired people can still walk!) Consider asking your students to close their eyes and tilt their heads in different directions. How can they tell the position of their heads? In addition to the semicircular canals, stretch receptors in the neck provide positional information.

15. Consider asking your students why each of us has two ears. In general, it helps us locate the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source.

Of course, there are exceptions.

16. Ask your class to consider the hypothesis that motion sickness results from mixed sensory inputs from the eyes and balance organs. For example, do students agree that they might be able to read while traveling down a straight highway, but become sick if they read on a winding road? How might standing on the outside of a boat be different from standing deep inside a boat, unable to see the horizon? Considering the causes of motion sickness affords an opportunity to practice informed critical thinking.

17. Students might wonder why their voice played back from a recording sounds different from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones, cartilage, and soft tissues.

These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air.

18. The range of human hearing and the effect of age can be demonstrated by a popular highpitched ringtone. Searching “high-pitched ringtone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ringtone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear.

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detection of danger or vital communication. Consider discussing these important safety concerns with your class.

20. Students that have sampled colognes or perfumes may have noticed that after an initial sniff, the scent tends to linger. Assuming that the scented liquid was not touched to the nose region, the lingering smell may result from its persistence in the mucus covering the sensory cells. Without the cilia of the olfactory region to sweep away the mucus containing the scent, the smell might last much longer.

Locomotor Systems Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored.

2. Muscle cells are only able to contract. None can actively relengthen. Challenge your students to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.)

3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that enables our bones to accommodate the effects of mass and motion.

Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.

2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design.

The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied.

3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints.

4. People do not often consume the nutritious elements inside of bone (although these tissues provide flavoring in soups that include a soup bone). However, in times and places with limited nutritional resources, boiling bones and/or breaking them open allows access to these additional nutrients.

5. Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass.

6. Students may need help understanding how the contraction of sarcomeres over microscopic distances results in the perceptible motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten 404

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each car by 1 foot, how much shorter will the train be? (Answer: 100 feet.) The collective contraction of sarcomeres adds up to much larger movements.

7. One way to help explain motor units is to provide an analogy with the controls for the sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just as in muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit).

8. Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases, additional nuclei have been adaptive. A general analogy is to a daycare. At some point, as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus.

9. The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles made up primarily of just one of these types of muscle fibers. Dark meat in birds has higher amounts of myoglobin, fat, and capillaries associated with sustained contractions.

White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick bursts, such as the contractions of the pectoral muscles to generate lift during takeoff.

Artificial selection has resulted in variations on these basic differences.

Key Terms action potential Alzheimer’s disease appendicular skeleton aqueous humor arthritis association areas astigmatism auditory canal autonomic nervous system axial skeleton axon ball-and-socket joints bipolar disorder brain brainstem cell body central nervous system (CNS) cerebellum cerebral cortex cerebrospinal fluid cerebrum chemoreceptors cochlea ..

cones cornea corpus callosum dendrites eardrum effector cells electromagnetic receptors endoskeleton Eustachian tube farsightedness hinge joint hypothalamus inner ear integration interneurons iris lens ligaments major depression mechanoreceptors medulla oblongata meninges middle ear motor neurons

motor output motor system motor units muscular system myelin sheath myofibrils nearsightedness nerve nervous system neurons neurotransmitter optic nerve osteoporosis outer ear pain receptors parasympathetic division peripheral nervous system (PNS) photoreceptors pinna pivot joint pupil receptor potential resting potential

retina rheumatoid arthritis rods sarcomeres sclera sensory adaptation sensory input sensory neurons sensory transduction skeletal muscles skeletal system spinal cord stimulus supporting cells sympathetic division synapse synaptic cleft synaptic terminal tendons thermoreceptors thick filaments thin filaments threshold vitreous humor

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Word Roots aqua = water; humor = fluid (aqueous humor: a thin watery fluid in front of the lens of the eye) arthro = joint; itis = inflammation (arthritis: inflammation of the joints of the skeleton) audi = hear (auditory canal: the tube that channels sound to the eardrum) auto = self (autonomic nervous system: a subdivision of the motor system of vertebrates that regulates the internal environment) bi = two (bipolar disorder: a manic-depressive disorder in which a person switches between two extremes) cerebro = brain (cerebrum: the largest and most sophisticated part of the human brain) chemo = chemical (chemoreceptors: sensory cells that respond to chemicals) dendro = tree (dendrite: one of usually numerous, short, highly branched processes of a neuron that conveys nerve impulses toward the cell body) endo = inner (endoskeleton: a skeleton inside the body) hypo = below (hypothalamus: the master control center of the endocrine system, located below the thalamus in the brain) inter = between (interneurons: an association neuron; a nerve cell within the central nervous system that forms synapses with sensory and motor neurons and integrates sensory input and motor output) myo = muscle (myofibril: a contractile thread in a muscle cell) neuro = nerve; trans = across (neurotransmitter: a chemical messenger released from the synaptic terminal of a neuron at a chemical synapse that diffuses across the synaptic cleft and binds to and stimulates the postsynaptic cell) osteo = bone; pori = a hole (osteoporosis: a disease of thinning and porous bones) para = near (parasympathetic division: one of two divisions of the autonomic nervous system) photo = light (photopsin: a light-sensing pigment found in cones) syn = together (synapse: the locus where a neuron communicates with a postsynaptic cell in a neural pathway) thermo = heat (thermoreceptors: sensory receptors that detect heat)

Relevant Songs to Play in Class “Insane in the Brain,” Cypress Hill

“19th Nervous Breakdown,” The Rolling Stones

“Check My Brain,” Alice in Chains

“Nervous Breakdown,” Rise Against

“Think,” Aretha Franklin

“Brain Stew,” Green Day

Answers to End-of-Chapter Questions The Process of Science 13. Suggested answer: The corpus callosum allows communication between the two cerebral hemispheres. This structure allows for the integration of information. This must be the damaged structure that accounts for the patient’s problems.

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14. Suggested answer: Students could suggest experiments that test the ability of a person to either have a better depth perception with two eyes or better location of a source of sound with two ears.

Biology and Society 15. Some issues and questions to consider: Some people might be against the use of embryonic stem cells for any disorder. This may be related to religious or moral beliefs, or the belief that people are attempting to clone people. Potentially, some people may not be aware of the source of these stem cells and may be against their use if they believe that the cells come from elective abortions. It is important to discuss where scientists get stem cells for research. Other people may agree with the use of stem cells in research due to the potential to cure diseases that currently can lead to a fatal outcome. Some people who may have a neutral opinion on the issue might be swayed by the thought of a loved one who might be helped by stem cell therapy.

16. Some issues and questions to consider: What is the role of alcohol in crime? What are its effects on families and in the workplace? In what ways is an individual responsible for alcohol abuse? The family? Society? Who is affected by alcohol abuse? How effective are treatment and punishment in curbing alcohol abuse? Who pays for alcohol abuse and consequent treatment or punishment? Is it possible to enjoy alcohol without abusing it?

17. Some issues and questions to consider: As with any known health risk, there is debate regarding how many and what type of warnings should be provided and what limits should be imposed on personal choices. Students might also debate whether warnings will be headed, and what else could be done to limit hearing damage.

Additional Critical Thinking Questions The Process of Science 1. Sixty degrees Fahrenheit at the end of a hot summer feels cold, whereas the same temperature at the end of a cold winter feels hot. How is it that the same stimulus produces two different sensations? Can you think of another stimulus, besides temperature, that produces this effect?

Suggested answer: Perception is always relative. The brain compares present experiences with previous ones and makes judgments based on that analysis. Therefore, at the end of a cold winter, 60°F is warm compared to 30°F, whereas at the end of a hot summer it is cold compared to 100°F. Also, hormone levels in our body such as thyroxine can alter our metabolism, which will also affect the way we perceive temperature. Another example that shows the same effect is taste. It is difficult to taste the sweetness of mildly sweet food after eating a candy bar.

2. When a person dies, muscles become rigid and fixed in position, a condition known as rigor mortis. Rigor mortis occurs because muscle cells are no longer supplied with ATP. Also, calcium flows freely into dying cells. Explain, in terms of the mechanism of muscle contraction described in this chapter, why the presence of calcium and the lack of ATP would cause muscles to become rigid, instead of limp, after death.

Suggested answer: ATP causes the myosin heads of the thick filaments to detach from the thin filaments. If there is no ATP present, the myosin heads remain attached to the thin filaments, and the muscle fiber remains fixed in position.

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Biology and Society 3. Athletes sometimes take anabolic steroids illegally to increase the muscle size that occurs with training. In young people, whose bones are still growing, steroids also act to speed up the conversion of cartilage to bone. With regard to bone growth, what might be some negative consequences of steroid use by young athletes? Does steroid use seem to you to be worth the risks? Why or why not? As a competing athlete, would you use anabolic steroids if you knew you could get away with it? Why or why not?

Some issues and questions to consider: The major negative consequence is that the bones will become completely hardened before they have grown to their full size. This means that the steroid user will be shorter than he or she would otherwise have been. Do steroid users know this? Do they think the effects of steroids are temporary or reversible? Why is such emphasis placed on appearance and athletic prowess? Will steroid users later regret their use? Even if steroid use were not against the rules, would it be acceptable? What are the long-term effects of steroid use? If athletes use steroids and they break a record, should that record be counted?

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CHAPTER

28

The Life of a Flowering Plant

Why This Chapter Matters 1. Plants provide humans with food, lumber, fabric, paper, industrial chemicals, and medicines.

2. Plants provide shelter, food, and breeding areas for animals, fungi, and microorganisms.

3. The human diet consists almost entirely of plants and animals that ate plants.

4. Humans could not survive without the oxygen produced by plant photosynthesis.

Chapter Objectives Biology and Society: The Buzz on Coffee Plants 1. Describe the history of coffee cultivation.

The Structure and Function of a Flowering Plant 2. Compare the structures of monocots and dicots.

3. Compare the structures and functions of root and shoot systems. Explain how “pinching back” a plant helps make the plant more bushy.

4. Describe and compare the structures and functions of a taproot, runner, rhizome, tuber, and tendril.

5. Compare the structure and function of xylem and phloem.

6. Describe the structures, functions, and arrangements of the dermal tissue system, vascular tissue system, and ground tissue system in roots, shoots, and leaves.

7. Compare the structure and function of parenchyma cells, collenchyma cells, sclerenchyma cells, tracheids, vessel elements, water-conducting cells, and food-conducting cells.

Plant Growth 8. Compare indeterminate and determinate growth. Distinguish between annuals, biennials, and perennials.

9. Distinguish between primary and secondary growth.

The Life Cycle of a Flowering Plant 10. Describe the parts of a flower and their functions. Relate this structure to the life cycle of an angiosperm.

11. Describe the processes and events that lead to double fertilization.

12. Explain how a seed forms and describe the advantages of seed dormancy.

13. Describe the structure, formation, and functions of fruit.

14. Describe the general process of germination in a pea plant.

Evolution Connection: The Problem of the Disappearing Bees 15. Explain how flowering plants and land animals each gain from their mutually beneficial relationship.

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Lecture Outline I. Biology and Society: The Buzz on Coffee Plants 1. Human progress has always depended upon expanding our use of plants for a. food, b. fuel, c. clothing, and d. other trappings of modern life.

