Campbell Essential Biology, 5E Eric J. Simon Instructor Manual.pdf (22)

21. Cytotoxic T cells synthesize and discharge a. proteins such as perforin, which makes holes in the infected cell’s plasma membrane, and b. other proteins that trigger a process that results in the death of the infected cell by lysis (bursting).

IV. Immune Disorders 1. If the interplay of immune cells goes awry, problems can arise that range from mild irritations to deadly diseases A. Allergies 1. Allergies are exaggerated sensitivities to harmless antigens in the environment 2. Allergens are antigens that cause allergies 3. The symptoms of an allergy result from a two-stage reaction 4. Anaphylactic shock a. is an especially dangerous type of allergic reaction and b. can be counteracted with injections of the hormone epinephrine.

B. Autoimmune Diseases 1. The immune system a. normally reacts only against foreign (nonself) substances but b. may attack i. our own tissues and ii. tissues transplanted into our bodies.

2. When the immune system improperly turns against the body's own molecules, it can lead to seriousautoimmune diseases such as a. lupus, b. insulin-dependent diabetes, c. multiple sclerosis, and d. rheumatoid arthritis.

C. Immunodeficiency Diseases 1.Immunodeficiency diseases a. result when one or more of the components of the immune system are lacking and b. leave affected people more susceptible to infections.

2. Immunodeficiencies may arise a. through inborn conditions such as severe combined immunodeficiency (SCID), b. from acquired illness such as Hodgkin’s disease, a type of cancer, or c. from radiation or drug therapies used against many cancers.

D. AIDS 1. AIDS (acquired immunodeficiency syndrome) a. has killed more than 30 million people worldwide and b. infects millions of new people each year.

2. HIV, the virus that causes AIDS, a. currently infects more than 33 million people worldwide, b. attacks helper T cells, and c. severely impairs humoral and cell-mediated immunity.

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3. Lives can be saved by a. reducing promiscuity and b properly using condoms. .

E. Evolution Connection: HIV Evolution 1. HIV has one of the fastest rates of mutation of any pathogen ever studied 2. The evolution of drug-resistant HIV strains is the main obstacle to eradicating AIDS 3. Drug-resistant HIV strains a. are now being documented in newly infected patients and b. exhibit how the virus readily adapts through natural selection.

Chapter Guide to Teaching Resources Innate Defenses Student Misconceptions and Concerns 1. Depending on their backgrounds, students may not be aware of the lymphatic system.

A quick review of its general structure and the movements and functions of lymph might be a helpful part of an introduction.

2. The concepts of innate and adaptive defenses are sometimes difficult distinctions to students Clothing new to the subject. Some analogies, such as the following, might help. can be considered a general defense against physical harm, excessive sunlight, and some minor chemical damage. Firefighters and their equipment often function like an adaptive

Teaching Tipsresponding after a problem has arisen in an attempt to limit damage. defense,

1. The inflammatory response is a good topic to hook students into this chapter on immunology. The inflammatory response is a reaction that is immediately apparent, with characteristics that can cause alarm. Students are typically more interested in subjects that have obvious relevance and that address threats to their health.

2. During a medical examination, a physician might feel for tenderness in the throat and axillary (armpit) regions. Students are unlikely to appreciate the significance of this part of the exam. Such relevancy can add meaning to your class discussions and generate additional interest in the subject.

3. In an interesting article on the effectiveness of common hygiene methods, “Hygiene of the Skin: When Is Clean Too Clean?” Elaine Larson reviews the relationship between skin hygiene and infection. It can be found at the CDC website at www.cdc.gov/ncidod/eid/vol7no2/larson.htm.

Students might be interested in learning that interferons are now mass-produced using 4. recombinant DNA technology. Clinical studies are under way to explore their use in treating viral infections and cancer.

5. Excessive iron in the human body can promote bacterial infections and other diseases.

Searching the keywords “iron supplements bacteria” on the CDC website www.cdc.gov/ leads to many articles on this subject.

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Adaptive Defenses Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.)

Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions.

