Biology Science for Life with Physiology, 4E Colleen Belk Solution Manual

INSTRUCTOR GUIDE

BIOLOGY Science for Life and

BIOLOGY Science for Life WITH PHYSIOLOGY FOURTH EDITION

Colleen Belk

Virginia Borden Maier

University of Minnesota, Duluth

St. John Fisher College

Jill Feinstein Richland Community College

CONTENTS

Chapter 1

Can Science Cure the Common Cold?

Introduction to the Scientific Method

1

Chapter 2

Are We Alone in the Universe?

Water, Biochemistry, and Cells

11

Chapter 3

Is It Possible to Supplement Your Way to Better Health?

Nutrients and Membrane Transport

17

Chapter 4

Fat: How Much Is Right for You? Enzymes, Metabolism, and Cellular Respiration

27

Chapter 5

Life in the Greenhouse Photosynthesis and Global Warming

35

Chapter 6

Cancer DNA Synthesis, Mitosis, and Meiosis

41

Chapter 7

Are You Only as Smart as Your Genes?

Mendelian and Quantitative Genetics

49

Chapter 8

DNA Detective Complex Patterns of Inheritance and DNA Fingerprinting

55

Chapter 9

Genetically Modified Organisms Gene Expression, Mutation, and Cloning

65

Chapter 10 Where Did We Come From?

The Evidence for Evolution

75

Chapter 11 An Evolving Enemy Natural Selection

85

Chapter 12 Who Am I? Species and Races

89

Chapter 13 Prospecting for Biological Gold Biodiversity and Classification

107

Chapter 14 Is the Human Population Too Large?

Population Ecology

119

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Chapter 15 Conserving Biodiversity Community and Ecosystem Ecology

135

Chapter 16 Where Do You Live?

Climate and Biomes

145

Chapter 17 Organ Donation Tissues, Organs, and Organ Systems

157

Chapter 18 Clearing the Air Respiratory, Cardiovascular, and Excretory Systems

163

Chapter 19 Vaccinations: Protection and Prevention or Peril?

Immune System, Bacteria, Viruses, and Other Pathogens

175

Chapter 20 Sex Differences and Athleticism Endocrine, Skeletal, and Muscular Systems

185

Chapter 21 Is There Something in the Water?

Reproductive and Developmental Biology

193

Chapter 22 Attention Deficit Disorder Brain Structure and Function

201

Chapter 23 Feeding the World Plant Structure and Growth

211

Chapter 24 Growing a Green Thumb Plant Physiology

219

Quick Reference Guide to Instructor Visual Resources

229

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CHAPTER

1 Can Science Cure the Common Cold?

Introduction to the Scientific Method OBJECTIVES Teaching Goals Most students have covered the scientific method in high school biology. However, when asked to define a hypothesis, the majority will say, “A hypothesis is an educated guess,” without any comprehension of what it really means. This chapter introduces the student to the scientific method as a way of thinking and explaining observations. This chapter also familiarizes students in the proper setup of experiments and statistical analysis of data. The emphasis should be on using critical thinking in everyday decision making—not just in a laboratory. Students are inundated with claims based on anecdotal evidence and misrepresentation of data. Your goal is to help the students evaluate such claims by critical analysis of the data.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe the characteristics of a scientific hypothesis.

• Compare and contrast the terms scientific hypothesis and scientific theory.

• Distinguish between inductive and deductive reasoning.

• Explain why the truth of a hypothesis cannot be proven conclusively via deductive reasoning.

• Describe the features of a controlled experiment and explain how these experiment eliminate alternative hypotheses for the results.

• List strategies for minimizing bias when designing experiments.

• Define correlation, and explain the benefits and limitations of using this technique to test hypotheses.

• Describe the information that statistical tests prove.

• Compare and contrast primary and secondary sources.

• Summarize the techniques you can use to evaluate scientific information from secondary sources.

LECTURE OUTLINE 1.1 The Process of Science (Figure 1.1) A. Scientific method allows for solving of problems and answering questions.

B. Hypotheses are explanations of how something works and must be testable and falsifiable.

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C. Scientific theories are supported by multiple lines of evidence from hypotheses that have been tested by deductive reasoning.

D. Construction of hypothesis involves inductive reasoning and hypothesis testing involves deductive reasoning. (Figure 1.3) 1.2 Hypothesis Testing A. Hypotheses are tested by experiments that should be controlled for variables and bias.

B. Correlation between variables may provide answers when other testing is problematic.

(Figure 1.10, Figure 1.11) C. Model systems are used when testing on humans is dangerous or unethicial.

(Figure 1.7) Lecture Activity 1.1 Lecture Activity 1.2 Lecture Activity 1.3 1.3 Understanding Statistics A. Statistical analysis can help researchers apply results from a small experimental group to a larger group without actually testing the larger group. (Figure 1.12) B. The significance of results is influenced by the size of the sample and the validity of the hypothesis. (Figure 1.15) C. Sampling error is the difference between a sample and the population that it is being compared to.

1.4 Evaluating Scientific Information A. Information from primary sources is used as the basis for news articles and websites.

(Figure 1.16) B. Different media sources have various levels of credibility and reliability.

Lecture Activity 1.4 1.5 Is There a Cure for the Common Cold?

A. Hand-washing is the best method for preventing the common cold.

Lecture Activity 1.1: Developing and Testing Hypotheses Estimated Time to Complete: 15–20 minutes, or longer with discussion Introduction: This activity gives students a chance to practice what they have learned about developing hypotheses and testing them. Students work in groups of three to four to promote interactive learning and discussion. An observation is given to each group, and the group members’ job is to create a testable and falsifiable hypothesis to explain that observation. The activity can stand alone, or it can become the basis of a discussion after completion. If desired, groups could report to the class on their observation, hypothesis, and experiment.

A handout is provided with a sample observation. Here are several more suggestions, and others can be made up as needed: • Algae appear in clean water left outside in a child’s plastic pool for a week.

• Lawn grass doesn’t grow at the beach.

• Mosquitoes bite some people more than others.

• Coleus plants grown inside are taller but have thinner stems than coleus plants grown outside.

• Ants eat some foods that they find outside, but not all.

• Bees visit some types of flowers, but not others.

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Chapter 1 Can Science Cure the Common Cold? 3

Material • Lecture Activity 1.1 Handout: Developing and Testing Hypotheses Procedures 1. Divide the students into groups.

2. Clearly explain that each group will receive an observation and that their job is first to formulate a testable hypothesis to explain that observation. They will then come up with an experimental protocol, including controls that would test their hypothesis.

3. Distribute a handout to each group, or give them their observation verbally. Groups can all receive the same observation, or a different observation can be used for each group.

4. Give the students 10–15 minutes to generate their hypothesis and experiment. Circulate around the classroom during that time to make sure that groups remain on task, that their hypotheses are reasonable and testable, and that the experimental procedure includes a control and makes sense.

5. If desired, ask groups to present their observation, hypothesis, and experiment to the class.

Assessment Suggestions: Have groups turn in their papers. Check that the hypotheses are testable and falsifiable and that control groups were used properly. Give students participation points for presenting their ideas to the class.

For an online course have students submit their hypotheses in a discussion forum and have the students discuss the results and determine if each hypothesis is in the correct format. Points are given following a rubric for participation.

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Lecture Activity 1.1 Handout: Developing and Testing Hypotheses Observation: Sea oats grow only near the beach.

Hypothesis:

Questions: 1. Is this hypothesis testable?

2. Design an experiment to test your hypothesis. Be sure to include a control group and use it properly.

Ask for help if you’re not sure.

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Chapter 1 Can Science Cure the Common Cold? 5

Lecture Activity 1.2: Do Bees See in Color?

Estimated Time to Complete: 15–20 minutes, or longer with discussion Introduction: This activity puts students into the shoes of a real scientist who is trying to answer a question about nature. The students read an account of some actual experiments done by Karl von Frisch to try to determine whether bees can see in color. They start with von Frisch’s observations, find out what he did, and work through the experimental method along with him. Working in groups, they see how von Frisch interpreted and then improved his experimental method to draw his conclusions.

Material • Lecture Activity 1.2 Handout: Do Bees See in Color?

Procedures 1. Divide students into groups.

2. Briefly introduce the activity and explain what students are to do.

3. Pass out handouts.

4. As students are working, circulate around the classroom to check that groups remain on track.

Sometimes they can get off on a tangent, hypothesizing, for example, that bees like sugar water.

They also tend to express themselves in vague generalities; keep them to specifics.

Assessment Suggestions: Collect and check group papers. A key for correcting the handout is provided.

Tell students that, using a similar set of experiments, von Frisch demonstrated that bees could not see the color red. Ask the class to describe the experiments and results that would have led von Frisch to reach this conclusion.

You could also put the handout online and have them fill out the handout online after completing the work in the classroom or have students work on this individually online and treat it like an assignment.

Handout Answer Key 1. What was von Frisch’s hypothesis? Von Frisch hypothesized that bees could see the color blue.

2. What conclusion should von Frisch draw from his results? He should conclude that the results supported his hypothesis—that the bees could distinguish the blue paper from the red paper.

3. What observation would have falsified von Frisch’s hypothesis? His hypothesis would have been falsified if the bees had swarmed around both bowls equally.

4. Which uncontrolled variable in his first experiment did von Frisch correct in the second experiment, and why was it important? The uncontrolled variable was color intensity. It is important because it is a way that bees could distinguish between the papers without actually being able to see their color.

5. How did von Frisch control for this variable in the second experiment? He put bowls on a series of gray papers with similar color intensity to the blue paper to see if that would confuse the bees.

6. What was the overall conclusion from von Frisch’s series of experiments? (Remember to refer to his original hypothesis.) Von Frisch concluded that his hypothesis was supported; bees can see the color blue.

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Lecture Activity 1.2 Handout: Do Bees See in Color?

Karl von Frisch studied the interactions between bees and flowers. He wanted to know how bees select which flower to go to. In particular, he wanted to know whether the bees could see different flower colors and would, therefore, select flowers based on their color.

In his first experiment, von Frisch put out pieces of red- and blue-colored paper, each of which had a bowl on top. In the bowl on the blue paper, he put sugar water; he left the bowl on the red paper empty.

Bees discovered the sugar water in the bowl on the blue paper and ate it, returning again and again with other bees to get more.

After a while, von Frisch took away the papers and bowls. He replaced them with two new bowls with colored paper, identical to the first pair except that both bowls were empty this time. He found that bees swarmed around the bowl on the blue paper, ignoring the bowl on the red paper.

Note that von Frisch already knew that bees like sugar water; this issue is not being tested in this experiment.

1. What was von Frisch’s hypothesis?

2. What conclusion should von Frisch draw from his results?

3. What observation would have falsified von Frisch’s hypothesis?

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It occurred to von Frisch that his experiment was not well controlled. Besides their colors, there was another difference between the papers that bees might use to tell them apart. The papers were very different in overall intensity of color; the red paper was much darker than the blue paper. In other words, even without color vision (like on a black-and-white TV), the papers would look different. Although you couldn’t tell what color the papers were, you could determine which was which if they were moved or rearranged. Perhaps the bees were responding to this intensity difference rather than to the actual color difference.

To check this new hypothesis, von Frisch took away the papers and bowls again. This time he set out a series of gray papers, some with the same intensity as the blue paper, and put the blue paper in the middle of these gray papers. All papers had an empty bowl on top. Once again, the bees flew directly to the blue paper and swarmed around its bowl.

4. Which uncontrolled variable in his first experiment did von Frisch correct in the second experiment, and why was it important?

5. How did von Frisch control for this variable in the second experiment?

6. What was the overall conclusion from von Frisch’s series of experiments? (Remember to refer to his original hypothesis.)

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Lecture Activity 1.3: Demonstrating the Importance of Control Groups Estimated Time to Complete: 10–15 minutes Introduction: This short demonstration helps students understand the importance of a control group in drawing inferences from data. Students are presented with data on the effect of drugs on the survival rates of several diseases, but then will realize that the data are meaningless without the ability to compare the experimental data to a control group.

Material • Copy or project the data given in steps 2 and 4.

Procedures 1. Ask students to imagine that they head up a research expedition to a remote location; they have a medical computer and some medicines, but no doctor with them. Three members of the research team come down with different illnesses, and the expedition leader must decide how to treat them.

The medical computer diagnoses their illnesses and finds out some basic data on treatment options.

Luckily, some of the drugs that have been used to treat their conditions in the past are available. The computer finds the information given in step 2.

2. Copy the following data onto a slide or transparency, or write it on the board: Disease A, treated with drug A, has a survival rate of 23%.

Disease B, treated with drug B, has a survival rate of 56%.

Disease C, treated with drug C, has a survival rate of 89%.

Based on these data, ask students what they think of these treatments and how they would choose to treat their assistants.

3. On giving the matter further thought, you realize that you are missing some important data. You can’t really understand the efficacy of the drug treatment unless you know the survival rates in the control groups that received no medications. A little more digging gives you additional data (see step 4).

4. Deliver the following data to the students in the same way, so that they can see both sets of data at the same time: Disease A, untreated, has a survival rate of 10%.

Disease B, untreated, has a survival rate of 54%.

Disease C, untreated, has a survival rate of 95%.

5. Ask students to reconsider their initial opinions and decisions in light of the new data and decide which disease to treat with which drug.

Assessment Suggestions: Discuss with the class the role of control groups in experimental design and explore how they allow scientists to draw reliable inferences.

Lecture Activity 1.4: Evaluating Scientific Claims in Advertisements Estimated Time to Complete: 10–30 minutes, depending on how many ads are used Introduction: We are saturated with stories from the newspaper, magazines, television, and the Internet about the effectiveness of many products, including cold remedies, health supplements, weight-loss products, and so on. These ads are difficult to assess, because we cannot completely determine the quality of the information or the extent to which the financial backers of a product are driving the information being presented. The purpose of this activity is to demonstrate a variety of media resources to the students and ask them their opinions about the effectiveness of the messages portrayed.

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Chapter 1 Can Science Cure the Common Cold? 9

Material • Any source of advertisements will do: magazines, websites, taped TV or radio commercials. Ads can be displayed or reproduced in any convenient fashion. Include ads for various types of products.

Procedures 1. Project or otherwise show students a variety of ads that make claims or promote products.

2. Ask the students to comment on the scientific validity and persuasiveness of the ads. This can be done as a single large discussion or in a small-group format. Discussion questions could include these: • Does the ad seem plausible? Why or why not?

• Are any data cited? Do those data seem complete? Are controls or comparisons included?

• Are testimonials used? If so, are they convincing? Why or why not?

• What other information do you wish the ad contained to better help you decide whether to buy the product?

• Would you buy the product based on this ad? Why or why not?

Assessment Suggestions: A suggested assignment would be for the student to find his or her own advertisement, similar to what the instructor showed in class, and analyze the material for reliability of the information.

In class discussion, poll students to see if any of them have tried or know someone who has used one of the products displayed. Have students compare opinion polling with hypothesis testing based on the use of these methods in advertising and their relative worth as sources of data.

For a group project, students could be assigned a specific health issue (e.g., cold remedies, arthritis relief) and asked to find conflicting testimonials or anecdotes from media sources. Each group could present to the rest of the class their findings on that particular issue and discuss what a primary resource indicates about the subject as compared to secondary sources.

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CHAPTER

2 Are We Alone in the Universe?

Water, Biochemistry, and Cells OBJECTIVES Teaching Goals This chapter introduces an invisible world that students often find difficult to grasp. Descriptive imagery and graphic representations are the basis for understanding atoms and cells. As a teacher, you must connect this invisible world to the visible world that students can see. Carbohydrates, proteins, and fats make more sense when seen on a food label, for example. Cells become real when connected to forensic evidence left at the scene.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe the properties associated with living organisms.

• List the components of water and some of the properties that make it important in living organisms.

• Describe how atomic structure affects chemical bonding.

• Compare and contrast hydrogen, covalent, and ionic bonds.

• Discuss the importance of carbon in living organisms.

• Describe the structure of carbohydrates, proteins, lipids, and nucleic acids and the roles these macromolecules play in cells.

• Compare and contrast prokaryotic and eukaryotic cells.

• Describe the structure and functions of cell membranes.

• Describe the structure and function of the subcellular organelles.

• Provide a general summary of the theory of evolution.

LECTURE OUTLINE 2.1 What Does Life Require?

A. All organisms operate using the same biological molecules, are composed of cells, and use feedback mechanisms to maintain homeostasis. (Figure 2.1) B. Atoms and subatomic particles play a role in chemical reactions and bond formation.

(Figure 2.3) C. Water is essential to life, and its properties are based on its polarity. (Figure 2.4, Figure 2.5, Figure 2.6) Lecture Activity 2.1 Lecture Activity 2.2

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D. Acids, bases, and salts play a role in chemical reactions.

E. Life on Earth is based on the carbon atom and its bonding capabilities to form macromolecules (carbohydrates, proteins, lipids, and nucleic acids). (Figure 2.9, Figure 2.10, Figure 2.11, Figure 2.12, Figure 2.13, Figure 2.14, Figure 2.15) 2.2 Life on Earth A. Cells are the basic unit of life on Earth.

B. Cells are either prokaryotic or eukaryotic. Prokaryotic cells, such as bacteria, do not have a separate nucleus and are less complex than eukaryotic cells. (Figure 2.17) C. All cells have a variety of parts that work together to enable them to function in particular environments. (Table 2.1) Lecture Activity 2.3 Lecture Activity 2.4 D. The diversity of cells and organisms is based on evolutionary theory. (Figure 2.19)

Lecture Activity 2.1: Understanding Chemical Bonding Estimated Time to Complete: 10–20 minutes Introduction: This activity is a basic introduction to the concept of chemical bonding. It is a short, in-class exercise that can follow the first discussion of atomic structure and bonding. Students will take the number of their birth month as their atomic number. Given this information, they will be able to determine the configuration of their electrons. They will then be able to determine how they, as atoms, will interact with other atoms, if at all. Students will form “bonds” with other students to make ions or molecules.

Material • Lecture Activity 2.1 Handout: Understanding Chemical Bonding Procedures 1. Briefly explain to the students what they will be expected to do on the worksheet.

2. Each student will complete a worksheet alone, but you can allow students to work together if you like.

3. Pass out worksheets, and circulate around the room to ensure that students get started correctly; answer questions that come up.

4. After they know which type of partner they need, encourage students to get out of their seats and walk around to find someone suitable.

Assessment Suggestions: Collect and grade the handouts. Use this assignment as the basis of a homework or test question.

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Lecture Activity 2.1 Handout: Understanding Chemical Bonding 1. What is the number of your birth month? (January = 1, February = 2, etc.) This is your atomic number.

2. Draw your appearance as an atom. Around the nucleus, put the correct number of electrons in their correct valence shells.

3. Which type of bond would you like to form to become stable?

4. Find one or more other students to bond with so that you form a stable bond. Draw the ion or molecule that you all formed.

5. Explain why you are stable in this configuration.

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Lecture Activity 2.2: Molecular Twenty Questions Estimated Time to Complete: 10–20 minutes Introduction: In this activity, students get an opportunity to test their knowledge of biological molecules.

The students will form groups of three to four. Each student will secretly receive the name of a biological molecule. The other students in the group will then take turns asking yes or no questions until one of them is able to correctly guess the identity of the molecule in question.

Material • Names of different molecules on pieces of paper cut from the bottom of this page.

Procedures 1. Divide students into groups of three to four. Explain how the game will work, and have the students determine who will go first in each group.

2. Pass around a hat or box containing small folded pieces of paper each with the name of a molecule. In a small class, you can pass out the papers initially to only one student in each group, and then have other students come up for another piece after each round. In a large class, have everyone take a paper at the same time.

3. The person going first in each group silently reads his or her molecule’s name, and then the other group members take turns asking a yes or no question to try to identify the molecule.

4. When students have a guess about the molecule, they must wait until it is their turn to say it.

5. Other members of the group then answer questions about their molecules until all members have had a turn, or until the allotted time is up.

Assessment Suggestion: You may have the students keep track of how many molecules they guess correctly, and give out a grade or extra credit for those who score above a certain number.

Molecule Names

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Chapter 2 Are We Alone in the Universe? 15

Lecture Activity 2.3: The Cell as a City Estimated Time to Complete: 5–10 minutes Introduction: Cells, because they are capable of independent life, must be able to carry out all of the processes necessary for life within themselves. In some ways they resemble cities; the functions of organelles can be compared to utilities and institutions that students are familiar with in the macroscopic world.

Material • None.

Procedures After discussing the functions of various organelles, ask students which organelle is most similar to the following institutions: • A public library (the nucleus stores information) • The U.S. Postal Service (the Golgi apparatus sorts and delivers materials) • A water tower (vacuoles store water) • A coal-burning power plant (mitochondria convert fuel to energy) • A solar power plant (chloroplasts convert sunlight to energy) • Manufacturing plants (ribosomes and endoplasmic reticulum build proteins) • A moving company (centrioles facilitate movement of chromosomes during mitosis) Assessment Suggestions: Use similar comparisons on test questions.

Lecture Activity 2.4: Cells Alive!

Estimated Time to Complete: 5–10 minutes Introduction: The concepts of living cells are central to every biology course. However, it is difficult for students to discuss life and its dynamics when they are exposed to only two-dimensional, static pictures.

This lecture activity brings the concepts of cells to life by letting students watch cancer and bacterial cells divide in real time. This activity can be used to discuss differences between prokaryotic and eukaryotic cells, cell structure, and the characteristics of life.

Material • A computer with projector capabilities and an Internet connection.

Procedures 1. In the classroom, project the following website: http://www.cellsalive.com.

2. Many areas related to cells can be explored at this website, but a favorite is “Cell Cam.” You can find this link along the left side of the “CELLS alive!” home page.

3. You will see two pictures: one of human cancer cells dividing and one of bacterial cells dividing.

When you click on one of these pictures, you will link to a page that has three picture frames. The first picture was taken earlier in the day; the time this picture was taken is shown at the top of the picture. The picture on the far right is the most recent picture taken; its time is also shown. The middle picture will look like the left picture until you change it by clicking the 1 and 2 buttons below the pictures.

4. The “CELLS alive!” website maintains a live link to a camera that takes pictures of these cells every few minutes. You can click on the +1 and +5 buttons below the pictures to view the pictures that were

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taken between the first and the current pictures. In this way, you can watch the cells divide as you click through the sequence of pictures taken that day.

5. If you remain on this site, you can watch the next pictures taken. Students really love the idea of the pictures being taken “live” right in front of them. They are actually witness to cell division events.

6. Demonstrate the division of human cells and bacterial cells by clicking consecutively through an entire day of pictures. Have students note how fast each cell type divides, what the size and shape of the cells are, and how the cells react to one another in the Petri plate.

7. Have students draw and label some of what they see. Are there internal structures evident in the pictures of these cells? Why or why not? How are these pictures different from the figures in the textbook? Can students visualize these cells dividing in this way in the human body?

Assessment Suggestions: Students may turn in their drawings and observations. There are also many ideas for follow-up activities on this website.

This could also be done as an online assignment. Provide students with the link and then create an assignment using a variety of questions.

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3 Is It Possible to Supplement Your Way to Better Health?

Nutrients and Membrane Transport OBJECTIVES Teaching Goals Many students read food labels but they don’t understand the significance of the information provided on those labels. In this chapter you should clearly differentiate between carbohydrates, fats, and proteins.

Your goal is to help students recognize and make healthful food choices by understanding food labels.

The concept of membrane transport is often difficult for students to grasp. Use visual aids and animations to enhance their understanding of osmosis, diffusion, and active transport.

Student Goals By the end of this chapter students should be able to accomplish the following learning objectives: • Describe the role of nutrients in the body.

• Describe the function of the water in the body.

• Describe the major dietary macronutrients and discuss the functions of each.

• List the major dietary micronutrients and describe their functions.

• Describe the structure and function of the plasma membrane.

• Distinguish between passive transport and active transport.

• Describe the processes of endocytosis and exocytosis.

LECTURE OUTLINE 3.1 Nutrients A. Macronutrients such as water, carbohydrates, proteins, and fats are nutrients that are required in large amounts.

B. Water is required to carry nutrients throughout the body and maintain an even temperature.

C. Carbohydrates can be either simple or complex; both types serve different functions in the body.

(Figure 3.1) D. Proteins are made of amino acids and are found in a variety of foods. (Figure 3.2) E. Fats serve as a source of energy as well as protection for organs. They are classified as saturated, unsaturated, or trans fats. (Figure 3.4)

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F. Micronutrients, which include vitamins, minerals, and antioxidants, are essential parts of a healthy diet. (Table 3.1, Table 3.2, Table 3.3) G. Whole foods contain more nutrients, vitamins, and minerals than do processed foods.

Lecture Activity 3.1 3.2 Transport Across Membranes Lecture Activity 3.2 A. Passive transport does not require an input of energy and can occur by diffusion, facilitated diffusion, or osmosis. (Figure 3.5, Figure 3.6) Lecture Activity 3.3 B. Active transport requires energy and uses proteins to move molecules from areas of lower concentration to areas of higher concentration. (Figure 3.7) C. Large molecules are taken into the cell by endocytosis and leave the cell by exocytosis.

(Figure 3.8)

Lecture Activity 3.1: Reading Nutrition Labels Estimated Time to Complete: 15 minutes Introduction: Students are repeatedly told that they need to eat a balanced diet, yet many are not able to evaluate the foods they eat. It is important that students learn how to read nutrition labels on the foods they eat and use this information to evaluate a product for its nutritional content.

Materials • Three nutrition labels: two from “healthy” foods and one from a “junk” food. Copy one of the “healthy” labels onto a PowerPoint slide or a transparency. Copy the other two labels side by side onto a PowerPoint slide or a transparency.

• Lecture Activity 3.1 Handout: Reading Nutrition Labels Procedures 1. Take 5 minutes to describe the parts of a nutrition label using the “healthy” food label on the transparency or slide. Include the following important points: A. %DV: If a nutrition label displays a 6% DV for Total Carbohydrates, this means that by eating a single serving of this food, you will be consuming 6% of your daily allotment for carbohydrates.

This figure is based on a 2000-calorie diet.

B. Total Fat value minus Saturated Fat value equals Unsaturated Fat value.

C. Total Carbohydrate value minus Fiber value minus Sugar value equals Complex Carbohydrate value.

D. Serving size is important. Most Americans eat more than a serving-size portion at one sitting.

E. Many labels also include the following information: 1 g Fat = 9 calories.

1 g Carbohydrates = 4 calories.

1 g Protein = 4 calories.

2. Show the second overhead transparency or slide, and direct the students to answer the questions on the handout in groups of two or three. Circulate among the groups to ensure that each group is on task. Answer questions to keep students moving forward.

3. Have a few students give oral reports on their findings and conclusions.

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Assessment Suggestions: Have students write their answers and calculations on the handout provided, and collect their group’s work. Evaluations may not be easily given for points, but this will be valuable material with which the instructor can assess the level of student understanding of this topic.

Ask students to choose a food label from a food they consider “unhealthy” and one from a “healthy” food. These labels should come from foods they consume in their personal diet. Have students use the food label information to support their position in a one-page paper.

You can do this assignment online by scanning in different labels and placing the questions online for them to answer. You could also do a group project and have students find five labels and then explain them in a one-page group paper.

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Lecture Activity 3.1 Handout: Reading Nutrition Labels Answer the following questions in your small groups. Be prepared to share your answers in a class discussion.

1. Circle the main type of carbohydrate present in the foods shown. fiber

simple sugar

complex carbohydrate

2. Why does the kind of carbohydrate matter when eating a healthy diet?

3. Are either of these foods high in saturated fat? Yes or No 4. Do you see any “hydrogenated” fats (a source of trans-fatty acids) listed in the ingredients? Yes or No 5. Do either of these foods have a good balance of fats, proteins, and carbohydrates? Yes or No 6. If your answer to question 5 was no, then which kinds of foods would you need to eat to balance out the rest of your day’s diet?

7. Is one of these foods healthier than the other? Yes or No 8. If the answer to question 7 is yes, write the name of the food.

9. What criteria did you use to determine the food’s “healthiness”?

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Lecture Activity 3.2: Interaction of Hydrophilic and Hydrophobic Substances Estimated Time to Complete: 15 minutes Introduction: To understand the structure and function of biological membranes, students need to understand some basic characteristics of biological molecules. This demonstration will reinforce the differences between hydrophilic and hydrophobic substances, and show that they create two distinct layers when mixed. When a hydrophilic solute is added, it will be more soluble in the water layer. In contrast, a hydrophobic solute will be more soluble in the lipid layer. This information could then lead to a discussion regarding the solubility or permeability of solutes in these layers.

Materials • 30 ml of water • 100-ml graduated cylinder or similar tall, thin container • Methylene blue, or blue or green food-coloring dye • 30 ml of vegetable oil • Lipid-soluble dye such as Sudan red (in powder form) • Parafilm or plastic wrap • Lecture Activity 3.3 Handout: Interaction of Hydrophilic and Hydrophobic Substances Procedures 1. Place 30 ml of water in the graduated cylinder.

2. Add methylene blue or food coloring; swirl.

3. Carefully pour 30 ml of vegetable oil on top so that two layers exist.

4. Add Sudan red dye.

5. Cover top of graduated cylinder with parafilm or plastic wrap. Shake the container, and place it on a desk to settle during the class period.

6. At the end of the period, discuss what is observed, using the assessment questions on the handout.

Assessment Suggestion: Use the handout provided for class discussion or individual assessment. You could also have students add some detergent to the graduated cylinder after step 5 and shake it to demonstrate how detergent allows hydrophobic and hydrophilic molecules to temporally mix.

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Lecture Activity 3.2 Handout: Interaction of Hydrophilic and Hydrophobic Substances Answer the following questions in your small groups. Be prepared to share your answers in a class discussion.

1. Describe what occurs when the oil and water are mixed together.

2. After the solution has been mixed and allowed to settle, describe what you observe.

3. Explain why this result occurred.

4. Relate this demonstration to what you know about membrane structure.

5. Explain why hydrophilic compounds such as amino acids and sugars require facilitated diffusion or active transport to cross a cell membrane.

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Lecture Activity 3.3: Demonstration of Osmosis Estimated Time to Complete: 5–10 minutes at the beginning of lecture; 10–20 minutes at the end of the lecture, depending on how many questions are assigned. (Note: You must begin soaking the eggs 3 days in advance.)

Introduction: This activity is an excellent demonstration of osmosis. Although some students may have seen this activity in an earlier biology class, it is worth repeating for those who may not have observed it.

In this experiment, you will use chicken eggs that have been soaked in vinegar for several days to remove the shell. The chicken egg is actually a large cell. The membrane, with the shell removed, can serve as a model of a cell membrane. Osmosis can be measured by changes that occur in the weight of the egg after soaking it in Karo syrup.

Materials • 2 eggs with the shell removed • Vinegar • Digital scale and weighing boat • Paper towels • Two 9-oz plastic cups • Water • Karo syrup (clear type) • Plastic spoons • Lecture Activity 3.3 Handout: Demonstration of Osmosis Procedures 1. Three days before the demonstration, completely immerse medium or large eggs in vinegar to dissolve their shells. Change the vinegar each day to ensure complete removal of the shell. On the day of the demonstration, rinse the de-shelled eggs gently and transfer them to water.

2. Obtain two chicken eggs from which the shell has been dissolved.

3. At the beginning of class, weigh each egg, making sure to carefully blot each egg on a paper towel before weighing it. Announce the results to the class.

4. Add one egg to a plastic cup that contains water; add the other egg to a cup of Karo syrup, which is a very thick, sugary solution.

5. Introduce the subject of osmosis. Ask the class what they think will happen to the two eggs.

6. Remove and weigh the eggs at 30 minutes and at 60 minutes (if you have time, weigh them again at 90 minutes). A plastic spoon will help you to lift each egg out of the cup without breaking it.

7. Record your results in the data table on the handout provided.

Assessment Suggestion: Use the handout on the next page for class discussion or individual assessment.

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Lecture Activity 3.3 Handout: Demonstration of Osmosis Data Table Initial Weight of Egg

Weight of Egg at 30 Minutes

Weight of Egg at 60 Minutes

Egg in cup 1 (water)

Egg in cup 2 (Karo syrup)

Questions 1. Did the eggs show a change in weight? Yes or No 2. Clearly explain why or why not.

3. Which substance was moving and caused the weight change?

4. Where did the energy for the movement come from?

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Weight of Egg at 90 Minutes

After severe blood loss or dehydration, patients are often treated with normal saline to help restore body fluids. Normal saline is 0.9% NaCl. 5. Why is the salt concentration important?

6. What would happen to the red blood cells of a patient who was treated with 0% saline?

7. What about 10% saline?

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CHAPTER

4 Fat: How Much Is Right for You? Enzymes, Metabolism, and Cellular Respiration OBJECTIVES Teaching Goals This chapter focuses on metabolism and the different chemical processes involved in metabolism.

Enzymes and the importance they play in metabolism are discussed. Introduce enzyme chemistry by giving examples of enzymes used in the food, textile, and fermentation industries. It is important to make the connection between cellular respiration and metabolism. Another goal is to explain the complications that arise with overweight and underweight individuals.

Student Goals By the end of this chapter students should be able accomplish the following learning objectives: • Define the term metabolism.

• Describe the structure and function of enzymes.

• Explain how enzymes decrease a reaction’s activation energy barrier.

• List several reasons why metabolic rates differ between people.

• Describe the structure and function of ATP. • Describe the process of cellular respiration from the breakdown of glucose through the production of ATP. • Explain how proteins and fats are broken down during cellular respiration.

• Compare and contrast aerobic and anaerobic respiration.

• Outline the health risks that occur with being overweight and underweight.

LECTURE OUTLINE 4.1 Enzymes and Metabolism A. Metabolism is regulated by enzymes that react with substrates. (Figure 4.2) Lecture Activity 4.1 B. Organisms have different metabolic rates that determine their caloric requirements. (Figure 4.3) 4.2 Cellular Respiration A. ATP is the universal storage molecule for energy. (Figure 4.4) B. Phosphorylation is the process of transferring a phosphate from ATP to be energized. (Figure 4.6)

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C. Cellular respiration is a series of chemical steps that use oxygen to break down carbohydrates, releasing carbon dioxide, water, and ATP. (Figure 4.12, Figure 4.15, Figure 4.16) Lecture Activity 4.2 Lecture Activity 4.3 D. Cellular respiration can occur without oxygen through fermentation.

4.3 Body Fat and Health A. Body mass index (BMI) is a measure of weight and health risk, but it does not account for individual differences due to gender and muscle mass.

B. People with a BMI of 30 or more are considered obese and are at higher risk of developing diabetes, hypertension, and heart disease. (Table 4.1) C. Underweight people can also face serious health consequences.

Lecture Activity 4.1: Energy in Chemical Bonds Estimated Time to Complete: 3–5 minutes Introduction: Students are told there is energy in chemical bonds. A two-dimensional, linear drawing of a chemical bond does not adequately convey the energy present there. This demonstration shows how the energy in a bond is significant and can be used to perform the work of a cell. It works especially well to show how energy is released from food molecules during their chemical digestion. It can also be used to demonstrate the energy in the phosphate bonds of ATP. Materials • Two medium-sized blocks or packs of index cards • One heavy-duty rubber band • Scissors Procedures 1. Place the blocks on a table side by side, touching one another.

2. Place the rubber band so it wraps one time around the blocks, holding them together, still side by side.

The blocks represent atoms, and the rubber band is the chemical bond that keeps the atoms together.

3. Pull the blocks apart so that students can see how the rubber band is stretched between the blocks.

Pluck the rubber band like a guitar string to show how bonds are not static, but rather are charged with energy. Discuss with the students what a chemical bond is and how it is used to hold atoms together.

When bonds are broken, energy is released that can be used to power other reactions in the cell.

4. Hold the blocks apart using one hand, and cut the rubber band in one spot with the other hand. The rubber band will fly away from the blocks in the direction away from the cut. Depending on the strength of the rubber band and the tension applied when the blocks are pulled apart, the rubber band has the potential to shoot all the way across the room. The blocks will be independent from each other, representing the broken bond.

5. Discuss with the students that when food molecules are chemically digested, energy is released from the bonds. This energy is captured by coenzymes, which use the energy to make high-energy phosphate bonds in ATP. When the phosphate bonds of ATP are broken, the liberated energy powers the work of the cell.

Safety Suggestion: When the rubber band is cut, make sure its projected direction is not directly toward a student. If the rubber band is strong enough or enough tension is applied, it could cause injury to the face and eyes.

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Chapter 4 Fat: How Much Is Right for You? 29

Assessment Suggestions: Ask students the following questions in a brief class discussion to ensure their understanding of the demonstration: 1. In this demonstration, what did the rubber band represent?

2. Why did it shoot across the room when cut?

3. What does this action represent at the cellular level?

4. How is the energy contained in chemical bonds used in the body?

Lecture Activity 4.2: Cell Respiration Summary Estimated Time to Complete: 15–20 minutes Introduction: This activity is a good way to review cell respiration in small groups in class, at the end of the lecture(s) on cell respiration. The entire process is summarized on a one-page handout.

Material • Lecture Activity 4.2 Handout: Cell Respiration Summary Procedures 1. Hand out the worksheets to students in small groups.

2. Instruct the students to use the Keywords to fill in the blank boxes and ovals in the figure.

3. Circulate among the groups during this activity to answer questions and keep groups on task.

4. After allowing students to work together for about 10 minutes, review the worksheet as a class.

Assessment Suggestion: Portions of the handout or the entire worksheet can be given as a quiz or used as the basis for exam questions. This activity be placed online by taking the worksheet and adding numbers to the blank boxes and ovals and having students type in their answers in essay format.

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Handout Answer Key (Cell Respiration Summary)

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Lecture Activity 4.2 Handout: Cell Respiration Summary

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Lecture Activity 4.3: Electron Transport Chain Skit Estimated Time to Complete: 5–10 minutes Introduction: Students often find it extremely difficult to grasp the concept of how the electron transport chain works and how it is related to the generation of ATP during cellular respiration. In this activity, students model how the electron transport chain works, translating its invisible and mysterious workings into something large enough to see and understand. The modeling is not extremely accurate in portraying events at the molecular level, but it gives students a taste of what is going on.

Materials • Four signs on a string (to be hung around students’ necks) labeled as follows: One sign saying “ATP Synthase” in large letters Three signs saying “Electron Transport Chain” in large letters • Ping-pong balls (or any other small, durable objects) • Large index cards with “NAD1” written on them; over the 1, put a small sticky note with an “e” on it.

• Large index cards with “ATP” written on them • Piece of paper with “OXYGEN” written on it Procedures 1. Ask for student volunteers: One is needed to represent ATP synthase, and three will be part of the electron transport chain. Explain that the jobs are not hard. Hang appropriate signs around their necks.

2. Bring the volunteers to the front of the room and give each electron transport chain (ETC) member a handful of ping-pong balls.

3. Have the three ETC volunteers line up from tallest to shortest.

4. Have the tallest person stand at one end of the group. The middle person sits on a chair next to the first person, and the shortest person sits on the floor at the end of the line. This represents the energy of the traveling electrons going from higher to lower energy levels. The ATP synthase person should sit or stand in front of the group and face them.

5. Give the remaining students (or some of them in a large class) a prepared NAD1 index card, but have them remain in their seats for the present.

6. The instructor holds the ATP cards and will narrate and direct the action.

7. Inform the class that they are now inside a cell. The area where the skit will occur is the mitochondria.

8. As the narrator, read the following passage or describe the process in your own words; students wait during this initial narration: During cellular respiration, glucose is first broken down to form pyruvate. In this process a small amount of ATP is formed, as well as some NADH. The pyruvate goes to the mitochondria, where it loses one carbon as carbon dioxide and enters the Krebs cycle. In the Krebs cycle, the rest of the carbon is lost as carbon dioxide. At the same time, electrons and protons from the original glucose molecule are picked up by NAD1, converting it to NADH. The NADH transports the electrons to the electron transport chain, and donates them at the highest energy level. The electrons travel down the electron transport chain to lower energy levels; as they do so, they cause protons to move from the mitochondrial matrix into the intermembrane space. The energy of having all of these protons in a small space is used by the ATP synthase to make ATP. 9. The narrator directs students holding NADH cards to proceed one at a time to the electron transport chain, handing their card to the standing person.

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Chapter 4 Fat: How Much Is Right for You? 33

10. The standing person removes the sticky note and gives the NAD1 card back to the student, who sits down again. The sticky note is held up over the head of the first person and then passed to the next person, who lowers the card and passes it on to the final person in the chain, who sticks it to the piece of paper labeled OXYGEN that is next to him or her on the floor. As each person takes a sticky note, he or she also tosses one of the ping-pong balls in front into the intermembrane space (the space in front of the person).

11. Meanwhile, the narrator explains what is happening to the electrons, protons, energy levels, and so on.

12. When all of the students holding cards have been to the electron transport chain (or the chain runs out of ping-pong balls), the narrator directs ATP synthase to gather up the ping-pong balls, bring them to the narrator, and exchange them for some ATP cards.

Assessment Suggestions: Ask students to summarize in their own words what happens during the electron transport process. Use the skit as the basis of a quiz or exam question.

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CHAPTER

5 Life in the Greenhouse Photosynthesis and Global Warming OBJECTIVES Teaching Goals The popular film An Inconvenient Truth brought climate change and global warming to the widespread attention of the public. Because these topics have become a political issue, your job is to help students see the science behind the media reports. Linking photosynthesis to global warming provides a “hook” for students to seek understanding of these important biological processes. Your goal is to illustrate the relationships between these chemical pathways without burying students in excessive detail.

Student Goals By the end of this chapter students should be able to accomplish the following learning objectives: • Describe the greenhouse effect.

• Explain why water is slow to change temperature.

• Compare and contrast the water cycle and carbon cycle.

• Discuss the origin of fossil fuels and their relationship to the carbon cycle.

• State the basic equation of photosynthesis.

• Describe the light reactions of photosynthesis.

• Explain the events that occur during the Calvin cycle.

• Describe the relationship between the light reaction and the Calvin cycle.

• Explain the role of stomata in balancing photosynthesis and water loss.

• Define photorespiration and why this process is detrimental to plants that experience it.

• Discuss how our own activities contribute to or reduce the risk of global warming.

LECTURE OUTLINE 5.1 The Greenhouse Effect A. Carbon dioxide is the major gas contributing to global warming.