2. Coffee is one of the most important agricultural products in the world today 3. Ground coffee is made from the seeds of plants belonging to several species in the genus Coffea 4. Coffee was discovered in Ethiopia during the 1200s 5. By the 1700s, imported coffee plants were an important crop in the Americas 6. People love coffee because of the jolt we get from caffeine, which a. is naturally produced by the coffee plant as a self-defense against herbivores and b. stimulates the nervous system of those who consume it.

II. The Structure and Function of a Flowering Plant 1. Angiosperms a. have dominated the land for over 100 million years and b. account for about 250,000 species alive today.

2. Most of our foods come from 100 or so species of domesticated flowering plants including a. roots such as beets and carrots, b. fruits of trees and vines such as apples, nuts, berries, and squash, c. fruits and seeds of legumes, such as peas, peanuts, and beans, and d. grains, fruits of grasses, such as wheat, rice, and corn.

A. Monocots and Dicots 1. On the basis of several structural differences, angiosperms are classified into two groups: a. monocots and b. dicots.

2. The names of the groups refer to cotyledons, the first leaves to emerge from a growing seedling a. A monocot embryo has one seed leaf. b. A dicot embryo has two seed leaves.

3. The largest group of dicots is the eudicots 4. Most flowering plants are eudicots B. Plant Organs: Roots, Stems, and Leaves 1. Plants have a. organs made up of different tissues and b. tissues made up of one or more types of cells.

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2. The evolution of plants onto land around 475 million years ago required a. structures for absorbing water and minerals from the soil, b. a large light-collecting surface, c. the ability to take in carbon dioxide from the air for photosynthesis, and d. adaptations for surviving dry conditions.

3. In a land plant, these vital functions are performed by a. roots (below ground) and b. shoots (above ground), including i. stems, ii. leaves, and iii. flowers.

4. Roots 5. A plant’s roots a. anchor it in the soil, b. absorb and transport minerals and water, and c. store food.

6. All of a plant’s roots make up its root system 7. Root hairs a. are tiny projections near the root tips and b. increase the surface area of the root, providing an extensive outer layer for absorption of water and minerals.

8. Large taproots a. occur in plants such as carrots, turnips, sugar beets, and sweet potatoes and b. store food in the form of carbohydrates such as starch.

9. Other types of modified roots include buttress roots, aerial roots that a. look like buttresses and b. support the tall trunks of the trees that produce them.

10. Stems 11. The shoot system of a plant is made up of a. stems, b. leaves, and c. structures for reproduction (flowers).

12. Stems generally a. grow above the ground and b. support the leaves and flowers.

13. A stem has a. nodes, the points at which leaves are attached, and b. internodes, the portions of the stem between nodes.

14. When a plant stem is growing in length, the terminal bud, at the apex (tip) of the stem, has a. developing leaves and b. a compact series of nodes and internodes.

15. The axillary buds, one in each of the crooks formed by a leaf and the stem, are usually dormant ..

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16. In many plants, the terminal bud produces hormones that inhibit growth of the axillary buds, a phenomenon called apical dominance 17. Removing the terminal bud can make a plant bushier 18. Stems can take many forms a. Strawberry plants have horizontal stems, or runners, that i. grow along the ground surface and ii. serve as a form of asexual reproduction. b. Iris or ginger plants have horizontal underground stems called rhizomes. c. A potato plant has rhizomes ending in enlarged structures called tubers. d. The “eyes” of a potato are axillary buds, which can grow into new plants, allowing potatoes to be easily propagated.

19. Leaves 20. Leaves are the primary sites of photosynthesis in most plants and consist of a. a flattened blade and b. a stalk, or petiole, which joins the leaf to the stem.

21. Leaves are highly varied a. Leaves can be either simple or compound. b. Grasses and most other monocots have long leaves without petioles. c. A modified leaf called a tendril can help plants such as sweet peas or grapes climb up their supports. d. The spines of the cactus are modified leaf parts.

C. Plant Tissues and Tissue Systems 1. Tissues are a group of cells that together perform a specialized function 2. A tissue system consists of one or more tissues organized into a functional unit within a plant. For example, vascular tissue called a. xylem conveys water and dissolved minerals upward from the roots to the stems and leaves and b. phloem tissue transports sugars from leaves or storage tissues to other parts of the plant.

3. Plant organs a. include roots, stems, and leaves, and b. are made up of three tissue systems: i. the dermal tissue system, ii. the vascular tissue system, and iii. the ground tissue system.

4. Each tissue system is a. continuous throughout the entire plant body but b. arranged differently in leaves, stems, and roots.

5. The dermal tissue system a. forms an outer protective covering and b. forms a first line of defense against physical damage and infectious organisms.

6. On leaves and on most stems, dermal cells secrete a waxy coating called the cuticle, which helps prevent water loss

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7. The vascular tissue system a. provides support and long-distance transport and b. includes xylem and phloem.

8. The ground tissue system a. accounts for most of the bulk of a plant and b. has diverse functions, including i. photosynthesis, ii. storage, and iii. support.

9. A cross section of a eudicot root illustrates the three tissue systems a. The epidermis (the outer layer of the dermal system) is a single layer of tightly packed cells covering the entire root. b. In the center of the root, the vascular tissue system forms a cylinder, with i. xylem cells that radiate from the center and ii. phloem cells that fill in the wedges between the spokes. c. The ground tissue system forms the cortex, where cells i. store food and ii. take up water and minerals. iii. The innermost layer of cortex is the endodermis, a thin cylinder one cell thick that is a selective barrier that regulates the passage of substances between the cortex and the vascular tissue.

10. All plant stems have vascular tissue systems arranged in numerous vascular bundles a. The location and arrangement of these bundles differ between monocots and eudicots. b. In eudicots, another part of the ground tissue system, known as the pith, i. fills the center of the stem and ii. is often important in food storage.

11. The three tissue systems occur in eudicot leaves a. The epidermis contains stomata, tiny pores between two specialized guard cells, which regulate the opening and closing of the stomata. b. The ground tissue system of a leaf contains the mesophyll, the main site of photosynthesis. c. The leaf’s vascular tissue system is made up of a network of veins.

D. Plant Cells 1. Most plant cells have three unique structures a. Chloroplasts are the sites of photosynthesis. b. A large central vacuole containing fluid helps maintain the cell’s firmness (turgor). c. A protective cell wall i. surrounds the plasma membrane and ii. consists largely of the carbohydrate cellulose.

2. Parenchyma cells a. are the most abundant type of cell in most plants and b. perform a variety of functions, such as i. food storage and ii. photosynthesis. ..

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3. Collenchyma cells a. resemble parenchyma cells in lacking secondary walls, but they have unevenly thickened primary walls and b. provide support in parts of the plant that are actively growing.

4. Sclerenchyma cells a. have thick secondary cell walls usually strengthened with lignin, the main chemical in wood, and b. provide support to the plant.

5. Angiosperms have two types of water-conducting cells: a. tracheids, long, thin cells with tapered ends, and b. vessel elements, wider, shorter cells that are less tapered.

6. Water-conducting cells a. are arranged in chains of hollow tubes with overlapping ends and b. form a system of water-carrying tubes.

7. Food-conducting cells a. are also arranged end to end, forming tubes, but b. unlike water-conducting cells, remain alive at maturity.

III. Plant Growth 1. Most animals are characterized by determinate growth, ending growth after reaching a certain size 2. Most species of plants have indeterminate growth, the ability to grow for as long as they live 3. The life span of plants varies greatly a. Annuals live for only a single year or growing season. b. Biennials i. live for two years and ii. typically produce flowers and seeds in their second year. c. Perennials may live for many years.

A. Primary Growth: Lengthening 1. Growth in all plants is made possible by tissues called meristems, undifferentiated (unspecialized) cells that divide when conditions permit, generating new cells and tissues 2. Apical meristems a. occur at the tips of roots and in the buds of shoots and b. enable primary growth, growth in length.

3. A growing root a. is pushed through the soil by primary growth and b. contains a root cap that protects the actively dividing cells.

4. Primary growth in a root is achieved by a. cell division and b. cell elongation, mainly by taking up water.

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B. Secondary Growth: Thickening 1. The stems and roots of many plant species also thicken by a process called secondary growth a. Such thickening is most evident in woody plants, including trees, shrubs, and vines. b. The stems of woody plants last from year to year and consist mainly of thick layers of mature, mostly dead xylem tissue called wood.

2. The vascular cambium is a cylinder of actively dividing cells between the primary xylem and primary phloem 3. Secondary growth adds cells on either side of the vascular cambium 4. Annual growth rings result from the layering of secondary xylem 5. The layers are visible as rings because of uneven activity of the vascular cambium during the year 6. When secondary growth begins, the epidermis is shed a. It is replaced with a new outer layer called cork, produced by a meristem tissue called the cork cambium.

7. Mature cork cells a. are dead and b. have thick, waxy walls, which protect the underlying tissues of the stem.

8. Bark consists of everything external to the vascular cambium, including the a. secondary phloem, b. cork cambium, and c. cork.

C. The Process of Science: What Happened to the Lost Colony of Roanoke?

1. In 1587, 121 English settlers landed on Roanoke Island, in present-day North Carolina 2. Three years later they were gone and the settlement was deserted 3. There were no signs of struggle, and all the buildings had been dismantled 4. Observation: A large number of very old bald cypress trees around Roanoke Island could provide a reliable record of the climate over the past 800 years 5. Question: Could the tree ring data provide insight into the colony’s mysterious disappearance?

6. Hypothesis: The loss of the colony corresponded to a period of drought 7. Prediction: Tree ring data would show abnormal growth during the years after settlement 8. Experiment: Dozens of trees that covered the period 1185 to 1984 were analyzed 9. Results: a. The colonists arrived at the start of the worst three-year drought in the southeastern United States in 800 years. b. The drought and the resulting inability of the colonists to cultivate plants could have forced them to abandon the settlement.

IV. The Life Cycle of a Flowering Plant 1. Many flowering plants can reproduce sexually and asexually 2. Asexual reproduction allows a single plant to produce many offspring quickly and efficiently 3. Sexual reproduction in plants involves fertilization, the union of gametes from two parents, to produce genetically distinct offspring ..

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A. The Flower 1. In angiosperms, the structure specific to sexual reproduction is the flower 2. The main parts of a flower are modified leaves: a. sepals enclose and protect the flower bud, b. petals are often colorful and fragrant, which may serve to advertise the flower to insects and other pollinators, c. stamen, and d. carpel.

3. The flower’s reproductive organs are the stamen and the carpel 4. A stamen consists of a stalk tipped by an anther, where meiosis occurs and pollen grains develop 5. A carpel has a long slender neck (the style) with a sticky stigma where pollen grains land 6. The base of the carpel is the ovary 7. Within the ovary are ovules, each containing a. one developing egg and b. the cells that support it.

8. The term pistil is sometimes used to refer to a single carpel or a group of fused carpels B. Overview of the Flowering Plant Life Cycle 1. The life cycles of all plants include alternation of a a. haploid generation and b. diploid generation.