Teaching Tips 1. Current research is investigating ways to use recombinant DNA technology to make genetic modifications to plants to produce vaccines. A Google search of “plant edible vaccine” reveals many research articles on this subject. If you do not know about Google’s search engine dedicated to research sites, called Google Scholar, consider adding it to your options at http://scholar.google.com/.

2. The authors suggest that the specific nature of the binding between an antigen and an antibody is like the relationship between a lock and a key. You might further this analogy by noting that the tremendous diversity of antibodies is like having a set of keys for virtually every possible type of lock.

3. Monoclonal antibodies are widely used in research for tagging specific molecules. Some cancers are treated with tumor-specific antibodies coupled with toxins to attack and destroy tumor cells.

4. Our own learning experiences provide an analogy to the greater swiftness and intensity of a secondary immune response. When first presented with a problem, we may struggle to determine how best to respond. However, with that first experience behind us, we expect to respond more quickly and effectively when we meet that challenge again. Although in each circumstance we benefit from a certain type of memory (experiential in one case, chemical in the other), their mechanisms are quite different. Consider noting these similarities and differences in your class discussion of primary and secondary immune responses.

Consider challenging your class to explain the adaptive advantages of the Y shape of an antibody. Why, instead, is an antibody not just a single heavy chain and light chain?

(Many biologists think that the Y shape permits the binding together of two antigens or antigen-presenting surfaces, permitting a chain reaction or form of clumping.)

Your students might enjoy developing some sort of fight analogy to the attack by a 6. cytotoxic T cell. The two cells “in battle” become interlocked, the infected cell develops “puncture wounds,” and a fatal poison is absorbed into these “wounds.”

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The recognition by a helper T cell of a self protein and a foreign antigen in combination is like the two-key system used by banks to access safe-deposit boxes.

The Centers for Disease Control and Prevention has extensive information about AIDS 8. and other public health threats at www.cdc.gov/hiv.

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Immune Disorders Student Misconceptions and Concerns 1. Student interest in diseases and allergies can be useful motivation for this final chapter section. However, interest in a medical subject without the necessary background to understand advice often leads to confusion. Consider “probing” for misunderstandings about allergies by asking students about allergy causes and treatments before discussing this final portion of the chapter. Because personal medical information is private, consider an anonymous survey of your students to learn who suffers from allergies, what are the allergens, and how they are treated.

2. Students may have a feeling that anything “natural” is somehow good. In addition to the many natural poisons found in animals and plants, our allergic responses to pollen, molds, and other environmental allergens reminds us that “natural” is not always healthy.

3. Students often do not understand the disproportionate distribution of HIV infections and AIDS in our world. Consider an Internet assignment, asking students to identify the regions of the world most affected by HIV and AIDS. 4. Despite efforts to educate the general public, many misconceptions about AIDS persist.

A list of 18 common misconceptions can be found at the website www.gng.org/currents/teachers/hiv101/misconceptions.html.

Teaching Tips 1. Allergic contact dermatitis occurs when an allergen triggers an immune response on the skin. A rash from exposure to poison ivy is an example.

2. Antihistamines are drugs that interfere with the action of histamine. They provide temporary relief from the symptoms of allergic reactions. Consider asking students if taking antihistamines when suffering from poison ivy might help.

3 The quickly evolving HIV virus is like an enemy that keeps changing uniforms. . Although the triggers of autoimmune diseases are not well understood, it does appear that 4 autoimmune diseases are not communicable, and cannot be caught through exposure to others with the disease. Family histories of autoimmune diseases do suggest some degree . of heritability, at least of predisposition. Thus, some family members may share degrees of a common autoimmune disease.

5. Students may enter your course knowing that the best types of tissue transplants are from a closely matched donor. However, what does it mean to have a tissue “match”? Few students can explain the specific reasons behind the need for tissue matching, or how such matching is done. Challenge your students to explain why we try to ensure a match between the tissues of a donor and a recipient. By posing such general questions, instructors can raise interest in the specific details of the answers.