B. The greenhouse effect occurs when reflected heat from the earth is trapped in the atmosphere.

(Figure 5.1) C. Water helps to moderate the earth’s temperature by storing and releasing heat. (Figure 5.2) 5.2 The Flow of Carbon A. Carbon travels through organisms as well as the soil, water, and air. Many human activities, such as burning fossil fuels, release large amounts of carbon. (Figure 5.4) B. Rising temperatures are directly related to the increasing concentration of carbon dioxide. (Figure 5.8) .

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5.3 Can Photosynthesis Reduce the Risk of Global Warming?

A. Plants transform the energy of the sun in a two-step process (light and dark): (Figure 5.12, Figure 5.13) (1) taking in carbon dioxide and water (2) producing carbohydrates and oxygen Lecture Activity 5.1 Lecture Activity 5.2 B. The combination of burning fossil fuels and deforestation prevents photosynthesis from reducing increasing carbon dioxide levels.

5.4 How Global Warming Might Reduce Photosythesis A. Transpiration is the movement of water through the stomata and photorespiration occurs when the stomata closes. (Figure 5.15) B. Plants have evolved to prevent water loss. (Table 5.1) 5.5 Decreasing the Effects of Global Warming A. Individuals can decrease their own greenhouse gases. (Table 5.2) B. Political leaders need to find ways to reduce emissions from different countrywide sources.

Lecture Activity 5.1: Global Warming and Photosynthesis Estimated Time to Complete: 10 minutes Introduction: There are many broad-reaching consequences of global warming that students are or may become concerned about. This class discussion helps solidify students’ understanding of the reading and class discussion of global warming and its relationship to photosynthesis.

Material • Assigned reading in textbook.

Procedures After reading the relevant sections in the text and discussing them in class, have a class discussion on the issues. Depending on class size, this activity can be a whole-class discussion or may be conducted in small groups. Pose the following questions to the class for discussion: 1. What is global warming, and what causes it? (Global warming is an increase in the average global temperature as a result of the buildup of greenhouse gases. A primary greenhouse gas is carbon dioxide.)

2. What is the relationship between photosynthesis and global warming? (Plants are carbon dioxide “sinks.” They use carbon dioxide from the atmosphere for photosynthesis, thereby decreasing the amount of atmospheric carbon dioxide.)

3. As carbon dioxide levels rise, what will happen to the rate of photosynthesis? (Some studies have demonstrated an increased rate of photosynthesis caused by increased carbon dioxide levels.)

4. What are the potential benefits of an increased rate of photosynthesis? What are the concerns? (If rates of photosynthesis increase, the amount of carbon dioxide utilization will also increase. Plants will grow more quickly, possibly producing more food. A concern is that an increased growth rate may lead to a decreased nutrient value per pound of vegetation.)

5. Will photosynthesis occur at a rapid rate indefinitely? Why or why not? (No, because most likely some other nutrient will become limiting.)

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Assessment Suggestions: Have student groups write down some of their answers for collection. Pose a similar question on a quiz or exam. You could post these questions in separate discussion forums online and ask students to answer each question and then respond to other classmates’ responses. This will stimulate a good discussion of the topic.

Lecture Activity 5.2: The Role of Carbon Dioxide in Photosynthesis Estimated Time to Complete: This activity will take about 10 minutes to set up at the beginning of class. The flasks need to stand in the light for approximately 20–30 minutes until observations can be made. If you assign the handout, students will need about 5 minutes at the end of class to answer the questions.

Introduction: This activity allows students to indirectly see carbon dioxide being taken up by photosynthesis.

Materials • Two 125-ml flasks with airtight stoppers • Water • 1% bromthymol blue solution • Drinking straw • Fresh Elodea • Bright light source (this can be a shop light) • Lecture Activity 5.2 Handout: The Role of Carbon Dioxide in Photosynthesis Procedures Begin with all solutions at room temperature. Distribute the handouts to the class, if desired.

1. Fill two 125-ml flasks (flask A and flask B) with water and a few drops of bromthymol blue.

2. Explain to the class that exhalation produces carbon dioxide, which dissolves to form carbonic acid, H 2 CO3 . Carbonic acid makes solutions slightly acidic. Students also need to know that the compound bromthymol blue will change from blue to greenish-yellow under acidic conditions.

3. Using a straw, blow gently into the water in both flasks until the solution turns a pale green.

4. Place a 6- to 8-cm sprig of Elodea into flask B. Make a fresh, angled cut in the stem of the Elodea.

It should be placed with the stem side up, immersed in the water.

5. Place an airtight stopper on each flask. This activity works best when there is not a lot of air left in the flask.

6. Place the flasks at a distance of 1.5–2 feet from a bright source of light.

7. At the end of the class period, note any color changes in the flask; have students answer the questions on the handout.

Assessment Suggestion: Use the questions on the following handout for individual assessment or group discussion.

Handout Answer Key 1. At the end of the class period, were there any changes in the colors of the solutions? Explain. The solution in the beaker with Elodea in it should return more quickly to the blue color, because Elodea uses the carbon dioxide for photosynthesis. This should be visible within the class period. The solution in the beaker without Elodea will not be blue.

2. What happens to the carbon dioxide after it is taken up by the Elodea plant? After the carbon dioxide is taken into the Elodea plant, it will be fixed (attached to an organic molecule, RuBP) and go through the reactions of the Calvin–Benson cycle. The carbon dioxide will ultimately be used to make glucose. .

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3. If the experiment was repeated with both flasks in the dark, what would you expect to happen? Why? The reactions of the Calvin–Benson cycle require ATP and NADPH from the light dependent reactions. Because the flasks are in the dark, photosynthesis and carbon dioxide utilization will not occur. Both flasks will remain a greenish color. In fact, as the cells of the Elodea plant continue to undergo cell respiration, more carbon dioxide may build up in flask B, causing the solution to become more yellow–green.

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Lecture Activity 5.2 Handout: The Role of Carbon Dioxide in Photosynthesis Data Table Color after Addition of Bromthymol Blue

Color after Blowing through Straw (addition of CO 2 )

Color after Exposure to Light

Flask A

(− Elodea)

Flask B

(+ Elodea)

Questions 1. At the end of the class period, were there any changes in the colors of the solutions? Yes or No Explain:

2. What happens to the carbon dioxide after it is taken up by the Elodea plant?

3. If the experiment was repeated with both flasks in the dark, what would you expect to happen?

Why?

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6 Cancer DNA Synthesis, Mitosis, and Meiosis OBJECTIVES Teaching Goals Few of the younger students in your class will have had cancer, but they will almost certainly have mothers and fathers and other relatives who have had the disease. Your goal is to help them understand how cancer cells form by looking at the mechanics of mitosis and the effect of mutations. You will need to stress the differences between mitosis and meiosis, including when each process occurs. Mitosis is associated with growth, maintenance, and repair; meiosis is responsible for reshuffling the genes and passing them on.

Student Goals By the end of the chapter, students should be able to accomplish the following learning objectives: • Describe the cellular basis of cancer.

• Compare and contrast benign and malignant tumors.

• List several risk factors for cancer development.

• List the normal functions of cell division.

• Describe the structure and function of chromosomes.

• Outline the process of DNA replication.

• Describe the events that occur during interphase of the cell cycle.

• Diagram two chromosomes as they proceed through mitosis of the cell cycle.

• Describe the process of cytokinesis in animal and plant cells.

• Describe how the cell cycle is regulated and how dysregulation can lead to tumor formation.

• Explain how genes and environment both impact cancer risk.

• Discuss the various methods of cancer detection and treatment.

• Explain what types of cells undergo meiosis, the end result of this process, and how meiosis increases genetic diversity.

• Diagram four chromosomes from a diploid organism undergoing meiosis.

• Explain the significance of crossing over and random alignment in terms of genetic diversity.

LECTURE OUTLINE 6.1 What Is Cancer?

A. Cancer cells differ from normal cells and are a result of uncontrolled cell division, which can produce either benign or malignant tumors that may metastasize. (Figure 6.1)

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B. Risk factors for cancer include increasing age, tobacco use, obesity, and lack of exercise.

(Table 6.1) 6.2 Passing Genes and Chromosomes to Daughter Cells A. Genes occur on chromosomes; the chromosomes are copied prior to cell division.

Lecture Activity 6.1 B. Asexual reproduction requires genetic input from only one individual, whereas sexual reproduction results from genetic input from two parents.

C. Copied chromosomes are called sister chromatids and are connected by a centromere. (Figure 6.5) D. DNA polymerase plays a key role in the replication of DNA. (Figure 6.4) 6.3 The Cell Cycle and Mitosis A. The cell cycle has three steps: interphase, mitosis, and cytokinesis. (Figure 6.6) B. Mitosis occurs in four stages and results in two identical cells. (Figure 6.7) C. Cytokinesis occurs after mitosis and results in the division of the cytoplasm into two cells.

(Figure 6.8) Lecture Activity 6.2 6.4 Cell Cycle Control and Mutation A. Cell cycle has controls in place to determine if a cell can continue to divide. (Figure 6.9) B. Mutations can occur in proteins that regulate the cell cycle, resulting in cancer cells.

(Figure 6.11, Figure 6.12) C. Proto-oncogenes are normal genes that can mutate and become oncogenes.

D. Cancer cells have an unlimited life span; in contrast, normal cells have a finite life span.

6.5. Cancer Detection and Treatment A. Detection methods vary based on the type of cancer. Many people who have cancer will display early warning signs of the disease. (Figure 6.14) B. Treatment may include chemotherapy and/or radiation.

6.6 Meiosis A. Karyotypes are used to visualize chromosomes.

B. Humans have 22 pairs of autosomes and 1 pair of sex chromosomes. (Figure 6.16) C. Meiosis occurs in specialized sex cells and cuts the number of chromosomes in half by dividing the homologous pairs and then the sister chromatids. (Figure 6.21) Lecture Activity 6.3 D. Random assortment of homologous pairs and crossing over provide variety in the resulting cells.

(Figures 6.22, Figure 6.23) Lecture Activity 6.4 Lecture Activity 6.5 E. If a homologous pair does not separate property (non-disjunction), an incorrect chromosome number will occur in the daughter cells. (Table 6.2)

Lecture Activity 6.1: Human DNA Model Estimated Time to Complete: 10–15 minutes Introduction: The structure of DNA is critical to its function. In this exercise, the students themselves act as the nucleotides, forming two long anti-parallel strands. This activity reinforces the concepts of complementary base pairing, the sugar–phosphate backbone, and the anti-parallel orientation of the two strands in DNA.

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Material • Small index cards with the letters of the four nitrogen-containing bases written on them, one base per card per student (optional).

Procedure 1. Divide the class (or a subset of a large class) into halves. The first half should line up single file, one student behind the other. Have each of these students hold the shoulder of the person in front with the left hand. Tell this group of students that they are human nucleotides: Their bodies represent the deoxyribose sugar, their left arms are the phosphate group, and their right arms are the nitrogenous base.

2. Have the second half of the class line up alongside the first line of students facing the opposite direction.

Each of these students should also hold the shoulder of the person in front with their left hand.

3. Have students extend their right arms and touch fingertips with their “complementary base” on the other strand.

4. Point out to students that the two lines must be facing in opposite directions for this scheme to work out. Explain that the relatively stronger grip they have on the person in front of them represents the strong covalent bond holding the backbone together. The relatively weak interaction represented by touching fingertips is analogous to the weak hydrogen bonds holding base pairs together.

Variation 1. Distribute index cards with letters representing the four bases to the first half of the class, designating which nitrogen-containing base they represent. Have them line up as described previously.

2. Have each member of the second half of the class line up next to a complementary base. Be sure to have the correct number of complementary bases in the second half of the class so that no students are left out of the line. This activity can also be modified to represent DNA replication, if the class is large enough.

Assessment Suggestions: After participating or watching, have students write up a short explanation of the demonstration. Include a short-answer question on a written exam—for example, “Explain why the two strands in a DNA double helix are said to be antiparallel.” Another question on an exam could be “Describe the main difference between the way the nucleotides of DNA’s sugar–phosphate backbone are bonded together and the way the complementary base pairs are joined.”

Lecture Activity 6.2: Design Your Own Cancer Treatment Estimated Time to Complete: 15–20 minutes Introduction: The goal of this activity is to allow students to review the details of the cell cycle. This activity is designed to be completed after the cell cycle has been completely discussed but before any discussion of cancer treatments. Students will work in groups and begin by drawing a cell as it goes through different stages of the cell cycle. Once this drawing is complete, they will be asked to analyze the picture and prepare a list of “problems” that might happen during the cell cycle that would prevent successful cell division. Finally, students will be asked to review the “problems” they generated and think about how these could be manipulated and used as a cancer treatment.

Material • None.

Procedures 1. Divide students into groups of two to four.

2. Begin by describing a cell to the students. Give them a diploid number for this cell (something reasonable to draw, such as six). .

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3. Ask them to write out the stages of the cell cycle and draw the cell as it progresses, making sure to emphasize the state of the chromosomes in each stage. You will particularly want to emphasize the stages of mitosis. Give them about 5 minutes to complete their drawings, and make sure they have formed daughter cells.

4. Circulate among the groups during this time, reviewing the diagrams to make sure everyone is on track.

5. Ask students to refer to their diagrams and make a list of “problems” that could interfere with mitosis in any of those stages. Give them 5 minutes, and they should come up with a wide variety of options for this part of the activity.

6. Ask some groups to volunteer some of their ideas for the class to hear. This discussion ensures that any groups that aren’t on the right track will have something to go with for the final part of the activity.

7. Ask students to look over some of the “problems” on their list and think about how these events could be manipulated to form the basis of a cancer treatment. This activity is completed before discussing cancer treatments, so make sure students understand that treatments for cancer aim to prevent cell division.

8. If desired, have volunteers from each group present their cancer treatment ideas to the class.

Assessment Suggestions: Collect the students’ work to assess their basic knowledge of the cell cycle.

Write test questions based on this activity.

An online discussion forum could be created where each group can post the potential problems and then have other groups give suggestions on treatments.

Lecture Activity 6.3: Meiosis Walk Estimated Time to Complete: 15–20 minutes Introduction: This activity will engage students in acting out the events of meiosis. Each student will play the role of a sister chromatid. The students will act out the motions of the chromosomes during both meiotic divisions, ultimately producing four daughter cells with unique collections of chromosomes. This activity reinforces the mechanics of meiotic division.

Material • Arm bands or bandanas. You will need 16 total, four each of four different colors.

Procedures You will need 16 students to simulate meiosis in a cell having four pairs of chromosomes. If you wish (and if you have the space), you can modify this activity to accommodate a larger number of students, but it doesn’t work well with fewer than 16. (If you have fewer than 16 students you can use pop bead chromosomes and have the students use these to simulate meiosis in small groups.) Students who are watching should be able to see the process (they can encircle the area in which the “chromosomes” will be moving), and they typically enjoy the simulation.

1. Give each participant an arm band or a bandana; those having the same color should find each other and pair up. Members of a pair will link arms to represent sister chromatids linked by a centromere (the linked arms). Ideally, each foursome will include two men and two women: The two men would link arms to represent a paternal chromosome, and the two women to represent the maternal chromosome.

2. Once you have eight chromosomes (four pairs of homologues), begin the simulation as follows: Have the linked pairs cluster in the middle of the room, representing the nucleus. They can wander around, with homologous pairs not spending any more time near each other than near other chromosomes.

3. Designate a line to serve as the equator of the cell, and two points to serve as poles. .

Chapter 6 Cancer 45

4. Announce that the cell is entering prophase I. Students should find their homologues (the other chromosome with the same-color arm band), and remain near each other. (Additional option: Attach a piece of cloth of the same color to each arm band using tape or Velcro prior to starting and then during prophase I have the sister chromatids perform crossing over.)

5. Announce that the cell is at metaphase I. Students should line up at the equator (an imaginary line), with homologues paired and oriented at random with respect to maternal and paternal homologues.

6. Announce that the cell is entering anaphase I. The homologues should move away from each other, toward the poles. Be sure that their arms are still linked!

7. Announce that the cell is entering telophase I. The chromosomes should be at their respective poles.

You should now designate new equators and poles for the second division.

8. Announce that the cells are entering prophase II. The students can just wander about, and you may want to point out that there is no homologue to pair up with.

9. Announce that the cells are at metaphase II. The chromosomes will line up at the equators of their respective cells.

10. Announce that the cells are entering anaphase II. The students’ arms will finally be unlinked, and sister chromatids will separate and move to opposite poles.

11. As soon as the students reach the poles, announce that the cells are at telophase II. The students should now be in four clusters, representing the nuclei of four daughter cells.

12. Once the process is complete, have the students examine the arm bands of the cells in each nucleus— there should be one of each color. If you were able to specify maternal and paternal homologues, emphasize their random assortment.

If time permits, you can run this activity one or two more times, perhaps with different students. If you do this exercise with the same students, it should reinforce the random assortment of homologues during meiosis.

Assessment Suggestions: Have students write a brief explanation of the differences between homologues and sister chromatids. Have students explain how random assortment of homologues leads to genetic diversity in gametes.

Lecture Activity 6.4: Exploring Crossing Over and Its Effects on Gametes Estimated Time to Complete: 10–15 minutes Introduction: This activity allows students to act out and/or visualize crossing over and see the effect that crossing over has on the types of gametes that can be produced. At least 12 student volunteers are needed to represent chromosomes. Each chromatid consists of three students. The middle student in each chromatid is the centromeric region; this student holds hands with the middle student in the sister chromatid. The two end students in each chromatid are the chromosomal arms; they hold onto the center student’s shoulders. Each end student carries a piece of cardboard or paper with a large letter written on it to signify an allele for a gene.

The genes on opposite arms of a chromatid are obviously different and can be any two Mendelian traits. One example would be the gene for earlobe shape (detached, D, is dominant relative to attached, d) and the gene for eyelash length (long, L, is dominant relative to short, l). One group of six students forms a chromosome with both dominant alleles; the other six form a chromosome with all recessive alleles.

After setting up the chromosomes, first the homologues and then the chromatids split and go to four separate areas in the room. Student observers in the class can now see that only DL and dl gametes are possible. Regroup the students in their original chromosomes, and have the homologous pairs synapse. Have the students on one arm switch chromatids—they are crossing over. Emphasize that this process commonly occurs in the cell. Now have each chromatid go to its designated area. The students should now see that four gametes are possible: DL, dl, Dl, and dL. The instructor can point out that in real life chromosomes usually contain thousands of genes, and crossing over can occur multiple times along a chromosome. Discuss how this process affects the possible offspring and the genetic diversity of the population. .

46 Instructor Guide Biology: Science for Life

Materials • Eight sturdy sheets of paper or cardboard (write the single-letter designation for each of the four alleles twice in a huge font).

• String, if desired, to hang the paper around each student’s neck.

Procedures 1. Ask for 12 student volunteers to form a pair of homologous chromosomes and demonstrate crossing over.

2. Have the students come to the front of the room and arrange themselves in groups of six.

3. In each group of six, ask two students to hold hands (or hold a pen between them). Have each of the other students in their group hold onto the shoulder of one of the pen-holding students.

4. Give each student on the ends a piece of paper with an allele on it. For one allele, do this correctly (e.g., L and L on one chromosome, l and l on the other). For the other allele, do it incorrectly (e.g., D and d on one chromosome).

5. Ask the class if the sister chromatids on these chromosomes are set up correctly for chromosomes prior to meiosis. If no one points out the mistake, ask for a show of hands for those who think it is correct, and those who think it is incorrect. Reveal the mistake. Use the opportunity to discuss replication and sister chromatids.

6. Have the misplaced students switch positions.

7. Have the students go through meiosis: Ask the homologous chromosomes to separate as in anaphase I, and then ask the sister chromatids to split as in anaphase II. Have each group go to one of four separate areas representing the four possible gametes.

8. After they are positioned, ask the class to describe the gametes that are present and their genotype.

9. Write the number (2) and genotypes (DL and dl) on the board.

10. Have the students re-form their chromosomes.

11. Have the chromosomes come together as they would in prophase I of meiosis. Discuss this stage as the normal part of gamete production.

12. Have two students on homologous chromosomes switch chromosome arms. This event represents crossing over.

13. Go through meiosis again: Have the homologues split in anaphase I, and the sister chromatids in anaphase II, and then go to separate areas of the room.

14. After they are positioned, ask the class to describe the number of different gametes that are present and their genotype.

15. Write the number (4) and genotypes (DL, dl, Dl, and dL) on the board.

16. Discuss how this difference would affect the number of possible offspring. Point out that human chromosomes contain thousands of genes and may cross over multiple times. Discuss how this process affects the number of possible offspring and genetic diversity within the population.

17. Thank the student volunteers, allow them to return to their places, and give them a minute or two to chat with their neighbors about what they just did and settle down as you prepare for the next part of the lecture.

Note: In a class without too many students and a large room, you could have all students participate in this activity at the same time.

Assessment Suggestions: Have students write down the possible gamete outcomes from this example.

The questions posed to the class during the demonstration provide a means of assessment. Use a similar problem in homework or an exam to test understanding of crossing over.

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Lecture Activity 6.5: Random Assortment Card Trick Estimated Time to Complete: 10 minutes as a demonstration and 15–20 with students performing the activity Introduction: Students often have a hard time realizing the vast number of possible arrangements of paternal and maternal homologues, even with a relatively small number of chromosomes. This exercise reinforces the concept of independent assortment during meiosis, placing particular emphasis on the large number of possible outcomes. Although the procedure describes this exercise as a demonstration, it can easily be adapted as an in-class exercise done by the students themselves.

Material • Two decks of playing cards, with backs of two contrasting colors or patterns. (If you do this activity as a student exercise rather than a demonstration, you will need more decks—two decks of cards will produce four sets, enough for 16 students or groups.)

Procedure 1. Introduce this topic to the students by explaining that a relatively small number of chromosome pairs can produce a huge number of possible configurations at metaphase I of meiosis. The instructor should review the math behind this concept, which is a simple exponential relationship. Perhaps begin by relating the story of the peasant who was offered either 1,000 shillings per day for 1 month’s work, or 1 shilling on the first day, 2 shillings on the second day, 4 shillings on the third day, and so on. The peasant, by choosing the second option, demonstrated his wisdom, because he became a very wealthy man long before the end of the month.

2. Create a deck of cards representing the chromosome set of an organism having 13 pairs of chromosomes by removing all the cards of one suit from both decks and combining them. There are enough cards in two decks of cards to create four such sets. (If you wish, you can create sets of 46 cards to represent the chromosome complement of humans.) This preparation should be done before class. The deck of 26 cards represents 13 pairs of chromosomes. The maternal and paternal versions of each chromosome are represented by the different colors or patterns of the backs of the cards.

3. When you have shuffled the deck, turn it so that the cards are face up. Deal the cards from the top.

You will create two rows of 13 cards, one above the other. There is no need to place the cards in numerical order. Alternatively, create several such decks, and have the students perform this exercise in groups of two to four.

4. Because there are two copies of each card in this deck (with the only difference being the color or pattern on the back of the cards), you will eventually turn up a second card of the same value.

5. When the first such duplicate (homologue) card is reached, start the second row by placing the card above its match in the first row.

6. Continue in this manner, placing the first homologue to turn up in the first row, and the second one in the second row, until the deck is depleted.

7. Once the cards are dealt, turn them over. The random arrangement of the maternal and paternal homologues should be evident.

This activity can be done several times. If so, it may be useful to record the results on the board, so that students can see that the combinations of homologues obtained with each shuffling are strikingly different.

Assessment Suggestions: Have students calculate the number of possible combinations for organisms with different diploid numbers. Have students explain the importance of random assortment in relation to variability of children in their own families, and then in relation to the offspring of a pair of sea urchins or fish that produce and fertilize hundreds of eggs at a time.

A discussion forum could be set up online to discuss the importance of random assortment. .

CHAPTER

7 Are You Only as Smart as Your Genes?

Mendelian and Quantitative Genetics OBJECTIVES Teaching Goals This chapter is fun for the students because it helps explain why someone would say “You have your father’s chin” or “You have your mother’s eyes.” Your goal is to engage students in the basics of genetics without getting into advanced issues. Concentrate on using examples of traits with which students are familiar to keep their interest.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe the relationship between genes, chromosomes, and alleles.

• Explain why cells containing identical genetic information can look different from each other.

• Define segregation and independent assortment and explain how these processes contribute to genetic diversity.

• Distinguish between homozygous and heterozygous genotypes and describe how recessive and dominant alleles produce particular phenotypes when expressed in these genotypes.

• Demonstrate how to use a Punnett square to predict the likelihood of a particular offspring genotype and phenotype from a cross of two individuals with known genotype.

• Define quantitative trait and describe the genetic and environmental factors that cause this pattern of inheritance.

• Describe how heritability is calculated and what it tells us about the genetic component of quantitative traits.

• Explain why a high heritability still does not always mean that a given trait is determined mostly by the genes an individual carries.

LECTURE OUTLINE 7.1 The Inheritance of Traits A. Human sperm and egg cells (each of which has 23 chromosomes) combine at fertilization to form a zygote with 46 chromosomes; those chromosomes contain the instructions for making a new individual. (Figure 7.1) B. Genes contain alleles that determine the phenotypes of individuals. (Figure 7.3) .

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50 Instructor Guide Biology: Science for Life

C. Mutation, crossing over, and independent assortment of homologous pairs create diversity in the offspring, except for identical twins. (Figure 7.4, Figure 7.7) Lecture Activity 7.1 7.2 Mendelian Genetics: When the Role of Genes Is Clear A. Phenotype is the physical expression of a genotype that describes the genetic composition of a particular trait in single-gene inheritance.

B. Genotypes may be made up of the same alleles (homozygous) or of different alleles (heterozygous).

C. Some diseases, such as cystic fibrosis and Huntington’s disease, are inherited. (Figure 7.13, Figure 7.14) D. The chance of inheriting a genetic disease can often be predicted using a Punnett square.

E. When looking at two traits you perform a dihybrid cross. (Figure 7.15) 7.3 Quantitative Genetics: When Genes and Environment Interact A. Traits such as height and musical ability exhibit a wide range of phenotypes (continuous variation) and are called quantitative traits. (Figure 7.16) B. Quantitative traits are usually the result of interaction with several genes; they may also be affected by the environment. (Figure 7.17, Figure 7.18) Lecture Activity 7.2 7.4 Genes, Environment, and the Individual A. Calculations on the heritability of a trait can be helpful but are subject to misinterpretation.

B. The forces of “nature” and “nurture” combine to affect expression of genetic traits.

Lecture Activity 7.3

Lecture Activity 7.1: Coin-Toss Meiosis Estimated Time to Complete: 10–15 minutes Introduction: One of the simplest and most effective ways to illustrate the assortment of alleles during meiosis and the associated probabilities is by flipping coins. This activity helps students understand how basic laws of probability affect events. They also learn to calculate the exponential increase in possible gametes as more alleles are considered, and they see the effect of homozygous versus heterozygous alleles.

Materials • Each student or group needs adhesive tape, one dime, one nickel, and two pennies.

• Lecture Activity 7.1 Handout: Coin-Toss Meiosis Procedures 1. Divide the students into groups.

2. Pass out supplies and handouts to each student; explain the activity. In a large class, you could provide just one set of coins per group.

3. Circulate during the activity to ensure that groups don’t get stuck on the math.

4. If desired, have groups read their answers aloud at various times during the activity to make sure all groups are on track.

Assessment Suggestions: Collect and grade the handouts. In addition, coin flips are easy to visualize and may be simulated on paper, allowing all forms of exam questions related to the activity.

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Chapter 7 Are You Only as Smart as Your Genes? 51

The handout could be placed online and the questions answered there as well as stimulate a good discussion question on genetic diversity.

Handout Answer Key 1. Flip a penny. How many possible outcomes are there for the flip? 2 2. Flip the penny and the nickel. How many different combinations are there? 4: ph nh, ph nt, pt nh, pt nt 3. What are the chances of getting any particular one of these possibilities? 1/4 or 25% 4. Flip the penny, the nickel, and the dime. How many different combinations are possible? 8: ph nh dh, ph nh dt, ph nt dh, ph nt dt, pt nh dh, pt nh dt, pt nt dh, pt nt dt 5. What are the chances of getting any particular one of these possibilities? 1/8 or 12.5% 6. Predict the number of possible outcomes if a quarter is added to the flip. 16 7. Try to think of a formula to predict the number of possible outcomes for any number of coins or pairs of alleles. 2n , where n = the number of coins or allele pairs 8. A coin represents a heterozygous pair of alleles. Why? Because the two sides are different.

9. What would the number of possible outcomes be if one of the coins were heads on both sides? 4 10. What does the double-headed penny represent in genetic terms? A pair of homozygous alleles 11. Considering the formula developed earlier, try to refine it in light of this new information to make it more accurate. 2n , where n = the number of heterozygous allele pairs

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Lecture Activity 7.1 Handout: Coin-Toss Meiosis Many simple genetic traits are controlled by two genes, which often exist in different forms called alleles.

For example, a gene for eye color could exist as a green pigment producer or as a brown pigment producer. Mendel’s principle of independent assortment tells us that the two alleles for the same gene are separated from each other when gametes are formed during meiosis, and that the probability of a particular gene from a pair of alleles being incorporated into a gamete is 50%—the same as the probability of a coin toss being head or tails. This activity uses coin tosses to model the random nature of the incorporation of alleles into gametes.

1. Flip a penny. How many possible outcomes are there for the flip?

If the alleles for two different traits are on different chromosomes, the principle of independent assortment states that the incorporation of an allele for one trait into a gamete has no effect on which allele of the other trait is also incorporated. Therefore, the probability of obtaining a gamete with a particular set of two different alleles is similar to flipping two coins at the same time. Neither the first flip nor the first allele has any influence on the second flip or second allele.

2. Flip the penny and the nickel. How many different combinations are there?

Write them down.

3. What are the chances of getting any particular one of these possibilities?

4. Flip the penny, the nickel, and the dime. How many different combinations are possible?

Write them down.

5. What are the chances of getting any particular one of these possibilities?

6. Predict the number of possible outcomes if a quarter is added to the flip.

7. Try to think of a formula to predict the number of possible outcomes for any number of coins or pairs of alleles.

8. Now think in terms of genetics. A coin represents a heterozygous pair of alleles. Why? 9. What would the number of possible outcomes be if one of the coins were heads on both sides? (To find out, tape your two pennies together so that both sides are heads, then flip the double penny, the nickel, and the dime.)

10. What does the double-headed penny represent, in terms of genetics?

11. Considering the formula developed earlier, try to refine it in light of this new information to make it more accurate.

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Chapter 7 Are You Only as Smart as Your Genes? 53

Lecture Activity 7.2: Polygenic Punch Estimated Time to Complete: 15 minutes Introduction: The genetic mechanism for polygenic traits is often complicated and difficult to visualize.

This activity utilizes variations in color hues and intensities to clearly demonstrate how several pairs of alleles can result in a wide range of phenotypic expression.

Materials • At least 20 glass or clear plastic 500-ml beakers.

• 500 ml each of blue, yellow, and red Kool-Aid or food-coloring solutions.

• 500 ml water.

Procedures (A suggested narrative is shown in italics.)

1. To begin the demonstration, pour food-coloring solutions into beakers as described in the following list, and arrange the beakers into pairs to represent allele pairs.

• Blue/plain water (dominant/recessive) • Blue/yellow (incomplete dominance) • Yellow/plain water (dominant/recessive) • Blue/red (incomplete dominance) • Red/yellow (incomplete dominance) • Red/plain water (dominant/recessive) Some traits are polygenic—that is, they are influenced by the actions of several pairs of alleles. Each pair of alleles contributes to the final phenotypic expression of the trait. Polygenic inheritance of various protein pigments, which would give a variety of colored phenotypes, is demonstrated by the colored solutions here.

In this case, six genes are influencing the final color phenotype. Each gene can have two alleles, which code for proteins that interact with one another to influence the final color.

2. One at a time, pour the pairs of beakers together into one beaker while commenting on the genetic analogies that can be made.

In a population of organisms, there are at least three possible combinations for each pair of alleles.

For example, for this pair of alleles (referring to the blue/plain water alleles), the combination in a particular individual could be blue/blue, blue/clear, or clear/clear.

3. Mix these combinations.

For this pair of alleles (referring to the blue/yellow alleles), the combinations could be blue/blue, yellow/yellow, or blue/yellow.

4. Mix these combinations and the ones for the remaining pairs if you have time and enough beakers.

Can you imagine the number of different phenotypes possible if each of these pairs can have these combinations and they are all independent of the other pairs?

5. Set up a row of at least 10 empty beakers and begin pouring in various mixtures of the combined pair colors. The range of colors should go from very dilute, simple colors (resulting from several plain

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54 Instructor Guide Biology: Science for Life

water/plain water pairs and perhaps one dominant recessive such as blue/plain water) to more concentrated, complex colors (resulting from mostly dominant combinations with many colors).

6. With input from the class, arrange these beakers in order from most diluted to most concentrated colors.

As you can see, polygenic traits may be expressed in a population by a continuous variation of phenotypes.

Assessment Suggestions: Elaborate on the concept of continuous variation. If enough beakers were used and distinct groupings of colors resulted, you can create a simple graph of the distribution of color groups and discuss the concept of normal distribution. Ask students to apply these ideas in proposing a possible genetic explanation for animals with complex color patterns, such as parakeets. Variations of the preceding scenarios may be described or demonstrated with associated exam items.

This would be good assessment to put online to discuss continuous variation. A lab report could be written and have them include a graph of the color groups to get practice at doing these concepts.

Lecture Activity 7.3: My Genes Made Me Do It! Estimated Time to Complete: 10–15 minutes, or longer if the students debate Introduction: Because genetics is important to so many aspects of human behavior, defense attorneys might attempt to use a defendant’s genetic constitution as a strategy to excuse criminal behavior. In this role-playing exercise, some students will take the side of the defense and present an argument about why a defendant’s genes should be considered as a factor in the criminal behavior. Others will take the prosecution’s side and present an argument about why a defendant’s genes do not excuse criminal behavior.

Material • None.

Procedures 1. Divide the students into groups with six members (give or take a member).

2. Explain the activity: Each group will divide into two halves: the defense and the prosecution. The defense will come up with arguments explaining why genetics should be considered when deciding the guilt of a person accused of a crime. The prosecution side will come up with reasons why genetics is not an important issue in deciding guilt.

3. Circulate during this time to ensure groups remain on task; answer any questions they may have.

4. Give the groups about 5 minutes to come up with these arguments, and then have them actually argue within their groups.

5. When they hear the other side’s arguments, each side can then spend a few minutes developing counterarguments.

6. If desired, groups can share some of their arguments, or the whole class or a subset of the class can stage an actual debate.

Assessment Suggestions: Have groups turn in papers listing their original arguments and counterarguments.

Give participation credit for those willing to share their ideas or participate in a debate.

The debate could be done in an online environment. Divide the students into the groups as stated but have them converse online in chat sessions or their own discussion forums. Then have a discussion forum where each group posts their arguments and counterarguments. This could stimulate a great discussion.

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CHAPTER

8 DNA Detective Complex Patterns of Inheritance and DNA Fingerprinting OBJECTIVES Teaching Goals This chapter covers both classical genetics (dihybrid, blood groups, and so on) and molecular genetics.

Your goal is to clarify inheritance patterns that do not involve single-gene inheritance and to help students understand that the DNA is the genotype discussed in Chapter 7. Most students will be familiar with DNA evidence because of recent court cases and the popularity of dramas such as CSI. Use examples from the news (e.g., the work of The Innocence Project) to illustrate the mechanics of DNA fingerprinting.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Differentiate incomplete dominance from codominance.

• Explain how polygenic and pleiotropic traits differ.

• Outline the inheritance of the multiple-allelic ABO blood system.

• Describe the mechanism of sex determination in humans.

• Explain how the inheritance of sex-linked genes differs from the inheritance of autosomal genes.

• Describe how X-inactivation changes patterns of inheritance.

• Explain how scientists use pedigrees.

• Explain the significance of DNA fingerprinting and how the process works.

LECTURE OUTLINE 8.1 Extensions of Mendelian Genetics A. Incomplete dominance patterns result in the heterozygote appearing as a blend of the two alleles.

(Figure 8.1) B. Both alleles are expressed in the heterozygote phenotype if the genetic pattern is co-dominance.

(Figure 8.2) Lecture Activity 8.1 C. The inheritance of the ABO blood type illustrates both co-dominance and the presence of multiple alleles in the population. (Figure 8.3) D. Blood typing can be used to eliminate people as parents and determine compatibilities.

(Table 8.1, Table 8.2) E. A single gene that has multiple effects is called pleiotropic.

F. Hemophilia is a pleiotropic blood clotting disorder carried on the X chromosome.

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8.2 Sex Determination and Sex Linkage A. Humans have 23 pairs of chromosomes, 22 pairs of autosomes, and 1 pair of sex chromosomes (X and Y). (Figure 8.4) B. In terms of sex chromosomes, females are XX and males are XY. C. X-linked genes can be passed to both sons and daughters and can result in unusual inheritance patterns. (Figure 8.6) D. Y-linked genes are passed only from fathers to sons and code for male characteristics.

E. X inactivation guarantees that females only get one set of proteins from the X chromosomes.

Lecture Activity 8.2 8.3 Pedigrees A. Pedigrees are diagrams that can illustrate inheritance patterns of a particular trait within families.

(Figure 8.9) B. Traits can be inherited in different ways: autosomal dominant, autosomal recessive, and sexlinked recessive. (Figure 8.10) C. The history of hemophilia in the Romanov family is well documented by their family tree.

(Figure 8.11) Lecture Activity 8.3 8.4 DNA Fingerprinting A. Small amounts of DNA are multiplied by the polymerase chain reaction (PCR) technique.

(Figure 8.12) B. DNA fingerprinting uses several analytical techniques to establish identity. (Figure 8.14) Lecture Activity 8.4 Lecture Activity 8.5

Lecture Activity 8.1: Practicing Mendelian Extensions Estimated Time to Complete: 20 minutes Introduction: The only way to become good at solving genetics problems is to practice them. After discussing in class how to do problems, students must try them on their own to be sure they understand the underlying concepts. In this activity, students practice solving problems in groups. This reinforces the understanding of students who already “get it” and allows them to help those students who are still struggling.

Material • Lecture Activity 8.1 Handout: Practicing Mendelian Extensions Procedures 1. After discussing Mendelian extensions in class and working out sample problems, distribute the handout to each student.

2. Allow students to work together to solve the problems, but ask each person to write out his or her own answers.

3. Circulate among the students during the activity to answer questions and keep groups on task.

Assessment Suggestions: Collect and grade the handouts. Include similar problems on quizzes and exams.

This assignment could be done as an online-only assessment for an online course.

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Chapter 8 DNA Detective 57

Handout Answer Key 1. a. What are the genotypes of the parents? Male Z1Z; female ZW b. Which gametes would each form? Male 1⁄2 Z1 , 1⁄2 Z; female 1⁄2 Z, 1⁄2 W c. Draw your Punnett square below and determine the sex ratios of living offspring.

Z

W

Z1

Z1Z

Z1W

Z

ZZ

ZW

Sex ratio of offspring: 2 males: 1 female, because the Z1W female will die.

2. Figure out which baby belongs to each set of parents.

Parental Blood Types (Phenotypes)

Possible Genotypes for Their Baby

Which Baby Is Theirs?

AB × O

I Ai or I B i

B

A×O

I Ai or i i

A

A × AB

I Ai or I B i or I A I A or I A I B

AB

O×O

ii

O

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Lecture Activity 8.1 Handout: Practicing Mendelian Extensions Working in groups, solve the following genetics problems. Show your work.

1. Sex determination in birds is different from that in humans. The sex chromosomes in birds are called Z and W, because males have two of the same chromosome (ZZ), while females have two different chromosomes (ZW).There is a Z-linked allele in some birds that causes the death of the embryo when the normal dominant allele is not present. What would be the sex ratio in the living offspring of a cross between a male heterozygous for the lethal allele and a normal female?

a. What are the genotypes of the parents? Male b. Which gametes would each form? Male

Female Female

c. Draw your Punnett square below and determine the sex ratios of living offspring.

2. Four human babies were accidentally mixed up in the maternity ward. The blood types of the babies were known to be A, B, O, and AB. The blood types of the four sets of parents were determined.

Figure out which baby belongs to each set of parents.

Parental Blood Types (Phenotypes)

Possible Genotypes for Their Baby

AB × O A×O A × AB O×O

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Which Baby Is Theirs?

Chapter 8 DNA Detective 59

Lecture Activity 8.2: XY Females?

Estimated Time to Complete: 15 minutes Introduction: After the X-Y system for sex determination has been introduced, some students may wish to know how the complement of sex chromosomes determines sex. This exercise introduces the concept with an applied example. The SRY region of the Y chromosome contains a gene that encodes a testisdetermining factor (TDF), which must be present for male sexual development in the embryo to begin.

One possible way for an XY individual to develop as a female is for a mutation in this gene to result in no functional TDF being produced. Such individuals will become XY females.

Material • None.

Procedures 1. Introduce the details of sex determination to the students, explaining the role of the SRY region and TDF. 2. Have students discuss the consequences of an XY female (with a defective Y chromosome, designated Y–) mating with an XY male, using the following questions as a guide for either class discussion or small group discussion (put the questions on a PowerPoint slide or a transparency): • What are the possible phenotypes and genotypes of the products of conception from this match?

1⁄4 XX female; 1⁄4 XY– female; 1⁄4 XY male; 1⁄4YY– embryo, which would die early in development • What ratio of boys to girls would be expected among their children? 2 girls to 1 boy • What proportion of conceptions would spontaneously abort early in development, and why?

1⁄4 of conceptions, on average, would receive the nonviable YY– genotype and would spontaneously abort early in development, because the X chromosome has many genes that are essential for development Assessment Suggestions: Assign the questions as group work to be turned in and graded. Include a similar question on a quiz or exam.

This could be done as a discussion forum in an online course.

Lecture Activity 8.3: Make Your Own Pedigree Estimated Time to Complete: 15–20 minutes Introduction: Students love learning more about themselves and their families. A good way to get them to understand how pedigrees work is to have them create one for their own families.

Material • Before you perform this activity, have students collect data on the occurrence of any genetic trait that they want (for example, blue eyes or widow’s peak or curly hair) in their family or in the family of a friend (in the case of adopted students).

Procedures 1. After pedigrees have been introduced and explained, announce to the class that students will make pedigrees of their own families.