2. The diploid plant body is the sporophyte 3. The haploid plant is the gametophyte 4. The sexual life cycle of an angiosperm involves a. fertilization, b. the ovule of a flower maturing into a seed containing the embryo, c. the ovary developing into a fruit, d. the seed germinating in a suitable habitat, e. the embryo developing into a seedling, and f. the seedling growing into a mature plant.

C. Pollination and Fertilization 1. Fertilization requires gametes, which are produced by gametophytes a. The male gametophyte is the pollen grain, which i. is essential for pollination and ii. produces sperm. b. The female gametophyte is a multicellular structure called the embryo sac, which produces the egg.

2. The first step leading to fertilization is pollination, the delivery of pollen grains from anther to stigma 3. Many angiosperms are dependent on insects, birds, or other animals to transfer their pollen

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4. Double fertilization occurs as a. one sperm fertilizes the egg, forming the diploid zygote, and b. the other sperm i. contributes its haploid nucleus to the large diploid central cell of the embryo sac and ii. produces a triploid cell that will give rise to the food-storing tissue called endosperm.

D. Seed Formation 1. After fertilization, the ovule, containing the zygote and the triploid central cell, begins developing into a seed 2. The zygote a. divides via mitosis and b. forms a ball of cells that becomes the embryo.

3. The triploid cell a. divides via mitosis and b. develops into the endosperm.

4. The result of embryonic development in the ovule is a mature seed, a plant embryo and endosperm packaged within a tough protective covering called a seed coat E. Fruit Formation 1. A fruit is a mature ovary that acts as a vessel, a. housing and protecting seeds and b. helping disperse seeds from the parent plant.

2. Fruits include a. corn kernels, b. peaches c. tomatoes, and d. pea pods.

3. Mature fruits can be either a. fleshy or b. dry.

F. Seed Germination 1. Germination of a seed usually begins when the seed takes up water 2. The hydrated seed expands, bursting its coat, and the embryo resumes the growth and development that was temporarily suspended during seed dormancy G. Evolution Connection: The Problem of the Disappearing Bees 1. Flowering plants and land animals have had mutually beneficial relationships throughout their evolutionary history a. Angiosperms depend on insects, birds, or mammals for i. pollination or ii. seed dispersal. b. Most land animals depend on angiosperms for food and shelter.

2. In late 2006, U.S. beekeepers noticed a sudden and drastic die-off in their bee colonies 3. The next year, similar problems were reported in Europe 4. Bees pollinate $15 billion worth of crops each year, which is about one-third of our food supply ..

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5. The cause of the die-off has not yet been explained, but several biological agents have been implicated, including mites or their pathogens

Chapter Guide to Teaching Resources The Structure and Function of a Flowering Plant Student Misconceptions and Concerns 1. Students often fail to see the applications of fundamental principles in biology. For example, many structural adaptations increase the surface-to-volume ratio in plants and animals. The divisions within the human lung, microvilli, leaves, and root hairs are examples. Increased surface areas are typically found where something is exchanged: gases exchanged at respiratory surfaces, nutrients absorbed by microvilli, light absorbed by leaves, and water and minerals absorbed by root hairs. If this chapter is one of the final topics addressed in your course, illustrating these broad principles from a variety of subjects can be a unifying review.

2. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor.

Teaching Tips 1. Table 28.1 is a visually simple and important comparison of monocots and dicots.

Consider showing this table when comparing these two groups.

2. The impact of the green revolution and the continued improvement of agricultural techniques and crops may be little appreciated by your students. Yet, from 1940 to 1980, wheat production doubled while the cost of production was cut in half. Consider sharing and discussing the importance of these developments as they relate to modern economies and world population.

3. Consider bringing living examples of monocots and dicots to class or using a short trip outside during a related lab to quickly compare examples.

4. Challenge your students to suggest circumstances when apical growth is more adaptive for a plant, and other situations in which branching would be more favorable.

5. Cellulose is the most abundant organic compound on Earth. Students often find this fact worth remembering.

6. Students might remember the function of phloem if you point out the “F” sound common to phloem and food.

7. The modifications of the three plant organs reveal the remodeling nature of evolution. As François Jacob noted, evolution works more like a tinkerer and not an engineer. The common ancestry of eudicots is revealed by the diverse modifications of three basic plant organs derived from the shared ancestors. Your students’ appreciation of the enormous evidence of evolution will grow with frequent examples noted throughout your course.

8. The functions of human epidermis have some similarities in plants. Like plants, our epidermis is a defense against physical damage and infectious organisms. In addition, oils on our skin help us retain water (and keep the epidermis flexible).

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Plant Growth Student Misconceptions and Concerns 1. Students often expect determinate growth in plants, because it is characteristic of humans.

However, most plant species show indeterminate growth, capable of growing as long as they can live.

2. Students typically expect that as a tree grows taller, the length of the trunk stretches upward. This expectation naturally arises from our own human experiences. However, as a tree grows, the trunk does not stretch upward. Instead, growth occurs at the upper ends and through expansion of the trunk. Therefore, initials carved into the trunk of a tree will be expected to remain at that height as long as the tree is upright and healthy.

Teaching Tips 1. Lobsters are one of the few animals that show indeterminate growth.

2. Students may not realize that the cork used to seal a wine bottle is the same cork that is discussed above. Cork can come from a variety of trees.

3. Students may not appreciate the many important functions of tree bark. Carving into bark, or peeling it away from a trunk, exposes the inner tissues to pathogens. In many ways, the functions of human skin and bark are similar.

The Life Cycle of a Flowering Plant Student Misconceptions and Concerns 1. Students’ knowledge of sexual reproduction in animals often results in an expectation of similar processes in plants. The double fertilization typical of angiosperms requires extra time and attention to distinguish it from processes seen in animals.

2. The distinctions between fruits and vegetables are often debated in public discussions of plants. Consider discussing the use and significance of the terms fruit and vegetable.

Teaching Tips 1. The four main parts of a flower, which are modified leaves, represent additional examples of evolutionary remodeling.

2. Students may better remember that stamens are the male organs because they remember sta-“mens.”

3. Plants that produce light windborne pollen are the major sources of allergies, because the pollen remains in the air longer than heavier pollen grains.

4. Coconut “milk” is an example of liquid endosperm. Coconut “meat” is solid endosperm.

5. Seed dispersal mechanisms are diverse and reflect specific adaptive strategies. The inventor of Velcro was inspired by the seed dispersal mechanisms of the common burdock plant.

6. Seed production in most plants clearly illustrates the ability of organisms to produce more offspring than can survive, a premise of natural selection. While discussing seed production, consider reminding students of this important principal well illustrated in plants.

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Key Terms annuals anther apical dominance apical meristem asexual reproduction axillary buds bark biennials blade carpel cell wall central vacuole chloroplasts collenchyma cells cork cork cambium cortex cotyledons cuticle dermal tissue system determinate growth

dicot double fertilization embryo sac endodermis endosperm eudicots fertilization flower fruit gametophyte germinates ground tissue system guard cells indeterminate growth internodes leaves lignin meristem mesophyll monocot nodes

organ ovary ovules parenchyma cells perennials petals petiole phloem pith pollen grain pollination primary growth rhizomes roots root cap root hairs root system sclerenchyma cells secondary growth seed seed coat

sepals sexual reproduction shoot system sporophyte stamen stems stigma stomata terminal bud tissue tissue system tracheids tubers vascular cambium vascular tissue system vessel elements wood xylem

Word Roots a = without (asexual reproduction: reproduction without sex) apic = the tip; meristo = divided (apical meristems: embryonic plant tissue on the tips of roots and in the buds of shoots that supplies cells for the plant to grow) bienn = every two years (biennial: a plant that requires two years to complete its life cycle) chloro = green (chloroplasts: the green, photosynthetic organelle common in plants) coll = glue; enchyma = an infusion (collenchyma cells: a flexible plant cell type that occurs in strands or cylinders that support young parts of the plant without restraining growth) di = two (dicot: a flowering plant whose embryos have two seed leaves) endo = inner; derm = skin (endodermis: the innermost layer of the cortex in plant roots) epi = over (epidermis: the dermal tissue system in plants; the outer covering of animals) gamet = a wife or husband (gametophyte: the multicellular haploid form in organisms undergoing alternation of generations, which mitotically produces haploid gametes that unite and grow into the sporophyte generation) inter = between (internode: the segment of a plant stem between the points where leaves are attached) meso = middle; phyll = a leaf (mesophyll: the ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis) mono = one (monocot: a flowering plant whose embryos have a single seed leaf) perenni = through the year (perennial: a plant that lives for many years) 420

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phloe = the bark of a tree (phloem: the portion of the vascular system in plants consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant) sclero = hard (sclerenchyma cells: a supportive cell with a very rigid secondary wall) sporo = a seed; phyto = a plant (sporophyte: the multicellular diploid form in organisms undergoing alternation of generations that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation) stam = standing upright (stamen: the pollen-producing male reproductive organ of a flower, consisting of an anther and filament) stoma = mouth (stomata: a hole in plant leaves through which water, oxygen, and carbon dioxide pass) vascular = little tube (vascular tissue system: a transport system of tubes for water and nutrients in plants) xyl = wood (xylem: the tube-shaped, nonliving portion of the vascular system in plants that carries water and minerals from the roots to the rest of the plant)

Relevant Songs to Play in Class “Send Me On My Way,” Rusted Root “The Dreaming Tree,” Dave Matthews Band

“High Hopes (Rubber Tree Plant),” Doris Day

“Seed to a Tree,” Blind Melon

“Autumn Leaves,” Tony Bennett

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: The botanist would need to look at a cross section of the tree trunks. By counting annual growth rings, the approximate age of the tree should be apparent. The annual growth rings are produced in the vascular cambium each year. The rings result from the interruption of secondary growth in the winter and the resumption of growth in the spring.

12. Suggested answer: Though closing may seem like a disadvantage because it limits the carbon dioxide that can enter the plant, when the stomata are left open, the plant loses water. When temperatures are very hot, as at noon in the summer, this dehydration can be damaging. Experiments varying the temperature and/or moisture levels of the environment would test this explanation.

Biology and Society 13. Some issues and questions to consider: Why are forests cut when preserving them is more beneficial for the future? Why are the developing nations not creating new forest products themselves? Should developing and developed nations share in the profits from the forests? What incentive is there for a company to create a new product if it cannot keep the profits? Should companies pay an exploration fee for exclusive rights to take plants from a certain area? Should the developing country get a percentage of the profits from new products? Are there reasons to preserve the forests, other than profits and beneficial new products? Do people or corporations in less industrialized nations (or any nation) have the right to cut down tropical forests for profit? ..

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14. Some issues and questions to consider: Most people are not as concerned about the cloning of plants as they are about the cloning of animals. The natural occurrence of plant cloning and the long history of human culturing of cloned plants may make some people more comfortable with plant cloning. The issue of cloning plants actually brings about some of the same concerns as animal cloning. These concerns might include lack of diversity in the population.

Additional Critical Thinking Questions The Process of Science 1. Why does thinning a forest by logging increase the diversity of the plants in the undergrowth?

Suggested answer: Thinning trees allows more light to penetrate the upper canopy. As more light reaches the ground, the greater the number of plants that can grow under the trees. Thinning creates a disturbance and increases the types of habitat in a forest, allowing more species to grow.

2 Since plants can make their own food through photosynthesis, why does a seed need stored nutrients for the plant embryo?