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Key Terms adaptive defenses complement proteins allergens cytotoxic T cells allergies effector cells antibody helper T cells antigen autoimmune diseases histamine humoral immune B cells cell-mediated immune response immune system response immunodeficiency clonal selection diseases

Word Roots

inflammatory response phagocytic cells innate defenses primary immune interferons response lymph secondary immune lymph nodes response lymphatic system T cells lymphocytes vaccination memory cells vaccine natural killer (NK) cells pathogens

anti = against; gen = produce (antigen: a foreign macromolecule that does not belong to the host organism and that elicits an immune response) auto = self (autoimmune diseases: when the immune system turns against the body’s own molecules) cyto = cell; toxic = poison (cytotoxic T cells: T cells that kill other cells) humor = fluid (humoral immune response: the immunity conferred by B cells, which secrete antibodies into blood) immuno = safe (immune system: the system that protects the body by recognizing and attacking pathogens and cancer cells) lymph = fluid (lymph: a fluid, similar to interstitial fluid) mono = one (monoclonal antibodies: the antibodies produced by a single clone of cells) patho = disease; gen = produce (pathogen: disease-causing viruses and microorganisms)

Relevant Songs to Play in Class “Disease,” Matchbox Twenty “The Boy in the Bubble,” Paul Simon “The HIV Song,” Ween “Catch My Disease,” Ben Lee

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: Before you start any tests, you might look for cases in which the selfnonself hypothesis does not explain observed phenomena or cases that have been interpreted as exceptions to the self-nonself concept. Why might this be a useful approach? Promoters of the “damage” hypothesis argue that immune system failures, such as autoimmune diseases, indicate that the self-nonself hypothesis is flawed. Why do you suppose they make this argument? One case being studied in detail is the immune system in newborn mammals. According to the self-nonself hypothesis, a newborn’s immune system is incapable of recognizing foreign antigens, and this ability develops during a critical period soon after birth. (You could read about this in a more advanced general biology textbook or an immunology book.) However, new evidence suggests that the neonatal immune system can respond to at least some foreign antigens. Does this evidence 358

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support the damage hypothesis? How so? To test the damage hypothesis, you might try to identify specific danger signals that trigger immune responses. Several research groups are currently focusing on such signals. A possible question is: Could damaged tissue cells signal the antigen-presenting cells (APCs) of the immune system, making the APCs in turn cause changes in T cells? Perhaps the signal is a protein that leaks from a damaged cell.

On the other hand, perhaps it is simply the loss of physical contact of an APC with a tissue cell that dies suddenly. Can you think of other possibilities? The idea that a body defense system would evolve in response to actual danger—that is, a threat to survival and the perpetuation of genes—is consistent with evolutionary theory. Natural selection would tend to favor those individuals with such a defense system and not favor individuals lacking such a system. Why would natural selection favor individuals whose body defense system distinguishes self from nonself? Could the ability to distinguish self from nonself molecules increase evolutionary fitness?

12.

Suggested answer: The primary response to antigens X and Y have the same general shape. In the secondary immune response to antigen X, the activated memory cells multiply quickly, producing a large new clone of lymphocytes, which in turn can produce larger amounts of antibodies.

Biology and Society 13. Some issues and questions to consider: There is no correct answer to this question.

Possible directions include the idea that if the donor felt strongly about the process, that a person’s wishes should be respected. The opposite position would be that the next of kin should be able to approve or deny the procedure. Other possible considerations would be appropriate, including positions based on religious beliefs or other strongly held values.

Are doctors less likely to try as hard to save a person if he or she is a donor? (This was actually an investigation on the TV show 60 Minutes.)

Additional Critical Thinking Questions The Process of Science 1. Mr. Smith was admitted to the emergency room after stepping on a sharp garden rake. The physician recommended that he receive immunization against tetanus. Upon questioning, it was learned that Mr. Smith had never been vaccinated against tetanus as a child. Based on this information, the physician gave him passive immunization: antibodies against the tetanus toxin. Explain why this was the preferred treatment at this time rather than the tetanus vaccine.

Suggested answer: Because Mr. Smith had never been immunized against tetanus toxin, he had never formed memory cells. This means that he had never mounted a primary immune response. Therefore, if he were only given the vaccine at this time, he would not produce antibodies quickly enough to protect him right away from the tetanus toxin. As a result, he might not have adequate protection. Passive immunity, although temporary, provides an immediate source of antibodies.