2. Use the board or an overhead projector to explain the basics of pedigree making while you demonstrate the process.

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a. Remind students that squares represent males and circles represent females, and have them start with their two parents (demonstrate on board). b. All of the couple’s natural children are listed underneath. Show how to make a symbol for an only child first, and then expand the pedigree to include a larger family. Explain that a couple’s children are placed in order of age from oldest to youngest, starting at the left. c. If desired, explain that deceased individuals are denoted with a slash through their symbol. d. Show identical twins as one line that starts from the offspring line and then separates into two lines, and fraternal twins as two separate lines starting from the same point on the offspring line. e. Include in your demonstration pedigree a second spouse for either husband or wife, and show half-siblings. f. Mention that individuals within the pedigree showing a particular genetic trait have their symbols colored in or designated in some other fashion.

3. After the demonstration, have each student make an accurate pedigree of his or her own family, and trace on it the occurrence of the chosen genetic trait.

4. Circulate among the students while they are working to answer questions.

Assessment Suggestions: Use a pedigree in a genetics problem on a quiz or exam. Ask students to sketch the pedigree of a family described to them. Design a pedigree chart and have the students come up with the genotypes of the circles and squares.

Lecture Activity 8.4: Paternity Testing Using VNTR Polymorphisms Estimated Time to Complete: 10–15 minutes Introduction: This exercise provides a practical but simplified demonstration of how variable number tandem repeat (VNTR) polymorphisms are used to determine paternity. It also gives students a chance to see what those rows of bars on an electrophoresis gel represent. The exercise uses only three VNTR loci; you should point out to your students that forensic analysis typically looks at a minimum of 10 loci, and often many more.

Material • Lecture Activity 8.4 Handout: Paternity Testing Using VNTR Polymorphisms Procedures 1. Introduce the exercise by reviewing VNTRs. Point out that half of a child’s chromosomes, and of the alleles the child carries, are inherited from each of his or her parents.

2. In the example provided, you can see that the bands are clustered into three groups; the b group shows everyone being homozygous for a single allele, except for Chris. Everyone is heterozygous for the a and c groups. Point out these patterns to your students, so that they can make the connection between these bands and alleles.

3. Once the students understand the background, pass out the handout or project a slide showing the gel.

Identify the individuals whose VNTRs are displayed, and explain the scenario leading up to the analysis: • Alex and Barb are a separated couple.

• Chris is Barb’s new boyfriend.

• Doug and Ellen are children born to Alex and Barb when they were still together.

• Frank was born after Alex and Barb separated. Barb wants Alex to pay child support.

• Alex doesn’t believe that Frank is his child. He asked for a genetic analysis to support his case.

4. Once the students understand the problem, allow them time to answer the questions on the handout.

5. Conclude the activity by reinforcing the idea that when many more loci are considered, the confidence with which you can say a person is identified as the father increases to the point that the possibility of making an error is minimal.

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Handout Answer Key 1. Can Alex be Frank’s father? Why or why not? No; Frank does not have a c-group fragment that could have come from Alex.

2. Can Chris be Frank’s father? Why or why not? Yes; Frank has a VNTR pattern consistent with inheriting one of each group from Barb and the other from Chris.

3. Does this test prove conclusively that either man is Frank’s father? No; it does not exclude others who might have a similar VNTR pattern to Chris.

4. Does this test prove conclusively that either man is excluded from being Frank’s father? Why or why not? Not completely; Alex could possibly be Frank’s father if a mutation changed the VNTR pattern that Frank inherited from Alex.

Assessment Suggestions: Have student groups write down their answers and grade them. Include a similar question on a written exam. Try to create a pattern of bands that differs significantly from the example used in class.

The questions could be put into a discussion forum or designed as an online assignment.

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Lecture Activity 8.4 Handout: Paternity Testing Using VNTR Polymorphisms This gel shows the results of the VNTR analysis for Alex, Barb, Chris, and the children:

1. Can Alex be Frank’s father?

Why or why not?

2. Can Chris be Frank’s father?

Why or why not?

3. Does this test prove conclusively that either man is Frank’s father?

Why or why not?

4. Does this test prove conclusively that either man is excluded from being Frank’s father?

Why or why not?

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Lecture Activity 8.5: Understanding DNA Fingerprinting Estimated Time to Complete: 20 minutes Introduction: This exercise could be used to support a typical lecture on the actual technique of DNA fingerprinting. When presenting this material, consider going into a little more depth about the fact that the probe is recognizing sequences that are common among humans and are repeated several times in the human genome. Because different individuals have different numbers of these repeats, different-sized DNA fragments result from the restriction enzyme digests. This exercise is designed to help students visualize how and why two individuals would have different DNA fingerprints.

Materials • Long rolls of paper or several pieces of cardboard, taped together to make the chromosomes. (Two distinct chromosomes will be generated, representing two of the same type of chromosome [e.g., two X chromosomes] from two different people. You can prepare the chromosomes before class as described, or do it with the class watching.)

• Tape.

• Sharpies or markers for writing on the chromosomes.

• Scissors.

• A whiteboard or chalkboard to serve as the “gel” on which the DNA fragments will be separated.

Procedures 1. Tape the two chromosomes up on a chalkboard, whiteboard, or wall. The chromosome on the left will represent individual 1, and the one on the left will belong to individual 2.

2. Near the top of one chromosome, write the word “repeat” four times, one under the other. Near the top of the other chromosome, write “repeat” only one time. Write large, so that the students can see what is being written. While you are writing, talk about repeated sequences in the genome, and so on.

3. On the first chromosome, write the word “repeat” twice, about two-thirds of the way to the bottom. In a similar position on the other chromosome, write “repeat” five times.

4. Along the length of each chromosome, write letters to represent allele designations. Put an “A” on one chromosome at the very top, above the repeats, and an “a” on the second chromosome. Just below the repeats, put a “b” on the first chromosome and a “b” on the second chromosome. Above the second group of repeats, put a “C” on the first chromosome and a “C” on the second chromosome.

At the very bottom of the chromosomes, put a “d” on the first chromosome and a “D” on the second chromosome. Explain as you are doing so that these are alleles coding for traits of these organisms; also point out that some are recessive and some dominant, in some the two organisms differ, and in some they are the same.

5. Add restriction sites. While doing so, remind the students what restriction sites and restriction enzymes are. Put one restriction site directly below each of the four groups of repeats. If done correctly, there will be six fragments of different sizes when the chromosomes are cut at the restriction sites.

6. Using scissors to represent restriction enzymes, cut the paper chromosomes into their respective fragments. Hold each one up and show the group that they are of different sizes.

7. Make a big rectangle the whole length of the chalkboard or whiteboard. This will be the gel to separate the fragments. While drawing it, make a few comments about how electrophoresis works.

Add some lines at one end to represent loading wells.

8. Recruit six student volunteers. Give each one a chromosome fragment, and bunch them all up together at the end of the electrophoresis apparatus with the loading wells. Explain that each student will move his or her chromosome fragment toward the other end of the gel: The smaller the fragment is, the faster it will move. Tell students to start moving when you say “start” and stop moving when you say “stop.”

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9. Monitor movement to ensure that the smallest actually are going fastest. When the smallest fragment reaches the end, yell “Stop.” Have each person hold out his or her fragment so that the class can see they are lined up by size.

10. The fingerprint made by individual 1’s chromosome can be compared to that made by individual 2’s chromosome. Use a marker to mark the fragments that contain repeated sequences, as those will be the ones recognized by the probe.

Assessment Suggestions: Have students write a short explanation of what they saw or did. Base a quiz or exam question on this exercise.

This could be easily placed online as a short paper or discussion forum.

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CHAPTER

9 Genetically Modified Organisms Gene Expression, Mutation, and Cloning OBJECTIVES Teaching Goals Genetic engineering is no longer in the future. Indeed, the manipulation of genes has already become part of several industries. Students may be familiar with ethical and political concerns related to genetic engineering because they are frequently the topic of media reports (e.g., disagreement about the use of stem cells). Your goal should be to present the mechanics of the process (in brief) and to show students existing and potential applications of DNA technology. This is a great opportunity to relate biology to daily life.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Define the term gene expression.

• Describe how messenger RNA (mRNA) is synthesized during the process of transcription.

• Describe how proteins are synthesized during the process of translation.

• Use the genetic code to identify the amino acid for which a DNA segment or a codon codes.

• Define the term mutation, and explain how mutations can affect protein structure and function.

• Explain why and how some genes are expressed in some cell types but not others.

• Outline the process of cloning a gene using bacteria.

• Describe how foods are genetically modified, and list some of the health and environmental concerns surrounding this practice.

• Describe the science behind and significance of stem cells, the Human Genome Project, gene therapy, and cloning.

LECTURE OUTLINE 9.1 Protein Synthesis and Gene Expression A. Genes contain instructions for cell proteins and can be modified to affect the production of proteins.

B. Transcription and translation occur as the information in DNA is converted to RNA, which is then used to manufacture the protein. (Figure 9.3, Figure 9.7) Lecture Activity 9.1 Lecture Activity 9.2 .

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C. Mutations in DNA may or may not have an effect on the protein being produced.

(Figure 9.8, Figure 9.9) D. Prokaryotic and eukaryotic cells regulate protein synthesis by different mechanisms.

(Figure 9.12) 9.2 Producing Recombinant Proteins A. Genes from one organism are removed and inserted into cells of another organism using tools developed for that purpose. (Figure 9.13) B. Bacteria are commonly used to produce cloned genes.

9.3 Genetically Modified Foods A. Crops may be modified to improve particular characteristics such as yield, maturation rate, and resistance to herbicides. (Figure 9.17, Figure 9.18) B. There is some controversy about genetically modified foods and their effect on human health and the environment.

9.4 Genetically Modified Humans A. Stem cells are undifferentiated and can potentially be used to replace damaged tissue.

B. Embryonic stem cells are totipotent, but their use is restricted in the United States by the federal government.

C. Gene therapy has been successful in some cases but also carries unknown risks. (Figure 9.22) Lecture Activity 9.3 Lecture Activity 9.4

Lecture Activity 9.1: Review of Transcription and Translation Estimated Time to Complete: 15–20 minutes Introduction: The processes of transcription and translation seem very mysterious and difficult when students hear or read about them, but they find the processes much easier to understand if they can actually work with them. The processes themselves are easily modeled in a paper-and-pencil exercise.

The worksheet for this activity allows students to practice what they have learned in lecture, and to make sure they understand the descriptions of transcription and translation that they have heard or read.

Material • Lecture Activity 9.1 Handout: Review of Transcription and Translation Procedures 1. After the lecture/discussion on transcription and translation, divide the class into small groups containing approximately four students.

2. Briefly explain what is expected, and pass out the handout. Explain how to use the genetic code table to find out which amino acid corresponds to each codon, and explain the amino acid abbreviations.

3. Circulate among the groups while they are working to answer questions and to keep groups on task.

4. Alternatively, if there is not enough time to complete the worksheet in class, it could be given as homework or done during a lab or recitation section.

Assessment Suggestions: Collect the worksheet and grade it using the key provided. Use the questions on the worksheet as the basis for test questions.

This assignment could be placed online and have the students answer the questions and submit the work online for grading.

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Handout Answer Key 1. Chemically, how does RNA differ from DNA? Three differences exist between RNA and DNA: (1) RNA contains the base uracil in place of DNA’s thymine; (2) the sugar found in RNA is ribose rather than the deoxyribose found in DNA; and (3) RNA is single stranded, whereas DNA is double stranded.

2. What are the base-pairing rules for making an mRNA transcript of a DNA gene?

RNA G C U A

DNA binds to binds to binds to binds to

C G A T

3. If the bottom strand of the DNA carries the gene, write the mRNA that would be transcribed from this section of the gene. GUAACCGUAUUGCAGCUAUUAGCAGCCAUG 4. Which strand (top or bottom) would the promoter be found on? Why? On the bottom strand, because that is where the RNA polymerase binds to actually begin the transcription process. The promoter is always found on the strand used for transcription.

5. Divide the mRNA that you wrote in question 3 into its 10 codons.

GUA ACC GUA UUG CAG CUA UUA GCA GCC AUG 6. Explain how mRNA and tRNA work together to get amino acids into their correct places in the protein. The codons of mRNA form complementary pairs with the anticodons of the tRNA. Each tRNA molecule has an amino acid attached to it. It brings that tRNA when its anticodon binds to the codon of the mRNA, and the amino acid is put into the protein chain in the position corresponding to the position of its codon in the gene.

7. Using the following genetic code table, determine which amino acids would go into this part of the protein. val thr val leu gln leu leu ala ala met 8. What would the new coding DNA strand and the new mRNA codons be?

DNA: CAT GGC ATA ACG TCG ATA ATC GTC GGT AC… RNA: GUA CCG UAU UGC AGC UAU UAG CAG CCA UG… 9. Which amino acids would be found in the mutated protein? val pro tyr cys ser tyr STOP 10. What effect do you think this mutation would have on the functioning of the protein? This mutation changes the sequence completely and shortens the protein because one of the codons was converted to a stop codon by the frameshift mutation. It would probably result in both an impaired protein that did not carry out its function and the normal protein, and the protein produced might potentially have no function at all.

11. What do you think determines the severity of the effect of a frameshift mutation on the protein? The position of the frameshift in the gene determines the severity. The closer the frameshift is to the beginning of the gene, the greater its effect will be. A frameshift mutation found very close to the end of the gene might have no effect at all on the protein.

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Course Section:

Lecture Activity 9.1 Handout: Review of Transcription and Translation 1. Chemically, how does RNA differ from DNA?

2. What are the base-pairing rules for making an mRNA transcript of a DNA gene?

3. Here is part of a gene: GTAACCGTATTGCAGCTATTAGCAGCCATG CATTGGCATAACGTCGATAATCGTCGGTAC If the bottom strand of the DNA carries the gene, write the mRNA that would be transcribed from this section of the gene:

4. Which strand (top or bottom) would the promoter be found on?

Why?

5. mRNA is divided into three base sections called codons. Divide the mRNA that you wrote in question 3 into its 10 codons.

6. Explain how mRNA and tRNA work together to get amino acids into their correct places in the protein.

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7. Using the following genetic code table, determine which amino acids would go into this part of the protein.

AAA AAC AAG AAU

Lys Asn Lys Asn

ACA ACC AGG ACU

Thr Thr Thr Thr

AGA AGC AGG AGU

Arg Ser Arg Ser

AUA AUC AUG AUU

Ile Ile Met Ile

CAA CAC CAG CAU

Gln His Gln His

CCA CCC CCG CCU

Pro Pro Pro Pro

CGA CGC CGG CGU

Arg Arg Arg Arg

CUA CUC CUG CUU

Leu Leu Leu Leu

GAA GAC GAG GAU

Glu Asp Glu Asp

GCA GCC GCG GCU

Ala Ala Ala Ala

GGA GGC GGG GGU

Gly Gly Gly Gly

GUA GUC GUG GUU

Val Val Val Val

UAA UAC UAG UAU

Stop Tyr Stop Tyr

UCA UCC UCG UCU

Ser Ser Ser Ser

UGA UGC UGG UGU

Stop Cys Trp Cys

UUA UUC UUG UUU

Leu Phe Leu Phe

8. In a frameshift mutation, one or more nucleotide bases of the DNA is accidentally lost or added. If a frameshift mutation occurred that caused the second T in the coding DNA strand above to be lost, what would the new coding DNA strand and the new mRNA codons be?

DNA: RNA: 9. Which amino acids would be found in the mutated protein?

10. What effect do you think this mutation would have on the functioning of the protein?

11. The effects of frameshift mutations range from severe disruption of the protein to having essentially no effect at all. What do you think determines the severity of the effect of a frameshift mutation on the protein?

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Lecture Activity 9.2: Transcription/Translation Skit Estimated Time to Complete: 10 minutes to get organized and 20 minutes to do the skit. (You may want to do the skits twice, once as a practice and then again when people have figured out their roles so it goes more smoothly.)

Introduction: As an alternative to a paper-and-pencil exercise, students can act out the processes of transcription and translation. This activity works well in a big class because many participants are available. The skit helps students practice (or at least see) how base pairing works, and it helps them visualize the processes of transcription and translation. It is particularly useful for the more visual learners in the classroom.

You may find that some students want to participate and will volunteer, whereas most of them won’t volunteer but also don’t mind doing it. Look for volunteers first, and then carry your signs out into the audience and give them away, starting at the back, by asking random students if they will help.

The role of the announcer is played by the instructor and is crucial to the success of the skit. The announcer must be very certain of all the pertinent facts and base-pairing rules to be able to help students if they forget. Skits work only if the instructor is excited by the idea and finds it fun. If the instructor is uncertain or nervous about it, students can sense this hesitancy and will not want to participate.

Materials • 72 (or 36) sheets of paper or thin cardboard • string and stapler to make signs for 36 students • blue, red, brown, green, and black markers Procedures 1. Before class, make signs by stapling two pieces of paper or cardboard together with strings about 15 inches long between them at both sides of their tops. Students will wear the signs like a sandwich board, with one piece of paper on their fronts and the other on their backs. Alternatively, you can just have students hold their signs and use a single sheet of paper per student.

2. Write on the signs as described in the following list; use large letters with broad-tipped markers. (Be sure that the letters face out on both signs.)

• The 14 DNA signs will say: CAG, TGG, CTT, AGA, TCA, CCA, TGA, GTC, ACC, GAA, TCT, AGT, GGT, and ACT. Make the letters large, using a blue marker.

• The seven mRNA signs will say CAG, UGG, CUU, AGA, UCA, CCA, and UGA. Make the letters large, using a red marker.

• One sign will say “RNA polymerase” in brown marker.

• The seven tRNA signs will have the anticodon written at the top and the amino acid that they bring written at the bottom. They should read as follows: The first will have GUC at the top and gln at the bottom, then ACC and trp, GAA and leu, UCU and arg, AGU and ser, GGU and pro, and finally ACU with a big STOP written in the center. (Having the needed amino acid on the tRNA sign makes it easy for the tRNAs to find their correct amino acid.) Make these signs using a green marker.

• The seven amino acid signs will read gln, trp, leu, arg, ser, pro, and STOP (or use the full names of the amino acids if you prefer). Make these signs using a black marker.

3. Start the skit by calling the students with the blue DNA signs to the front of the room. Have them form a length of double-stranded DNA. Each of the students making up one strand should hold the arm of the student next to him or her to indicate bonding of the backbone. The strand nearer the audience will be used for transcription and should read GTC ACC GAA TCT AGT GGT ACT; the complementary strand away from the audience should read CAG TGG CTT AGA TCA CCA TGA. Help the students to line up in the correct order, standing facing the audience, but let them find their own complements if they can.

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4. Have the other students with signs wait outside the door or to one side of the room to reduce confusion at the front of the class, and call them as needed.

5. Read the announcer lines and direct students to perform the actions needed.

Announcer: This piece of DNA is part of a gene. Look at the structure of the DNA molecule: You can see that there are two strands, and that each nucleotide on one strand is paired with its complement on the other strand. Each student represents a three-base codon. This gene codes for a protein that is needed now in the cell. First, the DNA strands must separate so the gene can be copied into RNA. Let’s have the two strands of DNA move apart. [Announcer shows by hand motions that the two sides of the DNA should separate.]

Student Actions: The two lines of students separate, with one line moving toward the audience and the other away from it.

Announcer: Only one side of the DNA, the sense strand, will be used to make a protein. The information on the sense strand is copied into mRNA, which is then used to direct the synthesis of a protein. Now the enzyme RNA polymerase will make an mRNA molecule that is complementary to the sense strand of the gene. Come on in, RNA polymerase and RNA nucleotides. RNA nucleotides, find your correct complementary partners on the DNA strand. [Help any students who seem to be having trouble with this task.]

Announcer: RNA polymerase, you attach the nucleotides together when they get to their correct places.

Student Actions: The RNA polymerase and RNA students walk into the skit area at random, and walk around looking for their complements. Each RNA nucleotide stands in front of its complementary DNA codon. The student labeled “RNA polymerase” attaches the nucleotides together by touching the hand of one student to the arm of the next. The announcer can prompt and talk about what the RNA polymerase is doing, especially in a large classroom where those in the back may not be able to see well. [You may find it helpful to talk all the time during these skits, pointing out what’s happening, reinforcing various ideas. This makes the student actors more comfortable, because it makes it clear that you are still in charge of what’s going on and they are following your direction rather than being expected to remember what to do.]

Announcer: When the mRNA is finished, it is released from the DNA, which winds up again. mRNA, stay in a line and walk to the side; DNA strands come together again.

Student Actions: The mRNA students walk off in a line to the right or left, and the second strand of DNA comes forward to interact with the first strand as at the beginning of the skit.

Announcer: We are done with the DNA now; thanks for your help. You may sit down. [Don’t forget to collect their signs as they sit down.]

Student Actions: The DNA students sit down.

Announcer: Here is the mRNA molecule that carries the information of the gene. It will take this information from the nucleus into the cytoplasm and find a ribosome. The ribosome helps the mRNA and tRNA work together to use the amino acids to make the correct protein. [You may or may not be able to designate part of your room as nucleus and cytoplasm; if not, don’t worry about it. The teacher’s desk makes a good ribosome; lead the line of students up to it.] Come on in, tRNAs and amino acids.

Student Actions: The tRNA and amino acid students come into the skit area.

Announcer: The tRNA molecules are first attached to their correct amino acids by enzymes. Each tRNA, find your correct amino acid. .

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Student Actions: The tRNA and amino acid students should pair up correctly, according to the signs on the tRNAs. Announcer: The tRNAs will now lead their amino acids to the ribosome to be put into the protein chain.

We’ll start with GUC and go in order. Each tRNA will then sit down. [As the first student pair comes up.]

Look at how the anticodon on the tRNA matches the codon on the mRNA. That’s how the correct amino acid gets put in at the correct spot.

Student Actions: The tRNA matching the first codon brings his or her amino acid over to the ribosome.

The amino acid is left at the ribosome, and then the tRNA sits down. Now the tRNA matching the second codon brings his or her amino acid and sits down, and so on, until all six amino acids have been brought.

When each amino acid is brought to the ribosome, it is attached to the chain at the ribosome and the rest of the amino acids move down a little. [It is unnecessarily complicated in this skit to designate E, P, and A sites on the ribosome, but it could be done if desired.]

Announcer: Each new amino acid is attached to the chain at the ribosome, and the end of the growing chain just floats in the cytoplasm nearby. [As the stop codon comes up.] This process continues until a special codon, called the stop codon, is reached. It does not code for an amino acid. When the ribosome gets to a stop codon, the protein is finished and released from the ribosome. Okay, protein, move away from the ribosome. And so our needed protein is made. Thanks very much to all the participating molecules! You may all sit down now.

Assessment Suggestions: There is really no way to assess the skit; it is just a demonstration. You can also base exam questions on the ideas presented in the skit.

Lecture Activity 9.3: Student Opinions on Human Cloning Estimated Time to Complete: 15–20 minutes, or longer with discussion Introduction: Human cloning is a topic in which students show great interest, because it is a controversial issue frequently addressed in the media. There have been reports of scientists who attempted to clone human babies, and other reports have indicated that this type of cloning has already been done, although no human clone has yet been tested and verified. Without a doubt, cloning will be an issue that affects everyone’s life in one way or another in the future.

This activity should be done after the lecture/discussion on Dolly, the cloned sheep, to give students a chance to think through and discuss their personal ideas about cloning. Because students may have strong opinions on this topic, caution the class that all opinions are to be respected in the discussion process and that ideas, but not individuals, may be attacked.

Material • None.

Procedures 1. After the process of cloning has been explained in class, remind students that there is currently a controversial debate on whether human cloning should be allowed, and for what reasons. Tell the students that human cloning has been supported and opposed by various groups for many different reasons. Make clear to them that human cloning can either be reproductive, resulting in the production of a baby, or therapeutic, resulting in production of a human organ, tissues, or cells only (not harvested from a complete organism).

2. Divide the class into groups, and give each group one of the scenarios described in step 4. More than one group can receive the same scenario.

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Chapter 9 Genetically Modified Organisms 73

3. Ask each group to give arguments both for and against the proposed cloning, and to come to a consensus opinion, if possible, on whether they support cloning for that reason. If a consensus cannot be reached, they can cite pros and cons to summarize their arguments separately. Students should never feel that their opinions are being forced or disregarded.

4. Assign the following questions to different groups: Do you feel that cloning should be allowed: • As a way for homosexuals to have genetically related children?

• As a way for two parents who both carry the gene for a severe genetic disease and who will not accept abortion of an affected fetus to have a genetically related child guaranteed to be free of the disease?

• As a way for parents to be able to choose many characteristics of their children, including gender, hair and eye color, metabolic rate (i.e., the tendency to be overweight), and IQ? • As a way to “bring back” a child who was killed accidentally?

• As a way to “bring back” an important or influential person—for example, Albert Einstein or John F. Kennedy?

• As a way for a couple to honor a parent or other important person in their life by choosing to have a genetically identical child?

• As a way to generate cells that could help heal a person suffering from a severe brain or spinal cord injury?

• As a way to generate new heart tissue for a person suffering from severe heart disease—tissue that would not require immune suppressants to fight rejection, because it would be genetically identical to the rest of the body?

• As a way to allow new types of research into cures for diseases?

5. After assigning a scenario to each group, allow 10 minutes for students to come up with their thoughts, and then ask each group to report its findings to the class or to summarize them on paper.

6. To add another twist, you could ask whether ability to pay should determine who has access to these cloning services and, if not, who or which agency should supply funds for people not able to afford these services on their own.

Assessment Suggestions: Collect and assess summary papers from each group. Give students points based on their oral reports and/or class participation.

This would make an excellent discussion question or questions online. You could divide students into groups and assign each group a question or group of questions and have them discuss it online. If you do this it is important to go through the rules of online discussion to make sure that there are no inappropriate comments.

Lecture Activity 9.4: Human Genome, Mutations, and Genetic Information Estimated Time to Complete: 10–20 minutes Introduction: After students have learned the basics of genetics, including gene regulation and mutation, they can begin to consider some of the more complex implications of our expanding knowledge of the human genome. This extended understanding is especially important in a non-majors course, because it is not the technical details of genetics that will be important to them in the future, but rather how these technologies will affect students, their families, and their lives. Getting a feel for the current and possible future uses of genetic technology helps motivate students, helping them realize why it is essential for them to develop a good understanding of genetics and molecular biology.

Material • None.

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74 Instructor Guide Biology: Science for Life

Procedures 1. Introduce the topic of the Human Genome Project (HGP) to your students by briefly describing the nature, scope, and accomplishments of the HGP. Point out that several genes were well understood before the HGP was completed, and that for some of these genes our knowledge now includes an understanding of specific mutations that cause (or may cause) specific diseases. This knowledge, in turn, can and has been used to develop screening tests to determine whether an individual carries one of these mutations.

2. Pose a set of questions to be discussed. This activity can consist of a class discussion, or you can break the class into small discussion groups. If you break the class into separate groups, you could assign different questions to each group and have each group summarize its discussion to the class as a whole. This approach would require more class time.

3. Present these questions to the class in any way convenient. Possible topics include the following issues: • Would you want your own genome to be sequenced?

• Would you wish to be screened for specific disease-causing mutations?

• Would you want to be screened for mutations that you know exist in your family?

• Would you want to be screened for specific mutations even if there was no cure for the disease?

• Would you want to screen your children before they were born for mutations or diseases?

• Do you think screening tests should be developed for nondisease conditions such as eye color, metabolic rate (which could influence the tendency to become overweight), or intelligence for the use of parents wishing to have children with only certain characteristics?

• Who should have the right to information about your genetic makeup?

• Who should control access to your genetic information?

• Should insurance companies be allowed to deny you coverage for specific conditions based on your genetic makeup?

• Should the FBI or other law enforcement agencies be permitted to keep a database of genetic material of convicted criminals? Of people charged with crimes but not convicted? Of anyone on whom the agency wants to keep tabs?

• Should members of the military or people in other dangerous occupations be required to supply DNA for identification purposes even if they don’t want to?

• What other ethical or moral consequences are there with respect to genetic information?

• If you carry a gene for an incurable condition, should you have children?

Assessment Suggestions: Have groups turn in written answers to one or more of the questions. Use the discussion as the basis of an exam question.

These questions could be used in an online discussion forum. Assign students into groups and give them a set of questions to discuss online. It is important to establish etiquette rules for online discussions to make sure there are no inappropriate comments.

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10 Where Did We Come From?

The Evidence for Evolution OBJECTIVES Teaching Goals Depending on the mix of students in the class, evolution can be a controversial topic. Many students are eager to explore the question “Where did we come from?”, whereas others, depending on their religious background, may feel threatened by the topic and can be quite vocal in their opposition to the idea of evolution. Introduce the concept of common ancestry by having students trace the evolution of communication or transportation or video gaming. Emphasize how modern DNA evidence supports what is shown in the fossil record.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Define biological evolution, and distinguish it from other forms of change in populations of organisms.

• Illustrate the theory of common descent using a tree diagram.

• Summarize how Darwin’s experiences led him to develop the outline of the theory of evolution.

• Detail the modern biological classification system, and explain how it supports the theory of evolution.

• Explain how homologies in anatomy and genetics, even in vestigial traits, support the theory of evolution.

• Describe how details of embryonic development support the theory of evolution.

• Define biogeography, and explain how it supports the theory of evolution.

• Explain how the fossil record provides direct evidence of evolutionary change in species over time.

• Articulate why the theory of evolution is considered the best explanation for the origin of humans and other organisms.

LECTURE OUTLINE 10.1 What Is Evolution?

A. Biological evolution is based on changes in populations that are based on inherited characteristics.

B. Members of the same species can interbreed but are most often studied as members of populations in specific geographical locations. .

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C. The theory of evolution explains the origin of species from a common ancestor and the resulting relationships among all organisms. (Figure 10.2) Lecture Activity 10.1 10.2 Charles Darwin and the Theory of Evolution A. Darwin was influenced by his travels and by contributions from scientists such as Hutton and Lyell.

B. During his five-year voyage on the HMS Beagle Darwin collected many forms of evidence for the theory of common descent.

C. Based on fossils and his extensive observations of plants and animals, Darwin proposed natural selection as the mechanism underlying evolution. (Figure 10.5, Figure 10.6) Lecture Activity 10.2 D. Alternative hypotheses were developed to try and explain the origin of modern organisms.

(Figure 10.7) 10.3 Examining the Evidence for Common Descent A. Linnaean classification grouped organisms based on similarities. (Figure 10.9) B. Anatomical similarities and shared developmental pathways provide evidence for the theory of common descent. (Figure 10.10, Figure 10.11) Lecture Activity 10.3 C. DNA evidence further supports the common descent theory. (Figure 10.12) Lecture Activity 10.4 D. The geographic distribution of organisms and fossil evidence give clues to the past history of organisms.

Lecture Activity 10.5 E. Fossils helped with providing evidence of human ancestors. (Figure 10.17) F. Multiple lines of evidence reveal that humans and apes came from a common ancestor.

G. Radiometric dating measures the amount of radioactive decay to determine the age of the fossils.

(Figure 10.20, Figure 10.21, Figure 10.22) 10.4 Are Alternatives to the Theory of Evolution Equally Valid?

A. Other suggested hypotheses do not explain the diversity of life as well as the theory of evolution.

(Figure 10.24) B. Evolutionary theory helps us understand what we see and predict reactions to changes such as global warming.

Lecture Activity 10.1: Thinking Like Darwin Estimated Time to Complete: 15–20 minutes Introduction: This activity introduces students to four different species of finch found on the Galápagos Islands. Students will examine features of these organisms and work in small groups to develop dichotomous keys that can be used to distinguish each of the different finch species from the others. Some or all of the keys developed during class can be shared in the larger group to determine if they work as expected. This lecture activity is modified from the following PBS website: http://www.pbs.org/safarchive/5_cool/galapagos/g53_more.html.

Material • Copy the picture of the finches for each group. (Other photos or sketches of “Darwin’s finches” can be used rather than this one, and other groups of organisms can also be used.)

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Chapter 10 Where Did We Come From? 77

Procedures 1. Introduce the concept of a dichotomous key. This type of key offers only two choices for each specific feature. You select the correct choice and are then directed to a different set of two choices.

Eventually, you end up with the correct name of the organism. A simple example for the class may include the development of a key to distinguish apples, bananas, oranges, and lemons. One key to distinguish these fruits is the following:

2.

3.

4.

5.

A. (1) The fruit is yellow. → Go to B. (2) The fruit is not yellow. → Go to C. B. (1) The fruit is spherical. → lemon (2) The fruit is long and narrow. → banana C. (1) The fruit peels easily. → orange (2) The fruit requires a knife for peeling. → apple Call attention to the fact that the number of questions required for using the key to identify the four fruits was one less than that number (i.e., three).

Have the students work in groups of three to four. They will look at the pictures of the finches and write down single words or phrases describing each one. For example, descriptive phrases could include “head larger than 2 cm vertically” or “beak with a flat-topped bill.”

Students will then use their descriptive words and phrases to categorize the finches into groups based on those features.

Ask students to develop a dichotomous key to use in distinguishing their organisms. Time permitting, some or all of the keys can then be shown to the larger group and assessed by determining their usefulness in correctly identifying the organisms.

Assessment Suggestions: As an extra level of complexity, groups of students could be assigned different groups of organisms. As an assignment or an exam question, give the students a dichotomous key of your own invention and some pictures or features of organisms to identify using the key. Give extra credit to those groups whose keys actually work.

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Top left = Camarhynchus Top right = Platyspiza Bottom left = Geospiza Bottom right = Certhdea

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Chapter 10 Where Did We Come From? 79

Lecture Activity 10.2: Blended Inheritance versus Mendelian Genetics Estimated Time to Complete: 15–20 minutes Introduction: The major weakness in Charles Darwin’s proposal that evolution occurs by natural selection was his lack of understanding of the principles of genetic transmission of traits from parents to offspring. This is not surprising, because Gregor Mendel’s work on determining these principles had not been done at the time of the publication of On the Origin of Species, and widespread understanding of genetics did not occur until well after Darwin’s death. Darwin, like most other biologists prior to Mendel’s breakthroughs, accepted the concept of blended inheritance, in which it was assumed that offspring express a mixture of the traits of both parents. For example, a tall male and a short female would be expected to produce medium-sized offspring.

In this activity, students compare the expected outcomes of genetic crosses, first using correct Mendelian inheritance principles and then using the incorrect concept of blended inheritance. They should be able to see that blended inheritance, if true, would actually reduce the opportunity for evolution, whereas Mendelian inheritance maintains that opportunity.

Material • None.

Procedures 1. Briefly review basic Mendelian genetic principles.

2. Introduce the concept of blended inheritance and Darwin’s belief in it to the class.

3. Write the following genetic cross on the board: RR × rr. Explain that the R allele is dominant and confers red flower color, and the r allele is recessive and produces a white-flowered phenotype.

4. Ask students to predict the expected offspring phenotypes and proportions from this cross according to Mendelian genetics. (Answer: All Rr offspring showing the red flower color.)

5. Ask students to predict the expected offspring proportions if blended inheritance were correct.

(Answer: All would be intermediate—Rr, with pink flower color, because there is no dominance of alleles under blended inheritance.)

6. Repeat this exercise for the cross Rr × Rr. (Answer: Mendelian inheritance predicts proportions of 1⁄4 RR, red; 1⁄2 Rr, also red; and 1⁄4 rr, white. Blended inheritance predicts all intermediate phenotypes [Rr, pink].)

Assessment Suggestions: Ask the following questions, as either a class or online discussion, a smallgroup discussion, or an assignment to be written and handed in class or online: 1. What would happen to a population containing a mixture of AA, Aa, and aa individuals with Mendelian inheritance? All three genotypes will remain in the population, because various types of matings produce all three.

2. What would happen with blended inheritance? Eventually, the entire population would consist of the intermediate (Aa) genotype and phenotype because extreme phenotypes are eliminated by the blending.

3. Would natural selection be effective in a population with Mendelian inheritance? Yes, the variation in the phenotype is maintained, so one phenotype may be favored over others and be more represented in later generations.

4. Would natural selection be effective on a population with blended inheritance? Not for very long, because the phenotypic variation would be quickly eliminated by the genetics. There would be no way for extreme phenotypes to be favored, unless they were to mate only with an individual with the same phenotype. Thus Darwin’s concept of inheritance, if true, would greatly restrict the possibility that a population could evolve by natural selection. Mendelian genetics allows evolution by natural selection to be possible.

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Lecture Activity 10.3: Common Past, Different Paths Estimated Time to Complete: 10–15 minutes Introduction: Similar developmental patterns are compelling evidence supporting the concept of common ancestry of vertebrates. Students are generally unaware of these similarities because they have disappeared by the time the babies are ready to be born or hatched. This Internet video briefly demonstrates the similarity in development of limbs from humans, pigs, and birds; it gets the class thinking about why these similarities exist, and why they exist only in the embryonic stages of life.

Material • Computer with projector and Internet access.

Procedures 1. Go to www.pbs.org and search for “Evolution Library Common Past, Different Paths.” Show the video from the Common Past, Different Paths Evolution Library (1 minute, 36 seconds) to your class.

2. After viewing the video, ask students to think about and discuss the following questions, either in small groups or as a whole class: • Why do vertebrate embryo limbs start out looking so similar? (If students struggle with this question, try to steer the class reasoning toward shared genes.)

• Why do the limbs end up looking so different? (Encourage answers emphasizing selection and/or adaptations to different environments.)

• From an evolutionary perspective, why do the limbs look different after birth or hatching but not before? Because selection doesn’t operate on limbs until after birth or hatching.

Assessment Suggestions: Have students turn in written answers to the questions, either individually or in groups. The questions could be placed online along with the link to the video and have this as a complete online assignment. Use the discussion as a basis for an exam question or as an online discussion forum.

Lecture Activity 10.4: Using Evolutionary Information to Create Phylogenetic Trees Estimated Time to Complete: 15–20 minutes (or more, depending on discussions) Introduction: This activity allows students to analyze data and use those data to create phylogenetic trees. In addition to reviewing the evidence used to generate trees, the students learn that scientific models are continually modified as new data become available.

Materials • Computer with a projector (alternatively the needed pictures could be provided on overhead transparencies or as handouts) • Document camera or transilluminator for projecting students’ answers, if desired • Lecture Activity 10.4 Handout: Using Evolutionary Information to Create Phylogenetic Trees Procedures This activity should be done after the class has covered phylogenetic trees and the history of evolutionary theory. Students should also be familiar with lines of evidence for evolution, including homology, vestigial structures, and the use of DNA and protein sequences in assessing relatedness of organisms. If desired, this activity can be broken up into parts, and each part can be done after its corresponding topic is discussed in lecture.

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Chapter 10 Where Did We Come From? 81

1. Before class, find pictures of a black bear, a sea otter, a harp seal, a harbor porpoise, a blue whale, a hippopotamus, and a penguin; also find pictures of their skeletons and basic information about each animal’s diet and habitat.

2. Show students images of the seven animals, and give them background information about each animal’s diet and habitat. See the next page for a handout that students can use to summarize this information.

3. Divide the class into groups of two to four students, and ask each group to develop a phylogenetic tree of the organisms based on the information given to them.

4. Collect the trees from some or all of the groups, and share several of them with the class using a document camera or transilluminator. (If one is not available, the trees can be quickly sketched on the blackboard, an overhead transparency, or a flipchart.) Several common misconceptions are typically revealed—for example, modern species serving as ancestors to other modern species; birds evolving from mammals, or vice versa. Take some time to provide feedback to the class about the phylogenetic trees and address these common misconceptions.

5. Show students the skeletons of the seven animals and ask them to revise their trees. Draw their attention to differences and similarities, especially in the limbs and pelvic bones.

6. Again collect, project, and discuss sample trees. At this point the students should have grouped the whale and porpoise together, because each species has a vestigial pelvis.

7. Give the students the following aligned partial DNA sequences from the seven species and ask them to revise their trees once more.

Portion of Cytochrome b ACAGC ACAGC ACCGC ACCGC ACCGC ACAGC CTGGC

DNA Sequence Sea otter Harp seal Harbor porpoise Blue whale Hippopotamus Black bear Penguin

8. Again collect, project, and discuss the trees. At this point the students should have grouped the hippo, whale, and porpoise together based on sequence similarities.

Assessment Suggestions: Collect the final phylogenetic trees for assessment. On an exam or as a homework assignment, ask the students to explain which homologous and vestigial structures were seen in these animals, and how they were used in the development of the phylogenetic trees.

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Lecture Activity 10.4 Handout: Using Evolutionary Information to Create Phylogenetic Trees

Diet

Habitat

Black bear Harp seal Hippopotamus Sea otter Penguin Harbor porpoise Blue whale

Other Observations Black bear Harp seal Hippopotamus Sea otter Penguin Harbor porpoise Blue whale

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Skeleton— Pelvis

Skeleton— Limbs

DNA Sequence

Chapter 10 Where Did We Come From? 83

Lecture Activity 10.5: Your Own “Fossil Record” Estimated Time to Complete: 20 minutes Introduction: Biologists base their understanding of the past on fragmentary pieces of evidence— fossils, comparisons of fossil material to living species, climatic information from chemical analysis of rocks, and other geological analyses. From this information, they try to construct an overall description of the organism and its environment—for example, where and under which ecological conditions the organism lived, how it performed various activities, and what its predators and food species may have been. Sometimes, you can tell a lot from just a little evidence.

In this brief activity, each student will list the contents of his or her own “fossil record”—those things that may provide a picture of the student’s life, activities, habits, and habitats. Each student then acts as an archeologist and tries to understand the life of another student.

Material • A piece of paper for each student.

Procedures 1. Introduce and explain the activity to the class. Discuss the random and fragmentary nature of the fossil record, and consider how scientists use these scraps of information in attempting to deduce facts about the biology of extinct species.

2. Have each student take a piece of paper and tear it into 20 fragments, and then write on each fragment an item that the student owns. Have students fold each fragment in half after writing on it.

3. Now each student must find a partner whom he or she does not know very well. One partner, acting as the archaeologist, randomly selects five of the folded slips of paper from the other partner, reads them, and makes some guesses about the other person. He or she then selects five more slips at random, reads them, and refines his or her initial guesses.

4. The partners then trade roles, and the other person acts as archeologist.

Assessment Suggestions: Use the following questions as a guide for a class or online discussion about this activity. You could also place these questions online for homework: 1. What could an observer with no previous knowledge of you or your life tell about you? The observer could tell your height, apparent age, physical features, hairstyle, clothing choices, and so on, as well as your current location (in a biology lab).

2. What could that observer not tell about you? The observer could not definitively determine things such as your beliefs, preferences, living situation, most recent meal, and so on. However, the observer may be able to make intelligent guesses based on the visible evidence, such as religious/symbolic items, a wedding ring, or clothing representing a school, sports team, or band.