Suggested answer: As the embryo emerges from the seed, the embryonic shoot must push through the soil before it comes in contact with sunlight and can begin photosynthesis. The stored nutrients sustain the embryonic plant long enough to begin the photosynthetic process.

Biology and Society 3. Plant scientists are searching Peru, Mexico, and the Middle East for the wild ancestors of potatoes, corn, and wheat. Why is this search important?

Some issues and questions to consider: Modern methods of plant breeding and propagation have increased crop yields but have decreased genetic variability, so plants become more vulnerable to epidemics. Primitive varieties of crop plants could contribute to gene banks and be used for breeding new strains.

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CHAPTER

29

The Working Plant

Why This Chapter Matters 1. The human diet consists almost entirely of plants and animals that ate plants.

2. Plants provide humans with lumber, fabric, paper, industrial chemicals, and medicines.

3. The ability to control and direct the mass production of plants and plant products is therefore essential to the welfare of humanity.

4. Understanding plant nutrition, growth, and reproduction is an essential part of modern agriculture.

Chapter Objectives Biology and Society: Planting Hope in the Wake of Disaster 1. Explain how phytoremediation is helping to address the damage caused by Hurricane Katrina and the 2011 earthquake disaster that struck Japan.

How Plants Acquire and Transport Nutrients 2. Explain where and how a plant obtains all the materials necessary to construct all the organic materials it needs.

3. Distinguish between micronutrients and macronutrients, noting examples of each.

4. Describe the advantages of organic farming.

5. Describe the structure and function of root hairs.

6. Explain how mycorrhizae help plants absorb nutrients from the soil.

7. Explain how and why most plants depend on bacteria to supply nitrogen.

8. Describe the special relationship between legumes and nitrogen-fixing bacteria.

9. Explain the transpiration-cohesion-tension mechanism responsible for the ascent of sap in xylem.

10. Explain how and when guard cells control transpiration.

11. Explain how, when, and where phloem conducts sap.

Plant Hormones 12. Describe the general roles and properties of plant hormones.

13. Describe the roles of the five major types of plant hormones.

14. Explain how plant hormones are used to manipulate agricultural crops.

Response to Stimuli 15. Define phototropism, gravitropism, and thigmotropism and explain their significance in plants.

16. Distinguish between short-night plants and long-night plants.

Evolution Connection: Plants, Mantises, and People 17. Explain how life is interrelated.

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Lecture Outline I. Biology and Society: Planting Hope in the Wake of Disaster 1. On March 11, 2011 a magnitude 9.0 earthquake originated beneath the Pacific Ocean.

This earthquake a. was one of the five strongest earthquakes ever recorded, b. produced a tsunami that swept six miles into northeastern Japan, c. killed more than 15,000 people, d. damaged or destroyed at least 125,000 buildings, and e. flooded the Fukushima Nuclear Power plant, leading to a core meltdown.

2. Cleanup of this disaster will take decades 3. Bioremediation a. is the use of living organisms to detoxify polluted sites and b. includes phytoremediation, the use of plants to help clean up polluted soil and groundwater.

4. Sunflowers and other domestic plant species are being used to help clean up after a. the Hurricane Katrina disaster of 2005 and b. this recent disaster in Japan.

II. How Plants Acquire and Transport Nutrients 1. About 96% of a plant’s dry weight is organic material synthesized from inorganic nutrients extracted from the surroundings 2. Plants obtain a. carbon dioxide (CO2) from the air and b. water (H2O) and minerals (inorganic ions) from the soil.

3. Plants produce sugars via photosynthesis using a. CO2 and b. H2O 4. A plant constructs all the other organic materials it needs using these sugars and minerals A. Plant Nutrition 1. A plant’s essential elements are chemical elements, a. obtained from its environment and b. needed to complete its life cycle.

2. Of the 17 essential elements, a. 9 are macronutrients, required in relatively large amounts, and b. 8 are micronutrients, which plants require in relatively small amounts.

3. Macronutrients 4. Six of the nine macronutrients, carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus, make up almost 98% of a plant’s dry weight 5. The other three macronutrients, calcium, potassium, and magnesium, make up another 1.5% of a plant’s dry weight

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6. What does a plant do with macronutrients? a. Carbon, oxygen, and hydrogen are the basic ingredients of a plant’s organic compounds. b. Nitrogen is a component of i. all nucleic acids, ii. all proteins, iii. ATP, iv. chlorophyll, and v. many plant hormones. c. Sulfur is a component of most proteins. d. Phosphorus is a major component of i. nucleic acids, ii. phospholipids, and iii. ATP. 7. Micronutrients 8. Eight micronutrients a. are required by all plants and b. make up the remaining 0.5% of a plant’s dry weight.

9. Micronutrients are a. recycled and therefore b. needed in small amounts.

10. Fertilizers 11. The quality of soil affects a. the health of plants and b. their nutritional value to organisms that eat them.

12. Nitrogen shortage is the most common nutritional problem for plants 13. Fertilizers are compounds given to plants via the soil to promote the plants’ growth 14. There are two basic types of fertilizers a. Inorganic fertilizers contain simple, inorganic minerals. b. Organic fertilizers are composed of chemically complex organic matter, such as compost, a soil-like mixture of decomposed organic matter.

15. Organic farming a. uses compost and other organic fertilizers, b. uses no (or few) synthetic pesticides, c. maintains and replenishes soil quality, d. avoids genetically modified organisms, e. conserves water, and f. is one of the fastest-growing segments of agriculture.

B. From the Soil into the Roots 1. A plant uses its roots to absorb water and essential nutrients from the soil 2. Root hairs a. are extensions of epidermal cells and b. dramatically increase the surface area available for absorption.

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3. All substances that enter a plant root are dissolved in water 4. To reach the xylem, the solution must pass through the selectively permeable plasma membranes of root cells 5. Many plants form mycorrhizae, mutually beneficial associations with fungi that a. increase the absorptive surface area of the roots and b. nourish the fungus.

C. The Role of Bacteria in Nitrogen Nutrition 1. Most plants rely on bacteria to supply them with usable nitrogen in the form of a. ammonium (NH4+) or b. nitrate (NO3–).

2. Soil Bacteria and Nitrogen 3. Three types of soil bacteria play an essential role in supplying plants with nitrogen a. Nitrogen-fixing bacteria convert atmospheric N2 to ammonium, a process called nitrogen fixation. b. Ammonifying bacteria add to the soil’s supply of ammonium by decomposing organic matter. c. Nitrifying bacteria convert soil ammonium to nitrate.

4. Root Nodule Bacteria and Nitrogen 5. Legumes a. include peas, beans, peanuts, and other plants that produce their seeds in pods and b. have their own nitrogen-fixing bacteria in root nodules that produce ammonium.

D. The Transport of Water 1. To thrive, a plant must be able to transport a. water and b. dissolved ions from its roots to the rest of the plant.

2. Xylem sap, a. is a solution of water and inorganic nutrients and b. is transported from the roots to the tips of the leaves through vertical xylem tubes.

3. The Ascent of Xylem Sap 4. Transpiration, the loss of water vapor from the leaves of a plant by evaporation, a. mostly occurs through the stomata of leaves and b. pulls xylem sap up the plant against gravity.

5. Transpiration relies on two special properties of water a. Adhesion is the sticking together of molecules of different kinds. b. Cohesion is the sticking together of molecules of the same kind.

6. Together, adhesion and cohesion create a continuous string of water molecules that stick a. to each other and b. to the inside walls of the xylem tubes. c. The ascent of xylem sap is called the transpiration-cohesion-tension mechanism.

7. The Regulation of Transpiration by Stomata 8. Transpiration a. helps to distribute water within a plant but b. can cause plants to lose large amounts of water.

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9. Plants adjust their transpiration rates to changing environmental conditions 10. In many plants, stomata are open during the day, which a. allows CO2 to enter the leaf from the atmosphere and b. keeps photosynthesis going when sunlight is available.

11. At night, when there is no light for photosynthesis, and therefore no need for CO2, many plants close their stomata 12. Stomata are opened and closed by changes in the shape of the two guard cells flanking each stoma E. The Transport of Sugars 1. Phloem sap contains a. inorganic ions, b. amino acids, c. hormones, and d. the disaccharide sugar sucrose a plant makes by photosynthesis.

2. Phloem sap moves in various directions, a. from a sugar source, where sugar is produced, b. to a sugar sink, where sugar is stored or consumed.

3. Phloem sap moves from a sugar source to a sugar sink by the pressure-flow mechanism 4. Plant Hormones 5. A hormone is a chemical signal that a. is produced in one part of an organism, b. is transported to other parts, and c. acts on target cells to change their functions.

6. Hormones in plants control growth and development by affecting the a. division, b. elongation, and c. differentiation of cells.

7. Plant biologists have identified five major types of plant hormones F. Auxins 1. Auxins a. are group of related hormones and b. are responsible for a wide range of growth and development effects in plants.

2. Phototropism and Cell Elongation 3. Phototropism a. is the directional growth of a plant shoot in response to light and b. is caused by the elongation of cells on the side of the stem that gets the least amount of light.

G. The Process of Science: Do Chemical Signals Affect Plant Growth?

1. Charles Darwin and his son Francis performed some of the earliest experiments on phototropism 2. Observation: Grass seedlings bend toward light only if the tips of their shoots are present 3. Question: Do the tips of the seedlings produce some kind of growth signal? ..

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4. Hypothesis: Plant tips sensed light and produced a growth signal in response 5. Prediction: Removing a shoot tip or blocking its access to light will prevent phototropism 6. Experiments: The Darwins performed several experiments to test their hypotheses 7. Results: a. Growth toward light was prevented by i. removing the tip of a grass shoot or ii. preventing the cap of a shoot from receiving light. b. Growth toward light occurred when placing i. a transparent cap on the tip of a grass shoot or ii. an opaque shield around its base.

8. Conclusions: a. The tip of the shoot was responsible for sensing light. b. The growth response, the bending of the shoot, occurred below the tip. c. Some unknown growth signal was transmitted downward from the tip to the growing region of the shoot.

9. The Action of Auxins 10. The hormones responsible for the phototropism observed by the Darwins are auxins produced by the apical meristem at the tip of the shoot 11. An uneven distribution of auxin on each side of a shoot causes a. higher auxin concentrations in the cells on the dark side, b. cells on the dark side to elongate, and c. the shoot to bend.

12. Auxins demonstrate that a. different concentrations of the same hormone may have different effects in the same target cell and b. the same concentration of a hormone may have different effects on different target cells.

13. Agricultural Applications 14. The use of synthetic plant hormones allows more food to be produced at lower cost 15. One widely used herbicide is a weed killer that a. is a synthetic auxin that disrupts the normal balance of hormones that regulate plant growth and b. affects monocots more than dicots.

H. Ethylene 1. Ethylene is a hormone that is released as a gas that triggers a variety of aging responses in plants, including a. fruit ripening and b. dropping of leaves.

2. Fruit Ripening 3. Fruit ripening is a. triggered by a burst of ethylene production in the fruit and b. spread from fruit to fruit by ethylene gas.