2. When you have strep throat (a sore throat caused by Streptococcus bacteria), the lymph nodes in your neck often enlarge. Does this have a purpose? Explain.

Suggested answer: Lymph nodes contain lymphocytes and macrophages. Lymph circulating through the lymph nodes may contain bacteria picked up at the infection site.

The macrophages ingest and destroy the bacteria while the lymphocytes are starting to mount an immune response against these bacteria. As a result, the lymph nodes will respond by enlarging to meet this need. .

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Biology and Society 3. A group of parents in your community became very concerned about vaccine-associated complications. They were contemplating forming a group to protest mandatory childhood vaccination programs. They knew that you had just completed a biology course and asked you to join them at their next meeting and give your opinion. Discuss some of the issues that you would talk about.

Some issues and questions to consider: Although some vaccines can cause side effects and, rarely, severe complications, the risk of contracting the deadly diseases that they protect against, such as polio, whooping cough, and hepatitis B, is much greater than the chance of suffering a serious complication. Where could you get authoritative information on this issue? What are the risks to the child and the community if they do not receive vaccinations? If more people decline vaccinations, then the community is at risk because vaccinations do not confer 100% immunity.

4. Concern is increasing over the rising rate of HIV infection among teenagers. Schools in some large cities have instituted programs to make condoms available to students, along with counseling about safer sex. These plans have divided school boards and communities.

Some citizens and church groups are opposed to giving condoms to students because it might appear to encourage sexual activity. By contrast, many school and public health officials view the situation as a health issue rather than a moral issue. The heart of the controversy seems to be whether the schools should take such a direct role in this part of student life. What are the reasons for and against distribution of condoms? What do you think the school’s role should be?

Some issues and questions to consider: How important is it to protect students from AIDS? Is this a function of schools? Do schools serve similar purposes? Should parents or citizens and church groups—on either side of the issue—have a say in this, or is it a matter between the school and the student? Does the distribution of condoms condone or sanction sexual activity or promiscuity? Is a school legally liable if a school-issued condom fails to protect a student? Are there alternative measures, such as education, that might be as effective for slowing the spread of AIDS? Does separation of church and state indicate that churches shouldn’t have a say? Recent studies indicate the importance of sex education in reducing the spread of sexually transmitted diseases and rates of teen pregnancy. These same studies have also shown that abstinence-only programs and no sex education actually result in higher rates of teen pregnancy and sexually transmitted diseases. Based on this data, how do you feel about certain groups who want to oppose these measures?

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CHAPTER

25

Hormones

Why This Chapter Matters 1 The abuse of steroids by athletes is a significant problem in society. .

The endocrine system is the primary mechanism for internal chemical regulation of the body.

2

Hormones reach all parts of the body, controlling whole-body activities such as growth, metabolic rate, maturation, and reproduction.

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3 Diabetes mellitus is just one serious hormonal disease that affects about 8% of Americans. .

Chapter Objectives

Biology and Society: Sluggers and Steroids 1. Describe the doubts and concerns related to the recent major league baseball home run records.

Hormones: An Overview 2 Define an endocrine system, endocrine glands, a hormone, and target cells. .

3

Compare the ways that water-soluble and lipid-soluble hormones trigger changes in target cells.

The .Human Endocrine System 4. Describe the different types and functions of vertebrate endocrine glands and the hormones they produce.

5. Describe the functions of and interrelationships between the hypothalamus and the anterior and posterior pituitary glands. Compare the two types of hormones that the hypothalamus uses to control the anterior pituitary.

6. Describe the functions of follicle-stimulating hormone, luteinizing hormone, growth hormone, and endorphins.

7. Describe the functions of the thyroid gland. Describe the symptoms of hypothyroidism, hyperthyroidism, and a goiter.

8. Explain how the thyroid and parathyroid glands maintain calcium homeostasis.

9. Explain how insulin and glucagon manage blood glucose levels. Describe the frequency, causes, symptoms, and treatments of type 1 and type 2 diabetes.