3. Is this an accurate picture of you and your life? Answers will vary, but it can be instructive to uncover the reasoning behind inaccurate guesses.

4. How is this activity similar to what scientists do when reconstructing natural history? The fossil record is often fragmentary, but it can lead to surprisingly extensive inferences about the distant past.

However, scientists’ underlying assumptions need to be examined carefully to avoid false conclusions.

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11 An Evolving Enemy Natural Selection OBJECTIVES Teaching Goals By opening this topic with the importance of understanding evolution today (e.g., antibiotic resistance, adaptation to climate change), you may be able to deflect some of the resistance to the topic of evolution.

While introducing the principles of natural selection, your goal is to use current-day examples to which students can relate. The work done on beak sizes in birds is well documented but means little to the students. Emphasize the ability of evolutionary theory to help predict changes (e.g., the widespread use of a new antibiotic almost guarantees that it will become ineffective within a few years).

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe the history of tuberculosis in human populations, and explain why current treatments are ineffective against some strains of the disease.

• List the four observations that led to the inference of natural selection.

• Explain how natural selection causes evolutionary change.

• Provide examples of evidence that supports the hypothesis that natural selection leads to the evolution of populations.

• Describe how natural selection works on allele frequencies in a population.

• Discuss why natural selection does not result in “perfectly adapted” organisms or drive organisms toward some ideal state.

• List the three patterns of selection, provide examples of each, and explain how they lead to different outcomes.

• Using your understanding of natural selection, explain why combination drug therapy is an effective tool to combat drug resistance.

LECTURE OUTLINE 11.1 Return of an Ancient Killer A. Tuberculosis is caused by a bacterium, Mycobacterium tuberculosis, and infects more than two billion people around the world.

B. MDR-TB and XDR-TB have evolved resistance to the main-line antibiotics used to treat tuberculosis.

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11.2 Natural Selection Causes Evolution A. Individuals in a population vary in their characteristics. (Figure 11.6) B. Some of the variation among individuals can be passed on to their offspring. (Figure 11.7) C. Not all organisms that are born will survive to reproductive age. (Figure 11.8) D. Differential reproduction and survival occur because of adaptations; natural selection passively selects for those adaptations that improve fitness. (Figure 11.9) Lecture Activity 11.1 E. Natural selection can be tested in the lab but is observed commonly in wild populations.

(Figure 11.11, Figure 11.12) 11.3 Natural Selection Since Darwin A. Mutation introduces variation into a population; natural selection promotes some variants over others. (Figure 11.13) B. Natural selection is random and does not progress to perfection.

C. There are misconceptions of natural selection. (Table 11.1) D. Directional, stabilizing, and diversifying are three patterns of natural selection. (Figure 11.16) Lecture Activity 11.2 11.4 Natural Selection and Human Health A. When a patient with tuberculosis takes antibiotics and then stops taking it before all bacteria is killed, the bacteria that survived will be resistant to that therapy and so will increase in the population. (Figure 11.17) B. A drug regimen consisting of multiple drugs for a longer period of time can combat the development of resistance. (Figure 11.18)

Lecture Activity 11.1: A World of Weird Adaptations!

Estimated Time to Complete: 5–10 minutes Introduction: Students are interested in the weird adaptations that have evolved in certain plants and animals. You might like to show a few slides of unusual organisms and challenge the students to guess why they look or act the way they do. This discussion then nicely leads into a review of natural selection.

Material • Pictures of organisms showing interesting adaptations.

Procedures 1. Before class, find pictures of organisms (from the Internet or other sources) showing interesting adaptations. Here are suggestions for the organisms: • Angler fish • Cleaner wrasse • Leaf insect • Sundew • Ant plant 2. Display one picture at a time to the students in any convenient way, such as through a PowerPoint presentation, overhead transparencies, or directly from the Internet. For each slide, ask the students which adaptation they see and why the feature is adaptive for that organism.

• The angler fish has its own fishing pole with bait to attract fish that want to eat it; the angler fish eats them instead.

• Cleaner wrasse are not afraid to swim inside the mouths of larger fish; they feed on parasites in the mouth and on the bodies of their “clients,” which never eat the cleaners.

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Chapter 11 An Evolving Enemy 87

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The leaf insect is very well camouflaged so it can lie in wait for its insect prey.

The long hairs on the sundew leaf bear large droplets of very sticky material; they capture and digest insects that blunder into it (nature’s flypaper).

• The inside of the ant plant develops large empty spaces in which ant colonies live. The ants defend their plants from attack and provide fertilizer in the form of droppings and dead bodies.

3. Ask students how these types of features evolved in the populations; encourage a general review of the tenets of evolution by natural selection.

Assessment Suggestions: Give another example of an adapted plant or animal, such as a cactus, polar bear, dolphin, rabbit, or other organism, and ask the students individually or in groups to describe its adaptations and how they evolved.

This could be converted to an online assignment with the students going to different websites to view the plant or animal and have a set of questions that they answer about each image.

Lecture Activity 11.2: Does Natural Selection Always Occur?

Estimated Time to Complete: 10 minutes Introduction: To emphasize the importance of natural selection in the evolutionary history of a population, this activity asks students to think about what would happen in the absence of evolution. The activity can be done in many ways, as a class or in small groups, and either as a discussion or as a smallgroup or individual written effort to be turned in.

Material • Lecture Activity 11.2 Handout: Does Natural Selection Always Occur?

Procedures After discussing natural selection in lecture, pose the questions from the handout to students, either in small groups or as a whole-class activity.

Assessment Suggestions: Have students turn in written answers to the questions. Include a similar question on an exam or quiz.

This could be easily turned into an online assignment with the students answering the questions online.

Handout Answer Key 1. Under which circumstances might a population not be subjected to natural selection? Encourage students to think about violating some of the observations that normally support the idea of natural selection—for example, if there is no variation in a population, if resources are not limiting and most offspring survive, and so on.

2. What do you think would be the genetic and evolutionary consequences to the population if it was not subject to natural selection? There might be an increase in the number of different genotypes that would survive and reproduce, the population might become less well adapted to its environment, and so on.

3. Can you think of a species on Earth today that may not be naturally selected? Most students will probably think of humans. Although natural selection certainly shaped human beings in the past, it is unclear whether it is still a factor in human evolution. The discussion could even be steered toward a conversation about cultural evolution and how that contrasts with natural selection.

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Lecture Activity 11.2 Handout: Does Natural Selection Always Occur?

What would happen in the absence of evolution? Answer the following questions.

1. Under which circumstances might a population not be subjected to natural selection?

2. What do you think would be the genetic and evolutionary consequences to the population if it was not subject to natural selection?

3. Can you think of a species on Earth today that may not be naturally selected?

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12 Who Am I? Species and Races OBJECTIVES Teaching Goals Students study ethnic origins and customs in social science classes, and the concept of race may be covered in those courses. However, the definition of the word race is unclear in scientific use. Your goal is to use clear examples to help students understand the differences between race and species. By identifying forces that cause changes in the gene pool such as reproductive isolation and genetic drift, they may see how phenotypic variations (used to determine race) occur. Discussion of cultural taboos (e.g., marrying someone from another race) can illustrate the power of reproductive isolation.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Define biological species, and list the mechanisms by which reproductive isolation is maintained by biological species.

• Describe the three steps in the process of speciation.

• Explain how a “race” within a biological species can be defined using the genealogical species concept.

• List the evidence that modern humans are a young species that arose in Africa.

• List the genetic evidence expected when a species can be divided into unique races.

• Describe how the Hardy-Weinberg theorem is used in studies of population genetics.

• Summarize the evidence that indicates that human races are not deep biological divisions within the human species.

• Provide examples of traits that have become common in certain human populations due to the natural selection these populations have undergone.

• Define genetic drift, and provide examples of how it results in the evolution of a population.

• Describe how human and animal behavior can cause evolution via sexual selection and assortative mating.

LECTURE OUTLINE 12.1 What Is a Species?

A. A species comprises a group of individuals that share a gene pool and that can interbreed with each other but not with members of other species.

B. Reproductive barriers isolate one species from another and may be either prefertilization or postfertilization barriers. (Table 12.1) Lecture Activity 12.1

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C. Speciation results from isolation and changes in the gene pool, as well as through the development of reproductive isolation mechanisms. (Figure 12.3) D. Darwin suggested that speciation occurs through gradualism, whereas Stephen Jay Gould proposed the concept of punctuated equilibrium. (Figure 12.8) 12.2 Are Human Races Biological?

A. Races are considered populations of a single species that have accumulated changes that distinguish them from other populations.

B. Genealogical species share unique evolutionary lines of descent and a common ancestor.

(Table 12.2) Lecture Activity 12.2 C. Physical characteristics such as hair texture, nose shape, and skin color are used to classify humans into races.

D. The majority of current evidence supports the hypothesis that all human populations are descendants of African ancestors.

E. Changes in gene frequency reveal evolutionary activity and can be calculated by using the Hardy–Weinberg formula. (Figure 12.10) Lecture Activity 12.3 F. No alleles specific to a particular race have been discovered.

G. Populations within a race are often as different as populations compared across races.

(Figure 12.12) 12.3 Why Human Groups Differ A. Natural selection plays a role in how human groups differ. (Figure 12.15) B. Convergent evolution can shape similar characteristics because of similar environments.

(Figure 12.17, Figure 12.18) C. Genetic drift, whether involving the founder effect or the bottleneck effect, produces changes in gene frequencies in a population by chance. (Figure 12.19) D. Sexual selection can create selective pressure toward particular traits. (Figure 21.21) E. Assortative mating is when individuals choose mates based on characteristics that are similar to their own.

Lecture Activity 12.4 Lecture Activity 12.5

Lecture Activity 12.1: Reproductive Isolation of Drosophila Species Estimated Time to Complete: 10–15 minutes Introduction: The biological species concept stresses that the defining characteristic of a species is that it cannot successfully interbreed with other species. Using this species concept, for two groups to be considered different species, some barrier must block their interbreeding. The process of speciation, regardless of whether the mechanism is allopatric, sympatric, or something else, involves the evolution of such barriers, or reproductive isolation mechanisms. These mechanisms may result in either prefertilization isolation, in which mating between the groups is somehow prevented, or postfertilization isolation, in which there are fitness problems with hybrid offspring or their descendants. Because of the way different types of speciation proceed, there may be differences in the amount of genetic divergence that occurs between two groups before isolating mechanisms become established.

This activity uses the example of closely related species of Drosophila fruit flies, one of the few organisms for which there has been extensive study of the genetics of speciation. The data used in this exercise are taken from the journal publication “Patterns of Speciation in Drosophila” by Jerry Coyne and H. Allen Orr (Evolution 43:362–381, March 1989). Coyne and Orr compiled data from published papers on reproductive isolation and genetic divergence in Drosophila and calculated several measures by comparing two species at a time: .

Chapter 12 Who Am I? 91

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Genetic distance: Calculated from the number of codon differences between homologous proteins of the two species, this measure ranges from 0 to 2, with 0 being identical and 2 being the highest level of difference measured among Drosophila species.

Prefertilization isolation: Based on mate choice tests, this measure ranges from 0 to 1, where 0 is “no mating isolation” (all possible between-species matings occur) and 1 is “complete mating isolation” (no mating between species at all).

Postfertilization isolation: For those species pairs that do successfully mate, this measure incorporates both hybrid inviability and sterility. It ranges from 0 to 1, with 0 being “no isolation” (all viable and fertile hybrid offspring) and 1 being “complete isolation” (both sexes of hybrid offspring are inviable or sterile). Usually, a measure of 0.5 means that one of the two sexes of hybrid offspring (usually males) is sterile or inviable.

Allopatric or sympatric: As used here, the term allopatric means that the species’ ranges do not overlap, and sympatric means that the species’ ranges overlap in some area.

In this activity, students look for patterns in a small subset of the data that is representative of the total data set. They then interpret what the patterns mean for the association of the two major types of speciation with genetic divergence.

Material • Lecture Activity 12.1 Handout: Reproductive Isolation of Drosophila Species Procedures 1. Briefly review the concepts of allopatric and sympatric speciation, and of prefertilization and postfertilization reproductive isolation.

2. Give the students the handout showing reproductive isolation among several species of the genus Drosophila, and explain the measures as described in the handout. Ask the students to look for patterns, guided by the handout questions.

3. While examining the data, discuss the handout questions with the class or have students work in small groups and write out the answers.

Assessment Suggestions: Have students turn in written answers to the questions. Design a quiz or exam question based on this activity.

This could be designed as an online assignment with the questions linked with a discussion forum to discuss the reproductive isolation of Drosophila.

Handout Answer Key 1. Is there an association between the allopatric/sympatric measure and the genetic distance measure?

Yes, allopatric species have higher genetic distance measures than sympatric species have.

2. What does this association mean? Allopatric species have diverged more than sympatric species, meaning that they have been independently evolving for a longer period of time.

3. Knowing the way that allopatric speciation works, why would you expect this outcome? Allopatric speciation requires a long period of separation for reproductive isolation to evolve as a by-product of separate evolution.

4. What pattern do you see in terms of premating and postmating isolation? Most species pairs show premating isolation, but postmating isolation cannot be measured if the two species don’t mate. For those that do mate, premating isolation is greater than postmating isolation.

5. What does this pattern mean? Speciation in Drosophila usually occurs with the evolution of premating isolation, whether it is allopatric or sympatric. If the premating isolation is only partial, postmating isolation may evolve later.

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Lecture Activity 12.1 Handout: Reproductive Isolation of Drosophila Species

Species 1

Species 2

Allopatric or Sympatric

Genetic Distance

Premating Isolation

Postmating Isolation

aldrichi

mulleri

sympatric

0.123

0.928

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aldrichi

mojavensis

allopatric

0.326

0.817

—

aldrichi

arizonensis

sympatric

0.289

1.000

—

arizonensis

mulleri

sympatric

0.232

1.000

—

mojavensis

mulleri

allopatric

0.324

0.972

—

arizonensis

mojavensis

sympatric

0.212

0.732

0.25

lacicola

montana

sympatric

0.210

0.954

0.00

lacicola

texana

allopatric

1.450

0.992

0.75

montana

texana

allopatric

1.510

0.985

0.50

— means “no measurement available.”

Source: Adapted from J. Coyne and H. A. Orr, “Patterns of Speciation in Drosophila,” Evolution 42 (March 1989): 362–381 (table 1).

•

•

•

•

Genetic distance: Calculated from the number of codon differences between homologous proteins of the two species, this measure ranges from 0 to 2, with 0 being identical and 2 being the highest level of difference measured among Drosophila species.

Prefertilization isolation: Based on mate choice tests, this measure ranges from 0 to 1, where 0 is “no mating isolation” (all possible between-species matings occur) and 1 is “complete mating isolation” (no mating between species at all).

Postfertilization isolation: For those species pairs that did successfully mate, this measure incorporates both hybrid inviability and sterility. It ranges from 0 to 1, with 0 being “no isolation” (all viable and fertile hybrid offspring) and 1 being “complete isolation” (both sexes of hybrid offspring are inviable or sterile). Usually, a measure of 0.5 means that one of the two sexes of hybrid offspring (usually males) is sterile or inviable.

Allopatric or sympatric: As used here, the term allopatric means that the species’ ranges do not overlap, and sympatric means that the species’ ranges overlap in some area.

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Answer the following questions based on the information in the table: 1. Is there an association between the allopatric/sympatric measure and the genetic distance measure?

2. What does this association mean?

3. Knowing the way that allopatric speciation works, why would you expect this outcome?

4. What pattern do you see in terms of premating and postmating isolation?

5. What does this pattern mean?

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Lecture Activity 12.2: Bicknell’s Thrush: A True Species?

Estimated Time to Complete: 10 minutes Introduction: Bicknell’s thrush has an interesting taxonomic history. The first specimen was found by Eugene P. Bicknell in 1881 in the Catskill Mountains of New York. It was originally described by Bicknell and Dr. Robert Ridgway of the American Museum of Natural History as a subspecies of the gray-cheeked thrush (Catharus minimus), a species whose range is far northern Canada. In the field, it is difficult to distinguish the two birds, but Bicknell’s thrush is generally smaller and has more yellow coloring at the base of the bill. Work in the 1990s indicated that the wintering and breeding ranges of the two birds do not overlap and that there is genetic divergence between them. As a result, in 1995 Bicknell’s thrush was given full species status—Catharus bicknelli. There is also experimental evidence of prefertilization isolation between the two species— specifically, Bicknell’s thrushes do not respond to the songs and calls of gray-cheeked thrushes.

This lecture activity can be used as a way to illustrate the difficulty of species designation and the criteria used to make such taxonomic decisions. It works best if the students first speculate on the species status based only on pictures of the two birds.

The excellent Bicknell’s thrush website by Don Busby of the Canadian Wildlife Service (go to http://www.atl.ec.gc.ca and search for “Bicknell’s thrush”) has additional photos, video, and audio files of this species, as well as a more detailed narrative of the history of its taxonomic designation. Media files can be accessed in class directly via the website (if the classroom has an Internet connection) or saved and presented by computer in class. The instructor may choose to display these files during or following this activity.

Materials • Lecture Activity 12.2 Handout: Bicknell’s Thrush: A True Species?

• Computer with projector (and Internet access for optional activity).

• Search the Internet for images of “gray-cheeked thrush” and “Bicknell’s thrush.”

Procedures 1. Briefly review the species concepts, and then display or distribute copies of pictures of the two birds (without labels of the bird names). Ask students to consider whether the birds are members of the same or different species.

2. This activity can be done either as a whole-class discussion or after breaking into smaller groups.

While viewing the two unlabeled pictures, ask the students or groups questions 1 and 2 on the handout.

3. After students complete questions 1 and 2, reveal the names, taxonomic designations, and taxonomic history of the two species either in its brief form (as in the introduction given in this manual) or in the more detailed form (presented at the websites listed earlier). Ask students to answer handout question 3.

4. Optional: Conclude the activity by presenting video and audio of Bicknell’s thrush.

Assessment Suggestions: Have students or groups turn in their written answers to the questions. Base an exam question on this exercise.

Create an online assignment with links to the pictures of the birds or create images and place them online with the assignment along with the questions. This could also be done as a discussion forum with you posting the images, asking for discussion, and then replying to the post with each question.

Handout Answer Key 1. Are these two birds members of the same species? Why or why not? Those who say no will probably point out the difference in coloration of the feathers, and perhaps the difference in beak coloration.

Some may notice the size difference based on the fingers visible in the picture, though that may be

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Chapter 12 Who Am I? 95

too difficult to see. Those who say yes might point out the birds’ similarities and suggest that the differences are variations within the species. Some might choose to withhold judgment without additional information, such as whether the birds interbreed.

2. What additional information would you want to make a better decision? Students will probably want to know whether the birds can or do interbreed (apparently not), whether one is male and one is female (we don’t know!), whether they are found in some of the same areas (no), and so on. Try to answer their questions as much as possible and have them reconsider their previous decision.

3. Now what do you think? Most will probably now say the birds are different species.

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Lecture Activity 12.2 Handout: Bicknell’s Thrush: A True Species?

Answer questions 1 and 2 after viewing unlabeled pictures of the two birds.

1. Are these two birds members of the same species? Why or why not?

2. What additional information would you want to make a better decision?

Answer question 3 after your instructor reveals more information about the two birds.

3. Now do you think the two birds are members of the same species?

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Lecture Activity 12.3: Demonstration of Genetic Drift Estimated Time to Complete: 15–20 minutes Introduction: This worksheet allows students to manipulate data and see for themselves how the founder effect, a genetic bottleneck, and sampling error can result in changes in allele frequency in a population.

Students may need help in determining allele frequencies at first. They will also need to remember how to do genetic crosses.

Material • Lecture Activity 12.3 Handout: Demonstration of Genetic Drift Procedures 1. After the class has talked about evolutionary changes due to genetic drift, divide the students into small groups, pass out the handout, and announce that each group has 15 minutes to complete it.

2. Because some groups may have trouble with the calculations, demonstrate to the whole class how to answer question 1.

3. As students are working, circulate around the room to answer questions and make sure groups are staying on task.

4. In questions 2 and 4 of the handout, students are asked to randomly choose animals or columns to work with. If you would like more accurate randomness, copy or project a page from a random numbers table and show students how to use it to make their random choices.

Assessment Suggestions: Collect written answers and grade (see handout answer key). Base an exam or quiz question on the handout.

Create online assignment or a discussion forum to do this handout.

Handout Answer Key 1. What are the allele frequencies of this population? (In other words, how many copies of the B allele are there, how many copies of the b allele are there, and what percentage of the total does each form?)

There are 113/200 B alleles (2 each from the 38 BB animals and 1 from each of the 37 Bb animals), accounting for 56.5% of the alleles; there are 87/200 b alleles, accounting for 43.5% of the alleles.

2. A small subgroup of these animals takes off and moves across a wide river to start a new population.

In the table above, choose 10 animals (underline the alleles) at random to move to this island. How many BB genotypes are there in the group? How many Bb? How many bb? Work out the allele frequencies for this new group of animals. The answers depend on the selection but are worked out in the same way.

3. A disaster occurs in the habitat of this animal. To simulate this event, place your hand over the population above. Circle the group of animals that appears uncovered in the space between your thumb and first finger (it’s okay if that includes some of the underlined animals).Those animals are the survivors of the disaster. Count the number of BB, Bb, and bb genotypes in this group, and determine the allele frequencies for B and b. Each group will have a different answer depending on their data.

4. Instead of the whole group being one population, assume each column is a separate small population.

Choose any column to work with. To illustrate the effect of sampling error, have your partner give you four numbers between 1 and 10 at random. Those are the animals that breed this year (the first and second mate; the third and fourth mate). If each pair has four offspring (with genotypes as expected for a Mendelian cross), compare the allele frequencies of the population before mating and the population after mating, which consists of the eight offspring of the two selected pairs. Students must figure out the allele frequency of the column representing the small population, work out the two crosses, and then determine the composition of the resulting population and its allele frequencies.

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5. How might these small, isolated populations evolve into separate races of the species over time?

Students should see that the allele frequencies are changing randomly due to these various treatments and understand that in small, isolated populations significant allele differences could build up easily; such conditions would be the starting point for the formation of biological races.

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Lecture Activity 12.3 Handout: Demonstration of Genetic Drift Imagine that you have a population of animals. The color of the animals’ fur can be brown or tan, with traditional Mendelian inheritance. Brown is dominant, so brown animals have the genotype BB or Bb; tan animals are bb. You have 100 animals in your population, as represented here: Bb Bb BB BB bb Bb Bb BB Bb bb

Bb BB Bb bb bb bb Bb Bb bb Bb

BB Bb bb Bb Bb BB Bb BB Bb bb

bb bb BB bb BB BB Bb Bb Bb bb

Bb BB BB BB BB BB BB Bb BB BB

Bb BB BB BB BB Bb BB BB Bb BB

BB bb bb Bb Bb bb BB bb bb bb

BB BB Bb Bb Bb bb Bb Bb bb Bb

bb Bb Bb Bb BB BB bb BB BB bb

bb Bb BB BB Bb BB bb BB BB Bb

This population consists of 75 brown animals, 38 with genotype BB and 37 with Bb, and 25 tan animals with genotype bb.

Questions 1. What are the allele frequencies of this population? (In other words, how many copies of the B allele are there, how many copies of the b allele are there, and what percentage of the total does each form?)

Copies of B allele Percentage of total Copies of b allele Percentage of total 2. A small subgroup of these animals takes off and moves across a wide river to start a new population.

In the table above, underline the alleles and choose 10 animals at random to move to this island. a. How many BB genotypes are there in the group? b. How many Bb? c. How many bb?

Work out the allele frequencies for this new group of animals.

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3. A disaster occurs in the habitat of this animal. To simulate this event, place your hand over the population above. Circle the group of animals that appears uncovered in the space between your thumb and first finger (it’s okay if that includes some of the underlined animals).Those animals are the survivors of the disaster. Count the number of BB, Bb, and bb genotypes in this group, and determine the allele frequencies for B and b.

4. Instead of the whole group being one population, assume each column is a separate small population.

Choose any column to work with. To illustrate the effect of sampling error, have your partner give you four numbers between 1 and 10 at random. Those are the animals that breed this year (the first and second mate; the third and fourth mate). If each pair has four offspring (with genotypes as expected for a Mendelian cross), compare the allele frequencies of the population before mating and the population after mating, which consists of the eight offspring of the two selected pairs.

5. How might these small, isolated populations evolve into separate races of the species over time?

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Chapter 12 Who Am I? 101

Lecture Activity 12.4: Case Study on Sexual Selection in Birds Estimated Time to Complete: 30 minutes Introduction: Case studies are a good way to let students see some actual data, get them thinking like biologists, and read about some interesting science. Students also have a chance to work together while trying to figure out the answers. The case study presented in this activity uses data from a paper on the reproductive success of birds whose tail markings had been altered. From the birds’ diminished reproductive success after this manipulation, students can get a firsthand look at the effects of sexual selection.

Material • Lecture Activity 12.4 Handout: Case Study on Sexual Selection in Birds Procedures 1. After the lecture and discussion on sexual selection, divide the class into small groups made up of about four students each.

2. Briefly explain the activity and pass out the handout.

3. Circulate while the students are working to answer questions and to keep groups on task.

Assessment Suggestions: Collect written answers and grade them online or in the classroom (see the handout answer key), or just use them for participation points. Base a quiz or exam question on the case study.

Handout Answer Key 1. Describe how natural selection might work to determine which of a group of male birds was able to reproduce and pass on its genes. In natural selection, the birds that survive to reproductive age are the ones to reproduce. Therefore, any bird that cannot find enough to eat, cannot evade predators, or succumbs to disease prior to breeding will not pass its genes on.

2. How does sexual selection differ, both in process and in outcome, from natural selection? The process of sexual selection differs from natural selection in establishing another set of requirements beyond those of natural selection. That is, birds still have to survive to reproductive age, but they also have to win the right to breed by using their desirable appearance to attract a mate. In outcome, birds that are naturally selected will show adaptations enhancing their ability to survive in their environment, but sexually selected birds may show characteristics that are actually nonadaptive in relation to survival.

The male peacock’s tail, for example, attracts enemies as well as mates and hinders its ability to escape a predator.

3. Why was this control done? The control helped to ensure that the process of catching and marking the birds did not result in a change in their reproductive fitness.

4. How would you describe the results shown in the table? Reduction in the size of the white spot on a barn swallow’s tail significantly reduced the average number of fledglings produced per season, mainly by reducing the likelihood of the birds’ producing a second brood. A larger reduction had a significantly greater effect on reproductive success than did a small reduction.

5. Given that feathers with many holes are likely to break, hypothesize how the large white spots of male barn swallows can signal important information about parasite load to possible mates. Males with large white spots are signaling that they have a small parasite load. If they were heavily infested with parasites, they might not be able to afford a large, weak, white spot that would be in danger of breaking.

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Lecture Activity 12.4 Handout: Case Study on Sexual Selection in Birds Birds frequently choose their mates by visual attributes not directly related to practical matters such as the ability to get food or build a good nest. This practice is called sexual selection. It is a form of selection because it is a process determining which animals are able to pass on their genes to the next generation.

The females usually do the selecting, so the males of many bird species exhibit characteristics that have been sexually selected rather than naturally selected. Examples of sexually selected characteristics include the bright coloration of male peacocks, the extremely long tail feathers of the long-tailed widowbird, and the large white spots on the tail feathers of barn swallows.

Questions 1. Describe how natural selection might work to determine which of a group of male birds was able to reproduce and pass on its genes.

2. How does sexual selection differ, both in process and in outcome, from natural selection?

In a paper entitled “Sexual Selection for White Tail Spots in the Barn Swallow in Relation to Habitat Choice by Feather Lice,” authors Kose, Mand, and Moller experimentally manipulated the size of white tail spots of male barn swallows to see whether there was an effect on reproductive success. They also tried to understand whether the size of a male’s white spot gave any useful information to a female barn swallow.

The scientists divided the birds in their experiment into three groups. In group 1, the birds’ white tail spots were made smaller by about two-thirds by coloring them in with black permanent ink. Birds in group 2 had their tail spots reduced in size by about one-fourth with the same black ink. For group 3, which was the control group, a naturally black part of the tail was colored with the same type of ink.

3. Why was this control done?

.

Some of the study results are as follows: Average Number of Group Fledglings per Season

Percentage Producing a Second Brood

Control

8.89

89%

Small reduction

6.20

53%

Large reduction 5.17 27% (All of these differences are statistically significant—in other words, they reflect real differences.)

4. How would you describe the results shown in the table?

To investigate whether the size of white spots gave female birds any useful information about the male birds, the biologists studied the pattern of holes made by feather lice. They found that feather lice are significantly more likely to eat the white part of feathers than the black part.

5. Given that feathers with many holes are likely to break, hypothesize how the large white spots of male barn swallows can signal important information about parasite load to possible mates.

Reference Kose, M., R. Mand, & A. P. Moller. Sexual selection for white tail spots in the barn swallow in relation to habitat choice by feather lice. Animal Behavior 58:1201–1205 (1999).

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Lecture Activity 12.5: Student Opinions on Human Race Definitions Estimated Time to Complete: 15–20 minutes, or longer with discussion Introduction: Race is a subject that is both very interesting and very personal to students, and they need a little time after the lecture to work out their feelings about the information that has been presented, especially if it is new to them. It is important to juxtapose the biological way of looking at race with the social way, to help students understand that there is more than one way to look at race. It is not really possible to get people to change or expand their understanding of such a personally significant topic if they do not confront their own opinions and ask themselves how these opinions stack up against the definitions and facts that have been presented. Group discussion is a good way to tackle this issue; other students may challenge a student more than he or she will challenge himself or herself. As this issue may inspire strong opinions, caution the class that all opinions are to be respected in the classroom and that ideas—but not individuals—may be argued.

Material • Lecture Activity 12.5 Handout: Student Opinions on Human Race Definitions Procedures 1. After the lecture/discussion on human races, break the class up into small groups of two to four students.

2. Have the groups discuss the questions on the handout and turn in a written summary of their answers.

Tell them that they will be called on to present one of their answers to the whole class.

Assessment Suggestions: Assign points for the questions. Post the best answers on the class website and reward the authors with a few points of extra credit. This would be a good discussion topic but you want to make sure to set guidelines on proper discussion etiquette. You could also do this as a standard online assignment.

Handout Answer Key 1. Define the biological species concept. A biological species is a population of organisms that can mate and produce fertile offspring.

2. How does the biological race concept compare with the biological species concept? Biological races are populations of a single species that have diverged from one another. During the process of divergence, the populations acquired unique alleles and different allele frequencies from one another.

3. In your own words, explain the difference between biological races and species. A biological race is a subdivision of a species that has some genetic differences from other races of the species. Members of different biological races are able to mate and produce fertile offspring. In contrast, members of different species have significantly greater genetic differences from one another. These differences usually either prevent mating from occurring or interfere with one of the processes of growth, development, or fertility after a cross has been made.

4. What does it mean to say that race, when applied to humans, is a social construction? Race is defined not in biologically meaningful ways, but rather in socially meaningful ways. Our definitions of, and attitudes toward, different races are largely based on our history of European colonialism and American slavery and oppression of native peoples.

5. Describe some ways, besides the ones commonly used in the United States today, in which human beings are or could be divided into races. Races could be determined by height, body shape, body adornment, language, religious practices, or many other possibilities.

6. What effect does assortative mating have on the maintenance of racial distinctions in the United States, in a biological way and in a social way? In assortative mating, people choose mates who resemble themselves. This tendency could contribute to the maintenance of racial distinctions, both

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Chapter 12 Who Am I? 105

biologically and socially. Biologically, parents who look alike will have children who look similar to them. Socially, parents who both consider themselves to be of one race will raise their children to consider themselves members of the same race.

7. In your opinion, are human races more likely to be biological races or socially constructed races?

Support your answer. If the group does not agree on this question, write down all answers. This is an opinion question; the answer must be accepted as long as some reasonable support is given for it.

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Lecture Activity 12.5 Handout: Student Opinions on Human Race Definitions Questions 1. Define the biological species concept.

2. How does the biological race concept compare with the biological species concept?

3. In your own words, explain the difference between biological races and species.

4. What does it mean to say that race, when applied to humans, is a social construction?

5. Describe some ways, besides the ones commonly used in the United States today, in which human beings are or could be divided into races.

6. What effect does assortative mating have on the maintenance of racial distinctions in the United States, in a biological way and in a social way?

7. In your opinion, are human races more likely to be biological races or socially constructed races?

Support your answer. If the group does not agree on this question, write down all answers.

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CHAPTER

13 Prospecting for Biological Gold Biodiversity and Classification OBJECTIVES Teaching Goals This chapter contains such a wealth of information it is tempting to skim over it. Get the students’ attention by introducing a list of commonly used products that illustrate the rich diversity in the kingdoms. Classification can be very boring, so your goal is to show not only the basis for it but also how it can be used for “prospecting.” Some of your students may have heard of shamans and Native American healers. Capitalize on their interest in the natural world by demonstrating the commercial application of this “biological gold.”

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Cite the current estimate of the number of species described by science, and explain why this number is only an estimate.

• List the three major domains of life, and describe basic characteristics of each domain.

• Provide a broad overview of the history of life on Earth.

• Summarize the endosymbiotic theory for the origin of eukaryotic cells.

• List the major characteristics of the four major kingdoms of Eukarya: Protista, Animalia, Fungi, and Plantae.

• Define adaptive radiation, and provide examples of where this has occurred in the history of life.

• Describe the characteristics of viruses, and explain why they are not considered living organisms.

• Provide examples of ecological traits in each of the various domains and kingdoms that have led to the evolution of biologically active compounds.

• Describe how evolutionary classifications of living organisms are created and tested, and explain how these classifications can be useful to scientists.

LECTURE OUTLINE 13.1 Biological Classification A. Biodiversity is the differences that exist between and within living organisms.

B. Geologic periods are characterized by groups of organisms that lived during that time period.

(Table 13.1) .

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C. Classification places organisms into three major domains, which are in turn further subdivided into kingdoms. (Table 13.2) 13.2 The Diversity of Life A. Organisms classified in the Bacteria and Archaea domains are prokaryotic and unicellular.

(Figure 13.7) B. Protista contains a wide diversity of organism that are eukaryotic. (Table 13.3) C. Eukaryotic organisms in the kingdom Animalia are multicellular and are a rich source of compounds for commercial application. (Figure 13.8, Figure 13.11, Table 13.4) D. Fungi include yeasts and molds; these organisms produce a wide variety of antibiotics.

(Figure 13.13, Table 13.5) E. Members of the kingdom Plantae provide their own food through photosynthesis; flowering plants make up the majority of this kingdom. (Figure 13.15, Figure 13.16, Table 13.6) Lecture Activity 13.1 F. Viruses consist of either DNA or RNA surrounded by a protein-covering capsid.

Lecture Activity 13.2 Lecture Activity 13.3 13.3 Learning about Species A. The rich diversity of organisms provides a target for those searching for commercially valuable compounds.

B. Knowledge of the ecology of organisms can help bioprospectors find useful products.

C. Cladistics can help us explore the evolutionary history of closely related species. (Figure 13.21) D. Evolutionary history can be tested by comparing DNA. Lecture Activity 13.4 E. Shamans and healers in indigenous cultures have a wealth of knowledge about helpful plants and animals in their geographical areas.

Lecture Activity 13.5

Lecture Activity 13.1: Classification of Plants and Fungi Estimated Time to Complete: 10 minutes Introduction: Fungi and plants were once classified together in one kingdom. After breaking the class into small groups, have students discuss reasons for this historical classification and reasons that the current separation of fungi and plants into two separate kingdoms is more appropriate.

Material • Lecture Activity 13.1 Handout: Classification of Plants and Fungi Procedures After discussing the plant and fungal kingdoms in class, pose the questions from the handout to students, either as a small-group discussion, a whole-class discussion, or a written assignment.

Assessment Suggestions: After students have a chance to discuss their ideas, regroup as a class and see if there is a general consensus about the topic. Include a question on an exam about this issue.

Have students discuss the topics of plant and fungal kingdoms online and then have them do the handout as an online assignment.

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Chapter 13 Prospecting for Biological Gold 109

Handout Answer Key 1. In the two-kingdom system, which was used until about 1969, scientists placed fungi and plants in the same kingdom. Which similarities between fungi and plants do you think led to this placement? Lack of motility, presence of cell walls.

2. Which important differences between plants and fungi later led to their placement into different kingdoms? Different forms of nutrition: autotrophy versus heterotrophy.

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Lecture Activity 13.1 Handout: Classification of Plants and Fungi 1. In the two-kingdom system, which was used until about 1969, scientists placed fungi and plants in the same kingdom. Which similarities between fungi and plants do you think led to this placement?

2. Which important differences between plants and fungi later led to their placement into different kingdoms?

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Lecture Activity 13.2: Microbe Identification Estimated Time to Complete: 15–20 minutes Introduction: This activity is a good way to get students to review and apply their knowledge of the characteristics of various types of microorganisms. Completion of the activity in small groups encourages the development of teamwork.

Material • Lecture Activity 13.2 Handout: Microbe Identification Procedures 1. Divide the students into groups of three to four.

2. Distribute the handouts and circulate to help the students get started and answer questions.

Assessment Suggestions: Follow up with a discussion of which characteristics could be tested or looked for (e.g., presence of a nuclear membrane, chloroplasts) and which organisms would be indicated by the results of each test. Include a question related to this activity on an exam.

This assignment could be placed online as a group project using a wiki or blog or as an individual project for each student.

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Lecture Activity 13.2 Handout: Microbe Identification You are working at a remote field station, and you have been given a container of unidentified, mostly microscopic organisms. Your job is to determine if the organisms are bacteria, unicellular algae, protozoans, or unicellular fungi. You can use your microscope, and the lab is stocked with all the chemicals you need to test for the presence of particular molecules and cellular components (for example, you might have a hypothetical chemical that would turn blue in the presence of chloroplasts, which should identify the organisms as belonging to one of the four groups listed earlier). Discuss your research goals and prepare a list of at least three tests that you will perform on the sample to determine which organisms it contains. Finally, indicate the test results you expect for bacteria, algae, protozoans, and fungi.

Hint: You need to think about which compounds and/or organelles make these organisms unique and different from each other, so you might start with that type of list. Your test chemicals do not have to be real chemicals. For instance, you might use the example of the fictitious chemical that turns blue in the presence of chloroplasts, or you might use a chemical that glows in the presence of something else.

Test 1:

Test 2:

Test 3:

Test Results:

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Chapter 13 Prospecting for Biological Gold 113

Lecture Activity 13.3: Challenge—How Do These Organisms Affect Our Lives?

Estimated Time to Complete: 5 minutes per kingdom Introduction: Students often don’t realize the extent of their interaction with representatives of various kingdoms of organisms and sometimes disregard them as unimportant. In this activity, students are challenged to think of the ways that their lives are affected by all types of organisms. Including prizes for the winning groups makes the challenge more fun and exciting for the students.

Material • Small prizes (e.g., candy, pencils) to be given to the winning groups.

Procedures (This assignment can also be given for out-of-class research.)

1. After each kingdom of organisms is described in lecture, allow students to get into small groups of three to four and give them 1–2 minutes to list as many ways as they can think of that a specific group of organisms from that kingdom (or products from those organisms) affects their lives, in either good or bad ways.

2. Have the group with the greatest number of items read their list aloud. Make sure that the items are legitimate and, if so, give each member of the group a small prize.

Assessment Suggestions: Follow up the contest with a short discussion of students’ lists, possibly adding some organisms from other groups’ lists. Include a related question on an exam.

Have students post their lists in an online discussion forum and have students respond to each other by adding organisms or making comments on the lists.

Lecture Activity 13.4: Molecular Systematics Estimated Time to Complete: 25 minutes Introduction: Systematists today compare nucleotide sequences of homologous DNA regions of various species in attempting to reconstruct the evolutionary relationships of these species. Sequence comparisons are often fraught with problems such as deletions and insertions of nucleotides during the evolutionary divergence of groups, but there are computer algorithms available to align DNA sequences. Once aligned, nucleotide positions that are variable have information about the relationship between the organisms; those pairs that have more matches between them are more closely related and by inference have shared a common ancestor more recently.

In this activity, students will compare three DNA sequences and formulate the relationships among them. All are sequences of the NADH dehydrogenase subunit 3 (ND3) gene, located on the mitochondrial genome. Sequence 1 is taken from Homo sapiens (human), sequence 2 is from Rattus norvegicus (rat), and sequence 3 is from Mus musculus (mouse). Students will find that the rat and mouse sequences are most closely related, and the human sequence is about equally related to both of the other two. The three sequences were obtained from the Entrez online genetic database sponsored by the U.S. National Center for Biotechnology Information (NCBI; http://www.ncbi.nlm.nih.gov/entrez), which allows free access and search capabilities.

Material • Lecture Activity 13.4 Handout: Molecular Systematics

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Procedures 1. Introduce or review the use of DNA sequence information in systematics.

2. Distribute the attached handout and, using the provided instructions, explain the exercise. Do not reveal the species from which the sequences are taken. Circulate to answer questions that come up.

3. Collect handouts for assessment. In the next class period, reveal the names of the species from which the sequences are taken.

Assessment Suggestions: Grade handouts using the answer key. Ask similar questions on a quiz or exam.

Handout Answer Key 1. Which two sequences are most closely related? How do you know? Sequences 2 and 3 are the most closely related, because they have the largest number of pairwise matches. There are about three times more matches in the sequence 2 and 3 comparison than in the other two pairs.

2. Is the least-related sequence about equally related to the other two? How do you know? What does this suggest about the evolutionary history of the three species? Yes, sequence 1 has about the same number of matches with sequence 2 (24) as it does with sequence 3 (26).This means that the ancestor to sequence 1 diverged from a common ancestor of sequences 2 and 3, and that sequences 2 and 3 have evolved at about the same rate over time.

3. Draw a phylogenetic tree diagram that shows the relationship between the three sequences. The tree should look something like the following picture:

4. Why are there some positions in which none of the three sequences match? These positions represent nucleotides that have evolved in at least two, and perhaps all three, of the species’ lineages since their divergence from the common ancestor.

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Lecture Activity 13.4 Handout: Molecular Systematics Three aligned DNA sequences are shown below. All three are sequences of the NADH dehydrogenase subunit 3 (ND3) gene, which is located on the mitochondrial genome—the small, circular DNA molecule carried in the mitochondria of eukaryotes. Each of the three sequences is taken from a different mammalian species, and it is your job to determine the evolutionary relationship of the three species using these data.