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5. Stored apples are often flushed with CO2, which inhibits the action of ethylene 6. Leaf Drop 7. The loss of leaves in autumn is affected by ethylene 8. Leaf drop is triggered by environmental stimuli that a. cause a change in the balance of ethylene and auxin and b. weaken cell walls in a layer of cells at the base of the leaf stalk.

I. Cytokinins 1. Cytokinins a. are a group of closely related hormones that act as growth regulators that promote cell division, b. are produced in actively growing tissues, and c. counter the inhibitory effects of auxin, resulting in complex growth patterns in most plants J. Gibberellins 1. Gibberellins a. are growth-regulating plant hormones and b. stimulate cell elongation and division in stems and leaves.

2. A combination of gibberellins and auxins can a. influence fruit development, b. make apples, currants, and eggplants develop without pollination and seed production, and c. make seedless grapes grow larger and farther apart in a cluster.

K. Abscisic Acid 1. Abscisic acid a. slows growth and b. can inhibit seed germination, allowing seeds to go dormant.

2. Some desert plants remain dormant until a downpour of rain a. washes out abscisic acid and b. allows the seeds to germinate when water is available.

III. Response to Stimuli 1. Plants can respond to physical stimuli from the environment, including a. light, b. touch, and c. gravity.

A. Tropisms 1. Tropisms are directed growth responses that cause parts of a plant to grow a. toward or b. away from a stimulus.

2. Phototropism is the directional growth of a plant shoot in response to light 3. Thigmotropism a. is a response to touch and b. occurs when a pea plant tendril coils around a string or wire it touches for support.

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4. Gravitropism a. is the directional growth of a plant organ in response to gravity and b. occurs when c. shoots grow upward and d. roots grow downward.

B. Photoperiod 1. Light a. provides energy for photosynthesis, b. directs growth, and c. regulates a plant’s life cycle, including i. flowering, ii. seed germination, and iii. the onset and ending of dormancy.

2. A photoperiod a. is the relative lengths of day and night and b. the environmental stimulus that plants most often use to detect the time of year.

3. Plants whose flowering is triggered by photoperiod fall into two groups: a. long-night plants and b. short-night plants.

4. Florists apply knowledge of the photoperiod of particular plants to bring us flowers out of season C. Evolution Connection: Plants, Mantises, and People 1. Plants rely on organisms from two other kingdoms to help acquire nutrients: a. soil bacteria and b. the fungi of mycorrhizae.

2. Nearly all land animals depend on plants or animals that ate plants for food 3. Consider the African mega mantis on the cover of the textbook a. The mantis depends on protists, plants, and animals for food. b. In turn, the mantis is eaten by other animals.

4. One of biology’s overarching themes is the interrelatedness of organisms a. Animals depend on other animals and plants. b. Plants depend on animals, fungi, and protists. c. All eukaryotic life depends on prokaryotes.

5. This interdependency reminds us once again that it is impossible to separate ourselves from all of the living creatures that share the biosphere

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Chapter Guide to Teaching Resources How Plants Acquire and Transport Nutrients Student Misconceptions and Concerns 1. Although analogies are often useful, some similarities can be misleading. The vascular tissues and movement of fluid through plants is in many ways unlike the circulatory system of animals, especially vertebrates. Vertebrates have one-way flow of fluids propelled by a contracting heart. Tissues in phloem can move in either direction, propelled instead by a pressure-flow mechanism.

2. It is important to distinguish between the acquisition of nutrients and the acquisition of food. Plants, unlike animals, do not obtain their food from the environment. Instead, plants are autotrophs that generate their own food. The essential elements required by plants are not sources of calories.

3. Students might assume that macronutrients are large in size and micronutrients are small.

Instead, the word roots “macro” and “micro” refer to the quantities of nutrients required in each category.

4. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the “win-win” nature of mutualism.

Teaching Tips 1. Cohesion of water enables some insects to walk or stand on a liquid water surface.

Cohesion and adhesion of water is also the reason why we need to dry ourselves off when we leave a shower—with water still clinging to our skin and hair.

2. Demonstrate or ask students to recall that when they use a soda straw and lift the straw out of the beverage, some of the beverage still sticks to the straw. This is an example of adhesion.

3. Many saps other than maple syrup are used commercially. For example, sap from rubber trees native to the Brazilian Amazon was once the major source of rubber. Now most rubber is synthetic, except for some specialized uses. Pine oil, derived from pine tree resin, is the active ingredient of Pine Sol. 4. With the exception of small amounts of glycogen from meat and lactose from dairy products, we get our dietary carbohydrates from plants.

5. Root hairs exhibit yet another example of an adaptation to increase the surface area of an organism. Alveoli within the human lung, microvilli, and plant leaves are other examples.

Increased surface areas are typically found where something is exchanged: gases exchanged at respiratory surfaces, nutrients absorbed by microvilli, light absorbed by leaves, and water and minerals absorbed by root hairs. If this chapter is one of the final topics addressed in your course, illustrating these broad principles from a variety of subjects can be a unifying review.

6. The change in shape of guard cells is due to turgor, internal fluid pressure, important in many other organisms. Turgor helps maintain the shape of plant cells, gives structure to the hydrostatic skeletons of sea anemones and earthworms, and causes a penis to become firm on erection. Before addressing guard cells, you may challenge your class to explain what leaves, sea anemones and earthworms have in common. The answer is turgor.

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Plant Hormones Student Misconceptions and Concerns 1. Students may think of plants as static, inert objects that passively interact with their environments. Without careful study and consideration, it can be challenging to explain how plants respond to their surroundings. This section on plant hormones reveals some of the significant mechanisms used by plants to respond appropriately to changing environmental conditions.

2. Students are unlikely to know about the many manipulations of plants in modern agriculture. Learning about them reveals the usefulness and importance of knowledge. In addition, some students will recognize the potential financial gains that come with the manipulation of plants and their products.

Teaching Tips 1. So much biology in courses answers questions, which students might have never thought to ask. Consider posing these questions before discussing plant hormones with your class.

What keeps seeds dispersed in autumn from sprouting in the winter? What keeps seeds in fruit from germinating immediately? As we explore biology, it is useful to wonder first, to prepare the mind for the explanation.

2. Although the analogies are limited, students might be challenged to identify human hormones that have effects similar to the plant hormones discussed in this chapter. For example, gibberellins and human growth hormone both promote growth.

3. Consider bringing a plant from someone’s office or greenhouse that distinctly shows a plant’s orientation in one direction. Before discussing phototropism, ask students to explain why the plant may have this orientation.

4. Before explaining the answer, ask your students to explain how some seedless fruits are produced. It is often an amusing question to consider when you do not know how it is done!

5. In the nineteenth century when coal gas was used to power streetlights, the leakage of gas from pipes caused nearby trees to drop their leaves prematurely.

6. Special bags that are made of a material that absorbs ethylene gas are now commercially available. They can extend the life of fruits and vegetables stored within each bag.

7. Biology and modern agriculture represent compromise. Modern agriculture and society must balance cost, quality, and environmental risks associated with our food supply. Share with your students the importance of science and education, to inform the decisions regarding these important issues regarding our food and the environment.

Response to Stimuli Student Misconceptions and Concerns 1. As noted just above, students struggle to see plants as active responders to their environments. In addition to internal changes in physiology produced by hormones, plants can move in response to environmental stimuli.

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Teaching Tips 1. Photographs or living examples of a germinating seed and a climbing vine are very useful for demonstrating gravitropism and thigmotropism, respectively.

2. Short video clips on plant tropisms can be found by searching “tropisms video” in Google.

Such short clips can quickly illustrate these activities.

3. You might challenge your students to predict what would happen to North American longnight plants that typically bloom in the fall, if we moved them to Australia. We would expect that in Australia, long-night plants would bloom in the spring, compared to North America.

Key Terms abscisic acid adhesion auxins cohesion compost cytokinins essential element ethylene

fertilizers gibberellins gravitropism hormones macronutrients micronutrients minerals mycorrhiza

nitrogen fixation organic farming phloem sap photoperiod phototropism pressure-flow mechanism sugar sink

sugar source thigmotropism transpiration transpirationcohesion-tension mechanism tropisms xylem sap

Word Roots aux = grow, enlarge (auxins: a class of plant hormones that promote cell elongation, stimulate secondary growth, and promote the development of leaf traces and fruit) co = together; hesita = stick fast (cohesion: the sticking together of molecules of the same kind) cyto = cell; kine = moving (cytokinins: a class of related plant hormones that retard aging and act in concert with auxins to stimulate cell division, influence the pathway of differentiation, and control apical dominance) gibb = humped (gibberellins: a class of related plant hormones that stimulate growth in the stem and leaves, trigger the germination of seeds and breaking of bud dormancy, and stimulate fruit development with auxin) gravi = heavy; trop = turn, change (gravitropism: directional growth of plants in response to gravity) macro = large (macronutrients: elements required by plants and animals in relatively large amounts) micro = small (micronutrients: elements required by plants and animals in very small amounts) myco = a fungus (mycorrhizae: mutualistic associations of plant roots and fungi) photo = light (phototropism: growth of a plant shoot toward or away from light) thigmo = touch (thigmotropism: growth of a plant in response to touch)

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Relevant Songs to Play in Class “The Dreaming Tree,” Dave Matthews Band

“High Hopes (Rubber Tree Plant),” Doris Day

“Seed to a Tree,” Blind Melon

“Autumn Leaves,” Tony Bennett

“Send Me On My Way,” Rusted Root

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: Hypothesis: When fixed nitrogen levels increase to a certain level in the soil, genes coding for nitrogen-fixing enzymes in nitrogen-fixing bacteria are switched off.

Test: Expose cultures of nitrogen-fixing bacteria (symbiotic and nonsymbiotic ones found in soil) to solutions of different concentrations of fixed nitrogen. Determine the concentrations of nitrogen-fixing enzymes produced by the bacteria in each sample.

Prediction: If your hypothesis is correct, and the fixed nitrogen concentration is high enough in some of the samples, you would expect the enzyme concentration to be measurably lower in samples whose fixed nitrogen concentration is above the level that causes negative feedback.

Biology and Society 12. Some issues and questions to consider: How were the farmers assigned or sold “rights” to the water? How is the price established when a farmer buys or sells water rights? Is there enough water for everyone who “owns” it? What kinds of crops are these farmers growing? What will the water be used for in the city? Are there other users without rights, such as wildlife? Is any effort being made to curb urban growth and conserve water?

Should millions of people be living in what is essentially a desert? What are the reasons for farming desert land? What kind of crops are the farmers growing? Do they require a lot of water? Are the crops sold locally in cities, thus reducing the need to transport crops a long distance, or are the crops (for example, alfalfa) used to feed horses and cattle?

13. Some issues and questions to consider: Do traces of the hormone or its breakdown products remain with the apples when they come to market? If so, is the hormone safe for human consumption? What are its effects in the environment? Could its production produce impurities or wastes that might be harmful? What kinds of tests need to be done to demonstrate its safety? How much does it cost to make and use? Are the benefits worth the costs and risks? Is it worth using an artificial chemical on food simply to improve its appearance? A scientist could seek answers by studying the stability of the hormone in a variety of laboratory simulations of natural conditions. The toxicity of the hormone, of the materials used to produce it, and of its breakdown products could be determined in laboratory tests.

Additional Critical Thinking Questions The Process of Science 1. Since gravity and light affect plants through auxin production, predict the effect on a seed planted upside down with a light source from below the plant.