Compare the functions of the hormones released by the adrenal medulla and the adrenal 10. cortex.

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Describe the benefits and risks of using glucocorticoid drugs to address pain and inflammation.

Describe the three major categories of sex hormones and explain their general functions.

Explain how the abuse of steroids may be related to violent mood swings.

Evolution Connection: Steroids and Male Aggression 14. Describe the effects of androgens in vertebrates. .

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Lecture Outline I. Biology and Society: Sluggers and Steroids 1. The 1998 major league home run records reflect another chapter in baseball’s shameful “steroids era.”

2. The abuse of anabolic steroids by athletes increases muscle mass and brings greater power to a batter’s swing

II. Hormones: An Overview 1. Hormones are produced by most plants and animals 2. Animal hormones a. are made and secreted mainly by endocrine glands, b. are usually carried by the circulatory system, and c. communicate regulatory messages to specific sites in the body.

3. The endocrine system a. consists of all hormone-secreting cells and b is the body’s main system for internal chemical regulation. .

4. Endocrine cells secrete into the bloodstream hormones that a. can affect many cells in many different body organs but b only affect target cells , cells that have receptors for that specific hormone. .

5. There are two general mechanisms by which hormones trigger changes in target cells: a. Water-soluble hormones trigger responses without ever entering their target cells. b Lipid-soluble hormones trigger responses after entering the target cell. .

III. The Human Endocrine System 1. The human endocrine system consists of about a dozen major glands that may have a. only endocrine functions or b endocrine and non-endocrine functions. .

2 The major endocrine glands in humans are spread about the human body . Hormones have a wide range of 3 a. target cells and . b effects. . Hypothalamus and Pituitary Gland A. The 1. The hypothalamus a. is part of the brain, b. is the main control center of the endocrine system, and c. receives information from nerves about i. the internal condition of the body and ii. the external environment.

2. The pituitary gland a. is a pea-sized structure that hangs below the hypothalamus, b. responds to signals from the hypothalamus, and c. secretes hormones that influence numerous body functions.

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3. The pituitary gland consists of two parts: a. The posterior pituitary i. is an extension of the hypothalamus, ii. stores hormones, and iii. secretes hormones made in the hypothalamus. b. The anterior pituitary i. synthesizes its own hormones, such as FSH and LH, and ii. secretes hormones directly into the blood.

4. The hypothalamus operates through the posterior pituitary to direct the activities of the kidneys a. The hypothalamus makes antidiuretic hormone (ADH) which is stored and released by the posterior pituitary. b. ADH helps kidney cells reabsorb water, preventing dehydration by decreasing urine volume.

5. The anterior lobe of the pituitary also secretes human growth hormone (HGH), which a. promotes development and enlargement of all parts of the body and b. can lead to i. dwarfism, if too little GH is produced, or ii. gigantism, if too much GH is produced.

6. Endorphins a. are produced by the anterior pituitary and b. act as natural painkillers.

B. The Thyroid and Parathyroid Glands 1. The thyroid gland a. is located in the neck just under the larynx and b. produces the hormones thyroxine and triiodothyronine, which increase i. oxygen consumption and ii. metabolic rate in all the cells of your body.

2. Hypothyroidism a. results from too little thyroid hormone in the blood and b. can result from i. dietary deficiencies of iodine or ii. a defective thyroid gland.

3. Hyperthyroidism (Graves disease) a. results from too much thyroid hormone in the blood and b. can lead to i. overheating, ii. profuse sweating, iii. high blood pressure, and iv. protruding eyeballs.

4. The parathyroid glands a. are four disk-shaped glands embedded within the thyroid and b. produceparathyroid hormone, which raises calcium levels in the blood. .

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5. Calcitonin a. isb. produced Calcitonin by theand thyroid parathyroid gland and hormone lowers calcium are levels in the blood.

6. antagonistic hormones, because they have opposite effects on calcium levels in the blood C. The Pancreas 1. The pancreas produces two antagonistic hormones that play important roles in managing the body’s energy supplies: a. insulin which reduces blood sugar levels and b. glucagon which increases blood sugar levels.