Systematists use computer programs to compare and analyze DNA sequence data. They also draw tree diagrams that graphically show the relationships between the sequences. These sequences were aligned and displayed as above using one such program. The analysis results has four lines. The first three lines show the aligned sequences, where a “dash” symbol (—) indicates a gap in the alignment. The fourth line has matching information for the three sequences; an asterisk (*) indicates that all three sequences match at that position, and a space indicates that all three do not match.

Analysis of the similarities between the sequences yields the following findings: • Only sequences 1 and 2 match in 24 places (i.e., sequence 3 is different in that position).

• Only sequences 1 and 3 match in 26 places.

• Only sequences 2 and 3 match in 74 places.

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Questions 1. Which two sequences are most closely related? How do you know?

2. Is the least-related sequence about equally related to the other two? How do you know? What does this suggest about the evolutionary history of the three species?

3. Draw a phylogenetic tree diagram that shows the relationship between the three sequences.

4. Why are there some positions in which none of the three sequences match?

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Lecture Activity 13.5: Who Should Profit from “Biological Gold”?

Estimated Time to Complete: 15–20 minutes or more, depending on the size of the class and how in depth the discussion becomes Introduction: In this activity, the students explore the ethics of bioprospecting. The chapter opening vignette presents the issue concerning Diversa’s arrangement with Yellowstone. This is an excellent launching point for this important bioethical discussion.

Material • None.

Procedures 1. You may choose to ask your students to ponder this topic prior to class and be prepared to defend one side of the argument. You might even assign sides and teams and set this discussion up as a class debate (assuming your class is small enough to make this idea feasible). Otherwise, this activity works well as a simple class discussion that does not require a lot of background information.

2. Review the material presented in the text concerning Diversa’s agreement with Yellowstone. Ask students to add any information they can recall from reading the text.

3. Working in groups or individually, have students compile a list of possible benefits from this arrangement. After a few minutes, discuss the items from the lists with the entire class.

4. Have students compile a list of potentially negative issues that could arise from this arrangement and discuss the items on those lists. Encourage the students to go deeper than the issues listed in the text!

5. Have students consider possible solutions to the problem that would maximize benefits and minimize negative consequences. Make sure they think about how their ideas could be enforced and who would be the decision maker in such cases. Ask students or groups to present their ideas to the class.

6. Have students consider other possible situations (unique ones that were not presented in the chapter) to which these dilemmas would apply.

Assessment Suggestion: You might ask students to follow up the discussion with a more in-depth review of their personal opinions on the issue in a short paper.

You might take the discussion online and set up the students in groups to defend each side of the argument.

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CHAPTER

14 Is the Human Population Too Large?

Population Ecology OBJECTIVES Teaching Goals A wealth of data is available to bring into your presentation on population growth. Allow students to analyze local information for your county, state, and country. This is a great chapter for compare and contrast scenarios, whether using nonhuman or human population data. Your goal is to focus attention on demographics and resources at the population level, rather than at the individual level, without leaving students thinking that their actions at the individual level do not affect population growth.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Define population, and list the aspects of populations that are typically measured by ecologists.

• Describe how a mark-recapture estimate of population size is performed, and estimate the size of a population from mark-recapture data.

• Explain how the size of a population that is experiencing exponential growth changes over time.

• Describe the demographic transition in human populations and how it contributes to population growth.

• Define carrying capacity, and explain how the existence of a carrying capacity causes a pattern of logistic growth as populations grow.

• Compare and contrast the effect of density-dependent and density-independent factors on population growth.

• List the evidence that the human population may not be near carrying capacity and the evidence that it may be near carrying capacity.

• Describe the conditions (in both human and other populations) under which a population crash can occur.

LECTURE OUTLINE 14.1 A Growing Human Population A. Ecologists study populations at several levels to understand and predict the ability of the population to outgrow its resources.

B. Size and distribution are important characteristics of a population. .

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C. Over time, the human population has grown in an exponential pattern. (Figure 14.3, Figure 14.4) D. The demographic transition occurs when birth rates decrease toward lowered death rates.

(Figure 14.5) 14.2 Limits to Population Growth A. For nonhuman populations, the carrying capacity can be calculated based on population size, resources, and predation. (Figure 14.6) Lecture Activity 14.1 B. For human populations, it is difficult to determine the carrying capacity because too many variables are involved.

Lecture Activity 14.2 C. Density dependent and density independent factors influence population growth rates.

14.3 The Future of the Human Population A. The overuse of nonrenewable resources can contribute to a population crash. (Figure 14.11) B. The type of population pyramid in a country can indicate some of the future risks that the country will face. (Figure 14.13) Lecture Activity 14.3 C. Policies to slow the population growth rate must concentrate on the status of women, including their education, access to employment, and health care. (Figure 14.14) Lecture Activity 14.4 Lecture Activity 14.5

Lecture Activity 14.1: Foxes and Bunnies Estimated Time to Complete: 20–30 minutes, depending on how many cycles are completed Introduction: This activity is a variation of the popular predator–prey simulation demonstrating the dynamics of population growth. It is well suited for the undergraduate classroom and may be modified to teach several concepts related to population growth.

Materials • Graph paper • Lecture Activity 14.1 Handout: Foxes and Bunnies Procedures 1. Divide the class into pairs. Distribute grid sheets, graph paper, and the handout to each student.

2. One partner is designated to represent the fox population, the other the bunny population.

3. Begin with both populations having 7 members.

4. Groups will conduct the simulation by progressing through 6–12 of the cycles described in this step.

The handout will help with the calculations.

• Record the number of individuals in both populations (starting with 7 for the first cycle).

• Place one X randomly in a box on the habitat grid to represent each member of the population.

(Students will start with 7 X’s). Bunnies and foxes have separate habitat grids, and partners must not be able to see each other’s grid.

• Compare grids. Any match = dead bunny (erase its mark).

• Double the surviving bunny population, and add in new X’s as needed.

• If the bunny population reaches or surpasses 100, then the population crashes and the bunny population drops to the starting population again. Use a new grid sheet.

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Chapter 14 Is the Human Population Too Large? 121

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Subtract one-fourth of the original fox population (round up to the nearest whole fox) and erase their marks.

• Add in one new baby fox for every dead bunny.

• Repeat all steps for 12 generations, or until time is up.

5. Graph the population data using a line graph with two lines (one for each population).

6. The random nature of the grid matching will allow many possible scenarios. Display the various population growth curves, and point out features such as exponential growth, predator lag time, and population crashes.

7. (Optional) Distribute the questions handout to assess the students’ understanding of population dynamics.

Assessment Suggestions: You can use the questions handout either in a class discussion, as homework, or as the basis for quiz or exam questions.

Handout Answer Key 1. Why did the fox population lag at first, and then start increasing? At first there were few chances of any matches. As the bunny population grew, the chance of matches increased.

2. Why was the population of foxes still large immediately following the rabbit crash? The foxes were still alive and surviving on stored energy and dead rabbits.

3. What did the rabbit crash at population size 100 represent in real life? A carrying capacity of 100 rabbits, or all the rabbits that the environment could support.

4. Will the peak in the fox population always lag behind the peak in the rabbit population? Probably— that is typical for a “bust or boom” population cycle.

5. Will this cycle continue indefinitely? What might cause it to stop? It could continue indefinitely, but if one species went extinct, the cycles would obviously end. It is also possible that the situation could reach a delicate balance where the populations stayed consistent without the “bust or boom” cycling.

6. What are the critical points where a population might go extinct? Right after a crash. The few bunnies could be eaten by the many foxes, or the few foxes could starve.

7. What would it signify if the grid were increased to 200 squares? A larger or more productive habitat, with a greater carrying capacity.

8. How would this change affect the two populations? The rabbit population would be allowed to increase, and then the fox population could increase.

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Lecture Activity 14.1 Handout: Foxes and Bunnies This activity simulates changes in the population sizes of predators and prey as they interact generation after generation.

Instructions for Carrying Out the Simulation 1. Designate one habitat grid for bunnies and one for foxes.

2. Begin with both populations having 7 members. Place X’s randomly on separate habitat grids, so that partners can’t see each other’s grid, to represent members of each population.

3. Compare grids. Any match = dead bunny. In other words, if there is a bunny on C3 on one grid and a fox on C3 on the other grid, the fox gets to eat the bunny (erase the bunny’s mark).

4. The bunny population doubles: Place one new mark randomly on the grid for every surviving bunny.

5. If the bunny population reaches or surpasses 100, then the population crashes and the bunny population drops to the starting population again. Get a new habitat grid, but keep recording numbers on the same handout.

6. Subtract one-fourth of the original fox population (round to the nearest whole fox); erase their marks.

7. For every dead bunny, a new baby fox is born (add their marks to the fox population).

8. Record the number of individuals in both populations at the end of each cycle.

9. Repeat all steps for 12 generations, or until time is called.

10. Graph the population data using a line graph with two lines (one for each population).

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E. Total Bunnies A. Starting B. Starting C. Number D. Remaining After Bunny Fox of Bunnies Bunnies Reproduction (A–C) (2D)* Generation Population Population Killed 1

7

7

2

3

4

5

6

7

8

9

10

11

12 ∗ Put this number into column A for the next generation. † Put this number into column B for the next generation.

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F. Fox G. Fox Population Population After Deaths After Births (B–1⁄4 B) (F + C)†

Habitat Grid for Lecture Activity 14.1: Foxes and Bunnies

1

2

3

4

A

B

C

D

E

F

G

H

I

J

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5

6

7

8

9

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Answer the questions concerning your data on bunnies and foxes.

1. Why did the fox population lag at first and then start increasing?

2. Why was the population of foxes still large immediately following the rabbit crash?

3. What did the rabbit crash at population size 100 represent in real life?

4. Will the peak in the fox population always lag behind the peak in the rabbit population?

5. Will this cycle continue indefinitely? What might cause it to stop?

6. What are the critical points where a population might go extinct?

7. What would it signify if the grid were increased to 200 squares?

8. How would this change affect the populations?

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Lecture Activity 14.2: A Sustainable Community Estimated Time to Complete: 20 minutes Introduction: As human populations get closer to Earth’s carrying capacity, it may become necessary to rely more and more on sustainable resources. This may involve using different resources or implementing new technology that could drastically change our lifestyle. Collaboration among people at many levels will likely be crucial to implement the required changes.

Material • None.

Procedures 1. Divide the class into small groups of four to six students.

2. Ask each group to determine what would be necessary for a small community of 100 people to be sustainable in terms of food and fuel resources while maintaining a lifestyle as close as possible to that of the typical middle-class American.

3. Have each group begin by brainstorming the requirements of their small community. Then, for each of these requirements, students should determine if there is a practical way to meet it with sustainable resources. Most groups will likely bring up the following issues: • Types of foods that may be grown • Land use • Water use • Sources of fuel • The amount of outside input needed for some resources • Managing, minimizing, or recycling waste products 4. After 10 minutes, allow each group to present a brief description of its community, and then pose the following questions to the entire class for discussion: • Were any of your ideas feasible on a wide scale? In other words, could numerous communities structured in this way function simultaneously?

• Would most people in our society be willing to participate indefinitely in the situation designed?

If not, what would it take to change their minds?

• Is it possible to implement only some of the components of your community, or is it an all-ornothing situation?

Assessment Suggestions: Have students briefly write up what they thought was the best community presented by the class. Include essay items on a written exam. These essay questions could also be used as discussion forum questions to stimulate students to discuss what they learned. Here are two examples: 1. Describe some practical ways of using sustainable resources on a small scale.

2. Discuss the major problems associated with maintaining contemporary lifestyles while attempting to use sustainable resources.

Lecture Activity 14.3: When the Pressure’s On, It’s “Frog Eat Frog” Estimated Time to Complete: 15–20 minutes Introduction: Cannibalism is generally viewed as a rare process and an aberration—for example, as the result of mental illness in humans (e.g., Jeffrey Dahmer) and an artifact of overcrowding in the laboratory.

However, evidence increasingly indicates that it is a frequent response in nature to overpopulation. Some well-studied examples include cannibalism among rodents, especially if their nests are invaded, and eusocial wasps. Cannibalism may also be involved in the origin of prions and the spongiform

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encephalopathies that they cause. Although many of these diseases are probably spread only within a species, some—such as bovine spongiform encephalopathy (mad cow disease)—can spread between species, such as from cattle to humans.

Materials • Computer with projector and Internet access, or transparencies with pictures from the Internet, to show cannibalistic versus non-cannibalistic morphs and the act of cannibalism (optional) • Tadpoles or other aquatic amphibian larvae in the classroom to help students visualize the dilemma faced by these animals when crowded together in a shrinking puddle or pond (optional) • Lecture Activity 14.3 Handout: When the Pressure’s On, It’s “Frog Eat Frog” Procedures 1. Begin by presenting the dilemma faced by amphibians that lay their eggs in temporary bodies of water as a case study. Why they choose such a habitat is worth mentioning: Because these temporary ponds and puddles do dry up, these bodies of water do not have populations of permanently aquatic species such as fish, which are normally major predators on amphibian larvae.

2. The concept of carrying capacity can be introduced as the number of larvae the pool can support at any given time. Note that the population can exceed its carrying capacity if too many females lay their eggs in too small a pool. Carrying capacity may also shrink as the pool begins to dry up.

Because too little food is available per individual for all of the larvae to survive, grow, and develop, getting the population to below the carrying capacity can be accomplished in one of two ways: by decreasing the number of larvae or by increasing the amount of food available to them.

3. Divide the class into small groups, and pass out the handout. Circulate around the classroom to answer questions and keep groups on task.

4. As the class is working, project pictures of cannibalistic and non-cannibalistic morphs of various species.

Assessment Suggestion: Collect and grade handouts using the answer key provided.

Place the handout online and have students answer the questions online individually or in small groups using wikis or discussion forums.

Handout Answer Key 1. Although separate cannibal morphs have been described in relatively few species, at least 1,300 species have been shown to practice cannibalism at some time or another (Polis, 1981). Under which circumstances is cannibalism favored? When would it be detrimental? Cannibalism may be favored whenever the size of a population greatly exceeds the food resources available to support it (i.e., when a population exceeds its carrying capacity). It would likely be detrimental under all other circumstances.

2. Bovine spongiform encephalopathy (mad cow disease) spread rapidly through the cattle population of Great Britain before it was identified and understood. How did this disease spread so rapidly even though cattle are not cannibals by nature? How was its spread halted? Cattle were fed meal containing ground-up cattle parts infected with the prions that cause the disease. The spread of BSE was halted by stopping the practice of using cattle remains in cattle feed and destroying all infected and suspected-to-be-infected cattle.

3. Why is it important that cannibals be able to recognize and preferentially avoid their own siblings?

Doing so helps explain how genes that “allow” this polyphenism could be selected for in a population. If cannibals kill off members of their own family, they will be decreasing the representation of their own genes in the population, thereby selecting against the cannibalism gene.

4. How do you think the change to the cannibal morph is controlled, given that cannibals seem to have the same genetics as non-cannibals do? Some or all animals must have the genes required to produce the cannibal morph. These genes are not activated unless a specific set of environmental criteria is met—for example, the presence of many competitors but not much other food in the pond.

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Lecture Activity 14.3 Handout: When the Pressure’s On, It’s “Frog Eat Frog” Case Study by David J. Zimmer For many animals that don’t practice parental care, growing up is a very risky proposition. You start out very small, which exposes you to predation by a host of animals. Due to your large surface-to-volume ratio, you’re also more prone to drying out, absorbing toxic levels of pollutants, and similar problems.

And Mommy and Daddy aren’t there to protect you. To compensate for your low probability of reaching maturity, your parents also gave you a multitude of siblings, with which you may have to compete for food. (Sound familiar? This is Darwin’s “struggle for survival.”)

As if growing up isn’t hard enough, some species also face tremendous time pressure to do so. For example, many amphibians lay their eggs in temporary ponds or puddles, requiring the hatching larvae to grow and metamorphose into terrestrial adults (frogs, toads, or salamanders) before their first home dries up.

And to make it a real crapshoot, there’s no way of predicting how long they’ll have or how much competition for resources they’ll face. If the spring is dry, the pond may dry up before any adults emerge.

And if many females lay their eggs in the same pond, competition for food such as algae and detritus may be so intense that growth and development rates are slowed, so none may mature in time even in a normal spring.

To increase the odds that at least some individuals mature even in years when resources are scarce due to overpopulation (i.e., when the population greatly exceeds its carrying capacity), a few amphibian species have evolved a novel strategy. Basically, a small number of individuals develop into cannibals!

Not only do they acquire a taste for their own species’ flesh, but they also develop into a distinctly different “morph” (form). Cannibal morphs have larger heads and bigger teeth that make them better at capturing and consuming their own kind. This process has been extensively studied in the spadefoot toad (Scaphiopus spp.) and tiger salamander (Ambystoma tigrinum).

One curious finding is that becoming a cannibal is not genetically programmed, but rather is brought on by an environmental cue such as crowding. Thus the cannibals differ phenotypically but not genotypically from the “normal” herbivorous or omnivorous morph. Also, cannibals can identify their own brothers and sisters, preferentially feeding on other families’ members if given the chance.

The benefits of this strategy are obvious. Not only is the resource base available to these lucky cannibals increased (and, by virtue of being biochemically identical, species-mates are also highly nutritious), but the number of their competitors is decreased. This brings the population below its carrying capacity, speeding growth and development of individuals within the population and increasing their chance of maturing in time. As a result, the population becomes more stable as well.

Is there a downside to this behavior? Eating your own kind may make you more likely to acquire diseases from your food than if you eat more distantly related species. This is because members of the same species are more likely to carry diseases to which you are susceptible. It has even been suggested that prion diseases like “mad cow disease” in cattle and Creutzfeldt–Jakob disease in humans owe their existence to cannibalism. One such disease, Kuru, was first described in humans in the Fore tribe in New Zealand, which practiced ritualized cannibalism until the practice was outlawed.

Nobody is suggesting humans adopt cannibalism as a means of population control (Jonathan Swift’s satirical A Modest Proposal aside), but for some species under some circumstances, cannibalism makes perfect sense. .

References Cowley, G. , et al. 2001. Cannibals to cows: The path of a deadly disease. Newsweek (March 12): 52–61.

Fox, L. R. 1975. Cannibalism in natural populations. Ann. Rev. Ecology and Systematics 6: 87–106.

Pfennig, D. W. 2000. Effect of predator–prey phylogenetic similarity on the fitness consequences of predation: A trade-off between nutrition and disease? American Naturalist 155: 335–345.

Polis, G.A. 1981. The evolution and dynamics of intraspecific predation. Ann. Rev. Ecology and Systematics 12: 225–251.

Questions 1. Although separate cannibal morphs have been described in relatively few species, at least 1,300 species have been shown to practice cannibalism at some time or another (Polis, 1981). Under which circumstances is cannibalism favored? When would it be detrimental?

2. Bovine spongiform encephalopathy (mad cow disease) spread rapidly through the cattle population of Great Britain before it was identified and understood. How did this disease spread so rapidly even though cattle are not cannibals by nature? How was its spread halted?

3. Why is it important that cannibals be able to recognize and preferentially avoid their own siblings?

4. How do you think the change to the cannibal morph is controlled, given that cannibals seem to have the same genetics as non-cannibals do?

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Lecture Activity 14.4: Effects of Age at First Reproduction on Population Growth Rate Estimated Time to Complete: 10–15 minutes Introduction: Many factors determine how fast a population can reproduce. The age at first reproduction exerts a surprisingly strong influence on the growth rate of a population, and it is an aspect of the human life cycle that is relatively easy to influence. With a simple graphical model, drawn on the board or overhead, you can demonstrate this concept by comparing two hypothetical organisms that differ only in age at first reproduction.

Materials • Chalkboard or whiteboard, or an overhead projector with an appropriate writing instrument • Life-history diagrams are central to this demonstration (shown on the following page).

Procedures 1. Start by informing the students about the importance of the age at first reproduction for the population growth rate.

2. Present or review the concept of life history of an individual. Note that an individual is born, has offspring (or not), and dies.

3. Illustrate a simple graph of a life history. Time moves from left to right. (Draw an arrow on the board and label it “time.”) The birth of an individual is illustrated by a short vertical line (at the time of birth). From this a horizontal line extends to the right, representing the life of the individual. This line ends with another short vertical line at the individual’s death. Births can be represented by vertical lines coming off the “life line” of the parent at the time of an individual’s birth, and then proceeding to the right to represent his or her life. (See Figure 1 on the following page.)

4. The simplest life history can be used to illustrate the concept of this exercise. Binary fission of an immortal organism is represented by a horizontal line starting with the “birth” of an individual (by a first act of binary fission) and ending at a vertical line leading to two new horizontal lines (representing the second act of binary fission and resultant “offspring”). (See Figure 2.)

5. Now graph two populations that are identical except for the time required for each individual to “reproduce.” Start each graph with one individual that divides into two, which then divide (synchronously) into four, and so on. To make things less complicated, have one population take exactly twice as long to reproduce as the other. (See Figure 3.)

6. Have students tally the number in each population at each time interval (this task is easier if you provide students with a time grid or the graphs are placed one over the other; they are tallied on Figure 3 at time = t, the dashed line, as an example) and produce a geometric growth graph. Point out that the only difference between the populations is age at (first and only) reproduction, yet one population grows much faster than the other.

Assessment Suggestions: Ask students to consider the implications of more women staying in school or entering the out-of-house workforce in developed countries and delaying childbearing until later in life.

How does this choice affect the population growth rate in developed countries versus developing countries? What role does contraception play in this difference? How might religious or social traditions affect this factor?

Ask students if this effect is limited to organisms that reproduce by binary fission or is more generally applicable to all life histories.

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Lecture Activity 14.5: Dynamic Population Age-Structure Diagrams Estimated Time to Complete: 10 minutes Introduction: The textbook tells students that the age structure of a population can be used to predict its future growth, but this dynamic concept often falls flat on the printed page. Luckily, the U.S. Census Bureau comes to the rescue with a web page that allows users to create dynamic age-structure diagrams for some 227 countries and areas of the world. The output is a series of age-structure diagrams at five-year intervals starting as early as 1950 (for the United States, although many other countries’ data begin only in 1990 or 1995) and going through population projections to the year 2050. By clicking a button below the image, students can also view a table containing all of the data used to make the diagrams. By comparing rapidly increasing, relatively stable, and declining populations, students will gain a real sense of the utility of these diagrams.

Material • Computer with high-speed Internet access and projector (slower access might work, but requires considerable time to display images).

Procedures 1. Begin by reviewing the concept of population age structure and the underlying concepts in play here (e.g., survivorship, fertility).

2. Visit the website http://www.census.gov/population/international.

3. Start with a developing country, such as Bangladesh. Point out that although death rates in this country have declined sharply in recent decades, fertility rates often remain high (i.e., the country has not yet completed the final stage of the demographic transition). To start the animation, highlight the desired country and choose “Dynamic” for the “Type of output.” (The “Large” graph size is most visible.) Initially (in 1995) the age-structure diagram has a very broad base, indicating that many individuals have not yet reached maturity. Show that as time progresses (in five-year steps to 2050), these younger classes “move up” but fertility rates remain high, leading to a large population increase over time (119 million in 1995 to 280 million in 2050). Stress that because the base is still broad in 2050, further increases beyond 2050 are expected.

4. Contrast the pattern for the developing country with the pattern seen in some developed countries with relatively stable populations. Sweden is an excellent example. Draw students’ attention to the “straight sides” of the diagram at the starting point (1995), with a population of 8.9 million. As the animation proceeds, point out that the base narrows somewhat more before stabilizing, with the 2050 population reaching only 9.1 million. Stress that the fertility rate is lower in this country than in the previous example.

5. Now choose a population that is actually expected to decline in size—for example, in the developed country of Japan. Show that the base is very narrow at the starting point (1990) and that it keeps narrowing as time progresses (to 2050). Over this time span, the population is expected to actually shrink from 123 million to just 100 million. This animation also clearly demonstrates the demographic dilemma that Japan’s economy is expected to face because a huge proportion of its population will be of traditional retirement age while a far smaller proportion of the population is of working age. Also, Japan has two unusually large age classes (15–19 years and 45–49 years) present in 1990 that can be easily tracked on the diagram over time. By following either of these age classes, especially for women, we can also envision a late loss survivorship curve because most individuals are expected to live at least into their seventies.

6. Additional countries can be chosen by the instructor or class. If the United States is chosen (which it probably will be), two cautions should be noted; First, the U.S. data go back to 1950, so the first half of the animation relies on historical data, when worldwide fertility rates were higher. Second, the present growth in the U.S. population is due almost entirely to immigration. The fertility rate is

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actually below the replacement level fertility (RLF) rate. As a consequence, the demographic dilemma discussed for Japan is also expected to arise in the United States.

Assessment Suggestions: Choose a country at random, or allow the students to choose one. Before showing the diagram, ask students to predict the age structure. Then show them the diagram and ask them to predict whether the population will grow, stay the same, or shrink. Do the results match their expectations? Why or why not? Have them consider the effects of legislation on family size (e.g., in China) or of social or religious traditions. Ask them to speculate on the economic effects of a changing age structure.

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15 Conserving Biodiversity Community and Ecosystem Ecology OBJECTIVES Teaching Goals Your students may already be familiar with conservation organizations such as World Wildlife Fund and Nature Conservancy and certainly will know something about endangered species. In this chapter you can explore how organisms are selected for the endangered species list and which factors have contributed to their potential extinction. By emphasizing the “part to whole” concept found in the food web and in the health of an ecosystem, you can illustrate the many variables that can affect the success or extinction of a species.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe how scientists can estimate current and historical rates of extinction, and provide the evidence that Earth is currently experiencing a mass extinction.

• List the major causes of extinction, and describe how each is related to human activity.

• Explain how the species-area curve is used to estimate species number in an area.

• Explain the principle of the trophic pyramid.

• Define predation, mutualism, and competition, and provide examples of each ecological interaction.

• Define food web, and explain the role of keystone species in a food web.

• Provide an example of a nutrient cycle.

• Explain why a loss of genetic diversity in a population is risky for both the population and individuals within the population.

• List strategies that will help reduce the number of extinctions going forward.

LECTURE OUTLINE 15.1 The Sixth Extinction A. The Endangered Species Act was passed to address concerns about the decline in biodiversity.

B. There have been five mass extinctions where many species were lost on a worldwide basis.

(Figure 15.2) C. Species may move closer to extinction because of several threats: loss of habitat, overharvesting, effects of pollution, and introduction of non-native species. (Figure 15.5) Lecture Activity 15.1

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15.2 The Consequences of Extinction A. Biological resources, both domestic and wild, are important to the economy of the human population. (Figure 15.11, Figure 15.14) B. The health of a community depends on the integrity of the food web and the resources that support it. (Figure 15.12) C. Predation, mutualism, and competition play crucial roles in our ecosystems. (Figure 15.14, Figure 15.15, Figure 15.16, Table 15.1) D. Keystone species are those organisms that are central to the functioning of the food web.

E. Energy travels through trophic levels while nutrients are recycled. (Figure 15.18) Lecture Activity 15.2 15.3 Saving Species A. Habitat preservation in biologically diverse “hot spots” encourages the survival of a larger number of species.

B. Genetic variability should remain high to increase the chance of species survival. (Figure 15.22, Figure 15.23, Figure 15.24, Figure 15.25, Figure 15.26, Table 15.2) Lecture Activity 15.3 15.4 Protecting Biodiversity Versus Meeting Human Needs A. To qualify for the endangered species list, organisms must be reviewed by a committee that also weighs their inclusion on the list in terms of its costs and benefits to humans.

B. Proactive steps can be taken to lessen the chance of a species becoming endangered.

(Table 15.3)

Lecture Activity 15.1: Characteristics of Rare and Endangered Species Estimated Time to Complete: 10–15 minutes in each of two class periods. The homework assignment takes approximately 20 minutes to complete.

Introduction: One way to monitor the present global biodiversity crisis is to evaluate the status of known species and to produce lists of those species that are most at risk of extinction. Such lists can help conservation biologists identify the characteristics of species that are most at risk as well as the kinds of human activities that place the most species at risk. Biologists and policy makers can then use the information provided by such lists to prioritize their efforts directed toward preserving species. The existence of such a list can also motivate the public to take action to preserve endangered biodiversity.

This exercise is intended to make students aware of the diversity of species that are known to be at risk, and to make them think about how endangered species lists can be used as a tool for conservation.

Materials • Lecture Activity 15.1 Handout: Characteristics of Rare and Endangered Species • A computer with Internet access and projector to go to the following websites: U.S. Fish and Wildlife Service Information on Endangered and Threatened Species: http://www.fws.gov/endangered The IUCN—The World Conservation Union Red List of Threatened Species: http://www.redlist.org Procedures 1. Explain the purpose of the official U.S. endangered species list and the IUCN Red List. Introductory background information can be found at the two websites given earlier.

2. If the classroom has computer projection with Internet access, demonstrate how to find information on U.S. endangered species at the U.S. Fish and Wildlife Service website, and on globally endangered

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species at the IUCN Red List website. As examples, look up information from each source on the shortnose and Lost River suckers.

3. Hand out the attached worksheet. Have students complete it before the next class period.

4. During the next class period, have students answer the following questions by tallying the answers from their worksheets: a. Where geographically are most endangered species found in the United States? In the world? b. What are the most important causes of endangerment?

5. To stimulate discussion of key issues, ask the students the following questions: a. What did you observe about the kinds of organisms that appear on the lists? b. What is the likely value of these lists? Is it worthwhile to attempt to preserve all of these species?

Why or why not?

Assessment Suggestions: Collect the worksheets to verify that the students have completed the homework. Discussion participation should reveal whether the students make the connections between this exercise and the chapter theme of conserving biodiversity.

Place the worksheets online as an assignment or ask key questions about the material in a discussion forum.

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Lecture Activity 15.1 Handout: Characteristics of Rare and Endangered Species Part A Surf through the list of official U.S. Fish and Wildlife Services Endangered and Threatened Species List at http://www.fws.gov/endangered. Click on the various categories of organisms and scan the lists (e.g., mammals, clams, or flowering plants).

Select one species from the list, and find the following information for it. Circle your answer; more than one answer can be circled for the “Where Found” and “Major Threats” categories.

Species Name: Kind of Organism: Plant Reptile

Arthropod

Mollusk

Fish

Amphibian

Bird

Mammal

Other

Central United States

Endangerment Status: Endangered Threatened Where Found: Northeast

Southeast

Southwest

Northwest

Alaska

Hawaii

Major Threats: Naturally small population

Habitat loss

Invasive species

Overexploitation

Pollution

Part B Surf through the IUCN Red List of Threatened Species at http://www.redlist. org. Go to the Search page, and type in the Text Search box the common name of an organism (e.g., oak, hawk, rabbit, turtle, or frog).

Also try searching by region of the world and country.

Select one species from the list, and find the following information for it. Circle your answer; more than one answer can be circled for the “Where Found” and “Major Threats” categories.

Species Name: Kind of Organism: Plant Reptile

Arthropod

Mollusk

Fish

Amphibian

Bird

Mammal

Other

Central United States

Endangerment Status: Endangered Threatened Where Found: Northeast

Southeast

Southwest

Northwest

Alaska

Hawaii

Major Threats: Naturally small population

Habitat loss

Invasive species

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Overexploitation

Pollution

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Lecture Activity 15.2: Tight Nutrient Cycling in Corals Estimated Time to Complete: 20 minutes Introduction: Coral reef ecosystems are among the most productive on Earth, yet they occur in extremely nutrient-poor waters. How is this possible? Corals are symbiotic “super-organisms” that have a very tight cycling of nutrients between their primary producers—the microscopic, single-celled algae (dinoflagellates) or “zooxanthellae”— and their primary “consumers”—the cnidarian polyps. This tight coupling ensures that nutrient losses to the environment remain minimal, thereby allowing both groups to be productive in an environment that is poor in both mineral nutrients and prey.

Materials • Having living corals on display sparks interest, but may not be feasible and is often not necessary.

• Photographs or video clips of corals and coral reefs, along with close-ups showing their zooxanthellae, are helpful. (They can be obtained from the Internet and inserted into PowerPoint presentations or turned into overhead transparencies.)

Procedures 1. Begin by introducing or reviewing the concepts of trophic levels and nutrient cycling. Point out that in most ecosystems, the cycling of nutrients from one organism to another is loosely coupled and rather wasteful. For example, much of the primary production in the upper waters of a lake (by microscopic algae called phytoplankton) is lost to decomposers because many algae die and sink into deeper waters, becoming unavailable to the primary consumers in the lake, tiny zooplankton.

2. Set the stage by noting that the waters in which most coral reefs are located have very low concentrations of nutrients needed for primary production—namely, usable forms of nitrogen and phosphorus. (This deficiency occurs because there is a continual loss of nutrients into deeper waters as just described for lakes, though in deeper parts of the oceans these nutrients are never returned to the surface.) Also, this lack of nitrogen and phosphorus means little photosynthesis occurs by freeliving producers outside of corals. As a consequence, there is a scarcity of prey available for predators such as cnidarians.

3. Explain that the cnidarians don’t actually eat the algae, but rather house the algae inside their tissues.

The algae carry on photosynthesis inside the transparent bodies of the polyps, and 90% or more of their photosynthate is passed on to the cnidarian. This is the primary source of energy and carbon for the cnidarian, which supplements this supply with rather meager catches of tiny zooplankton prey.

Because its prey contains excesses of both nitrogen and phosphorus beyond its needs, the cnidarian releases these extra amounts to the algae, which use them to synthesize their proteins, nucleic acids, ATP, and so on. Point out that most other animals would simply discharge these materials into the environment, where they would disperse and be diluted before being taken up by producers.

4. Point out that although this relationship is rather one-sided—the cnidarian polyps seem to benefit more than the algae, which have to pay a high price for their accommodations—it obviously works well. Show an image of a densely populated (by fish) coral reef to demonstrate this concept.

5. A somewhat different kind of relationship is seen between a few species of small, marine gastropod mollusks (sea slugs) and their algae prey, whose chloroplasts they hijack and retain within their branching digestive tracts. Point out that although the ingested algae soon die, their chloroplasts survive and function for weeks, passing the photosynthate they produce on to their molluscan captors.

It is, in fact, difficult to say whether this relationship represents mutualism, parasitism (in which the host lives inside the parasite!), or predation.

6. Point out that the relationship between the coral polyps and their zooxanthellae is so good at retaining nutrients in nutrient-poor environments that many coral reefs are apparently being damaged by increased nutrient inputs. These inputs occur when rivers carry fertilizer and sewage into their waters.

This process appears to allow free-living, weedlike fleshy corals to grow on the surface of the reef

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corals, shading and crowding out their zooxanthellae brethren. Without the added nutrients, the sea weeds cannot grow. This phenomenon may be one cause of the dramatic worldwide declines noted in coral reefs, one of the hot spots for biodiversity.

Assessment Suggestions Ask students to speculate about how the relationship between coral polyps and their zooxanthellae may have evolved. What were the likely first steps? Which kinds of accommodations must two species make to live with each other? (This particular relationship may have started out as a predatory relationship, but those cnidarians that didn’t kill the algae may have benefited. The algae have to be able to lose lots of photosynthate, and the cnidarians cannot digest the algae.) These questions could be used as a multithreaded discussion forum online.

Ask students if they can think of any other nutrient-poor environments that might support mutualisms similar to the corals. (Lichens occur on bare rock, tree bark, and so forth. In lichens, however, the two trophic levels are primary producers [the algae] and nutrient-scavenging decomposers [the fungi].)

Ask students why, if this relationship is so beneficial, it is not more common. Are there any potential drawbacks or problems? (Whenever your well-being depends on another species, you will suffer if something happens to your partner.)

Lecture Activity 15.3: Dynamics of Small Populations Estimated Time to Complete: 20 minutes Introduction: When the population size of a species is large, population fluctuations are relatively small compared to the average population size. When the population size of a species is small, however, fluctuations in population size due to chance patterns of births and deaths can be relatively large, putting the population in serious risk of extinction.

In this exercise, the class will examine the population dynamics of a hypothetical endangered animal species with a simple life history. The annual survivorship is 50%. Per capita annual reproduction equals two offspring (on average, one male and one female). To study the population dynamics, the class can simplify things by doing what population ecologists routinely do: Keep track of females only.

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Materials • 80 coins per group (want a minimum of 5 groups) • Lecture Activity 15.3 Handout: Dynamics of Small Populations Procedures 1. Explain the scenario described in the introduction.

2. Divide the students into groups of 4–6 students each. Give a handout to each group.

3. Have students count out 40 coins. This represents the (female) population size at year 1.

4. Have students flip the 40 coins. Remove any that are tails; these are deaths. Add a coin for each coin that remains. These are (female) births. Count the total coins. This number represents the (female) population size of the hypothetical species at year 2. Record the data in the handout.

5. Repeat this process an additional 18 times, until 20 years of census data are simulated. If the population becomes extinct (0 coins) before reaching year 20, go to the next step.

6. Have the students in each group count out 10 coins. This represents the population size at year 1.

7. Simulate another 19 years of census data, in the same way as in the 40-coin exercise. If the population becomes extinct (0 coins) before reaching year 20, go to the next step.

8. Have each group graph the population dynamics of the two populations they simulated (initial 40, initial 10) on the graphs in the handout.

9. Have the class compare the population dynamics of replicate populations of the two initial population sizes.

Assessment Suggestions: Discuss the graphs and questions as a class. Collect and grade the handout, using the answer key provided.

This could be done online if the students know how to create graphs on the computer. This could make a nice lab report where students use the questions to create the key components of the report including the graphs.

Handout Answer Key 1. Why do the population dynamics of replicate populations that have the same initial size differ across years? Chance fluctuations in the number that die: On average, half of the population dies, but by chance some years more than half die, and some years fewer do.

2. Which initial population size is at greatest risk of extinction? Initial population size 10.

3. What would happen if births were based on probability as well in this scenario? For example, instead of every member of the population always having one offspring, what if each individual had a 50% chance of producing two offspring and a 50% chance of producing none? Chance population fluctuations will be even greater than before, so the risk of extinction will increase. As an additional exercise, students could simulate this scenario with the coins and discover the answer empirically.

4. What would happen if there were probabilistic “good years” and “bad years” that affected all members of the population equally? For example, instead of every member of the population having one offspring each year, what if there was a 50% chance that it was a good year, when every member of the population could produce two offspring, and a 50% chance of a bad year, when none could successfully reproduce? Chance population fluctuations will be much greater than before, so the risk of extinction will increase significantly. As an additional exercise, students could simulate this scenario with the coins, flipping one coin to decide whether it is a good or bad year, and discover the answer empirically.

5. Which factors place populations at elevated risk of extinction due to probabilistic population fluctuations? Small average population size; highly probabilistic occurrences of births and deaths.

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Lecture Activity 15.3 Handout: Dynamics of Small Populations Data Table Record the number of females in your virtual populations, for 20 generations.

Generation 1

Initial 40

Initial 10

40

10

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

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Graph Complete the graphs, using the data in the previous table.

Questions Answer the following questions by comparing the population dynamics of the replicate populations of the two initial population sizes.

1. Why do the population dynamics of replicate populations that have the same initial size differ across years?

2. Which initial population size is at greatest risk of extinction?

3. What would happen if births were probabilistic as well in this scenario? For example, instead of every member of the population always having one offspring, what if each individual had a 50% chance of producing two offspring and a 50% chance of producing none?

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4. What would happen if there were probabilistic “good years” and “bad years” that affected all members of the population equally? For example, instead of every member of the population having one offspring each year, what if there was a 50% chance that it was a good year, when every member of the population could produce two offspring, and a 50% chance of a bad year, when none could successfully reproduce?

5. Which factors place populations at elevated risk of extinction due to probabilistic population fluctuations?

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CHAPTER

16 Where Do You Live?

Climate and Biomes OBJECTIVES Teaching Goals Your goal in this chapter is to help students understand which factors influence the climate where they live and why that climate is different from the climate in other places. Because the climate is different, the vegetation will be different. Contrast the changes in the biomes as one travels from east to west across the United States with the changes encountered as one travels from north to south. By discussing the ecological footprint of the local community, you can stimulate interest in how individuals can lessen their personal footprints by making informed choices.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe the factors that determine temperature and precipitation patterns on a global scale.

• List factors that influence climate on a local scale, and explain how they affect local temperature and precipitation patterns.

• Briefly describe the climate and vegetation characteristics of the terrestrial biomes, including tropical, temperate, and boreal forests; chaparral; tropical and temperate grasslands; desert; and tundra, and give examples of animal and plant adaptations in these environments. Describe some of the threats to these biomes imposed by human activity.

• Briefly describe the characteristics of the aquatic biomes, including freshwater lakes, rivers, and wetlands and saltwater oceans, coral reefs, and estuaries, and provide examples of organisms found in these biomes. Describe some of the threats to these biomes imposed by human activity.

• List the ecological requirements of human communities, including food, energy, and waste disposal, and describe how these needs are met in various human societies.

LECTURE OUTLINE 16.1 Global and Regional Climate A. Solar irradiance varies in regions based on their distance from the equator and the tilt of the Earth’s axis. (Figure 16.1, Figure 16.2, Figure 16.3) B. Local temperatures are affected by nearness to water, local surface and vegetation, and altitude.

(Figure 16.6, Figure 16.7) C. Precipitation patterns depend on nearness to water and surface features, such as mountains.

(Figure 16.5, Figure 16.6, Figure 16.7, Figure 16.8) Lecture Activity 16.1 .

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16.2 Terrestrial Biomes A. Variations in climate divide the land masses into specific regions called biomes. (Figure 16.11) Lecture Activity 16.2 B. Based on the different types of trees, temperature, and rainfall found in each region, the forest biome can be divided into tropical, temperate, and boreal forests. (Figure 16.10, Table 16.1) Lecture Activity 16.3 C. The chaparral and grasslands are both maintained by fire. (Figure 16.16, Figure 16.17) D. Deserts experience less than 20 inches of annual rainfall.

E. Regions in the tundra have extremely cold temperatures and decreased light for portions of the year. (Figure 16.22) 16.3 Aquatic Biomes A. Freshwater is marked by low salt concentrations and occurs as lakes, rivers, or wetlands.

B. Oceans, coral reefs, and estuaries make up the saltwater, or marine, biomes. (Table 16.2) 16.4 Human Habitats A. Unlike the natural biomes, human habitats require imported energy.

B. Cities make demands on natural resources in an area and create large volumes of waste.

(Table 16.3) C. Air pollution is a by-product of the fuel source of humans, whether it be fossil fuels in the more developed areas or wood in the less developed areas.