Suggested answer: The shoot will emerge from the soil and the roots will grow into the soil.

Once the shoot emerges from the soil, it will begin to grow toward the light below the pot.

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2. Jon just started a new job as night watchman at a plant nursery. His boss told him to stay out of a room where chrysanthemums (which are long-night plants) were about to flower.

Around midnight, looking for the restroom, Jon accidentally opened the door to the chrysanthemum room and turned on the lights for a moment. How might this affect the chrysanthemums? What could Jon do to correct his mistake?

Suggested answer: The red wavelengths in the room lights quickly convert the phytochrome in the mums to the Pfr form, which inhibits flowering in a long-night plant.

The mums will not flower unless Jon can rig up some far-red lights. Exposure to a burst of far-red light would convert the phytochrome to the Pr form, allowing flowering to occur.

Biology and Society 3. The clear-cutting of the tropical rain forest has global effects, which can be seen in carbon dioxide buildup and a drop in rainfall totals. The land created for farming becomes useless quickly because of depleted nutrients. Do we have any right to tell other countries how to manage their lands, such as rain forests? If we explain the consequences of clear-cutting the rain forests but that government decides to continue with the process, should we interfere?

Some issues and questions to consider: Our government has a responsibility to us to protect our environment but we also value freedom and cannot take that from other countries. Education and agricultural assistance may be our best means of preserving the rain forests. Can other countries interfere if one country’s actions affect nearby countries?

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APPENDIX

Great Ideas for Teaching Biology In the following pages you will find ideas and strategies submitted by instructors on a variety of topics ranging from freshening lectures to helping students retain information. These articles were originally published in the Pearson newsletter for science instructors, Strategies for Success. Past issues of the newsletter are available at http://www.pearsonhighered.com/strategies.

Popular Music Can Enliven Your Classroom Eric J. Simon, New England College esimon@nec.edu No subject in the science curriculum intersects with today’s popular culture more than biology. As teachers, we can take advantage of the current “golden age of biology” by emphasizing the myriad ways that curricular content relates to students’ lives outside the classroom. Biology abounds in movies (travel to the Galapagos Islands with Russell Crowe in Master and Commander or consider a near-future society where genetic makeup determines social status in GATTACA), television shows (CSI reigns as the most popular show in America, and medical-themed shows can be seen nightly on the Discovery Channel), and music.

Most students today are popular culture sponges; it is what they think about during their free time. By making references to these media, we can remind our students that biology exists outside the four classroom walls. We can also entertain and enliven the teaching/learning environment—benefits of particular importance in the non-majors introductory course, where gaining and holding students’ attention can be half the battle.

One easy way to bring popular culture into the classroom is to play music before class. In my introductory courses (one for science majors and one for nonscience majors), I play a song relevant to each day’s lesson before the period starts. I then ask the same set of questions: Who can name the song and artist? Why am I playing this particular song today? Students enjoy the brain teaser of making the connection between the song and the subject under discussion. As a teacher, it is always gratifying to realize that students are thinking about the course material before the opening bell. This technique also allows you to create a loose, interactive atmosphere without sacrificing any actual class time.

During my lecture, I add the song (at half volume) to the PowerPoint slide that most closely relates to the song’s significance. The recurrence of the song can provide an “Aha!” moment for students, and some have said that the aural connection helps them remember the topic.

There are popular songs that intersect (often frivolously) with almost every topic in the introductory biology curriculum, either through the song title, the content of the song, or the name of the artist. Some are fairly obvious (“Do the Evolution” by Pearl Jam), others require a bit more thought (“More Than Words” by Extreme, used when discussing archaea), and a few induce groans (“I’ve Got You Under My Skin” by Frank Sinatra when discussing anatomy, or “Tiny Bubbles” by Don Ho when discussing protists). Here are a few more: • Introduction to Science: “She Blinded Me With Science” (Thomas Dolby), “Weird Science” (OingoBoingo), “The Sounds of Science” (Beastie Boys) • Introduction to Biology: “Wonderful World” (aka “Don’t Know Much Biology” by Sam Cooke), “Alive” (P.O.D.) ..

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• Nutrition and Digestion: “Sugar Sugar” (The Archies), “Eat It” (Weird Al Yankovich), “The Middle” (Jimmy Eat World) • The Cell: “Tainted Love” (Soft Cell), “Golgi Apparatus” (Phish) • Photosynthesis: “Don’t Turn Off the Lights” (Enrique Iglesias), “Walking on Sunshine” (Katrina and the Waves) • Reproduction: “Reproduction” (Grease 2 soundtrack), “Let’s Talk About Sex” (Salt N Pepa) • Cloning: “I Think I’m a Clone Now” (Weird Al Yankovich), “Hello Dolly” (Broadway musical soundtrack) For a list of over 60 relevant songs that I have compiled (with the help of many colleagues)—or to contribute your own suggestion to this list—please e-mail me at esimon@nec.edu.

If you are not familiar with popular music yourself, you can easily turn this idea into an active learning exercise for your students. After you’ve played a few songs in class, you can offer your students one bonus point for each relevant song they suggest. Few professors would begrudge a student extra credit for actually thinking about biology during their free time!

One easy (and free and legal) way to play music in a computer-equipped classroom is to access music sites like itunes.com or amazon.com. There, you can play free samples of songs (typically 30 seconds). These sites also provide search engines that can find song titles or artist names containing relevant keywords (try entering “cell” into the iTunes search engine for a lot of interesting band names!).

While popular music is unlikely to impart content knowledge to your students, it can help grab and retain their attention, show the relevancy of the subject matter to the world around them, and perhaps even cause them to engage the subject matter outside the classroom.

Among introductory students, such small victories can be significant.

Freshen Lectures by Connecting Unrelated Concepts David Eakin, Eastern Kentucky University david.eakin@eku.edu For most students, the concept of “lively lectures” is as meaningful as the thunderous silence we experience at the end of most lectures. It is an oxymoron. Unfortunately, some instructors still approach the act of teaching using the Middle English concept of lecture—“the act of reading.” Worse are those who have adopted Webster’s second definition, “a lengthy rebuke or scolding.” We fare no better when we investigate the synonyms for the word “lively”—and there are many: vigorous, full of spirit, marked by animated intelligence, invigorating, refreshing, sparkling, effervescent, dynamic, full of life and energy. Need I continue?

Each of these words suggests the single ominous antonym for the word, namely DULL! Following my own advice to communicators, I will address my remarks to the audience for whom this newsletter is written: those who are willing to work to become better at their craft! When I die, “dull as a doorknob” would not be my preferred epitaph! And while technology has added the possibility of innovation and freshness to the classroom, a bad teacher will be a bad teacher whether they have a piece of chalk or a laser pointer in their hand.

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I will use Darwin’s Concept of Natural Selection to illustrate one way to freshen your lectures. We all know what needs to be presented, and even how and where it is covered in our text. But sometimes a change of place and context will add a refreshing element of interest to our presentations. Why not put this essential concept in the context of the equally important concepts of biotic potential and population growth curves? And then add a dash of information on Darwin’s ability to do lateral thinking? Do I have your attention now?

Let’s see how this can apply to the five essential parts of Darwin’s thinking.

1. Populations tend to increase at an exponential rate.

2. Over time, populations tend to remain remarkably constant.

These are obviously ideas Darwin gleaned from the famous essays on human populations penned by Thomas Malthus. In modern terms, number one above is the J-shaped curve for biotic potential, while number two is the S-shaped curve for normal population growth and stabilization. Hence, we have a curve representing potential growth and one representing real growth. For me, cockroaches work well here, but you can use whatever great example of exponential growth excites you. In each case, there is the potential for billions in a short period of time, yet the reality is far less than the potential. The difference between the two curves is best explained by individual competition for limited resources. Thus Darwin’s third idea: 3. Competition exists between individuals of a species.

The beauty of this approach is that we can add the concept of lateral thinking. Leaving the ideas of Malthus, Darwin shifts to his experience with the artificial selection techniques used by breeders. From this experience he deduces his fourth idea and conclusion: 4. No two individuals in a population are exactly the same genetically, thus: 5. Those individuals with the most favored genetic characteristics will survive, passing these characteristics to their offspring, and subsequently changing the genetic makeup of the population.

And what is the importance of adding lateral thinking to the process? Most of us just keep digging deeper in the same hole when stymied by some difficult problem. What characterizes the genius of Darwin and others like him is their ability to dig a new hole and then connect seemingly unrelated concepts. When a World War II bomber crew lost their hydraulic fluid to flak, they were saved because someone shifted their thinking and suggested that the hydraulic system be filled with urine instead—something they could produce themselves. Darwin was able to connect seemingly unrelated concepts from genetics and population studies to develop his now famous concept of natural selection!

Perhaps this strategy will stimulate you to consider new approaches, ideas, and technologies in your lectures—things that bring to the classroom and your students your passion and excitement for the subject!

What Freshmen Don’t Know William J. Higgins, University of Maryland wh16@umailsrv0.umd.edu About five years ago I returned from a detour into administration to teaching. I was so enthralled with the idea of returning to teaching, that I assigned myself an introductory biology course for new freshmen. While I have not regretted my decision, I have wrestled with a question faced by many faculty: why do so many freshmen do so poorly in introductory science courses? ..

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During the first semester with my freshmen, I was rolling along until the first lecture examination. Disastrous! Shameful! Just plain ugly! Over 50% of this brilliant group of students scored less than 65% on an easy, straightforward test. What went wrong? Who messed up, teacher or students or both? I decided to get some answers.

First, I asked for an early anonymous written evaluation from each student. According to my class, I was THE MAN. After reading notes full of superlatives, I realized that my freshmen were judging the quality of the class and the instruction by my enthusiasm and humor.

They were unable to identify problems with the learning process. They too were frustrated by their performances on an examination they judged to be “fair,” “on material they expected,” and “really fairly easy in hindsight.” I resolved to dig deeper into this mystery.

I got my first glimpse of the problem while I was attempting to answer a student’s question after class by referring to her lecture notes. I couldn’t find the section of her notes that covered the topic in question. I knew that she had attended every lecture and wrote frenetically as I spoke. But where in her notes was the stuff I wanted to show her? I hurriedly grabbed notebooks from every other student still in the lecture hall and frantically turned pages. The difficulty became obvious. During my lecture, students were accurately capturing less than 60% of the information and actually hearing and processing much less than that. Then they dutifully put the notebooks away until the next class, never revisiting those notes until the week of the test.

The root of the problem was apparent to me: my freshmen came to me with a collection of facts learned in high school, solid SAT scores that predicted brilliant academic careers, but no tools or strategies for handling college-level work. They needed a plan, an organized set of guidelines and strategies to help them survive until they evolved into mature, sophisticated learners.

How to generate this? I assembled a group of “volunteers” in my laboratory late one afternoon. Together we drafted the first version of what is now known to Maryland’s freshmen as the “Higgins Plan”—eight strategies for academic success.