2.Diabetes mellitus is a serious hormonal disease in which body cells are unable to absorb glucose from the blood either because a. there is not enough insulin produced (type 1, or insulin-dependent diabetes) or b. the target cells do not respond normally to insulin (type 2, or non-insulin-dependent diabetes).

3. Diabetes affects about 8% of all Americans 4. More than 90% of those affected have type 2 diabetes, which is associated with being a. overweight and b. underactive.

5. People with diabetes use glucose meters to measure the amount of glucose in the blood D. The Adrenal Glands 1. The adrenal glands are paired structures resting atop each kidney 2. Each adrenal gland consists of two glands: a. the centraladrenal medulla and b. the outeradrenal cortex .

3. The adrenal medulla secretesepinephrine and norepinephrine, hormones that a. enable a rapid, short-term response to stress and b. produce the “fight-or-flight” response.

4. Stressful stimuli activate nerve cells in the hypothalamus that send signals to stimulate the adrenal medulla to secrete a. epinephrine and b. norepinephrine.

5. The adrenal cortex a. is also stimulated by the hypothalamus and b. secretes corticosteroid hormones (includingglucocorticoids) that provide a slower, longer-lasting response to stress.

E. The Gonads 1. The gonads secrete sex hormones that a. affect growth and development and b. regulate i. reproductive cycles and ii. sexual behavior.

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2. Males and females have the same three types of sex hormones: a. estrogens, b. progestins, and c. androgens.

3. Estrogens a. maintain the female reproductive system and b. promote the development of specific female features, such as breasts and wider hips.

4. Progestins, such as progesterone, are primarily involved in preparing the uterus to support a developing embryo 5. Androgens , mainly testosterone, stimulate the development and maintenance of the male reproductive system F. The Process of Science: Do ‘Roids Cause Rage?

1. Observation : Doctors observed an apparent link between abuse of anabolic steroids and violent mood swings 2. Question: Could scientists measure a relationship between steroids and mood in the lab?

3. Hypothesis: The administration of increasing doses of steroids to volunteers would produce measurable changes in behavior 4. Prediction: Scientists could document mood swings resulting from anabolic steroid injection 5. Experiment : Twenty male volunteers between the ages of 18 and 42 who had no history of drug abuse or psychiatric problems were given a. a placebo drug with no steroids for days 1–3, b. a low dose of steroids for days 4–6, c. a high dose of steroids for days 7–9, and then d. a placebo for days 10–12.

6. Results : The experiment revealed a significant increase in ratings for hostility, anger, and violent feelings during the high-dose period G. Evolution Connection: Steroids and Male Aggression 1. Testosterone and other androgens a. promote the development and maintenance of the human male reproductive system and b. play a similar role in all vertebrates.

2. In addition to determining the male sexual condition, in many vertebrates, androgens a. are responsible for male vocalizations and b. promote aggressive behavior.

3. The different roles for androgens among vertebrates illustrate two central aspects of life resulting from Darwinian evolution: a. the unity of life (a consistent effect on the development of the male gonads) and b. the diversity of life (the variety of secondary effects).

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Chapter Guide to Teaching Resources Hormones: An Overview Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies on a good understanding of cell membranes and basic cellular chemistry.

If these subjects have not been addressed previously or recently in your course, consider a brief refresher before distinguishing between these mechanisms.

2. Students might not appreciate the diverse ways to coordinate activities in our world.

Endocrine glands send out hormones in the body similar to the way that radio stations and satellites broadcast signals over the Earth. Only certain cells with the right receptors are affected by a specific hormone, just as only a radio tuned to a particular station’s frequency (like target cells) will receive a specific radio signal. The nervous system provides direct connections between the sender and receiver, much more like a land-based telephone call. These analogies might help establish the basic mechanisms of the endocrine system and avoid early confusion.

Teaching Tips 1. The nervous and endocrine systems coordinate and regulate most other systems of the body.

You might consider comparing the speed and duration of each system’s response. The nervous system generally responds faster but for shorter duration than the endocrine system.