Lecture Activity 16.4

Lecture Activity 16.1: Air Pressure, Temperature, and Moisture Content Estimated Time to Complete: 15–20 minutes; 20 minutes prep time Introduction: This chapter describes two distinct instances in which air rises and cools, resulting in condensation of its water vapor into precipitation (rain and/or snow). One occurs near the equator in the tropics, where the rising is caused by the heating of the air by intense solar radiation, causing it to expand and its density to fall. The other occurs when wind pushes air up over a mountain range. In either case, part of the cooling is due simply to the expansion of each “parcel” of air, as the pressure on it from the column of air above it diminishes. The results are high precipitation in the tropics and on the windward sides of mountain ranges.

This activity demonstrates that when air expands, it cools. It also describes (or demonstrates) condensation of water vapor as air cools. The opposite process—heating of air as it is compressed—is discussed, and evaporation is demonstrated. Students should understand that evaporation rates increase as temperature rises. These latter processes result in deserts at roughly 30ºN and S latitudes and the “rain shadows” on the leeward sides of mountain ranges.

Materials • Glass soda bottle (at room temperature) • A few small toy balloons • 2 water baths (plastic dishpans work well) • Hot water for hot-water bath (very hot tap water or water heated on a hot plate) • Can of compressed air used for cleaning computers (often called a duster), available at most computer and office supply stores (at room temperature) • Thermometer (at room temperature) • Ice and cold water for cold-water bath and for drinking glass to demonstrate condensation (if desired) • Drinking glass to demonstrate condensation (if desired) • Blackboard • Damp sponge .

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Procedures 1. Demonstrate that heated air expands.

• You can trap a parcel of air inside a glass soda bottle by placing a balloon over its opening. The base of the balloon must be tight-fitting, and the balloon should be limp.

• Place the bottle into the hot-water bath, keeping its top and the balloon above the surface and in full view. In a short time, the heating of the air inside the bottle will cause the air to expand, blowing up the balloon slightly. (Alternatively, you can start with the glass soda bottle cooled in an ice-water bath; then add the balloon and allow it to return to room temperature, or place it in the hot-water bath. Don’t have the water so warm that the thermal shock breaks the glass, however.)

• Ask students why the balloon expanded. (Air molecules speed up, moving away from one another faster and exerting more pressure against balloon.)

• Point out that this expanding air is less dense and rises (like the air in the tropics) and that the same principle explains why hot-air balloons rise.

2. Demonstrate that expanding air cools.

• Point out that as air rises (either because it has been heated or because it is forced over a mountain), there is less pressure from the column of air above it pressing down, so it tends to expand. This expansion actually causes the air to cool. This idea can be demonstrated by allowing the compressed air inside a bottle of computer-cleaning duster to escape.

• Have a student read aloud the ambient room temperature on a thermometer. (Make sure the student doesn’t touch the thermometer bulb, which would increase its temperature.) Then, release the air in a stream over the bulb of the thermometer for a few seconds. Have the same student read aloud the new, lower temperature. Point out that temperature is a measure of the density of kinetic energy in the air: Because the same amount of air now occupies more space, and heat energy has not been added or subtracted, the temperature has fallen.

• Explain that this principle is also used in refrigeration, where compressed gas (formed by the compressor, which actually heats the gas; see procedure 3) is allowed to expand and cool.

3. Describe (or demonstrate) that cooling air holds less water vapor, causing water vapor to condense. a. Most students will have had one or more experiences with this process. Examples you can relate include these: • Water vapor condenses on the outside of a glass of an iced beverage on a hot and humid day.

• Water vapor in your exhaled air condenses to form a “cloud” as it cools on a cold day (i.e., seeing your breath).

• Water vapor condenses on the inside of a windshield on a cold day (moisture mostly from your exhaled air).

• “Steam” forms on a mirror when you take a shower.

• Fog forms when the temperature drops after a warm, wet period, as the water vapor condenses into low-level clouds.

• Condensation forms on the surface of pipes carrying cooled gas in air conditioners, and “frost” in freezers. If you are performing this activity on a warm, humid day, you can actually demonstrate the first example in class. b. Point out that this condensation normally starts on a surface, such as a beverage glass, windshield, or mirror. In the atmosphere, this surface is a dust particle, called a condensation nucleus. Clouds form first, as vapor condenses into an aerosol of fine particles. As these particles coalesce, they eventually become too large to be suspended in the air and fall as precipitation.

4. Demonstrate that cooling air contracts, becoming denser.

• In the atmospheric circulation described in the text, air rises in the tropics, then cools and moves horizontally until it reaches about 30ºN or S latitude. At that point, it has cooled sufficiently to sink. You can demonstrate that cooling air causes it to contract (making it denser) by using a glass soda bottle and balloon.

• Start with the balloon slightly inflated (either by taking it out of the hot-water bath or by blowing into it and placing it on the bottle without letting the air escape).

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•

Place the bottle in the ice-water bath (cold water with ice added). The balloon should soon noticeably deflate.

• Ask students what happened. (The molecules slowed down. Because they were not pushing away from one another as rapidly, the parcel of air was condensed.)

5. Describe how falling air is compressed and becomes heated. a. While difficult to demonstrate in the classroom, the facts that (1) falling air is compressed and (2) compressed air heats up can be inferred because they are the reverse of two processes demonstrated earlier. When air falls (either as it cools while moving away from the equator or as it moves down the leeward side of a mountain), a larger column of air presses down on it from above, which compresses the air. b. Point out that, if a bicycle pump were hooked up to a sensitive thermometer, we could see the temperature rise as the air was compressed in the cylinder (if the air is prevented from leaving the pump). Also note that the compressor in an air-conditioning unit generates heat (beyond the normal waste heat associated with friction and other factors). The key to an air conditioner’s cooling performance is that much of this heat is allowed to dissipate outside (under the hood of the automobile or outside the building) before the (now cooler) compressed air is allowed to expand and cool further inside (in the passenger compartment or inside the building).

6. Describe or demonstrate how heated air holds more water and speeds evaporation.

• Evaporation is easily demonstrated in a classroom equipped with blackboards.

• Wipe the board with a damp sponge. The water will darken the surface of the board. Within a few seconds (the exact time depends on the temperature and humidity of room air), the color will begin to lighten as the water evaporates.

• Ask students what happened to the water. (It evaporated: Molecules in the liquid water with sufficient kinetic energy escaped into the air.)

• Ask students to suggest ways of speeding up this evaporation. (Create air flow over the board; this stream carries away water-laden air from the surface of the board. Heat the board or the air; this action increases the average kinetic energy of water molecules and speeds the rate of evaporation.)

• Describe how a hair dryer and a clothes dryer employ both of these strategies. Also note that, as air warms, it can hold more water. In the case of air falling at 30ºN or S latitude or on the leeward side of a mountain, the air has already lost most of its moisture as precipitation (in the tropics or on the windward side of the mountain), so it is relatively dry (i.e., has low relative humidity). As a result, it can pick up moisture from the land (in the same way that the air from a hair dryer picks up moisture from your hair), leaving the land warm and dry. This causes the bands of desert at 30ºN and S latitudes and the rain shadow on the leeward sides of mountains.

Assessment Suggestions: Assessment questions are integrated into the procedures. Ask students how global warming (i.e., a rise in average global temperature) might affect precipitation levels, evaporation rates, and overall water availability for land plants. (It may decrease precipitation rates because warmer air can hold more moisture. It may increase evaporation rates because water molecules speed up and more readily escape into the gaseous phase. Both of these effects would decrease water availability for land plants.)

Lecture Activity 16.2: Mission—Biomes Estimated Time to Complete: 10–15 minutes, in 1- to 3-minute segments throughout the lecture Introduction: The textbook authors talk about a wide variety of biomes, describing typical vegetation and climate patterns. The Missouri Botanical Garden maintains a website devoted to biomes, which fits perfectly with this discussion and provides pictures as well as other information that students will find interesting.

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Material • A computer with Internet access and projector Procedures 1. While discussing biomes in class, go to the Missouri Botanical Garden’s website at http://mbgnet.mobot.org. After presenting each type of biome to the class, click on the icon for that biome on the website.

2. For each biome, the website provides pictures and a list of topics on the left that can be explored. Try clicking on the animals and plants and showing the class examples of organisms adapted to each biome.

Assessment Suggestions: Have students briefly discuss how the plants and animals shown are adapted to their biomes. Include similar questions on a quiz or exam.

Lecture Activity 16.3: Rain Forest Methods Borrowed from Pest Control, Mountaineering, and Construction Estimated Time to Complete: 10–15 minutes Introduction: We’ve all heard that tropical rain forests are biodiversity hot spots, containing far more of the world’s species than their land area alone would predict. Less well known, however, is the fact that many of these species—and much of the workings of the rain forest for that matter—were unknown until just a few decades ago. The main reason for this belated discovery is that most of the primary production occurs—and many of the species only exist—in the forest canopy, which is 30 meters (100 feet) or more off the ground.

This activity describes how methods developed for pest control, rock climbing, and building construction have been borrowed and adapted by forest ecologists to explore this unique environment.

These methods have allowed scientists to efficiently bring mobile organisms down from the canopy (in the case of insecticide foggers) or take themselves up to it (in the cases of climbing ropes and construction towers), greatly increasing the types of research they can do. Our understanding and appreciation of this important ecosystem has increased dramatically as a result.

Material • A computer with Internet access and projector and images of the rain forest and its canopy and of the methods and equipment described (e.g., insecticide foggers, climbing ropes and walkways, construction towers in the forest) Procedures 1. Begin by reminding students of the tremendous vertical scale of the tropical rain forest, with some trees rising as high as 50 meters (150 feet) above the forest floor. Ask students why trees grow so high, and what limits their height. (The intense competition for sunlight, as each tree tries to avoid being shaded out by its neighbors, is balanced by the physical limits on height imposed by mechanics and transpiration.)

2. Show students a photo or two, looking up at the canopy from below, to help make these points.

3. Point out that only a limited amount of information can be obtained by studying the tropical rain forest, or any forest for that matter, from the ground. Birds and monkeys can be studied using binoculars and/or by listening to their vocalizations, and material that has fallen (or been shot down) from the canopy can be collected and analyzed. These crude research methods often lead to false generalizations and severe underestimation of the number of species present and the complexity of their interactions.

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4. Relate the story of Terry Erwin, the Smithsonian Institution scientist who developed the method of using insecticide foggers to collect canopy arthropods. These foggers, which are basically blowers that create an aerosol of insecticide that can be directed up into the canopy from the ground, were originally developed for pest control purposes. Erwin had the idea of using these devices in the rain forest and setting out collectors on the ground to get representative samples of the huge number of insects, arachnids, and other creatures that fell from the trees. This method allowed Erwin to collect many species that had not been identified prior to his work. Using this information, along with his finding that many plant-eating insects appeared to be limited to just one host tree species, Erwin revised the estimate of the number of insect species in the tropical rain forest from 1.3 million (as earlier researchers had suggested) to 30 million. It was later revealed that many of these insects actually utilize more than one tree species in the same genus, resulting in a downward revision of the estimated number of species to 6 million. Nevertheless, Erwin’s work pointed out the importance of conserving large, interconnected blocks of forests, not just small fragments. Photos of Erwin fogging and his collectors (search the Internet or the Smithsonian National Museum of History website http://www.mnh.si.edu for Terry Erwin) can be shown during this part of the presentation.

5. Ask students what they think are the limitations and drawbacks of Erwin’s method. (It didn’t tell him anything about interrelationships among the species; it did not collect every species—for example, those living inside bromeliads; it killed almost everything in the tree, so observations of the activities or behavior of the organisms was impossible.)

6. To overcome these limitations, researchers needed a way to access the canopy directly. From rock climbing and mountaineering, they adapted methods to climb trees and suspend themselves within the canopy in relative safety and comfort. Basically, a beanbag (or a leadweight slingshot) can be thrown over a sturdy branch. This weight is attached to a light line that is then used to pull a heavier climbing line over the branch. Using climbing gear (e.g., harnesses, block and tackle, carabiners), researchers can hoist themselves up into the canopy, where they can construct slings, walkways, and so on. These platforms ease their efforts considerably. Photos of the gear used and of people climbing using such gear are helpful for explaining these concepts. If you are a climber or if you have students who climb, you may want to have a show-and-tell session as well.

7. Inform students about one of the more recent developments in forest canopy access: the construction of canopy cranes. These devices were originally developed for construction of tall buildings, but several have recently been built in various forest ecosystems throughout the world. The cranes are flown in by helicopter in sections and then assembled on the site. Gondolas suspended beneath the cranes’ large, movable arms allow researchers to work for extended periods safely. Photos of several cranes, along with much more information about the experiments being conducted using this method, can be obtained by performing an Internet search on the words “canopy crane.”

8. If you have time, you can also mention some of the other methods used to gain access to the forest canopy: tethered hot-air balloons, large rafts resting on the treetops, ultralight aircraft, and so on.

Assessment Suggestions: Assessment questions are integrated into the procedure. The benefits of these new methods of research for the advancement of forest ecology are unquestionable. At the same time, their adoption by the ecotourism industry is controversial, as is the growing recreational sport of tree climbing. Have students discuss the pros and cons of this type of ecotourism and of this new sport. Pros include their ability to raise needed capital while maintaining the forest and to raise public awareness and concern about conservation. Cons include potential damage to trees (for example, novice climbers standing on branches have destroyed centuries-old moss mats covering branches in the Pacific Northwest’s temperate rain forests), the entry of development (e.g., roads and sewage) into the forest, and disturbing of wildlife.

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Lecture Activity 16.4: The Unfortunate (Double) Legacy of Thomas Midgley, Jr. Estimated Time to Complete: 20 minutes Introduction: Time can dramatically alter our opinion of events. The truth of this statement is clearly demonstrated by the two major career accomplishments of Thomas J. Midgley, Jr.: the discovery that tetraethyl lead can stop internal combustion engines from “knocking” and the development of Freon® as a refrigerant. This activity presents the technical problems these inventions solved, but also highlights the public health and environmental problems they created.

Materials • Computer with Internet access and projector (optional) • Lecture Activity 16.4 Handout: The Unfortunate (Double) Legacy of Thomas Midgley, Jr. Procedures 1. Introduce Thomas Midgley, Jr., and briefly describe the handout and assignment.

2. Divide the class into groups. Give a handout to each person but ask that each group complete the questions together on a separate sheet of paper and turn in the group-developed answers. Announce that groups have 15 minutes to complete the handout.

3. Circulate while groups are working to answer questions and keep groups on task.

4. Poll groups for some of their answers in a general class discussion at the end, if there is enough time.

Assessment Suggestions: Collect and grade handouts using the answer key provided. Have a class discussion based on the handout questions.

This could be done online, first as an online discussion followed by students answering the questions on the handout online and turning them in. Students can get points for participation in the discussions and the assignment.

Handout Answer Key 1. What are the pros and cons of tetraethyl lead use in gasoline? Pros include reduced engine wear and hence maintenance costs, increased fuel efficiency and hence less demand for oil, less production of greenhouse gases, and potentially less international strife over oil reserves. Cons include the obvious human public health problems and irreversible contamination of the environment.

2. Even before TEL was developed as a gasoline additive, it was known that ethyl alcohol (or ethanol) could eliminate knocking when added to gasoline at 10–15% by volume. It achieves this outcome without contaminating the environment. In fact, Midgley’s own research proved the feasibility of the resulting “gasohol” even before 1921. It has been suggested that development of this alternative, renewable additive was suppressed because Ethyl Corporation could not corner the market and hence reap huge profits on ethanol as it could on TEL. Does this information change your opinion about the use of TEL? This additional information makes it clear that TEL need not have been used. All of the costs associated with the use of leaded gasoline use were entirely avoidable.

3. Ethyl Corporation also developed MMT (methylcyclopenta-dienyl manganese tricarbonyl) as an antiknock additive, and the compound was subsequently adopted for this purpose by Canada and several other countries. Because use of this additive releases manganese into the environment and manganese is also a known neurotoxin, do you think that MMT is a good substitute for TEL? No; it presents similar health risks.

4. Canada was successfully sued by Ethyl Corporation after the country tried to ban the use of MMT in 1997, using restraint-of-trade clauses in the North American Free Trade Agreement (NAFTA). How does the “free trade at all costs” attitude that such agreements promote affect the environment, public health, and national sovereignty? Such agreements can prevent officials in one country from passing laws that protect their citizens or environment if the laws can be shown to restrict trade with another country.

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5. What are the pros and cons of chlorofluorocarbon use? Pros include the ability to save lives and property with these less flammable and toxic refrigerants. Refrigeration also reduced food spoilage, increasing food availability and decreasing the incidences of food-related illness. The growth of air conditioning made life more comfortable, especially in the Sun Belt, which boomed in population and productivity as a result. Cons clearly include increases in skin cancer rates and associated deaths and damage to primary producers from increased ultraviolet radiation levels at ground level.

6. What lessons do you think can be learned from the TEL story regarding deregulation of industry?

Can industries be trusted to police themselves? For example, should we trust industry claims that genetically modified food organisms and irradiated foods are safe? Do we really need regulatory agencies like the Environmental Protection Agency and Food and Drug Administration? The TEL story clearly indicates that industry cannot be trusted to do the right thing with respect to public health and the environment. For-profit companies misrepresented the need for TEL—claiming there were no good alternatives when ethanol was already a proven antiknock additive—and covered up the health risks for decades. Government regulation, in the form of the EPA and FDA, is crucial in protecting the health of the population and integrity of the environment.

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Lecture Activity 16.4 Handout: The Unfortunate (Double) Legacy of Thomas Midgley, Jr. A case study by David J. Zimmer Read the case study and answer the questions following it.

Time can dramatically alter our opinion of events. This is clearly demonstrated by the two primary career accomplishments of mechanical engineer-turned-industrial-chemist Thomas J. Midgley Jr. (1889–1944): the discovery that tetraethyl lead can stop internal combustion engines from knocking, and the development of chlorofluorocarbons (CFCs) as refrigerants.

In 1921, Midgley discovered that adding a small quantity of tetraethyl lead (TEL) to gasoline prevented engine “knock.” This engine-damaging malfunction is caused by premature ignition of fuel in the cylinder as it is being compressed. Adding TEL to gasoline eliminated this problem, allowing manufacturers to increase the engine’s compression ratio, thereby yielding more power and greater fuel efficiency. To sell this additive to gasoline refiners, a new company called Ethyl Corporation was formed as a joint venture of General Motors, DuPont, and Standard Oil of New Jersey. Gasoline with the additive was called ethyl.

In 1928, Midgley was called on to solve another problem. The refrigerants of the day—gases that were cyclically compressed to a liquid and then allowed to vaporize, absorbing heat—were either very toxic or highly flammable, or both. Because many were also corrosive, they tended to leak, resulting in many deaths from exposure to the toxins. Midgley sought a gas that avoided these problems and (reportedly in just three days) found one. This compound was dichlorofluoromethane, the first of the chlorofluorocarbons (CFCs), a group later trademarked as Freons. Midgley demonstrated dichlorofluoromethane’s benign properties at a meeting of the American Chemical Society in 1930 by inhaling a lungful of the gas and gently blowing it over a lit candle, which was extinguished. The development of other CFCs followed quickly, with these compounds being used for a variety of applications—for example, as aerosol propellants, as expanding foams, and in air conditioners.

For his efforts, Midgley received many honors during his lifetime. After his death in 1944, however, his legacy began to unravel. Lead, whose neurotoxicity had been known since antiquity, was increasingly seen as a public health problem, causing learning disorders in children, kidney failure, hypertension and heart disease, and some cancers. In fact, within a year of the start of ethyl production in 1923, a number of workers on the ethyl production line went insane and died from acute lead poisoning, prompting a ban on the sale of TEL-based gasoline until an inquiry could be conducted. To alleviate these fears, Midgley held a press conference during which he poured TEL over his hands and inhaled the vapor. Despite protests by many prominent scientists, the ban on sales of ethyl was quickly lifted. Only recently has it been discovered that Midgley, suffering from severe lead poisoning, subsequently took a prolonged leave of absence in 1924 to recover from his stunt.

Over the next several decades, nearly all the research on the effects of TEL was funded by Ethyl Corporation. Not surprisingly, the company’s researchers failed to find conclusive evidence that leaded gasoline posed a public health risk.

The U.S. Environmental Protection Agency (EPA) began phasing out leaded gasoline use in the 1970s, a process that was completed in 1996. This move was actually motivated as much by the fact that lead fouled the newly mandated catalytic converters as by concerns over lead contamination of the environment. (Catalytic converters reduce emissions of nitrogen oxides, hydrocarbons, and carbon monoxide from exhaust, alleviating smog.) .

Over the 60-some years of TEL’s use, an estimated 7 million tons of lead was released into the environment from the burning of leaded gasoline in the United States alone. This increased our average lead exposure to 300 to 500 times that of “normal” (pre-Midgley) levels. As many as 68 million young children are believed to have received toxic levels of lead between 1927 and 1987, and as many as 5,000 deaths per year may have been caused by lead-related heart disease before TEL use was phased out. Lead burdens in humans have already declined dramatically since the phase-out.

Midgley’s other major “invention,” CFCs, fared just as poorly. In 1974, Mario Molina and F. Sherwood Rowland published a paper describing how stratospheric ozone gas, which absorbs harmful ultraviolet radiation (UV) from the sun, was being destroyed by chlorine released during the breakdown of CFCs. They, along with Paul Crutzen, shared the 1995 Nobel Prize in chemistry “for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone.” While ozone levels worldwide were soon shown to be dropping fast, of particular concern was the vast reduction in ozone levels noted each year in the Southern Hemisphere around Antarctica in the so-called ozone hole.

Before long, a sharp rise in skin cancer rates was noticed in the area, presumably due to elevated UV levels. It turns out that the stability of CFCs, which was a plus for their role as refrigerants, worked against them in the environment because it allowed many molecules to reach the stratosphere before they were split by the intense UV radiation there.

To make matters worse, CFCs were discovered to be greenhouse gases with Earth-warming potentials thousands of times as great as carbon dioxide. Given the serious health and climate implications, industrialized nations signed the Montreal Protocol (in 1987) and subsequent treaties to phase out CFC production and use.

In light of these two rather dubious (in hindsight) inventions, historian John McNeill remarked in his book on the environmental history of the twentieth century that Midgley “had more impact on the atmosphere than any other single organism in earth history.” Midgley’s changing legacy can be summed up by a line from a poem by James Russell Lowell: “Time makes ancient good uncouth.”

References Bryson, B. 2003. A Short History of Nearly Everything. New York: Broadway Books.

Kitman, J. L. March 20, 2000. “The Secret History of Lead,” The Nation, http://www.thenation .com/doc/20000320/kitman.

McNeill, J. R. 2001. Something New Under the Sun: An Environmental History of the Twentieth-Century World. New York: Norton.

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Lecture Activity 16.4 Handout: The Unfortunate (Double) Legacy of Thomas Midgley, Jr. Questions 1. What are the pros and cons of tetraethyl lead use in gasoline?

2. Even before TEL was developed as a gasoline additive, it was known that ethyl alcohol (or ethanol) could eliminate knocking when added to gasoline at 10–15% by volume. It achieves this outcome without contaminating the environment. In fact, Midgley’s own research proved the feasibility of the resulting “gasohol” even before 1921. It has been suggested that development of this alternative, renewable additive was suppressed because Ethyl Corporation could not corner the market and hence reap huge profits on ethanol as it could on TEL. Does this information change your opinion about the use of TEL?

3. Ethyl Corporation also developed MMT (methylcyclopenta-dienyl manganese tricarbonyl) as an antiknock additive, and the compound was subsequently adopted for this purpose by Canada and several other countries. Because use of this additive releases manganese into the environment and manganese is also a known neurotoxin, do you think that MMT is a good substitute for TEL?

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4. Canada was successfully sued by Ethyl Corporation after the country tried to ban the use of MMT in 1997, using restraint-of-trade clauses in the North American Free Trade Agreement (NAFTA). How does the “free trade at all costs” attitude that such agreements promote affect the environment, public health, and national sovereignty?

5. What are the pros and cons of chlorofluorocarbon use?

6. What lessons do you think can be learned from the TEL story regarding deregulation of industry? Can industries be trusted to police themselves? For example, should we trust industry claims that genetically modified food organisms and irradiated foods are safe? Do we really need regulatory agencies like the Environmental Protection Agency and Food and Drug Administration?

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17 Organ Donation Tissues, Organs, and Organ Systems OBJECTIVES Teaching Goals Students will have covered much of this chapter in high school biology classes, so your goal is to highlight the usefulness of this information in their lives. Focus their attention by starting with the prospect of trafficking in human organs; then introduce information about tissues and organ donations to help explain the matching of organs. Students may not be familiar with the concept of feedback regulation in their bodies, but most are aware of the customer rating system of sellers on e-Bay and other feedback mechanisms in commerce, which can be used as an analogy for this process. Connect the “How’s my driving?” bumper sticker to the internal regulation of their body systems.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe the structure and function of epithelial tissues.

• Compare the structures and functions of the six connective tissues.

• Compare the structures and functions of the three types of muscle tissues.

• Describe the structure and function of nervous tissues.

• Explain what an organ is and how organs interact in an organ system.

• List the structures and functions of the liver.

• List the organs of the digestive system, and outline their functions.

• List the accessory organs of the digestive system, and outline their roles in digestive processes.

• Explain how positive and negative feedback mechanisms help in the maintenance of homeostasis.

LECTURE OUTLINE 17.1 Tissues A. A tissue is made up of similar cells.

B. Epithelial tissue lines the body’s surfaces (inside and out) and is responsible for protection, secretion, and absorption functions there. (Figure 17.1) C. Connective tissue varies by function (support or connection) and may be categorized as loose, adipose, blood, fibrous, cartilage, or bone. (Figure 17.2) D. Muscle tissues, which are able to contract or expand, may be classified as either smooth, cardiac, or skeletal. (Figure 17.3)

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E. Nervous tissue (made of neurons) is responsible for communication in the body, including receiving and responding to stimuli. (Figure 17.4) F. Under certain conditions, tissue can be transplanted to repair or replace damaged tissue.

Lecture Activity 17.1 17.2 Organs and Organ Systems A. Organs and organ systems are composed of different types of tissues.

B. Liver transplants can come from a living donor because a lobe of the liver can regenerate to form a full-sized liver.

C. The human body has 12 organ systems, all with different functions. (Table 17.1) D. Humans have a complete digestive system that is responsible for the breakdown and distribution of nutrients. (Figure 17.8) 17.3 Regulating the Internal Environment A. Animals have sensors and systems that help them regulate their internal environment within the narrow range required for survival.

B. Body temperature and glucose levels are regulated by negative feedback. (Figure 17.11) C. Some systems are regulated by positive feedback, which enhances the response to the stimulus.

Lecture Activity 17.2 D. There are long waiting lists for kidney, liver, heart, and lung transplants. (Figure 17.12) Lecture Activity 17.3

Lecture Activity 17.1: Case Study on Connective Tissues Estimated Time to Complete: 20 minutes Introduction: In this activity, a simple case study is used to explore dense connective tissues and their structure.

Material • Lecture Activity 17.1 Handout: Case Study on Connective Tissues Procedures 1. Introduce the case and divide the class into groups of three to four students.

2. Hand out copies of the case. Give groups 10 minutes to answer the questions.

3. If desired, have the groups discuss their answers to the questions; otherwise, collect and grade the cases.

Assessment Suggestions: The answers to the questions can be graded as an individual or group assignment using the answer key provided, or the groups can reassemble for a large classroom discussion of the answers.

The questions could be put online as an assignment.

Handout Answer Key 1. Which types of human tissues are represented by the injuries suffered by this patient? Ligaments are considered a form of fibrous connective tissue. Cartilage is considered a form of specialized connective tissue.

2. Describe the structure of the two types of tissues that have suffered damage. Ligaments contain collagen fibers that are densely packed together in an orderly parallel arrangement. Cartilage contains widely spaced cells that are surrounded by a thick, nonliving matrix (space) filled with collagen.

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3. Using what you know about the structure of these tissues, explain how they are designed to withstand the stress placed on this joint during a football game. Collagen fibers are very strong and flexible. In addition, the arrangement of the collagen fibers within a tissue can affect the strength of the tissue.

Ligaments and cartilage are strong because they contain collagen, and the orderly arrangement of the fibers in ligaments adds to the strength needed to hold the knee joint together when it is under stress.

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Lecture Activity 17.1 Handout: Case Study on Connective Tissues The Football Game Andre Billings, a 24-year-old male, presents in the emergency room with complaints of severe left knee pain and knee instability. The patient describes a violent “hit” during a football game that caused his left knee to buckle. The patient describes having heard a “pop” as he fell to the playing field.

An initial examination of the knee reveals inflammation and a reduced range of motion. Flexion (bending) is reduced to 64 degrees, and extension (straightening) is incomplete. An examination of the joint indicates a major instability. The physician orders an MRI (magnetic resonance imaging) and schedules exploratory arthroscopic knee surgery for the following week. The results of the tests show that Andre has torn his anterior cruciate and medial collateral ligaments. In addition, there is a tear in the medial meniscus (knee cartilage).

Questions 1. Which types of human tissues are represented by the injuries suffered by this patient?

2. Describe the structure of the two types of tissues that have suffered damage.

3. Using what you know about the structure of these tissues, explain how they are designed to withstand the stress placed on this joint during a football game.

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Lecture Activity 17.2: Non-biological Examples of Feedback Estimated Time to Complete: 15 minutes Introduction: In this activity, students are asked to describe non-biological examples of feedback and identify whether they represent positive or negative feedback systems.

Material • None.

Procedures 1. Divide students into small groups and have them list as many non-biological examples of feedback as they can think of. The regulation of the temperature in a house used in the chapter is a good example of a non-biological negative feedback system.

2. After students have had 5–10 minutes for discussion, have the groups report to the class and write the results down on a master list that everyone in the classroom can see.

Assessment Suggestions: Give groups points for correct examples. Include a similar question on a quiz or exam.

This could be done as a discussion question online. Start with each student posting a list of nonbiological examples of feedback, and then have each student respond to at least two other classmates’ postings. After the discussions are over, the instructor can compile the students’ posts for the entire class to view.

Lecture Activity 17.3: The Ethics of Organ Donation Estimated Time to Complete: 15–20 minutes Introduction: The President’s Council on Bioethics (http://www.bioethics.gov) describes five principles that could be used to govern an organ procurement system: 1. “Giving and receiving”: the current system of altruistic organ donation.

2. “Taking and getting”: a system of routine retrieval of all organs without the explicit consent of the deceased or the surviving family.

3. “Selling and buying”: a system of organ markets that would possibly encompass even living donations lethal to the donor.

4. “Honoring and shaming”: a system of public medals and community pressure.

5. “Compensating and providing”: a system of public payment or tax credits for organ “donors.” In this activity, students get a chance to think about the costs and benefits of each system.

Material • None.

Procedures 1. Explain to the class the five sets of principles that could potentially govern organ donation, and jot down the designation for each principle on the board or overhead as it is described.

2. Divide students into small groups and give them 10 minutes to write down as many pros and cons as they can think of for each system. If you have only five groups, you could assign a different principle to each group. This would allow for more in-depth discussion.

3. Initiate a short class discussion by having groups read off parts of their answers.

4. Have an overall show of hands to find out which system or systems that most students think is the fairest. .

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5. Ask the students to imagine themselves as the family member of a very sick person. Their loved one is soon to pass away, but could be saved by an organ donation if one is available in time, which appears unlikely. Ask students to vote again under these new circumstances, and see if the result changes.

Assessment Suggestions: Collect the group notes. Substitute an individual written vote, with a paragraph of explanation, for the show-of-hands vote in steps 5 and 6 of the activity.

This could be done as five separate discussion forums. Divide the students into five groups and assign a forum to each. Have each group do responses to the other four groups’ postings. The instructor can participate by asking questions to the students as mentioned above.

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18 Clearing the Air Respiratory, Cardiovascular, and Excretory Systems OBJECTIVES Teaching Goals Your goal in this chapter is to emphasize the interconnections that exist between the respiratory, cardiovascular, and excretory systems. Many students are already familiar with the harmful effects of smoking on the lungs and heart but may not know about the effects on the bladder and kidneys. Use as much imagery as possible to show the relationship of these three systems to one another and how chemicals in cigarette smoke affect all three.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • List the components of the mammalian respiratory system, and describe the path of air into the body.

• Describe the muscles involved in breathing, including the diaphragm, and explain how their movements facilitate air movement into and out of lungs.

• Explain the role of hemoglobin in gas exchange.

• List the organs and tissues of the mammalian circulatory system, and describe the function of each.

• Describe how blood moves through the double circulation system of the heart.

• Explain the steps of the cardiac cycle, including the role of the heart’s electrical system.

• List the structures of the mammalian urinary system.

• Describe the steps in the process of urine excretion.

• Describe the effects of smoking on the respiratory, cardiovascular, and urinary systems.

LECTURE OUTLINE 18.1 Effects of Smoke on the Respiratory System A. A passive smoker inhales the same chemicals as an active smoker, albeit not in the same concentrations.

B. Carbon monoxide and particulates are two major components of secondhand smoke.

C. Respiration is basically a mechanism for exchanging gases—oxygen in and carbon dioxide out—and requires the coordination of several structures. (Figure 18.2, Figure 18.5) D. Hemoglobin, which normally picks up oxygen in the lungs for transport to the tissues, will preferentially bind to the carbon monoxide found in smokers’ lungs. (Figure 18.6) E. Exposure to smoke can damage the vocal cords and respiratory surfaces necessary for gas exchange. (Figure 18.7, Figure 18.8)

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F. Particulates found in cigarette smoke contribute to the development of bronchitis, asthma, emphysema, and lung cancer.

Lecture Activity 18.1 18.2 Spreading the Effects of Smoke: The Cardiovascular System A. The heart, blood, and blood vessels work together to distribute gases and other materials throughout the body.

B. Blood consists of various components (plasma, red and white blood cells, and platelets), all of which serve different functions. (Figure 18.9, Figure 18.10, Figure 18.11) Lecture Activity 18.2 C. The heart is the pump mechanism that moves the blood through the blood vessels using the cardiac cycle. (Figure 18.12) D. Arteries bring blood away from the heart, and the wave of blood through them is called the pulse. (Figure 18.13) E. Veins bring blood toward the heart, and capillary beds are network of capillaries that are responsible for gas exchange in tissues. (Figure 18.14, Figure 18.5) F. The cardiovascular system and the respiratory system are closely linked, with oxygen being distributed through the body and carbon dioxide being removed from it. (Figure 18.16) G. Smoking is a contributing factor to heart disease, clot formation, and high blood pressure.

(Figure 18.17) Lecture Activity 18.3 Lecture Activity 18.4 18.3 Removing Toxins from the Body: The Urinary System A. The kidneys are responsible for retaining nutrients while releasing waste products.

(Figure 18.18) B. Nephrons are the functional unit of the kidneys and perform four vital functions. (Figure 18.19) C. Toxins in cigarette smoke can damage the kidneys as well as contribute to bladder cancer.

(Figure 18.20)

Lecture Activity 18.1: Forced Exhalation and Emphysema Estimated Time to Complete: 15–20 minutes Introduction: In this activity, students explore the forces associated with forced exhalation in both a normal lung and the lung of a patient with emphysema. Students should be familiar with the anatomy of the lung and the structure and function of the trachea, bronchi, bronchioles, and alveoli.

Materials • Lecture Activity 18.1 Handout: Forced Exhalation and Emphysema: Normal Lung • Lecture Activity 18.1 Handout: Forced Exhalation and Emphysema: Emphysema Lung Procedures A. Normal Lung 1. Give each student a copy of the picture diagramming exhalation in a normal lung, and orient them to the various parts. Emphasize that this picture has been simplified for demonstration purposes. Have students break into small groups to fill in their diagrams and discuss the questions you have posed.

2. Show a transparency or project these pictures to the class during the activity.

3. Discuss the three forces that cause air to leave the lungs during exhalation: The chest collapses, the diaphragm moves upward, and the lungs recoil like a rubber band. These forces put pressure on the lungs, and the air is forced out. .

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4. Discuss what happens during a forced exhalation: Forces are added by contracting muscles that collapse the chest and abdomen.

5. Using simple numbers, work with students to show how these forces work together to create the positive pressures in the lungs that help expel the air.

• Begin by having the students write a “40” in the box next to the label “Chest Wall and Diaphragm.” This represents the value of these forces during exhalation.

• Have students write a “15” next to the label “Elastic Lung.” This represents additional force placed on the air in the lungs when the lung recoils like a rubber band during an exhalation.

• Ask students: What would be the total force on the air in the alveoli? (The total force would be 55. Have the students write a “55” in the box inside the label “Alveoli.”)

6. Explain that as this air leaves the lung, it enters a series of increasingly larger tubes (bronchioles, bronchi, and trachea). Ask students: What will happen to the pressure of this air as it enters these ever-larger tubes? (The pressure will drop as it moves up the respiratory tree.)

7. A useful analogy to use here is water flowing through a hose of a specific diameter under constant pressure. Ask students: If a hose with a much larger diameter is attached to the end of the smaller hose, what happens to the water pressure as it moves into the larger hose? (It will decrease.)

8. Using the figure, have students move up the tube to each box and drop the pressure by 5 as they reach each new box. The sequence should now read 55–50–45–40–35–30.

9. Have students identify the point at which the pressure in the “tube” drops below the pressure exerted by the label “Chest Wall and Diaphragm.”

• Ask students: Why is this point significant? (Because the lungs are enclosed in the chest cavity, all of the bronchioles and bronchi feel the pressure exerted by the chest during forced exhalation.

The result is that the chest could cause the tube to collapse when the pressure inside the tube falls below the pressure exerted by the chest. The very force that helps expel the air can interfere with its ability to leave the lungs. This airway collapse would interfere with a person’s ability to exhale.)

• Ask students: Why do the airways in a normal lung not collapse when we perform a forced exhalation? (In a normal lung, the point at which the pressure in the tube falls below the pressure exerted by the chest is very high in the respiratory tree. If students are familiar with the anatomy of the respiratory system, they will remember that at these high points, the pathway is reinforced with semicircular bands of stiff cartilage that help prevent these tubes from collapsing under pressure.)

10. At this point, the students should be able to explain why the airway in a normal lung does not collapse when a forced exhalation is performed.

B. Emphysema Lung 1. Hand out the picture of the emphysema lung diagram to each student.

2. Explain that in a patient with emphysema, the elasticity of the lung is lost as the alveoli disintegrate and the elastic tissue degrades. Ask students: What will loss of elasticity do to the forces that are used in a forced exhalation? (The elastic recoil force becomes much smaller, and patients begin to rely on the contraction of muscles to perform forced exhalation.)

3. Have students write a “40” in the box for the “Chest Wall and Diaphragm” force and a “5” in the box for “Elastic Lung.” Emphasize the lower number for the elastic force of the lung, and explain how it relates to emphysema.

4. Using concepts similar to those in part A of the procedure, have students fill in the rest of the boxes.

Ask students to consider the following discussion questions in their small groups or as a classroom: • What happened to the point at which the pressure in the tube fell below the “Chest Wall and Diaphragm” force? (This point moves farther down in the respiratory tree.)

• What implications would this change have for the patient with emphysema? (Because chest pressure exceeds tube pressure much earlier in the process, the tubes are likely to collapse.

Bronchioles of various sizes do not have the cartilage support seen much higher in the respiratory

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tree. If the airway collapses, the person will not be able to move the air and will exhale a much smaller volume of air.)

• Why do patients with emphysema need to perform forced exhalations? (Without the elasticity of the lung helping to move the air, a person with emphysema will exhale a much smaller volume of air during a normal breath. To exhale more air, a forced exhalation must be performed.)

5. For further discussion: When individuals with emphysema rely on normal breathing, the volume of air they exhale is reduced as compared to the volume exhaled from a normal lung; this difference reflects the loss of lung elasticity that occurs with emphysema. Over time, the amount of CO2 in the blood will increase, and the control center of the brain will signal the body to increase respirations to help expel this excess gas. Forced exhalations are necessary to prevent the hyperventilation that would occur as the CO2 levels accumulate. The irony is that a forced exhalation in a patient with emphysema has the potential of causing airway collapse, which would interfere with the removal of CO 2 . Conscious control of breathing rate and depth in severe emphysema is an important part of managing this disease. One way to significantly reduce your risk of developing this debilitating disease is to quit smoking (or to never smoke at all).

Assessment Suggestions: Assessment questions are integrated into the steps outlined in the “Procedure” section.

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Lecture Activity 18.1 Handout: Forced Exhalation and Emphysema: Normal Lung

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Lecture Activity 18.1 Handout: Forced Exhalation and Emphysema: Emphysema Lung

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Lecture Activity 18.2: Vessel Diameter and Blood Pressure Estimated Time to Complete: 10 minutes Introduction: Using simple analogies, you can demonstrate the principles underlying blood pressure and vessel diameter, and relate them to blood pressure abnormalities and cardiovascular disease.

Material • Lecture Activity 18.2 Handout: Vessel Diameter and Blood Pressure Procedures 1. This activity can be done as a full-class discussion or in small groups consisting of two to three students. Each description is followed up with discussion questions relating to important principles.

2. The following material can be read to the class or handed out as individual scenarios (see the handout) for discussion.

Scenario 1: A hose is hooked up to a faucet, and the water is turned on. Water leaves the end of the hose under a specific amount of pressure. a. Ask students: What happens to the pressure in the hose as I put my thumb over the opening? (It goes up.)

Scenario 2: Hoses are built to withstand a certain amount of pressure. a. Ask students: What would happen to the hose if the pressure were always near its maximum pressure? (It would be under strain and might eventually rupture.) b. Ask students: How is this outcome related to what happens in a blood vessel in someone with atherosclerosis? Remember that atherosclerotic vessels become rigid and lose their elasticity. (In a person with atherosclerosis, because the blood vessel is stiff and cannot expand to accommodate the surge of blood associated with the heart pumping, the blood pressure goes up and the vessel is in danger of rupturing.)

Scenario 3: A hose is hooked up to a faucet, and the water is turned on. Water leaves the end of the hose under a specific amount of pressure. You now attach another hose to the end of this one that has a much larger diameter. a. Ask students: How does water leaving this hose compare to the water leaving the hose with the smaller diameter? (The water leaves at a much lower pressure.) b. Ask students: What happens to the pressure as water leaves the narrow hose and enters the hose with the larger diameter? How does this outcome relate to vessel diameter and blood pressure?

(The water pressure drops immediately and significantly. The same thing would happen in the body when a small blood vessel empties into a much larger one.)