Strategies for Academic Success The plan is simple, straight-forward things each student should do to insure success in difficult courses. Rule 1: Go to class, sit up front, and speak to the professor. Hey, you may be physically present, but it doesn’t mean you’re there! Rules 2 and 3: Form a study group of 3 or 4 students and recopy your lecture notes using the double column method after each class. This yields a complete set of notes rephrased in a student’s own words. The adjacent column of extra notes indicates corresponding pages in the text (highlights the important material and focuses the study effort), identifies material given special emphasis by the lecturer, and refers students to specific review questions in exams from previous semesters. Rule 4: Always have the examinations from previous semesters and use them to test your understanding. Rules 5 through 7: Practice, get help early, and manage your time well! My favorite, Rule 8: Things to do and behaviors to avoid on the day of the examination. The students have summarized this rule as, “Keep your cool so you don’t lose your . . . buttocks.”

Experienced seniors employ these or other similar strategies. They have figured out that you really know or understand something when you can explain or teach it. Hence, they study in groups. I now incorporate these learning strategies into my freshman lectures. Most listen to my message only after the first exam.

I, too, had to learn new things. I now put my lecture notes on the Web so everyone has the outline and knows where we are going. No, I don’t worry about students skipping class. I do want them to be relaxed listeners, confident that they’ll mentally replay the lecture, and fill in the gaps in their study group session. I generate tons of sample questions and post old examinations on the Web. I look at the notebooks of every student who comes to speak with me. I play 440

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matchmaker, banding strangers together into study teams. As a class we discuss strategies for learning, the value of group learning activities, and the importance of doing well.

Each fall I speak to Maryland’s incoming freshmen about the details of the Higgins Plan in special seminars in the residence halls. I put an abbreviated version on the Web at www.life.umd.edu/classroom/bsci230/higgins/. But, the most effective and influential presentation of these concepts comes as part of a class. Most freshmen are willing to work long and hard to be successful, but often do not because they simply don’t know what to do. We, the faculty, must give them the methods along with the information.

Exams with a Group Component Thomas Terry, University of Connecticut thomas.terry@uconn.edu When we think of the function of an exam, we usually think of assessing student learning and providing a grade that (hopefully) is a valid measure of that learning. We rarely give much thought to making the exam a learning experience in itself. As I went through my own learning curve as a teacher, I discovered that my students were very interested in learning what the correct answers to exam questions were, but the longer the time lag before they got this information, the less they cared. If I held a review class to “go over the exam” a few days or a week later, almost no one came. On the other hand, if I posted detailed answer keys online immediately after the exam, over 90% of students checked them within 8 hours. I wished I had some way to get them to look over the exam immediately after taking it, so they could see what they had done wrong and learn from their mistakes, but I couldn’t think of a mechanism to do this.

The Group Exam Technique Several years ago, a colleague at a teaching conference described a group exam technique he used. He gave exams that were shorter than the time available, and used the last part of the exam period for students to retake the same exam in small groups. Most of each student’s grade still came from their first, individual, performance, but he allowed a small addition to each student’s grade if the group outperformed its highest scorer. This sounded promising, and I tried it out in a large microbiology class. It worked surprisingly well, and I’ve used it ever since. My students spend the first 40 minutes of the 75-minute period taking the exam individually and recording their answers on a cover sheet that is handed in (students keep the exam). Then they reassemble into previously formed groups of 3–4 students, and each group is given the remaining half hour to move to its own space in the classroom, discuss the exam, and fill out a single group answer sheet. Watching the classroom during this group exam is an educator’s dream! In each group, students argue passionately for their answer, and occasionally laugh or even moan when they discover some of their mental follies. They walk out of the classroom having processed the exam thoroughly, and having taught each other.

Grading Rules Grades are the motivator for students to participate, so I spell out the grading rules very carefully. A group has to score higher than its best individual performer for the group to earn any bonus points. For example, if the group scores 95 out of 100, and its individual members scored 60, 70, 80, and 90, the group bonus is 5 points. I add that bonus to each member’s grade, so their final grades are 65, 75, 85, and 95. I disallow any group bonus greater than 5 points, even if the group scores 10 or even 25 points higher that its highest member (this does happen occasionally). If the group scores lower than its highest performer, the group bonus is zero—I don’t subtract points. In my experience, roughly 2/3 of groups earn a bonus on any given exam. ..

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The same groups don’t always earn bonus points, but over three exams, less than 5% of groups fail to earn a bonus at least once. The average bonus over many semesters has consistently been about 3.6 points. It’s important that the bonus not be so large that groups who fail to earn it feel penalized. I’ve encountered situations where a group included someone who scored so high (e.g., 98 or 100) that the group could not earn bonus points. To prevent this from being a problem, I use a maximum grade of 95 for all individual scores, so every group has the potential to earn a 5 point bonus, but I restrict the maximum grade to 100.

Challenges Any procedure involving groups is bound to involve some challenges. I’ve tried various strategies for forming groups, and I’ve settled on letting students form their own groups with my prodding during earlier classes. I use group activities for other purposes, so by exam time most groups have had some experience working together. I allow students to change groups after each exam, but seldom find the need. Students who rarely come to class are the biggest problem, since they often miss periods when groups form and learn to work together before exams.

Time is the other main challenge. I have not used this format in classes with 50-minute periods—it always takes at least five minutes to collect individual exam papers (even with several proctors), cajole the slower students into handing in their papers, get the groups together and working, hand out the group answer sheet, and deal with problems (students who don’t know their group, groups missing too many members to function effectively, etc.). I find a 75-minute class period to be workable, but students must be able to complete the exam in less than 40 minutes in order for the exam to be a useful measure of accomplishment.

This format allows an exam to function both as an assessment tool and a learning experience, and over 90% of students rank it as adding value to their course. As one student said “The only thing I don’t like about the group exam is that I used to have the luxury of several days after taking an exam when I could sustain the illusion that I’d done better than I had— now I walk out of the exam knowing all the mistakes I made.”

Modeling Exercises Improve Understanding Jean Heitz, University of Wisconsin jgheitz@wisc.edu When I began my career, I thought that my students would learn more if I were a better teacher or if my presentations were better. However, as my presentations improved, student learning didn’t. I worked harder to increase student understanding— using PowerPoint and searching for color photos, diagrams, and animations. For one lecture presentation I selected the best animation of protein translation I could find. After the animation I projected slides recapping the steps in the process. I explained what each slide illustrated, and later asked the 200+students in the class if they understood. Many nodded, and no students admitted they didn’t.

Twenty-two of those same students went to their discussion section immediately after the lecture. Their teaching assistant gave them each five minutes to either write a brief description of translation or diagram it. None of the students in the class could do this. What was the problem?

I later attended a colleague’s lecture where he showed an animation of DNA replication.

The animation included a recent discovery on how the RNA primers on Okasaki fragments are removed. I left the lecture feeling that “I really understood how it worked,” but when I tried to explain it to another colleague, I discovered that I couldn’t. Finally, the light dawned.

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My students didn’t understand for the same reason as I—neither of us had translated what was “obvious” in the animations into something that could be retained. How could I solve this problem and get my students to learn more? I needed to concentrate on how to help my students learn, rather than focusing on my knowledge and how I could do better.

Now I approach teaching differently. I still use animations in class to give my students a good feeling for the dynamic nature of processes that they otherwise couldn’t see. However, I have learned that after showing an animation, I need to work through my own interpretation of it on the blackboard. I’m not an artist. (Both Grandma Moses’s work and cave drawings would beat mine in any contest.) I use annotated stick figures, simple symbols, and line drawings to do the interpretation. For students to understand my drawings, I need to explain what each symbol or stick figure is supposed to represent. In the long run, however, my artistic shortcomings prove advantageous for two reasons.

First, after seeing my drawings, students never worry that their drawing ability is inadequate. Second, translating the animation into a very simple model helps them put all the associated terms and ideas into context. It also makes it easy for them to take notes. As a result, the process makes more sense and is easier to understand and remember.

Modeling to Learn and Retain To help insure that my students really understand the process, I don’t give them a copy of my diagram to memorize. I have them draw, diagram, or model the process themselves. For example, as a discussion exercise, I give the students a list of the different organelles, structures, and components that are required for translation. Using this list I have them work in groups of three to develop a model or diagram that they could use to teach translation.

The rules are simple: • Each group has to include all the listed items in their model or diagram. They can use their notes and textbooks while doing this.

• The model has to be simple. Drawings have to be in the form of stick-figure-type drawings or cartoon characters.

• For domino-effect processes (e.g., step 1 triggers 2 which leads to 3), I recommend they use play dough and develop “claymation” models. They can also diagram these as “Rube Goldberg” systems. I give students the following clip art and remind them of the board game “Mouse Trap®” as examples of this type of system.

• Each member of the group has to understand the process because, when they are done, I will randomly select one member of each group to teach a part of the process.

As the student groups develop their models, I move from group to group and ask questions to help direct their efforts. When their models are completed, each group is asked to explain theirs to another group. With ten minutes left in the period, I call on a student from each group to teach a specific part of the process of translation.

The following week, when I quiz the students on translation, almost all of them demonstrate a solid understanding of the process.

This type of modeling exercise will help students understand any kind of structure or process that is otherwise hard to view directly, which includes structures and processes that oc..

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cur at the molecular, and cellular, as well as global levels. For example, I have asked students to draw an annotated flow diagram (or Rube Goldberg type handout) to explain how the various components of the ear interact to produce the sensation of sound in the brain. In another exercise, I asked them to diagram and explain the interactions among B and T cells in immune responses. At the other end of the spectrum, I have asked students to diagram and explain global air circulation patterns.

To make sure they understand the processes I add a few “what if” questions. For example: AIDS targets T4 cells and kills them. What effect would this have on a person’s ability to fight off bacterial infections? What will happen to rainfall in the tropics as more and more of the tropical rainforests are destroyed? How could this affect weather patterns in Wisconsin?

These types of questions not only test their understanding of the process, they give students a reason for knowing the process. They also help students see how this new knowledge fits in with what they already know about the rest of the world. As a result they are more likely to retain that knowledge.

Doing Science Collaboratively with Investigative Case-Based Learning Margaret Waterman, Southeast Missouri State University, mwaterman@semo.edu, and

Ethel Stanley, BioQUEST Curriculum Consortium, Beloit College, stanleye@beloit.edu Investigative case-based learning (ICBL) is a type of problem-based learning that is especially good for structuring collaborative work. ICBL uses realistic cases to engage students in a science topic, turning one of humanity’s oldest teaching strategies—telling stories—into a tool for collaborative science learning. Students frequently work as part of a group while they analyze the case and raise questions, as they conduct related scientific investigations, and as they prepare and present their findings. ICBL requires students to develop teamwork, communication, and information management skills—precisely the abilities needed for the workplace and for lifelong learning!

The story that follows is a composite of our own experience with ICBL and that of several biology instructors who have been in our ICBL workshops over the last five years. “Bob Powers” is a fictional instructor using an ICBL case with a general biology class.

Bob Powers Uses ICBL After years of teaching the macromolecules section of introductory biology, Bob Powers was still dissatisfied with how this part of the course went. The text was fine, the lectures well organized, and the labs were appropriate with students doing exercises in groups. The problem was that the students never seemed to get really interested and the group work seemed artificial.

Bob decided to use an ICBL case he found online (see expanded article for references) to try to hook the students and have them see that the information about macromolecules applied outside the classroom. He had read a little about cases and problem-based learning and thought it might be a way to use groups for more realistic science problem solving.

During lecture, Bob told his class that they would be using an ICBL case. Very few of his students had used cases before, so he assured them that he would show them how to do this.

He then passed out a single sheet that had a short case on one side and a case analysis sheet 444

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with room for notes on the other (see below). He asked a student volunteer to read the case out loud.

How Now Mad Cow

Stacy Kiser, Lane Community College, www.bioquest.org/lifelines My mother and I were driving to a nursery to buy plants for Mother’s Day when I asked her for a breath mint. She offered me some gum, but said, “I don’t have any breath mints after the big scare.”

I said, “Oh give me a break! What big scare?”

She said, “Well, I read on the Internet that you can get Mad Cow Disease from those mints made in England. After all, they’re made in Great Britain and they do have gelatin in them.”

And sure enough: (a picture of the mint box with “contains gelatin” and “Made in Great Britain” circled in yellow).

Case Analysis Sheet 1. Recognize potential issues and identify major topics. Working individually, underline or list terms or phrases that seem to be important for understanding what the case is about. Then discuss these with your group.

2. Pose specific questions.

By yourself, or better yet, in a group, think about what you know that is related to the case and its topics. Keep track of questions that arise with the Know/Need to Know chart below.

What do we know?

What do we need to know?

Identify 1–3 questions or issues from the “need to know” list that you or your group wants to explore.

3. Obtain additional references or resources to help answer or explore questions.

List four different resources you think would be helpful.

“Wow. Is that really true?” a student asked aloud.

“We’ll see,” Bob said. “So what do you all think this case is about?” Several students raised their hands. “Mad cow disease.” “Gelatin and getting sick from it.” “Wild rumors on the Internet.” “Regulation of foods.”

Next, Bob asked the whole class if any of them had any experience with some element of the case. How has Mad Cow Disease affected them? Do they ever use gelatin? Has anyone been in the UK lately? By asking these questions Bob was modeling the kinds of questions the students should be asking each other.

Bob next asked the class to work together in small groups discussing the case and raising questions for a few minutes. He asked them to use the case analysis sheet to structure their discussion and, particularly, the Know/Need to Know chart as a way for them to keep track of their ideas. He asked one volunteer from each group to take notes for the group on the Know/Need to Know chart.

Bedlam broke out momentarily as students rearranged themselves and their chairs. Then, quiet conversation began as students began to ask each other questions and to share what they knew about Mad Cow Disease, breath mints, and gelatin. “Gelatin is what???? Cow skins and hooves? Yuck!” “But it’s good for fingernails because it’s protein.” “What is Mad Cow Dis..

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ease?” “It’s a problem with the brain.” “Can people get it?” “How?” “Do we have it in the US?” “Is it over or still going on, ’cause we’re going to Europe next summer . . .”

Every group worked intently for 10 minutes or so. When they seemed to be slowing down, Bob called the class back together to hear a sampling of the ideas and questions that the groups had. Here are some ideas the students felt they knew: • Gelatin comes from boiled cow parts.

• Gelatin contains protein.

• Enzymes are proteins.

• Hair is protein.

• Eggs contain protein. When you boil eggs, you are changing the structure of the proteins; that’s what makes them harden.

• Mad cow disease affects the brain. People can get it, and there’s no cure. If you’re worried, don’t eat beef.

• They slaughtered thousands of cows and sheep (?) a couple of years ago in Europe.

• The disease is something you can “catch.” It might be caused by a virus.

Students wanted to know: • What causes Mad Cow Disease?

• If gelatin is a possible source, is the disease caused by a protein?

• How can a protein cause a disease? What do proteins do?

• Can you really get the disease from breath mints?

After this brief discussion, Bob had a pretty good idea of student background knowledge on proteins. Some students had learned quite a bit already. Just hearing each others’ ideas showed the students that no one person knew all the answers. They also learned that their fellow students were worth listening to.

The rest of that week the topic was proteins. In lecture, they learned about prions and Mad Cow Disease, as well as protein structure and enzyme function. Students worked in pairs with molecular models to see how amino acids are put together. In lab, Bob used activities he had done before, but now students seemed to have specific questions about proteins.

Students formed research teams in lab to examine the effects of pH, enzymes, or heat on protein structure. Bob set out some materials to work with: gelatin (hardened), egg whites (runny), a variety of fruits (including kiwi and fresh pineapple), vinegar, water, bleach, and a heat source, but encouraged groups to design and conduct their own investigations. Each group made posters to persuade their peers of their experimental methodologies and interpretations of results. The groups also used a computer simulation of an enzyme lab, varying parameters such as enzyme concentration, substrate, and inhibitors to explore enzyme function.

They had to run at least two simulations and explain their results.

For extra credit, individual students could use an Internet resource that Bob had identified for the class to complete—a personal risk analysis of getting Mad Cow Disease.

While students worked on their research designs, Bob observed the groups in action. He noticed what types of resources students consulted, how they worked together in groups, if they were posing questions, presenting results, and generating ideas. Such informal observations are a type of assessment that Bob used to help groups stay on task and work effectively.

In addition to these informal observations, the students produced a variety of products that Bob could choose to grade: the Know/Want to Know sheets, the group research designs, the posters, outputs from the simulations, and the risk analyses.

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After using “How Now Mad Cow,” Bob asked his students to answer a short survey about learning with cases. (He modified it from one available at www.bioquest.org/ lifelines/studentsurvey.doc.) The response was positive.

Given these data and his own impressions, Bob felt that the chemistry section went better this time and that he was able to accomplish several goals. First, his students were intrigued by the case, and he and they kept trying to connect their questions to new information discussed during the section on proteins. Second, Bob used collaborative methods in a lecture setting as students analyzed the case. Their analysis served as an informal assessment of what the class as whole already knew about proteins. Third, the case also raised interest in subsequent lectures and lab investigations. In effect, the case and case analysis discussion set a context that made lab and lectures more meaningful. An unintended outcome was that one student shared, “Hey, this is just like what my cousin is doing in med school—working on a case to learn how to use medical information!”

ICBL Is Based on Scientific Inquiry As we developed ICBL teaching strategies, we found the BioQUEST 3Ps to be helpful as a framework for instruction: Problem Posing, Problem Solving, and Peer Persuasion are based on the actions taken by practicing scientists. Students who learn with investigative cases utilize a similar three-phase approach.

I. Problem Posing: Analyzing a Case • Introduce the case • Recognize potential issues and major concepts • Pose specific questions via Know/Need to Know analysis

II. Problem Solving: Investigating the Questions • Obtain additional references/resources • Define problems more by sharing views and concerns • Design and conduct scientific investigations

III. Peer Persuasion: Supporting Methods and Reasoning • Produce materials that support understanding of conclusions Learn More About ICBL Getting started with any new teaching approach such as ICBL is easier if you are working with other faculty who are also learning to use this new tool. The expanded version of this article, available on the Strategies for Success website at www. pearsonhighered.com/strategies, includes information on the many ways ICBL can be used, preparing students for ICBL, assessing ICBL learning, and a wealth of cases and online resources for ICBL in biology.

Critical Analysis in the Laboratory

Cathy Switzer, Tomball College cathy.switzer@nhmccd.edu Keeping students engaged makes teaching and learning more fun for everyone, but the quality of student engagement is critical in determining the amount of actual learning taking place. Students can be engaged in laboratory activities that require memorization, but still have no ability to apply the knowledge to their daily lives. Most of all, students can be so immersed in the details of biology that they fail to see the beauty of its interconnectedness. Biology becomes a series of disjointed facts memorized and regurgitated on an exam—bulimic biology. ..

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To help students with retention and problem-solving skills, I assign a current event article for each laboratory subject covered. Students are asked to read their articles and individually prepare a 1–2 page report, which will be discussed in class.

Reporting on the Article The report must include the following information: Title, author, bibliographic information.Students are asked to provide this information in MLA format. This reinforces the need to understand the value of bibliographic information as it appears in texts, journals, and other sources of scientific information.

Brief summary.The length of this summary should be relative to the length of the article.

As a general rule of thumb, I ask students to write one sentence for every one or two paragraphs. This is an excellent way to challenge their critical reading and writing skills as well as their ability to rephrase the thoughts of others.

Connections to the textbook.This challenges students to use the textbook as a resource and to venture outside the current chapter to look for other information related to this assignment. This helps students see that biology is not a series of categories to be covered, but rather a large, interconnected field of knowledge.

Connections to the lab exercise. This carries the connections just a little further to make sure that the students have read their lab exercise and know how it relates to the text and the article.

Scientific vocabulary.Reinforcing vocabulary is important in biology; therefore, students must list scientific words and their definitions. We often forget that this truly is a foreign language to most students, and requiring definitions helps dispel confusion.

Evidence of faulty reasoning.Students have a tendency to believe that everything written about a scientific topic must be true—it’s science. This activity helps students to become more critical readers, not just in science, but in all subjects. This is the hardest section for most students, and it will require some patience on the part of the instructor. However, the goal is for the student to show progress over the course of the semester. I provide my students with a handout that summarizes the following errors in reasoning: • Ad hominem: Criticism of the person rather than the argument. (Also known as “thought stoppers” because they evoke emotional rather than rational responses.)

• Appeal to authority: Acceptance as fact based upon the power or position of the person making the claim. (Obvious when no supporting data is offered.)

• Begging the question: Making something appear true when it is not. (Can be accomplished with visual aids as well as statements.)

• Equivocation: Introduction of words with multiple meanings to confuse the reader.

(Beware of slang terminology that derives meaning from context and voice inflection.)

• False dichotomy: Providing only two alternatives and inferring there are no other choices. (Either/or statements that corner readers into making a choice.)

• Red herring: Excessive information that detracts from the focus of the argument. (Information is off-track and might be more appropriate elsewhere.)

• Slippery slope: Conclusion of a cause-effect relationship between two events or actions. (May be in the form of a generalization.)

Using the Article in Lab Sessions Using the report in class is the next step. For example, prior to our first laboratory assignment on bacteria, students were assigned a reading from a common news magazine on a recent bacterial outbreak. After completing the assignment, I asked students to divide up 448

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based upon who thought it was a scientifically sound article and those who did not. Each side described their rationale based upon their search for faulty reasoning. Although I limited the discussion to ten minutes, this exercise became the key to development of critical reasoning.

As students explained their positions, quality discussion followed. Students who were less adept at analyzing articles learned quickly from their classmates, performed much better on subsequent analyses, and participated more in later discussions.

The most exciting results occurred during the actual laboratory exercise. Students remained engaged in both the execution of their lab exercises and in meaningful discussion during the entire lab period. Questions changed from hollow inquiries like, “Do I have to know this for the practical?” to more thoughtful questions like, “How does this organism evade the human immune system as compared to the one we read about?” The quality of answers to essay questions has improved, and student feedback on these assignments has been very positive. Many have returned to tell me how they have applied these analytical skills in other courses and at work.

This format can be adapted in a number of ways to fit most any science course. I have used it to focus on organisms in the news, bioethics, and environmental issues. It can be expanded into a large project or compressed into a smaller exercise done in class. It can also be done individually or in groups. It can even be done effectively online. My preference is to make the written portion of the assignment an individual responsibility to encourage freedom of expression. The classroom discussion allows immediate feedback and assistance for those who struggle with the critical analyses.

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