Assessment Suggestions: Student understanding can be assessed from the answers to the class discussion/handout questions. Include similar questions on a quiz or exam.

This could be an online assignment. Set up three different discussion forums, divide the students up among the forums, and have them answer the questions. Have the other groups respond to the other two scenario responses.

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Lecture Activity 18.2 Handout: Vessel Diameter and Blood Pressure Scenario 1: A hose is hooked up to a faucet, and the water is turned on. Water leaves the end of the hose under a specific amount of pressure. a. What happens to the pressure in the hose as I put my thumb over the opening?

Scenario 2: Hoses are built to withstand a certain amount of pressure. a. What would happen to the hose if the pressure were always near its maximum pressure?

b. How is this outcome related to what happens in a blood vessel in someone with atherosclerosis?

Remember that atherosclerotic vessels become rigid and lose their elasticity.

Scenario 3: A hose is hooked up to a faucet, and the water is turned on. Water leaves the end of the hose under a specific amount of pressure. You now attach another hose to the end of this one that has a much larger diameter. a. How does water leaving this hose compare to the water leaving the hose with the smaller diameter?

b. What happens to the pressure as water leaves the narrow hose and enters the hose with the larger diameter? How does this outcome relate to vessel diameter and blood pressure?

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Lecture Activity 18.3: The Aquatic Lung: Breathing Liquid Estimated Time to Complete: 15–20 minutes Introduction: Doctors and scientists have been experimenting for many years with the idea that a liquid could be introduced into the lungs and support oxygen and carbon dioxide exchange. Researchers have had some success with a group of compounds known as perfluorocarbons, as described in this case study.

For more background information on these products or their uses, do an Internet search for perfluorocarbons.

Materials • A computer with Internet access and projector, if desired • Lecture Activity 18.3 Handout: The Aquatic Lung: Breathing Liquid Procedures 1. Introduce the idea of liquid ventilation, in which a liquid that can support oxygen and carbon dioxide exchange is introduced into the lungs.

2. Divide the class into small groups, pass out the handout, and give the students 15 minutes to complete the case study. Circulate around the classroom during this time to answer questions and keep groups on task.

Assessment Suggestions: Collect and grade the case study, using the answer key provided. Include similar questions on a quiz or exam.

This could be done as an online assignment.

Handout Answer Key 1. If the human lung has evolved to exchange oxygen and carbon dioxide with air, how is it possible that this exchange can occur when the lung is bathed in a liquid? Animal respiratory systems are designed to facilitate gas exchange through the process of diffusion, in which molecules move from areas of higher concentration to areas of lower concentration. In the case of liquid breathing, the medium through which the lung is exposed to the gases is different, but the actual concentration gradients can be maintained. The trick is finding a fluid that will support a gradient that is similar to the air we breathe.

2. Why would liquid breathing be beneficial to a scuba diver? When a diver descends, the increased pressure of the water at depth collapses the air-filled lungs. To prevent this collapse, divers breathe compressed air, which delivers the needed oxygen and keeps the lungs inflated. Unfortunately, other gases such as nitrogen are delivered to the body under pressure. This excess nitrogen is responsible for problems such as nitrogen narcosis and decompression sickness. A liquid would not be as compressible and would match the pressure of the surrounding water. The problems associated with breathing compressed gas could then be avoided.

3. How might this technology be useful for organ transplants? The preservation of a harvested organ is crucial for the success of a transplant. Once an organ is procured, it is quickly transported on ice to an awaiting surgical team, which performs the transplant. Without its blood supply, the organ quickly begins to starve for oxygen unless it is cooled on ice. To help preserve the organ, oxygen-saturated liquids can be circulated through as a temporary blood substitute, or the organ might be bathed in the liquid for transport.

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Lecture Activity 18.3 Handout: The Aquatic Lung: Breathing Liquid A Case Study by James Hewlett

The 1989 movie The Abyss (20th Century Fox) popularized the idea that animals can breathe liquid as long as the liquid has oxygen-carrying properties similar to those of the air we breathe. In the movie, a mouse is shown submersed in a mysterious pink liquid. After recovering from the initial shock of inhaling a fluid, the mouse begins to breathe as it normally would in standard room air.

Although water does contain dissolved oxygen, it does not have enough carrying capacity to be able to deliver a sufficient amount of oxygen to support our tissues. The human lung evolved to exchange gases with the air we breathe. When filled with water, the gas-exchange surface is unable to meet the demands of the body, and our tissues begin to starve for oxygen. At the same time, our ability to expel carbon dioxide as a waste product becomes compromised. The mystery behind the pink liquid in The Abyss is that it contains a molecule called perfluorooctyl bromide.

The concept of liquid breathing was first explored by Dr. J. Kylstra at the State University of New York at Buffalo. By forcing oxygen into a simple saline solution, Kylstra was able to significantly increase the amount of oxygen carried by this liquid. The mice in Kylstra’s lab were able to breathe the liquid and receive adequate amounts of oxygen. Problems arose when it was discovered that the saline was unable to effectively remove carbon dioxide from the mice. Carbon dioxide levels quickly rose to lethal levels in Kylstra’s test subjects.

Many different formulations have since been tested, but the current use of liquid breathing media relies on perfluorocarbons. In addition to being able to carry 20 times more oxygen than Kylstra’s saline, these compounds have excellent carbon dioxide carrying capacities. The oxygen and carbon dioxide carrying capacities of these compounds are only two of the many unique characteristics that make perfluorocarbons useful in liquid ventilation and oxygenation of tissues.

When most scuba divers drop below the surface of the ocean, they rely on a tank that has been filled with compressed air to supply them with oxygen and to keep their lungs inflated against the greater pressure of the surrounding water. Sometimes this air has been modified to reduce the amount of nitrogen, which has been shown to be the source of a wide variety of diving injuries and sicknesses. It may be many years before scuba tanks are routinely filled with a liquid breathing medium, but the medical applications of this technology are now being realized.

Questions 1. If the human lung has evolved to exchange oxygen and carbon dioxide with air, how is it possible that this exchange can occur when the lung is bathed in a liquid?

2. Why would liquid breathing be beneficial to a scuba diver?

3. How might this technology be useful for organ transplants?

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Lecture Activity 18.4: The Cough Estimated Time to Complete: 25 minutes Introduction: In this case study, students explore the role of the respiratory system and its relationship with the circulatory system.

Materials • A copy of the textbook or other reference material.

• Lecture Activity 18.4 Handout: The Cough Procedures 1. After discussing the respiratory and circulatory systems in class, divide the students into small groups of three or four.

2. Hand out the case study, and ask for a volunteer in each group to read the case aloud and act as a facilitator to work through the case questions and discuss the answers. It is important that the groups have the textbook or other material on chronic obstructive pulmonary disease available to use as a reference.

3. After the small groups have had 15 minutes to discuss the answers, reassemble the class for a wholeclass discussion. Have the groups take turns reporting their answers to the questions to the class, and encourage other groups to add information as the discussion continues.

Assessment Suggestion: If desired, instead of a class discussion, you can collect handouts and grade them using the answer key provided.

This could be done as an online discussion or assignment.

Handout Answer Key 1. An arterial “blood gas test” was performed to measure oxygen levels. Explain why the blood was taken from an artery and not from a vein. The fluid in the lungs and “blue” appearance of this patient suggest that this person is not getting enough oxygen to the tissues. The blood was drawn in an artery because these vessels (other than the pulmonary artery) are responsible for delivering oxygenated blood to the tissues. A measure of the amount of oxygen in the blood of these vessels will help determine if there is a problem.

2. In the blood gas test, the oxygen measurement is reported as saturation. How is oxygen carried in the blood, and what exactly is being saturated with oxygen? Oxygen in the blood is bound to a protein called hemoglobin that is carried in the red blood cells. When oxygen mixes with blood, it binds to the hemoglobin. The hemoglobin is considered 100% saturated when there is no more room for oxygen to bind.

3. Why does this person have low oxygen saturation? What is preventing him from having saturations in the normal range? The fluid in his lungs is preventing the normal diffusion of oxygen from the air into the blood at the alveoli. Less oxygen is diffusing into his blood, and the amount of oxygen in his blood is lower than normal.

4. How does the abnormal oxygen saturation value relate to the patient’s cyanotic (blue) appearance?

When oxygen binds to hemoglobin, this protein turns a bright red color. When hemoglobin is not bound to oxygen, it is much darker and appears blue under the skin. The low oxygen saturation in this patient means that more of the deoxygenated hemoglobin is present. This excess of deoxygenated hemoglobin produces the blue (cyanotic) appearance.

5. How does the abnormal oxygen saturation value relate to the patient’s elevated heart rate? Because this patient is carrying an abnormally low level of oxygen in the blood, the heart must compensate by moving the blood faster to deliver an adequate amount of oxygen to the tissues. This delivery rate can be increased with an elevated heart rate.

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Lecture Activity 18.4 Handout: The Cough Raymond Harrison, a 64-year-old male, was admitted to the hospital with fever, shaking chills, a nonproductive cough, and chest pain for 6 days. A chest X-ray revealed extensive accumulation of fluid in both lungs. The patient had mild hypertension (high blood pressure) and a smoking history of 275 packs per year. A physical exam revealed a blood pressure of 150/90 mm Hg and a body temperature of 101.8°F. The patient was cyanotic (looked blue) and in respiratory distress. The patient’s heart rate was elevated at 100 beats per minute.

An arterial blood gas test was performed, and the oxygen saturation of the arterial blood was found to be 72% (normal would be 94–100%). The blood test revealed an elevated white blood cell count. Initial treatment consisted of antibiotics and bronchodilators.

Questions 1. An arterial “blood gas test” was performed to measure oxygen levels. Explain why the blood was taken from an artery and not from a vein.

2. In the blood gas test, the oxygen measurement is reported as saturation. How is oxygen carried in the blood, and what exactly is being saturated with oxygen?

3. Why does this person have low oxygen saturation? What is preventing him from having saturations in the normal range?

4. How does the abnormal oxygen saturation value relate to the patient’s cyanotic (blue) appearance?

5. How does the abnormal oxygen saturation value relate to the patient’s elevated heart rate?

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CHAPTER

19 Vaccinations: Protection and Prevention or Peril?

Immune System, Bacteria, Viruses, and Other Pathogens OBJECTIVES Teaching Goals This chapter provides a brief overview of pathogens and the body’s immune response to them. Your goal is to make this issue personal for the students. Look for examples of outbreaks (spinach/E. coli 0157: H7, SARS) to emphasize modes of transmission. Contrast the benefits of the immune response following the flu vaccination with what happens when someone has the flu. Compare prevention of a bovine spongiform encephalopathy (BSE, also known as “mad cow disease”) outbreak to the measures needed to stop a flu pandemic.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Compare the structure of bacteria to that of viruses.

• Contrast bacterial replication with viral reproduction.

• List the structures involved in the first line of defense against infection, and describe how they function in protecting the body against pathogens.

• List the participants in the second line of defense against infection, and describe their functions.

• List the two different cell types involved in the third line of defense against infection, and compare how they recognize and eliminate antigens.

• Explain allergic reactions.

• Explain the process immune cells undergo to be able to respond to millions of different antigens.

• Describe the process used to determine whether a cell is foreign or native to the body and what happens when this process fails.

• Explain the role of memory cells in helping to protect against infection.

• Explain the role of helper T cells in allowing infection by the AIDS virus.

• Describe the mechanism by which vaccines help confer immunity.

LECTURE OUTLINE 19.1 Infectious Agents A. Pathogens are organisms that cause disease and may or may not be contagious.

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B. Bacteria are unicellular, prokaryotic organisms that divide by binary fission. They may be resistant to certain antibiotics. (Figure 19.1, Figure 19.2, Table 19.1) Lecture Activity 19.1 C. Viruses, which are noncellular organisms, contain nucleic acid (DNA or RNA) inside a capsid that may or may not be covered by an envelope. (Figure 19.4, Figure 19.5, Table 19.2) D. Fungi, protozoans, and worms are eukaryotic pathogens that vary in their transmission and disease patterns. (Table 19.3) Lecture Activity 19.2 Lecture Activity 19.3 19.2 The Body’s Response to Infection: The Immune System A. The body’s first line of defense consists of the skin and mucous membranes; it is designed to prevent entry of infectious agents. (Figure 19.7) B. The second line of defense consists of a wide variety of defensive proteins and cells found in the bloodstream and the lymphatic system.

C. Specific in nature, the third line of defense is regulated by B cells and T cells (lymphocytes) and responds to a wide variety of antigens. (Figure 19.10, Figure 19.11, Figure 19.12) D. In antibody immunity, B cells stimulate the production of antibodies; this process forms the basis for vaccination. (Figure 19.15) Lecture Activity 19.4 Lecture Activity 19.5 E. T cells are responsible for cell-mediated immunity and attack foreign or infected cells.

(Figure 19.16) F. Successful pathogens have evolved different mechanisms to avoid the immune response. For example, HIV infects immune system cells.

Lecture Activity 19.1: Visualization of Bacteria That Are All Around Us Estimated Time to Complete: 15–20 minutes total in two different class periods Introduction: This activity can be introduced by asking students if they can see the bacteria that are all around them and finding out how many bacteria they think might be present in the room or on them. This demonstration will enable students to visualize colonies of bacteria that grow after nutrient agar is simply exposed to the air or their (what may appear to be clean!) fingers.

Materials • Several nutrient agar (NA) plates (petri dishes into which a basic nutrient agar has been poured) • A felt-tip or china marker to mark the plates • An incubator for incubating the plates overnight (nice, but not necessary) • Tape Procedures 1. Bring the petri dishes to class.

2. Leave one dish open for 10–15 minutes while covering other material. Use more if you want to sample different areas in the room, especially if it’s a large room.

3. Have a few student volunteers smear their fingers on different NA plates. Try to get some students who routinely use antibacterial soap and some who do not. Cover the plates after the students touch them.

4. Be sure the bottoms of all plates are labeled correctly with their location or the name of the student who touched the plate.

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5. Incubate plates overnight in an incubator, or leave them to grow at room temperature; the latter approach will work but will take more time.

6. Bring the plates back to class once growth has occurred and bacterial colonies are visible, and show them to the students. Tape the top and bottom plates together so that they do not accidentally come open while students are handling them.

Assessment Suggestions • Initiate a discussion about which area (if multiple areas are sampled) of the room appeared to have the most bacteria, and why. See if the number of bacterial colonies on a plate has any relationship to whether a student uses antibacterial soap.

• Ask students if antibacterial soap kills all bacteria and, if not, why not. (No; some bacteria are likely to be at least partially resistant to these commonly used antibacterials.)

• Ask students whether they are alarmed by the number of bacteria that grew on the plates. This is a good way to emphasize (assuming some students will indicate alarm) that most bacteria are harmless to us and amazingly important in their ecosystems (as producers or decomposers).

• A fun way to ask about this activity on an exam is to include a question asking students why they are never alone even when they think they are.

Lecture Activity 19.2: Comparison of Pathogens Estimated Time to Complete: 10–15 minutes Introduction: After they have heard about the differences between bacteria, viruses, eukaryotic pathogens, students may benefit from reviewing these facts and drawing conclusions about why illnesses caused by these various pathogens are treated differently. This activity provides a good review of the facts for students after they have completed the sections describing these pathogens.

Material • Lecture Activity 19.2 Handout: Comparison of Pathogens Procedures 1. After discussing the various types of pathogens in class, either divide the class into small groups and distribute the handout provided, or initiate a discussion based on the questions.

2. If you conduct this activity as a small-group exercise, give students 10 minutes to complete the handout, and circulate during this time to answer questions and keep groups on task.

Assessment Suggestions: Grade the handout using the answer key provided. Ask similar questions on a quiz or exam.

This could be done as an online assignment.

Handout Answer Key 1. What are the essential differences between bacteria, viruses, and prions based on their structure and chemical makeup? Bacteria are composed of living cells, whereas viruses are nonliving and noncellular. Bacteria contain all types of molecules needed to form cells and carry out metabolism, viruses contain only protein and genetic material, and eukaryotic pathogens are single cells protozoans and worms and fungi.

2. Why is it so much more difficult to treat viral diseases than bacterial diseases?

Antibiotics kill bacteria by exploiting differences between human and bacterial cells; parts of bacterial cells are attacked that human cells don’t have, such as the cell wall. Because viruses and prions are nonliving, they can’t be “killed” in the same way that bacteria can. Viruses enter our own cells and use our cellular materials, so it is difficult to attack them without damaging our own cells.

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Prions are just proteins, and are very similar to proteins found in our own cells; there is currently no way to single out and attack only the incorrect form of the protein.

3. Why don’t doctors prescribe antibiotics for viral or eukaryotic pathogen infections such as colds or fungal infection? Viruses and eukaryotic pathogens do not respond to antibiotics. Also, overuse of antibiotics encourages the evolution of antibiotic-resistant bacteria, a trend that doctors are working to avoid.

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Lecture Activity 19.2 Handout: Comparison of Pathogens 1. What are the essential differences between bacteria, viruses, and eukaryotic pathogens based on their structure and chemical makeup?

2. Why is it so much more difficult to treat viral diseases than bacterial diseases?

3. Why don’t doctors prescribe antibiotics for viral or eukaryotic pathogen infections such as colds or fungal infections?

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Lecture Activity 19.3: Epidemic in the Classroom!

Estimated Time to Complete: 15 minutes or more, depending on class size Introduction: Students have some appreciation of the spread of disease, especially when the cold and flu season hits the campus. It is less readily apparent to them just how quickly the infectious agent can spread throughout a population and create an epidemic. This activity illustrates the nature of an epidemic by having students exchange colored beads or marbles and follow the “infected” beads throughout the population.

Materials • Beads or marbles of different colors (establish one of the colors as the “infectious agent”) • Drink cups to hold approximately 10 beads or marbles Procedures 1. Put 10 beads or marbles of the same color into each of the cups. (In a large class, you can use more than one cup with the same color.)

2. Have each student take a cup. Do not tell the students which color represents the infected individual.

3. Have the students write down the color of beads that they start with, and ask them to note the new colors as they get them.

4. Inform the students that for the next 5 minutes, they are to exchange individual beads from within their cup with beads from their neighbors. Keep the students exchanging beads as many times as possible, with as many neighbors as possible, in the 5-minute period. Each person must maintain a total of 10 beads, but the beads do not remain a uniform color once the exercise begins.

5. At the end of 5 minutes, stop the exchange. Announce to the class that one of the colors is actually the influenza virus. Ask the class who started with just that color in his or her cup, and then ask the rest of the students if they have now that color in their cups. Tally the number of currently “infected” individuals.

6. Ask how many students had that color in their cups at one time. These individuals had the disease and passed it on to someone else. Tally this number as well.

Assessment Suggestions Initiate a discussion about the modes of transmission of infectious agents. Go through the numbers with the students: Based on the initial percentage of the population that was infected, how did the number change once the virus had been spread to others? What does this finding suggest about the possible epidemic nature of viral illnesses? (Such illnesses can spread very rapidly, even when they start from only a small number of infected individuals.)

Ask students how this epidemic could have been prevented. (If the student knew in advance that he or she was infected, would that person have exchanged beads with others? People could get flu shots, increase their hand washing, and take other preventive measures.) Discuss how the simulation differs from reality: If a person gives away the virus, it doesn’t mean that the person is “free” of the virus, because more viruses can replicate within that individual.

Base a quiz or exam question on this activity. Another option is to have an online discussion following this exercise in the classroom.

Lecture Activity 19.4: Antibody Diversity Estimated Time to Complete: 5 minutes Introduction: The human immune system is capable of recognizing a seemingly limitless number of microbes. This activity addresses the immune system’s ability to recognize myriad antigens. The students

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will act as B cells and create their own antibody by combining fragments from three different groups of fragments. This exercise is a good way to introduce the section on antibody diversity. It can also be done after the discussion of antibody diversity to give students hands-on experience with just how much diversity you can get from recombining genes from multiple “decks” involving hundreds of possibilities.

Materials • Either a PowerPoint slide, an overhead transparency, or a chalkboard/whiteboard to write on • Lecture Activity 19.4 Handout: Antibody Diversity Procedures 1. Before-class preparation: Put the following three columns on the slide or board: Column 1: List C1–C14 (don’t include numbers 3, 5, 7, and 13).

Columns 2 and 3: List V1–V14 (don’t include numbers 3, 5, 7, and 13).

The letters and numbers in each column represent different antibody fragments.

2. During class, display the columns.

3. Tell the class that each student will play the role of a developing B cell and must pick one antibody fragment from each of these columns to construct his or her own antibody.

4. Give students 20–30 seconds to make their selection.

5. After they have made their selections, ask some students to share the structure of their antibodies with the rest of the class. (In a smaller classroom, you can have all of the students share the structure of their antibody. In a large classroom, have about 10 students share their structures, and then ask if anyone else in the class has an identical match.)

6. Discuss how recombination can lead to great diversity, and ask why few, if any, students had the same antibody.

Assessment Suggestions: Use the handout questions for generating discussion or for postactivity assessment.

This could be done as online discussion or assignment to be done after the activity is performed in class.

Handout Answer Key 1. How many different antibodies could you construct from these three columns? 1,000 (10 × 10 × 10).

2. Now think about what that number would look like if the columns had hundreds of different fragments per column. How are antibodies able to recognize so many different antigens that they have never seen before? Through sheer diversity. This question can lead into a discussion of the potential for different antibodies if real B cells have multiple “columns,” with hundreds of different fragments each, from which to choose. It can also lead into the coverage of antibody diversity in the lecture.

3. How does T-cell receptor diversity compare to antibody diversity? These structures come by their diversity in the same way, so their level of diversity will be similar.

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Lecture Activity 19.4 Handout: Antibody Diversity 1. How many different antibodies could you construct from these three columns?

2. Now think about what that number would look like if the columns had hundreds of different fragments per column. How are antibodies able to recognize so many different antigens that they have never seen before?

3. How does T-cell receptor diversity compare to antibody diversity?

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Lecture Activity 19.5: Neutralization of Toxins by Antibodies Estimated Time to Complete: 3–5 minutes Introduction: Toxins, such as snake or insect venom, cause damage by interacting with cellular components in the body and impairing their function. This interference in normal functioning causes cell and tissue damage, which could lead to the affected organism’s death. Antibodies recognize and bind to antigens on toxins in the blood or extracellular fluid. By binding to toxins, the antibodies change the toxins’ shape and thwart their ability to do damage. This demonstration of how antibodies neutralize toxins is a quick, simple way to reinforce the concepts of the “lock-in-key” interaction between antibodies and their antigens. It also highlights the importance of structure to function, particularly when discussing proteins.

Materials • Old doorknob assembly with key that fits it • Lecture Activity 19.5 Handout: Neutralization of Toxins by Antibodies Procedures 1. Hold up the key and compare it to a toxin.

2. Explain that many toxins are proteins and can cause their damaging effects only by interacting in a specific way with molecules in a cell. The molecules’ ability to function depends on their shape.

3. Hold up the doorknob and compare it to an antibody.

4. Put the key in the keyhole of the doorknob. Antibodies bind to their antigens in a lock-in-key fashion.

Assessment Suggestions: Use the handout questions for a class discussion or a post-activity quiz.

This could be done as an online discussion or assignment.

Handout Answer Key 1. Can the toxin function with the antibody attached to it? Why or why not? No; because the shape has changed, the toxin can no longer function properly.

2. How can an antibody against a venom be made? Extract the venom and inject it in small doses into an organism such as a horse or rabbit, so as to elicit an immune response. The animal will produce venom antibodies, which can then be purified from its blood.

3. How might an antibody against a toxin be used? It could be used to counteract the damaging effects of the toxin.

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Lecture Activity 19.5 Handout: Neutralization of Toxins by Antibodies 1. Can the toxin function with the antibody attached to it? Why or why not?

2. How can an antibody against a venom be made?

3. How might an antibody against a toxin be used?

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20 Sex Differences and Athleticism Endocrine, Skeletal, and Muscular Systems OBJECTIVES Teaching Goals Students recognize that males and females excel at different sports. For instance, in gymnastics, males (upper body strength) compete on the still rings, and females (lower center of gravity for balance) compete on the balance beam. Show some clips of athletes competing in the Summer Olympics and then introduce the biology that underlies gender differences. Your goal is to help students understand why these differences exist, yet to also appreciate the wide range of abilities that exist in the population.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Differentiate between protein and steroid hormones.

• List the major endocrine glands, the hormones they secrete, and the effects these hormones have on their target organs.

• Describe the main structural components of the skeleton and their functions.

• Discuss the process of bone remodeling.

• Describe the main structural components of the muscular system and their functions.

• Outline the structure of a muscle fiber, and describe how muscles contract.

• List several sex differences in body composition.

LECTURE OUTLINE 20.1 The Endocrine System A. Hormones are messengers secreted by endocrine glands that stimulate a response in a target cell.

(Figure 20.1) Lecture Activity 20.1 B. Endocrine glands and cells produce hormones that regulate levels of a variety of molecules, such as calcium. (Table 20.1) C. Chemicals from the hypothalamus and pituitary glands regulate functions ranging from body temperature to reproduction.

D. Gender-specific characteristics are affected by hormones secreted by different endocrine glands.

(Figure 20.3) .

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20.2 The Skeletal System A. Serving as an internal framework, the skeletal system provides support and protection and assists in movement. (Figure 20.5) B. Various types of joints, such as those found in the hip and knee, allow movement in different directions. (Figure 20.6) C. Cells that are found in bone respond to signals from calcium levels. (Figure 20.8) D. Skeletal differences between males and females result from the timing of puberty and are an underlying reason for the two sexes’ success in different athletic endeavors. (Figure 20.9) 20.3 The Muscular System A. Muscles, tendons, and bones interact to facilitate contraction of muscles. (Figure 20.10) Lecture Activity 20.2 B. The structure of the sacromere leads to muscular contraction. (Figure 20.11) C. Muscle fibers and mass increase in size in response to testosterone produced in males.

20.4 Other Sex Differences That Influence Athleticism A. The location and amount of body fat differ in males and females, resulting in gender-specific capabilities.

Lecture Activity 20.3 B. Even though males and females exhibit contrasting abilities in different sports based on biological differences, the amount of time involved in the sport is an important factor in any particular individual’s performance.

Lecture Activity 20.1: Amplification of Hormonal Signals Estimated Time to Complete: 10 minutes Introduction: Protein hormones, which are water soluble, must use membrane receptors to get their messages into cells. Many times, the hormone acts as a first messenger to deliver the message to the cell.

The binding of this hormone to the membrane receptor initiates a second messenger pathway, which then relays the message to the inside of the cell. This second messenger is often cAMP. Once the second messenger has been activated, it initiates a cascade of enzyme-catalyzed reactions. Each stage of the cascade involves increasingly more molecules, which greatly amplifies the original signal. In this activity, students play the roles of the different signaling molecules and demonstrate the activation of a second messenger system.

Material • Lecture Activity 20.1 Handout: Amplification of Hormonal Signals Procedures 1. Before starting, explain to students that in this activity, students will play the roles of the different signaling molecules and demonstrate the activation of a second messenger system. Next, recruit the following volunteers from near the back of the classroom: one person to act as the hormone, one person to act as the receptor, and one person to act as cAMP. 2. Inform the first row of seated students that they represent the first level of inactive enzymes waiting to be activated by cAMP. 3. Inform the second row of seated students that they represent the second level of inactive enzymes waiting to be activated by the first level of activated enzymes.

4. Inform the third row of seated students that they represent the reactants waiting to be turned into product in the last step in the pathway.

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5. A touch on the arm represents activation. Once activated, cAMP and the enzymes will be active for five seconds (counted off by the student).

6. To start the reaction, the hormone approaches and activates the receptor. The receptor then reaches out and activates cAMP. In turn, cAMP walks to the first row and taps as many students as possible in the five-second time period.

7. When students (enzymes) in the first two rows are tapped (activated), they should immediately stand up and tap as many students in the next row as possible during their five-second time period.

Enzymes should sit down after their five seconds are up.

8. Students in the third row should stand up when tapped and remain standing. The students left standing in the third row after the signaling pathway is complete represent the number of end-product molecules produced by the single hormone messenger.

Note: This activity is described as it would occur in a large theater-style lecture hall with fixed rows of chairs. In a small classroom with individual desks, cAMP and enzymes can activate students from anywhere in the classroom.

Assessment Suggestions: Use the handout questions for a post-demonstration discussion or quiz in class or online.

The last question on the handout can lead into an interesting class discussion about the effects of drugs such as Viagra that enhance second-messenger systems. In Viagra’s mechanism of action, cGMP is the second messenger in the signaling pathway that causes erections. It promotes smooth muscle relaxation, increased blood flow to the penis, and erection. Viagra inhibits cGMP-specific phosphodiesterase 5 (PDE5—the enzyme that breaks down cGMP), thereby increasing the amount of time during which cGMP is active.

Handout Answer Key 1. What are two significant effects that we get from this type of system? Amplification and persistence—a small number of hormones results in a large number of reactions occurring, and the effect can significantly outlast the hormone–receptor interaction.

2. What are possible sites at which to shut off this response? Block the receptor; block cAMP; block any of the enzymes.

3. How could you get even further amplification from this system? Increase the amount of time that the hormone is bound to the receptor or the amount of time that any of the components of the pathway are active.

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Lecture Activity 20.1 Handout: Amplification of Hormonal Signals 1. What are two significant effects that we get from this type of system?

2. What are possible sites at which to shut off this response?

3. How could you get even further amplification from this system?

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Lecture Activity 20.2: Steps in Muscle Contraction Estimated Time to Complete: 10 minutes Introduction: Students benefit from problem-solving exercises when they are learning about complex physiological concepts such as the sliding-filament mechanism. In this activity, students work as a class, or in small groups, to assemble a sequence of events that accurately describes the sliding-filament mechanism. As part of this exercise, students are required to consider both the anatomical structures and the physiological processes involved.

Materials • Lecture Activity 20.2 Handout: Steps in Muscle Contraction • Copy of Figure 20.11 as a slide or overhead Procedures 1. Briefly explain the activity, telling students that they are not to use their books; pass out the handouts and give students 10 minutes to complete the task.

2. Project and discuss Figure 20.11 as a guide to the anatomical parts involved in the process.

3. Circulate to answer questions and keep groups on task. It is important that you do not give the students any answers, but feel free to give them hints to help them figure out the sequence on their own.

Assessment Suggestions: Collect and grade handouts using the answer key provided. Include a similar question on an exam or quiz.

This could be done as an online assignment or as an online essay question.

Handout Answer Key d. ATP binds to myosin. b. Myosin is released from its binding on the actin filament. f. ATP is broken down. c. The myosin head changes shape by cocking back. g. The myosin head binds to an actin molecule. a. Myosin changes shape, pulling actin toward the center of the sarcomere. e. The muscle fiber shortens.

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Lecture Activity 20.2 Handout: Steps in Muscle Contraction

Following are the steps in muscle contraction, but they are in scrambled order. Working in small groups, put these steps in their correct order. You may not use your book or notes for this activity.

Steps in Muscle Contraction a. Myosin changes shape, pulling actin toward the center of the sarcomere. b. Myosin is released from its binding on the actin filament. c. The myosin head changes shape by cocking back. d. ATP binds to myosin. e. The muscle fiber shortens. f. ATP is broken down. g. The myosin head binds to an actin molecule.

Correct Order Letter

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Lecture Activity 20.3: Show Me the Data: Muscle Mass and Fat Distribution in Males and Females Estimated Time to Complete: 20 minutes Introduction: Nonbiology majors are usually not exposed to data analysis as a regular activity. They generally depend on what the professor tells them, general explanations in the textbook, and any Internet sites they happen to stumble upon. It’s important to remind students that what we know and understand about biology arises because of experimentation and the production and interpretation of data. In this activity, muscle mass distribution data are used to support the information provided in the chapter regarding gender differences and athleticism.

Materials • A copy of the article “Skeletal Muscle Mass and Distribution in 468 Men and Women Aged 18–88 yr.” in J. Applied Physiology 89(1)2000: 81–88. The full text of the article can be found by searching “Skeletal Muscle Mass and Distribution in 468 Men and Women Aged 18–88 yr.” on the Journal of Applied Physiology website (http://jap.physiology.org). In the search results, select the option for “Full Text” to the right of the article title.

• Make slides or overhead transparencies of Figures 1 and 2 from the article. Also make enough copies of the figures to give a copy to every two people in the class.

• Prepare a slide or an overhead transparency of Figure 20.14 from the textbook.

Procedures 1. Before class, read the article cited earlier for background information.

2. Hand out the figures in class, and place the figures one at a time on the overhead projector.

3. Tell the students the title of the article. Help them to read each graph accurately by relating what the various axes mean and explaining the legend.

4. As students work in groups, have them determine what each graph tells us about the distribution of muscle mass in the male and female bodies. Ask students to discuss both the differences and the similarities between males and females. Encourage them to explore how age affects gender differences, and how data consisting of averages (Figure 1) differ from data presented as a scatter plot of individuals (Figure 2).

5. Show an overhead transparency of Figure 20.14 from the textbook. Ask students to interpret this figure and compare it with the muscle mass data.

6. Provide students with the following problem: If a 30-year-old individual has 28 kg muscle mass and 25% body fat, is the individual most likely male or female? Students should use the data to make this determination.

Assessment Suggestions: Have each group draw a graph of what they think data from their class would look like in a scatter plot for muscle mass distribution. The graph should include the appropriate age groups and show overlap in male and female values.

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21 Is There Something in the Water?

Reproductive and Developmental Biology OBJECTIVES Teaching Goals Your goal is to convey the important concepts of the chapter without losing the students in the details.

This chapter basically focuses on reproduction and the many factors that influence it. Students may be familiar with in vitro fertilization and surrogate mothers, so you may want to begin with these alternative methods of reproduction. When you introduce the concerns about endocrine disruptors, be careful that you don’t leave the students with the idea that “everything” is an endocrine disruptor. Given the wide disparity in sex education in public schools, you cannot assume a common level of understanding among your students. You may want to assign some independent work for students outside of class and let them use the class time to share the information they have uncovered.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Contrast asexual and sexual reproduction.

• List the male reproductive structures and their functions.

• List the female reproductive structures and their functions.

• Compare the processes of spermatogenesis and oogenesis.

• Describe the events that occur during the menstrual cycle and how they are hormonally regulated.

• Outline the paths sperm and egg must follow for fertilization to occur.

• Describe the stages of early development from the rapid, early divisions through early tissue differentiation.

• Compare the events leading to differentiation of male and female reproductive organs.

• Outline the hormonal controls regulating pregnancy and birthing.

LECTURE OUTLINE 21.1 Principles of Animal Reproduction A. Asexual reproduction is essentially cloning; an exact genetic copy is made of one organism through processes such as budding and binary fission. (Figure 21.1) B. Sexual reproduction involves the combination of genetic material from two parents, resulting in offspring that are genetically diverse. .

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C. In sexual reproduction, fertilization may be internal or external. With external reproduction, the gametes may be more exposed to pollutants.

21.2 Human Reproduction A. The male reproductive system consists of numerous components that are responsible for the production and delivery of male gametes to the female. (Figure 21.3) B. The female reproductive system is primarily internal and is responsible for the production of eggs and the nurturing of the zygote after fertilization. (Figure 21.4) C. Infertility can occur in either the male or female. It may result from infection (STD), endocrine disruptors, or the action of other chemicals. (Table 21.1) D. Gametogenesis (production of sex cells) is a multiple-step process called spermatogenesis in the male and oogenesis in the female. (Figure 21.5, Figure 21.6) E. Egg development and release in the menstrual cycle are regulated by hormones and are controlled by feedback mechanisms. (Figure 21.7, Figure 21.8) F. Many different types of birth control methods vary in their merits and efficacy. (Table 21.2) 21.3 Human Development A. Fertilization occurs in the oviduct when the sperm penetrates the zona pellucid covering the egg.

(Figure 21.10) B. The embryo reaches the uterus as a blastocyst, which then begins to differentiate into the endoderm, mesoderm, and ectoderm. (Figure 21.11) Lecture Activity 21.1 C. Hormones continue the development of the fetus. This development can be affected by endocrine disruptors in the environment. (Table 21.3) Lecture Activity 21.2 Lecture Activity 21.3 D. Three stages of labor rely on the positive feedback loop of oxytocin. (Figure 21.14, Figure 21.15) 21.4 Is the Water Safe to Drink?

A. The Environmental Protection Agency (EPA) is the federal agency responsible for monitoring and testing the quality of drinking water in the United States.

B. Owing to concerns about the effects of endocrine disruptors on wildlife, further research about these chemicals’ effects in humans is necessary.

Lecture Activity 21.1: Fetal Stem Cell Research Class Discussion Estimated Time to Complete: 20–30 minutes, depending on class enthusiasm and instructor objectives Introduction: Stem cell research is a controversial issue in the United States. Many scientists argue that advances in the treatment of many diseases could be realized by conducting fetal stem cell research. For example, repair of nervous system damage using fetal neural stem cells has been successful in an animal model. Many political, religious, and public-interest groups oppose the use of human stem cells in research because, in effect, human blastocysts must be harvested (usually from abortion clinics) to produce a sufficient quantity of cells for such studies.

Material • None.

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Procedures 1. Give students a basic introduction to the use of stem cells in research and the controversies associated with it. Alternatively, have students research the use of stem cells before class.

2. Break the class into groups of four students, and ask them to compare the medical benefits and the ethical problems associated with stem cell research and therapeutic use. In which situations does the group believe that fetal stem cell research is justified? Under which conditions does the group believe that the use of fetal stem cells should be denied?

3. Give groups 10–15 minutes to talk about these questions. Emphasize that all opinions are to be treated respectfully.

4. After time has expired, lead the entire class in a discussion that considers the pros and cons of stem cell research. Compile the points made on the blackboard or an overhead. It is important for the instructor to stay impartial during the discussion, and to emphasize that both sides have legitimate views that need to be expressed.

Assessment Suggestions: Have students write an essay expressing their viewpoint on stem cell research.

Include a related question on a quiz or exam.

This could be done as an online discussion question. Be sure to explain to students the proper etiquette for online discussions with sensitive topics.

Lecture Activity 21.2: Case Study on Environmental Estrogens Estimated Time to Complete: 15–20 minutes Introduction: Both male and female bodies produce the sex hormone estrogen. In addition, estrogen is found in the environment. Estrogen-like chemicals, called xenoestrogens, are made by plants and fungi and are also found in pesticides, herbicides, and plastics. Exposure of both humans and other animals to these xenoestrogens may have a variety of effects, both negative and positive. To obtain more information on this topic, do an Internet search for “phytoestrogens” and “xenoestrogens.”

Material • Lecture Activity 21.2 Handout: Case Study on Environmental Estrogens Procedures 1. Introduce the idea of environmental estrogens and briefly mention their problems.

2. Divide the class into small groups and distribute the handout.

3. Give students 15 minutes to complete the case study; circulate during this time to answer questions and keep groups on task.

4. If desired, poll groups for their answers, and lead a class discussion on the questions.

Assessment Suggestions: Collect and grade handouts using the answer key provided. Include a similar question on a quiz or exam.

Alternatively, place the handout online as an individual or group assignment.

Handout Answer Key 1. How do estrogens affect the body? Estrogens are produced primarily by the ovaries in females and, to a much lesser extent, by the testes in males. Estrogens are released starting from the fetal stages onward and influence development, behavior, and cognition, in addition to driving development of secondary sexual characteristics during puberty and regulating various aspects of reproduction, such as egg cell maturation, menstruation, and pregnancy.

2. How do xenoestrogens differ from phytoestrogens? Xenoestrogens, also called environmental estrogens, are any of a variety of natural or synthetic compounds that are not produced in the animal

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body, yet mimic the effects of the natural estrogen hormones produced by animals. Phytoestrogens are xenoestrogens that are produced by plants or fungi.

3. Why do you think estrogens and xenoestrogens may have different effects on the body? Estrogens and xenoestrogens bind with different strengths to estrogen receptors and may evoke responses of different strengths. Also, exposure to xenoestrogens may reduce the body’s own estrogen production.

4. Do you think women should use phytoestrogen supplements to prevent cancer or relieve the symptoms of menopause? Explain your answer. Recent studies have shown that certain phytoestrogens do not alleviate symptoms of menopause such as hot flashes. Other studies have shown that women who consume diets high in phytoestrogens have lower circulating levels of estrogen, which may play a role in their having a lower risk of certain cancers. Although these studies suggest a possible link between phytoestrogens and lowered risk for certain cancers, this link has not yet been proven definitively, and the possible side effects of long-term use of phytoestrogen supplements are unknown. For this reason, women should rely on a diet rich in fruits and vegetables to supply their phytoestrogens, instead of taking phytoestrogen supplements.

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Lecture Activity 21.2 Handout: Case Study on Environmental Estrogens Since the 1940s, ecologists have documented dwindling natural populations of many species. This decline in populations, which reflects a reduction in fertility of eagles, otters, gulls, alligators, and other species, was traced to pesticide contamination of the food chain. Metabolites of pesticides apparently acted like the female sex hormone, estrogen. Young males exposed to high levels of environmental estrogens became “feminized” and, consequently, sterile. These environmental estrogens, which are called xenoestrogens, could be a problem for human populations, too. They may play a role in the decline in human sperm counts observed since the 1950s.

Pesticides aren’t the only source of xenoestrogens. Environmental estrogens are all around us, coming from both synthetic and natural sources. Synthetic xenoestrogens enter the environment from pesticides, herbicides, plastics, and by-products of manufacturing processes. Phytoestrogens—that is, xenoestrogens that occur naturally in many plants and fungi—have always been a part of the human diet. Phytoestrogens occur in high concentrations in soybean, alfalfa and bean sprouts, tubers (yams, cassava, potato), flaxseed, and unrefined grain products. Populations that have diets rich in phytoestrogens have significantly lower risks of developing estrogen-related cancers of the breast, ovary, endometrium, and prostate. For example, the traditional Asian diet is rich in phytoestrogens, and Asian women have lower levels of plasma estrogen and a lower incidence of breast cancer than do women in Western countries. Are phytoestrogens responsible for these health benefits? Clinical studies will be required to answer that question, particularly because intake of phytoestrogens is only one of many differences in diet and lifestyle between Asian and Western cultures.

So why is exposure to some types of environmental estrogens harmful, and exposure to other types seemingly helpful? The answer to that question is not completely understood, but some evidence suggests that the difference relates to how the estrogens bind to estrogen receptors. Binding by some phytoestrogens is thought to weaken the estrogen response, whereas binding by some synthetic xenoestrogens might strengthen the estrogen response.

Many phytoestrogen supplements are now being marketed for relief of symptoms of menopause.

Because recent studies show that long-term use of estrogen and progesterone—the traditional components of hormone replacement therapy—by postmenopausal women increases the incidence of many estrogenrelated cancers, women are turning to phytoestrogens to alleviate their symptoms. However, studies that have tested specific phytoestrogens show no relief of the symptoms of menopause, such as hot flashes and night sweats. Also, because phytoestrogens are considered to be food supplements, many have not been tested in clinical trials, so we do not know about the possible side effects of their long-term use. In fact, some phytoestrogens may bind to the estrogen receptor just as tightly as estrogen does and have the same deleterious effects as some of the synthetic xenoestrogens do. Can certain phytoestrogens provide relief from the symptoms of menopause or even some protection against cancer? Only further research will tell.

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Questions 1. How do estrogens affect the body?

2. How do xenoestrogens differ from phytoestrogens?

3. Why do you think estrogens and xenoestrogens may have different effects on the body?

4. Do you think women should use phytoestrogen supplements to prevent cancer or relieve the symptoms of menopause? Explain your answer.

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Lecture Activity 21.3: Prenatal Care Class Discussion Estimated Time to Complete: 10–30 minutes, depending on class enthusiasm and instructor objectives Introduction: Discussing ethical dilemmas raised by our knowledge of biological systems can be an intellectually and emotionally engaging exercise, particularly when the dilemmas directly affect humans.

In this activity, students explore the question of how we should use our knowledge of human embryonic development, and to what extent the knowledge obliges us to use it.

Material • None.

Procedures 1. Set the scene: Inform the class that many children are born with birth defects and/or a variety of behavioral and emotional disorders because of their mothers’ drug or alcohol consumption, or even exposure to environmental toxins during pregnancy. Note that some individuals have suggested legislation be passed to hold mothers criminally responsible for the consequences of their actions during pregnancy.

2. Divide the class into small groups. The groups should discuss the pros and cons of legislation of this type, with the instructor acting as an intermediary and devil’s advocate to further discussion. The instructor should be prepared to provide a number of counterarguments to the class sentiments, making sure the students examine all sides of the argument. For example, consider the following provocative questions: If a woman became addicted to drugs or alcohol before she became pregnant, should she be held responsible if she claims her addiction kept her from stopping her use of these substances? Should cigarette or pharmaceutical companies be held liable for any subsequent birth defects?

If a mother is held responsible for her actions during pregnancy, what about the father?

Secondhand smoke has been shown to have adverse effects on human development: If the father is a chain smoker and refuses to stop smoking around the mother, what then?

If the mother works in an environment where she may be exposed to toxins (including cigarette smoke) that could harm the fetus, should she be forced to stop working during pregnancy?

Are these scenarios any different from those that may occur when a person harms or kills another individual while driving under the influence of drugs or alcohol?

Would legislation of this type be just another case of “Big Brother” trying to control our lives? Is this action justified or not? Why? Assessment Suggestions: Collect notes from the group discussion for points. A bonus question on an exam or quiz, or extra credit essay is appropriate.

This could also be done as an online discussion.

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22 Attention Deficit Disorder Brain Structure and Function OBJECTIVES Teaching Goals You may have students in your class with attention deficit disorder (ADD) who have been on medication for several years; if they volunteer this information, you could ask them to share their experiences. As you present information on the nervous system, use concrete examples of brain injuries to draw the students’ interest. Introduce the concept of traumatic brain injury (TBI), which has affected so many of the veterans returning from the wars in Iraq and Afghanistan. As with the previous chapter, avoid drowning the students in detail.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe the roles that sensory, motor, and interneurons play in the nervous system.

• Describe the manner in which general senses such as touch and vision relay information.

• Explain how reflexes work.

• List the components of the nervous system, and differentiate between the central and peripheral nervous systems.

• Outline the structure and function of the cerebrum, thalamus, hypothalamus, cerebellum, and brain stem.

• Describe the structure of a neuron.

• Differentiate between neurons comprising white and gray matter.

• Describe the events involved in generating an action potential.

• Describe how an action potential is relayed across a synapse.

• List several neurological disorders, including a description of the biology underlying the disorder.

LECTURE OUTLINE 22.1 The Nervous System A. Nerves are bundles of neurons (sensory, motor, interneurons) that receive sensory messages (stimuli) and trigger responses. (Figure 22.2) B. General senses are temperature, touch, pain, pressure, and body position. Special senses are those for smell, taste, hearing, vision, and equilibrium. (Table 22.1) C. Neurotransmitters are chemical messengers that are released from one neuron to enable it to communicate with another neuron.

D. Quick responses in humans are the result of the reflex arc. (Figure 22.4) Lecture Activity 22.1 .

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22.2 The Brain A. The cerebrum consists of two hemispheres and controls language, decision making, memory, and sensations. (Figure 22.6) B. The thalamus is the connector between the spinal cord and the cerebrum. The hypothalamus is the control region for several functions, including sex drive, hunger, and body temperature.

(Figure 22.7) C. The cerebellum is responsible for balance, movement, and coordination. The brain stem governs respiration and heartbeat. (Figure 22.8) D. The brainstem is composed of the midbrain, pons, and medulla oblongata which control numerous activities. (Figure 22.8) Lecture Activity 22.2 Lecture Activity 22.3 22.3 Neurons A. Neuron structure consists of dendrites, cell body, axon, and terminal boutons. (Figure 22.9) B. Nerve impulses are conducted down axons by action potentials which are sped up by myelin sheath. (Figure 22.10) C. Action potential consists of three phases, resting, depolarization, and repolarization.

(Figure 22.11) D. Synaptic transmission is when the message (an electrical signal) travels from the axon of one neuron across the synapse (Figure 22.12) to the dendrite of another neuron. (Figure 22.9) Lecture Activity 22.4 E. Problems with neurotransmission are indicated in several diseases, such as Parkinson’s and Alzheimer’s.

Lecture Activity 22.1: Touch Detection/Discrimination Estimated Time to Complete: 10 minutes Introduction: Our perception of, and interaction with, our environment is entirely dependent on our senses. Each organism has its own unique “view” of the world, based on the types of sensory receptors that it possesses as well as on the sensitivities and ranges of energy detected by those receptors. Humans have many different types of receptors in our skin that allow for the detection of touch, vibration, heat, cold, pain, and so forth. This activity exploits one of those types of mechanoreceptors in the skin to demonstrate some basic features of sensory receptors, including detection threshold and discrimination of characteristics of the signal.

Materials • Several different gauges of monofilament fishing line (from a local hardware store) • Scissors • Ruler • Glue • Popsicle sticks • Marker • 7 paper clips • Opaque tape • 1 blindfold • Lecture Activity 22.1 Handout: Touch Detection/Discrimination

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Procedures Before Class 1. Build your own Von Frey hairs (used to measure stimulation of skin receptors) by cutting approximately 4 cm of each gauge of fishing line and gluing one each (at right angles) to the end of a Popsicle stick. Write the gauge of the line on the Popsicle stick.

2. Unfold the paper clips and bend them so that the tips are different distances (1, 2, 3, 4, 5, 8, and 10 mm) from one another. Bend a piece of opaque tape back on itself and tape it to the curved end of the paper clip. Write the distance between the tips on the tape.

During Class 1. Threshold detection: a. Recruit a volunteer from the class, and blindfold him or her. b. Touch the volunteer’s skin with the different gauges of fishing line, applying just enough pressure to bend the line. Ask the student if he or she felt anything after each touch. Repeat on different parts of the body, such as the fingertip, the palm, and the forearm. c. Make a chart summarizing the data on the board or overhead.

2. Two-point discrimination: a. Recruit another volunteer, and blindfold him or her. b. Using light pressure, touch different paper clips to the volunteer’s skin to determine the minimum distance necessary to distinguish the two points. Repeat on different parts of the body, such as the fingertip, the palm, and the forearm. c. Make a chart summarizing the data on the board or overhead.

3. Have students complete the handout or discuss the handout questions as a class.

Assessment Suggestions: Use the questions from the handout to initiate and direct a post-activity discussion or quiz. For question 1, you should show a picture of the somatosensory cortex. Point to areas of the homunculus and ask the class to decide which area would have lower detection thresholds or better two-point discrimination based on its representation in the somatosensory cortex.

You can also expand this discussion by introducing examples of energies (e.g., magnetic fields, electric fields) and ranges of energies (e.g., ultraviolet, ultrasonic) that other animals detect but humans cannot.

Handout Answer Key 1. What could account for the differences in detection threshold or two-discrimination accuracy?

Differences in the densities of all receptors or specific types of tactile sensory receptors could account for the difference in performance for the various body parts. In addition, greater representation of an area of the body in the somatosensory cortex means a higher ratio of cortical association neurons to receptor cells, which could lead to a more accurate representation of certain features of the signal.

2. Is our “picture” of the world an exact representation? How do our senses “color” our perception? Our picture of the world is shaped by the types of receptors that we have and the ranges and sensitivities of those receptors to the energies that they transduce. While it isn’t an exact representation, it is accurate enough that we can do what is needed to stay alive.

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Lecture Activity 22.1 Handout: Touch Detection/Discrimination 1. What could account for the differences in detection threshold or two-discrimination accuracy?

2. Is our “picture” of the world an exact representation? How do our senses “color” our perception?

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Lecture Activity 22.2: Convergence/Divergence Estimated Time to Complete: 10 minutes after introducing the activity Introduction: Two basic functions of the human nervous system are (1) to receive information from the world (external or internal) and (2) to use that information to direct appropriate responses. Falling between those two is a third crucial function, integration. The processes of integrating information from many different sources and then using that information to coordinate complex responses are called convergence and divergence, respectively. For example, when we have a conversation with another person, our nervous system integrates many different types of visual and auditory information about that person, in addition to signals from our own bodies about where we are in space. This processing of stimuli allows us to perceive a coherent picture of the scene—so that the person’s voice comes from the same place as the visual image of that person, for example. In addition, we can appropriately orient ourselves in space—so that we are facing the other person and not talking blindly into the space over their left shoulder, for example.

This demonstration highlights the importance of convergence by altering a single, specific input and looking at the effects on the production of a motor behavior. During this demonstration, prism lenses are used to shift the visual world by 15 degrees to the left or right. The effect of the shifted visual field is observed on a relatively simple motor act, like throwing a beanbag at a target. The motor system can adapt fairly quickly to the shift, so that after 10–12 throws, the thrower will be able to hit the target again.

Once the motor system has adapted to the shifted visual field, the prism lenses are removed and the behavior is observed again. The thrower will now throw to the opposite side of the target. There is typically a quite satisfying gasp from the class when this happens, because they don’t yet appreciate the adaptation of the motor system and expect that when the lenses are removed, the thrower will be back to normal immediately.

Materials • Prism lenses, 30 diopter (you can order these from Fresnel Prism and Lens Company, http://www.fresnel-prism.com) • Safety goggles • 6–10 small beanbags (juggler’s beanbags work well) • Lecture Activity 22.2 Handout: Convergence/Divergence Procedures 1. Before class, assemble the goggles according to the instructions on the lenses. Cut the prism lenses to fit over the lenses of the safety goggles. Be sure to line up the lenses so that the prisms for each lens face in the same direction. Place the lenses on the goggles with a small amount of water (prism lenses will adhere to safety goggles without adhesive).

2. To begin the demonstration, recruit a pair of volunteers from the class—one student to throw beanbags and the other to catch them.

3. Place the pair of students 10 feet apart at the front of the classroom.

4. Have the thrower toss (not meant to be a hard throw) the beanbags to the catcher, to demonstrate his or her initial accuracy.

5. Have the thrower repeat step 4 while wearing the prism lens. The initial throws will be to the left or right of the catcher, depending on the direction of the shift in visual field. Prompt the students not to intentionally compensate for the deviation in their throw. The thrower should continue until his or her accuracy is pretty normal.

6. Have the thrower remove the goggles and then throw the beanbag again. This time the throw should go to the opposite side of the target.

7. After the demonstration, students can answer the questions on the handout.

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Assessment Suggestion: Collect and grade the handouts.

Handout Answer Key 1. Why does the thrower miss the target after putting on the prism glasses? The prism lenses shift the incoming visual information, so that objects directly in front of the thrower are perceived to be 15 degrees to the left or right. Because the thrower’s motor system does not “know” about the visual shift, the person will throw the beanbag to where the target is perceived to be.

2. Why does the thrower’s accuracy improve with successive throws while the thrower is still wearing the prism glasses? When the thrower misses the target, this information is used to help retune the motor output to the new visual information and improve accuracy. This adaptation is taking place at the motor output level.

3. Why isn’t the thrower accurate immediately after removing the prism lenses? When the glasses are removed, the image that is perceived to be in front of the thrower is actually in front of the thrower.

However, the thrower’s motor system has learned that the visual system is off by 15 degrees to the right or left, so it will continue to throw that way until experience teaches it otherwise.

4. If the thrower put the prism lenses on and sat quietly for several minutes without throwing a beanbag, do you think that the accuracy of his or her throw would be impaired after removing the lenses? Why or why not? The accuracy would remain the same. The visual field has been shifted by the lenses, but because the student is not physically interacting with his or her environment, there is no feedback to the nervous system to let it know that the visual information is inaccurate. Thus no adaptation of the motor system is taking place.

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Lecture Activity 22.2 Handout: Convergence/Divergence 1. Why does the thrower miss the target after putting on the prism glasses?

2. Why does the thrower’s accuracy improve with successive throws while the thrower is still wearing the prism glasses?

3. Why isn’t the thrower accurate immediately after removing the prism lenses?

4. If the thrower put the prism lenses on and sat quietly for several minutes without throwing a beanbag, do you think that the accuracy of his or her throw would be impaired after removing the lenses? Why or why not?

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Lecture Activity 22.3: Olfaction Contributes to Taste Perception Estimated Time to Complete: 5 minutes Introduction: Olfaction and gustation are two very important chemical senses. Gustation (taste) consists of detection of molecules dissolved in water; olfaction (smell) involves detection of airborne molecules.

There are five major taste receptors: (1) sweet, (2) salty, (3) sour, (4) bitter, and (5) umami (a recent addition, named for the Japanese word meaning “delicious”).

With only five taste receptors, how do we perceive so many different flavors? In part, this diversity reflects combinations of these five tastes, but the majority of our sense of flavors comes from olfaction.

Aromatics from the food we are eating diffuse into the nasal cavity and contribute most of the complexity and nuance to our sense of taste. This activity demonstrates the distinct contribution from both gustation and olfaction to our perception of flavors.

Materials • 1 (or several) blindfolds • Different-flavored candies or jelly beans • 1 (or several) pairs of nose plugs Procedures 1. Recruit one or several volunteers from the class.

2. Blindfold the students and offer them candies or jelly beans of different flavors. Have the students name the flavors.

3. Repeat step 2 while the students either hold their noses or use nose plugs.

Assessment Suggestions: Use the following questions to initiate and direct a post-activity discussion in the classroom or online.

1. Relate the results of this experiment to what happens when you get a cold. (The loss of ability to smell when you have a head cold is what causes the loss of ability to taste anything other than the five basic tastes [sour, sweet, bitter, salty, umami].)

2. Speculate on how much of a role other cues—visual or tactile—play in our experience of taste. (The presence of something in your mouth plays a role in taste because smell alone, when you have nothing in your mouth, doesn’t typically elicit sensations of taste. Visual cues, especially color, can influence taste. Many sodas, candies, and popsicles have colors that go along with their flavor. How many of these might taste indiscriminately sweet without that visual cue? This activity could be expanded to include a taste test of different sweet/flavored sodas, some colored and some clear. The taste test could be conducted with blindfolds and then without.)

3. How much does recent experience or anticipation affect the experience of flavors? Have the students volunteer incidents where experience or anticipation has greatly changed the flavor of something.

(For example, consider the taste of orange juice after using toothpaste, or of tasting something salty when you are expecting sweet. This could lead into a discussion of receptor adaptation and consideration of why your first drink of V-8 juice might seem salty, but after you eat a handful of salty potato chips, the second drink doesn’t seem salty.)

Lecture Activity 22.4: Exploring Neuron Function Estimated Time to Complete: 10 minutes Introduction: This quick exercise tests students’ comprehension of neuron function.

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Material • Lecture Activity 22.4 Handout: Exploring Neuron Function Procedures 1. After discussing the topic of neuron function in class, divide the class into small groups.

2. Pass out the handout to students and have them fill it out in their groups.

3. Give the groups three minutes to jot down their thoughts on the question; circulate during that time to answer questions and keep groups on task.

4. After three minutes, collect the groups’ notes or have a class discussion based on different groups’ answers.

Assessment Suggestions: Collect and grade the handout. Include a similar question on a quiz or exam.

This could be done as an online discussion forum.

Handout Answer Key What would happen to a person if Na + could be prevented from moving across the neuron membrane?

Can you think of a use for a chemical with that property? Preventing Na + from moving across cell membranes would stop nerve transmission. This pathway is extremely useful; it is the mechanism of action for many local anesthetics.

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Lecture Activity 22.4 Handout: Exploring Neuron Function What would happen to a person if Na + could be prevented from moving across the neuron membrane?

Can you think of a use for a chemical with that property?

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23 Feeding the World Plant Structure and Growth OBJECTIVES Teaching Goals Students have little recognition of the importance of plants to their life. Although this chapter stresses plants as a source of food, you could also introduce nonedible uses of plants, such as textiles. Depending on your students’ background, they may have no understanding of the food-to-table process and the environmental toll of some agricultural methods. One goal is to help them see the trade-offs of monoculture farming—the food may be cheaper, but the practice has a higher unseen cost.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • List the tissues and structures found on angiosperm plants, and describe their functions.

• Define alternation of generations, and describe how the importance of the two plant generations has changed over evolutionary time.

• Describe the process of reproduction in angiosperms, including the role of double fertilization.

• Compare and contrast primary and secondary growth in dicot plants.

• Describe the role of water availability in maximizing a plant’s exposure to sunlight and carbon dioxide.

• Provide examples of important nutrients for plant growth, and distinguish between how these occur in natural systems and how they are made available in agricultural systems.

• Describe the costs associated with modern agriculture, and list some possible ways these costs could be reduced.

LECTURE OUTLINE 23.1 Plants as Food A. Most plants with agricultural value are angiosperms and are classified as either monocots or dicots. (Table 23.1) B. Xylem (conducts water from roots to leaves) and phloem (distributes the sap—that is, food—in the plant) are the two types of vascular tissue in plants. (Figure 23.3) Lecture Activity 23.1 C. Roots, stems, and leaves make up the nonreproductive organs of angiosperms.

D. Flowers and fruits are the reproductive organs of the angiosperms. (Figure 23.9, Figure 23.12) Lecture Activity 23.2

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23.2 Plant Growth Requirements A. The height of a plant comes from primary growth, whereas the thickness of the stems, trunks, and other structures results from secondary growth. (Figure 23.13, Figure 23.14, Figure 23.16, Figure 23.17) Lecture Activity 23.3 B. Plant productivity is influenced by the amount of sunlight, water, and activity of pests (i.e., weeds, disease, insects). (Figure 23.19, Figure 23.20, Figure 23.22) C. Macronutrients and micronutrients needed by the plant for growth either are found in the soil or must be added to the soil as fertilizer. (Table 23.2, Figure 23.24) D. Legumes have nitrogen-fixing bacteria living in their roots and require less fertilizer.

(Figure 23.25) E. Pests can be controlled by the application of pesticides or by cultural methods. (Figure 23.26) F. Geneticists have modified the genetic makeup of crops to make them more productive.

23.3 The Future of Agriculture A. Farming methods in common use today (e.g., monoculture, reliance on pesticides) require a tremendous input of natural resources, such as water and oil, and damage soil. (Figure 23.27) B. The heavy use of pesticides results in increasing concentrations of pesticides in the food chain and contamination of water supplies. (Figure 23.28) C. Sustainable agriculture involves different cultural techniques and less reliance on toxic pesticides and inorganic fertilizers. (Table 23.3)

Lecture Activity 23.1: Plant Tissue/Cell Types and Functions Estimated Time to Complete: 20–25 minutes (this includes prep time) Introduction: Plants are composed of three tissue types: epidermal, vascular, and ground tissues. The epidermis protects underlying tissues within the plant’s body, the vascular tissue provides transport, and the ground tissue in between the other two types of tissues serves as storage or metabolic function.

Part I of this activity demonstrates vascular function, illustrating that vascular tissue alone is responsible for liquid transport. Part II demonstrates that starch storage in roots and seeds is limited to the ground tissue and does not occur in the epidermis or the vascular tissue. This activity works best in a lab setting.

Materials Part I • Stem with easily visible vascular tissue—celery, carnation, daisy, chrysanthemum • Single-edged razor blade • 150-mL beaker or similar container • 5% eosin stain (or any water-soluble stain) • Glass slides or petri dishes • Dissecting microscope, document camera with zoom, or overhead projector Part II • Root, tuber, and/or seeds that function in starch storage—radish, Irish potato, rice (rice soaked overnight to allow softening) • Single-edged razor blade • Iodine stain • Lecture Activity 23.1 Handout: Plant Tissue/Cell Types and Functions .

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Procedures Part I 1. Cut or recut the stem under water to avoid a vascular embolism. Place the freshly cut stem in a glass or beaker filled to 2–3 inches deep with water-soluble stain.

2. Allow the stain to be drawn up in the vascular tissues of the stem. This process will take a few minutes and will be readily visible. Remove the stem from the stain and cut it slightly above the region where the stain is visible on the outside of the stem.

3. Make a few thin cross sections of stem in this region to observe the vertical transport of the stain.

Place the cross sections on a slide or petri dish, and then display them on a dissecting scope, document camera with zoom capability, or overhead projector. Even though the stain is not visible from the outside of the stem, students will be able to see that the stain is present within the stem and is limited to the veins.

4. Take a few cross sections from the stem below the area cut previously. This stem will look visibly stained from the outside, indicating that the stain has been transported laterally to tissues surrounding the veins.

Part II 1. Slice the storage structures and allow the students to observe the unstained sample. Explain that the iodine stain will turn dark purple/black when it encounters starch. Ask students to predict which areas of the sample will turn black (i.e., which areas contain starch; the ground tissues and not the epidermis or vascular tissue).

2. Apply a few drops of the stain and observe.

3. Pass out the handouts and have students answer the questions. Students can answer the handout questions on their own or in groups.

Assessment Suggestion: Collect and grade the handouts.

Handout Answer Key 1. Which tissue type transports liquids? Vascular tissue.

2. Is the transport vertical, lateral, or both? Explain. Both; it is initially vertical, upward through the xylem, but eventually becomes lateral, as liquids move out of the xylem and into nearby phloem and other cells.

3. Did the stain indicate starch in the expected tissues? Presumably so.

4. What is the function of starch storage for plants? In starch, plants store excess products of photosynthesis that they can access and use later on, during darkness, winter, in nonphotosynthetic organs, or in general whenever photosynthetic production does not keep pace with respiratory demand.

5. How do we use these structures? Starch-storing plant organs are major suppliers of nutrients to animals, including humans and our meat- and milk-producing livestock.

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Lecture Activity 23.1 Handout: Plant Tissue/Cell Types and Functions 1. Which tissue type transports liquids?

2. Is the transport vertical, lateral, or both? Explain.

3. Did the stain indicate starch in the expected tissues?

4. What is the function of starch storage for plants?

5. How do we use these structures?

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Lecture Activity 23.2: Is It the Seed That Grows? Hey, There’s a Baby Plant in There!

Estimated Time to Complete: 5 minutes of preparation time the day before; 10 minutes of class time Introduction: Most commonly, we say that seeds grow. But which part of the seed is actually the new plant? By looking inside a large, mature seed, we can see the embryo that will grow and become the seedling when the seed germinates.

This activity can be done as a demonstration by the instructor and shown to the class, or it can be done by each student or student group independently.

Materials • Large dried lima beans (available from a grocery store) • Plastic petri dishes, either one for the instructor’s demonstration or one for each student or group • Document camera with zoom or dissecting microscope, if this activity is to be done as a demonstration, or enough seeds for each student or group to have a few, if students are doing it at their desks • Methylene blue (or food coloring) to accentuate the veins of the embryonic leaves • Lecture Activity 23.2 Handout: Is It the Seed That Grows? Hey, There’s a Baby Plant in There!

Procedures 1. Before class, soak the bean seeds for about 18 hours in enough water to cover the beans by 3–4 inches.

2. Pass out soaked beans in petri dishes to each student or student group, if desired.

3. To begin the demonstration, remove the paper-thin seed coat from the softened seed. If using, show results on the camera or microscope.

4. Split the seed lengthwise with your fingernail, and open it gently. The embryo will adhere to one of the cotyledons. Notice the locations of the root, hypocotyl, and embryonic leaves. The entire plant is present in this embryo within the seed.

5. Put a drop of stain or food coloring onto the embryo to accentuate the veins of the embryonic leaves.

6. Have students sketch the embryo, labeling its parts, and answer the handout questions in their groups.

Assessment Suggestions: Have students turn in their answers to the handout questions or, alternatively, have a group discussion.

Handout Answer Key 1. Which part of the seed will actually emerge and grow into the seedling? The embryo.

2. Why are the embryonic leaves of the seed white instead of green? They haven’t been exposed to light yet. Light is needed for development of chloroplasts.

3. Why do you think that the embryonic root does not have any root hairs yet? The root hairs develop in the region of maturation, which hasn’t developed yet. If root hairs were present in the embryonic root, they would be damaged as the root emerged and pushed between soil particles.

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Lecture Activity 23.2 Handout: Is It the Seed That Grows? Hey, There’s a Baby Plant in There!

1. Which part of the seed will actually emerge and grow into the seedling?

2. Why are the embryonic leaves of the seed white instead of green?

3. Why do you think that the embryonic root does not have any root hairs yet?

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Lecture Activity 23.3: Secondary Growth Estimated Time to Complete: 10–15 minutes Introduction: Secondary growth provides increased strength in stems, storage of waste materials, and transport for the plant. Darker areas of small-celled, thick-walled secondary xylem growth occur during the summer when the xylem cells have less water available and expand less. In contrast, cells have much more water available in the spring and expand more; this provides a lighter-colored appearance. Annual rings are visible from this contrast between the dark summerwood of the previous year and the adjacent spring growth of the next year. We can estimate the age of secondary growth by counting the annual rings. There is also a relationship between the width of the rings and the rainfall; that is, years with more rainfall have wider spring-wood.

Materials • Cross-section slices from young trees that have a variation in the growth rings, or photos of these cross sections • A projector to display growth ring photos or copies of the photos for the students • Lecture Activity 23.3 Handout: Secondary Growth Procedures 1. Pass out the handout. Have groups of students count the growth rings on the cross sections or pictures and reach a consensus about the age of the tree. (Check the projection visibility in the classroom before this exercise to be sure the students can see the rings.)

2. Have students note any rings that are noticeably narrower or wider than the others.

Assessment Suggestions: Have students answer the handout questions as a group or as a separate written or online assignment.

Handout Answer Key 1. Approximately how old was the tree? Answers will vary.

2. How many dry (approximately half the width of the average year annual ring) years occurred during the lifetime of the tree? Answers will vary.

3. Do you expect trees that grow in a tropical rain forest to have growth rings? What about trees in tropical seasonal forests (forests that have a rainy season and a dry season)? A tree from a nonseasonal tropical rain forest would not show any rings. A tree from a tropical forest in which a dry season alternated with a wet season would be likely to show rings. In some areas, there is more than one wet season per year, and in those trees the number of rings would not be equal to the age of the tree.

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Lecture Activity 23.3 Handout: Secondary Growth 1. Approximately how old was the tree?

2. How many dry (approximately half the width of the average year annual ring) years occurred during the lifetime of the tree?

3. Do you expect trees that grow in a tropical rain forest to have growth rings? What about trees in tropical seasonal forests (forests that have a rainy season and a dry season)?

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24 Growing a Green Thumb Plant Physiology OBJECTIVES Teaching Goals Depending on the background of your students, it may be difficult to interest them in this chapter.

By creating scenarios familiar to them, you can focus their attention by explaining why one plant is successful in an area and another is not. The concept of “managing” a plant for fruit and flower production is probably foreign to them. Your goal is to combine the biology of managing plant growth with achieving desired results, whether it is increased productivity for a farmer or more blooms for the home gardener.

Student Goals By the end of this chapter, students should be able to accomplish the following learning objectives: • Describe how water moves up a plant stem.

• List the modifications of plant physiology and anatomy that reduce water loss or make plants more drought tolerant.

• Describe the pressure flow mechanism of phloem transport.

• Define photoperiodism, and explain the mechanism by which plants respond to day length.

• List the environmental factors that cause tropism in plants, and describe how differences in cell expansion lead to directional growth.

• Define plant hormone, and describe a number of ways in which one hormone, auxin, affects plant growth.

LECTURE OUTLINE 24.1 The Right Plant for the Place: Water Relations A. Through transpiration, plants lose water through their leaves in the form of water vapor. (Figure 24.1) B. Transpiration is reduced in some plants through either modifications to photosynthesis (C4 and CAM plants) or changes in leaf structure.

Lecture Activity 24.1 C. Plant productivity is decreased by lack of water, but overwatering can also kill a plant. (Figure 24.6) D. Many plants are affected adversely by freezing temperatures, as ice may form inside the plant cell (damages membranes) or on the leaves (interferes with osmotic flow).

(Figure 24.7)

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24.2 A Beautiful Garden: Sap Translocation, Photoperiodism, and Flower and Fruit Production A. Sugar produced in a plant is distributed throughout the plant through translocation.

(Figure 24.9) B. Through pruning and timing of water and fertilizer application, the gardener can affect the quality and quantity of flower and fruit production. (Figure 24.11) C. Plants can be categorized according to their response to the ratio of daylight to dark hours, as this response reflects their concentration of phytochrome. (Figure 24.12, Figure 24.13) 24.3 Pleasing Forms: Tropisms and Hormones A. Plants grow directionally in response to different factors such as gravity, touch, and light.

(Figure 24.15) Lecture Activity 24.2 Lecture Activity 24.3 B. Varying hormone production in plants is a technique that may be used to regulate growth responses. (Figure 24.16, Table 24.1)

Lecture Activity 24.1: Environmental Control of Stomata Estimated Time to Complete: 20 minutes Introduction: Stomata are pores in leaves and herbaceous stems that open and close to regulate CO2 and water content within the plant. Pores are opened and closed by the guard cells that surround them. Guard cells swell with the uptake of water by osmosis, opening the pores. Guard cells contract with water loss, closing the pores. This process of osmosis is controlled by changes in potassium concentrations in the guard cells. Movement of potassium into and out of guard cells is stimulated by several environmental factors, including daylight. In daylight, potassium levels increase, resulting in a lower water concentration within the stomata. Water responds by entering the guard cells by osmosis and causes the stomata to open.

This activity demonstrates the differences in epidermal peels of leaves that are exposed to daylight versus those that are kept in the dark.

Materials • Epidermal peels (from Zebrina or any plant with a thick epidermis) of leaves taken from plants that were exposed to daylight for at least 1 hour and from leaves that were covered with aluminum foil or left in the dark for several hours • Glass slides and cover slips • Water • Dissecting microscope or document camera with zoom • Lecture Activity 24.1 Handout: Environmental Control of Stomata Procedures 1. Make the epidermal peel by snapping the leaf in half and drawing one edge across the other to peel back the epidermis. It will look like an uneven tear.

2. Place the leaf half with visible epidermis on a glass slide with several drops of water, and put a cover slip on top. Stomata are easily visible in the green sectors of Zebrina leaves.

3. Use a dissecting microscope or a document camera with zoom to compare the epidermal peel from plants exposed to light to those kept in the dark.

Assessment Suggestions: Have a group discussion or have students turn in written answers to the handout questions.

This could be done as an online assignment or as a discussion forum.

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Handout Answer Key 1. Why do most plants close their stomata in the dark? There is no reason for the stomata to remain open, losing water, when the plant can’t use carbon dioxide for photosynthesis.

2. Why might stomata close during the day? To prevent excess water loss under drought conditions.

3. Why do some people think that increasing the carbon dioxide concentration in the atmosphere will alleviate some drought problems? Under higher carbon dioxide conditions, stomata can close more to conserve water without affecting the plant’s ability to photosynthesize.

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Lecture Activity 24.1 Handout: Environmental Control of Stomata 1. Why do most plants close their stomata in the dark?

2. Why might stomata close during the day?

3. Why do some people think that increasing the carbon dioxide concentration in the atmosphere will alleviate some drought problems?

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Lecture Activity 24.2: Gravitropism in Shoots Estimated Time to Complete: 45–75 minutes. A 5- to 10-minute introduction is required, followed by a minute or so of measurements every 10–15 minutes for the rest of the period. If there is not adequate time during class, start the process before class begins. A 5-minute discussion period at the end of the class is nice if you have enough time.

Introduction: The saying goes, “As the tree is bent, so it grows.” This is true if the physical pressure is continuous. But if the young sapling is bent (for example, by another tree falling over the supple trunk) and the top of the tree is not damaged, growth at the tip of the tree will turn toward the sky. In other words, the tree will not continue to grow parallel to the ground. Many of us have seen an unusual tree with an extreme angle in the trunk. Although trees in this situation are responding to both light and gravity, this classroom demonstration allows students to visualize the effect of gravity alone on stems.

Materials • Four 3- to 4-week-old bean plants (preferably in square pots that will not roll) • Ruler • Cardboard box, large enough to cover two of the plants lying on their sides • Lecture Activity 24.2 Handout: Gravitropism in Shoots Procedures 1. At the beginning of class (or before, if there will not be time for the response to occur during class), place two of the pots on their sides and measure how many millimeters the apical meristems are from the tabletop. Record the distances in a chart on the board or on an overhead slide. Then place the box over the plants so no light reaches them.

2. Do the same thing with the other two plants, but don’t place a box over them. This allows a comparison between gravitropism and any movement due to light. Add their initial measurements to the chart.

3. Ask the students to predict what will happen (question 1 on the handout).

4. Every 10 to 15 minutes during the class period, measure the distance between the tabletop and the apical meristems, and record the data on the chart.

5. If possible, leave the plants undisturbed for a few days. Their bending will then be very striking. The plants can then be placed upright and will form another bend upward.

Assessment Suggestions: Follow up with questions 2–4 on the handout. Students can answer the questions on their own or in groups in the classroom or online. This would be a good activity to have students do a lab report.

Handout Answer Key 1. Write your prediction for what will happen with the plants. a. Plants with boxes over them: Answers will vary. b. Plants without boxes over them: Answers will vary.

2. Did the expected outcomes occur? Answers will vary based on students’ predictions.

3. How does the plant control growth to achieve bending? Through plant hormones such as auxin.

4. Was there a difference between the plants that were placed in the dark and those that were placed in the light? Why? Phototropic movements may enhance or interfere with the gravitropic movements, depending on the strength and orientation of light in the room.

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Lecture Activity 24.2 Handout: Gravitropism in Shoots 1. Write your prediction for what will happen with the plants. a. Plants in the dark:

b. Plants in the light:

2. Did the expected outcomes occur?

3. How does the plant control growth to achieve bending?

4. Was there a difference between the plants that were placed in the dark and those that were placed in the light? Why?

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Lecture Activity 24.3: Is It Possible to Plant a Seed Upside Down?

Estimated Time to Complete: 10 minutes to set up, 3–4 days to see the results, and 5–10 minutes in a later period for a group or class discussion Introduction: Often, novice gardeners think that seeds that don’t grow may have been placed or settled into the ground upside down—that is, with shoots emerging from the seed facing away from the soil surface. Actually, seeds that don’t produce seedlings were most likely inviable or were planted too deeply. The emerging shoots and roots are affected in opposite ways by the same hormone, auxin. In response to gravity, auxin accumulates on the lower side (side closest to the pull of gravity) of the embryonic shoot and root. The shoot responds to the auxin by cells elongating. The root senses gravity in the root cap and responds in the opposite way, and cell elongation on the underside of the root is inhibited, causing it to bend down into the soil.

This activity can be done either by the instructor as a demonstration or by handing out materials to students or student groups and allowing them to set up their own experiments.

Materials • Cheesecloth or soft paper towels • Seeds of various types. Corn, wheat, rye, and beans are examples that work well. Use seeds that have distinct shapes that allow easy distinction of different orientations.

• Foil • Lecture Activity 24.3 Handout: Is It Possible to Plant a Seed Upside Down?

Procedures 1. Dampen the cheesecloth or paper towel completely.

2. Arrange seeds in different orientations, snaring them in the cloth or paper to prevent them from dropping out. Lay another damp cloth over them and enclose the seed “sandwich” in foil, pressing it tightly closed.

3. Place the seed sandwich upright (not flat) by leaning it against a wall or on a bookshelf. Allow seeds to germinate for 3–4 days.

4. After 3–4 days, carefully open the foil packets (don’t lose track of which side was up) and examine the germinating seeds inside.

5. Have students draw the orientation of each seed and show how the embryonic roots and shoots became elongated. Go through the assessment questions that follow.

6. If there is time, use a razor blade to cut off just the tip of some of the roots (the root cap), and mark the location with ink on the cheesecloth. Replace everything in the foil and turn the packet 90°. Allow it to sit that way for two more days, and check the orientation of the cut roots versus the uncut roots.

Ask the students what caused the difference and why. (The root cap is the part of the root that senses gravity; when it is removed, the root can’t tell up from down.)

Assessment Suggestions: Ask the handout questions for either group or class discussion; answers can be given orally or handed in as a written assignment.

This could be done as online discussion or assignment.

Handout Answer Key 1. Did the roots always grow down and shoots always grow up? Yes. 2. What was the hormone involved? Auxin.

3. Why is planting a seed too deep much more likely to reduce germination than planting a seed upside down? The roots and shoots can orient themselves correctly if planted upside down. If they are planted too deeply, however, the shoot may not have enough energy reserves to make it out of the soil.

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Lecture Activity 24.3 Handout: Is It Possible to Plant a Seed Upside Down?

1. Did the roots always grow down and shoots always grow up?

2. What was the hormone involved?

3. Why is planting a seed too deep much more likely to reduce germination than planting a seed upside down?

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Lecture Activity 24.4: Case Study: A Chemical Cry for Help Estimated Time to Complete: 20 minutes Introduction: Although it may not seem possible, plants can actually communicate with animals and with one another. Plants don’t have much to talk about, but one thing they are interested in is danger.

Plants have evolved methods to summon animals that can help them when they are under attack, and to warn nearby plants that danger may be coming.

This case study describes the tomato/hornworm/braconid wasp system. For photos, search the Internet for “The Tomato Hornworm: A Parasitic Host.”

After reading the case study (part of the handout), students are challenged to design an experiment to see whether tomato plants under attack by hornworms can summon help from braconid wasps that parasitize the hornworms.

Materials • Lecture Activity 24.4 Handout: Case Study: A Chemical Cry for Help • Additional sheets of paper for students to write their experiment • Computer with Internet access and projector, if desired Procedures 1. Briefly describe the case study; show pictures from the Internet, if desired.

2. Hand out the case study, and announce that students have 15 minutes to complete it.

3. Circulate during this time to answer questions and keep groups on task.

4. Ask some groups to read their answers to stimulate a group discussion at the end of the exercise if there is enough time.

Assessment Suggestion: Collect handouts and grade written answers.

This could be done as an online assignment.

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Lecture Activity 24.4 Handout: Case Study: A Chemical Cry for Help The tomato plants in your garden are under attack; some stems are stripped of their leaves, and many remaining leaves seem to have large bites taken out of them. Peering closely at the damage, you are startled to see a green caterpillar, as large as your index finger, voraciously munching away. The tomato plant seems helpless against the tomato hornworm (the caterpillar stage of the sphinx moth).

In fact, the 100-million-year war between plants and their parasites and animal predators has led to the evolution of sophisticated plant defenses that surprise people who are accustomed to thinking of most plants as passive, helpless organisms. Researchers studying how plants respond to attack by predators or disease-causing viruses have recently discovered that plants under attack help protect themselves (and even neighboring plants) by releasing volatile chemicals into the air around them.

Tomato hornworms, as they prey on plants, are themselves prey for some insects. If you look carefully at enough tomato hornworms, you may spot one with small white cylinders adhering to its skin.

These are the cocoons of a parasitic wasp. The wasp finds a caterpillar and injects eggs into its body. The eggs hatch and develop into larvae that feed inside the caterpillar and then burrow out through its skin.

Here, they attach and form cocoons, within which they metamorphose into small wasps. How does the wasp find the caterpillar? Is the plant really a passive victim?

A Chemical Cry for Help Recently, researchers have discovered that when attacked, some plants release a “chemical cry for help.”

Working with maize (a relative of corn), researchers have identified a sophisticated form of communication between plants and animals: The maize plant calls in a predator to attack a caterpillar that is munching on it.

The plant responds to the caterpillar’s attack by releasing a mixture of volatile chemicals, which attract a parasitic wasp that lays its eggs in the body of the caterpillar. This “biological time bomb” kills the caterpillar as the larvae hatch and consume their host from the inside out. Scientists have discovered that merely tearing the leaves, as a caterpillar does, will not elicit the chemical alarm signal; the attack on the plant had to come from an actual caterpillar. Recently, the reason for this relationship was discovered: A chemical called volicitin in caterpillar saliva is required to cause the response.

Plants also can defend themselves against diseases. Many plants produce salicylic acid, the compound from which aspirin is derived. Ilya Raskin and colleagues at Rutgers University found that tobacco plants infected with a plant virus produce large quantities of salicylic acid. The salicylic acid activates an immune response in the plants, helping them fight off the viral attack. The plant also converts some of the salicylic acid to methyl salicylate (the substance used to flavor “wintergreen” candy). This highly volatile compound diffuses into the air from virus-infected plant tissues and is absorbed by other plants nearby. The healthy neighbors reconvert the methyl salicylate to salicylic acid, thereby enhancing their own immune defenses and making them better able to resist the viral infection. These findings suggest that future farmers may treat their plants with aspirin or similar substances instead of toxic pesticides to protect them against diseases and plant predators. As Ilya Raskin explains, “Plants can’t run away and they can’t make . . . noises. But they are wonderful chemists.”

Is your tomato plant releasing a cry for help? Assume you work in a lab with a well-equipped greenhouse, healthy tomato plants, tomato hornworms by the dozen, and a supply of the parasitic wasps that attack tomato hornworms. Design a controlled study that will support or refute the hypothesis that tomato plants, like maize, can summon the wasps when attacked by a hornworm. Be sure to control for other types of attack. Describe your study on additional sheets of paper.

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