2. Consider this analogy to compare the two mechanisms by which hormones trigger changes in target cells. Imagine that a house is like a cell. Ringing the doorbell and having someone answer it is like using a signal transduction pathway. Pushing the doorbell, like a hormone binding to plasma membrane receptors, causes an internal change. The second mechanism, using steroid hormones, is like walking up to the house, opening the door, and walking inside to speak to a friend. Here the signal (the person) passes through the surface and interacts deep within the home to directly communicate a message.

The Human Endocrine System Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate endocrine organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information.

2. A central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension.

Teaching Tips 1. Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat.

However, additional research is necessary to fully appreciate the benefits and potential risks of human growth hormone injections in the elderly.

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2. The abuse of growth hormones and steroids is of great concern in the world of professional and amateur sports. The following website of the National Institute of Health provides additional details at www.drugabuse.gov/ResearchReports/Steroids/AnabolicSteroids.html.

3.

Morphine and other opiates bind to the same cell receptors that naturally bind 4. endorphins, producing powerful pain-killing effects.

Students might not have carefully considered the benefits of pain. Consider 5. emphasizing the an adaptive nature of pain to your class. The authors note the risks of stopping pain in

6.

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injured part of the body. Given this, challenge students to next explain why endorphins might have evolved.

Hypothyroidism produces symptoms that are like turning down the temperature in a home during slower a cold winter. When thyroid levels are low, cells produce ATP and heat at a rate, and the person feels colder and is more lethargic than others in the same room.

This reminds students that aerobic respiration produces heat and ATP. Hyperthyroidism is just

8. the opposite, with an overproduction of heat as the consequence.

The use of calcitonin and parathyroid hormone to hold blood calcium levels steady is similar to the use of a furnace and air conditioner in a home to keep temperatures steady. The same analogy can be applied to the contrasting functions of insulin and glucagon.

9. Scientists are exploring the use of pancreatic cell transplants into patients with type 1 diabetes as a new source of insulin. Pancreatic cells may be derived from donors and/or modified from other cells using stem cell technology. One website devoted to this 10.

subject is http://diabetes.niddk.nih.gov/dm/pubs/pancreaticislet/.

11.

The effects of the “fight-or-flight” response will likely last many minutes after the initial events that triggered the response. Telling a person experiencing this response to calm down is unlikely to help. Instead, removing the person from the stimulus (if possible), engaging in mild exercise such as walking, and allowing many minutes of time will more likely reverse the condition.

Key Terms There seems to be no equivalent of menopause in males. Although men experience a adrenal steady cortex decline in diabetes mellitus gonads parathyroid glands testosterone production as they age, they can retain the ability to adrenal father glandsoffspring endocrine glands human growth parathyroid hormone through at least 80 years of age. adrenal medulla endocrine system hormone (HGH) (PTH) The North American Menopause Society is a scientific nonprofit organization that may androgens endorphins hormones pituitary gland antagonistic hormones epinephrine hypothalamus posterior pituitary be anteriorapituitary estrogens useful reference for related questions. insulin They can be reached at progestins www.menopause.org/. calcitonin glucagon norepinephrine target cell between the In humans, differences in the concentrations of sex hormones decrease corticosteroids glucocorticoids pancreas thyroid gland

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sexes in such as muscle367 tone CHAPTER 25 Hormones andlate adulthood. Differences in secondary sexual characteristics hair growth may diminish as a natural part of aging. Students with interests in geriatrics may enjoy assignments or extra credit to investigate this topic.

Word Roots andro = male; gen = produce (androgens: the principal male steroid hormones, such as testosterone, that stimulate the development and maintenance of the male reproductive system and secondary sex characteristics) endo = within (endorphins: the body’s natural painkillers) epi = above, over (epinephrine: a hormone produced as a response to stress; also called adrenaline) gluco = sweet (glucagon: a hormone that increases blood sugar levels) hyper = excessive (hyperthyroidism: the excessive production of thyroid hormones) hypo = below (hypothalamus: the master control center of the endocrine system, located just below the thalamus in the brain) mellit = honey (diabetes mellitus: a hormonal disease in which cells cannot obtain glucose from blood, resulting in high glucose levels in blood and urine) para = beside (parathyroid glands: important endocrine glands located next to the thyroid gland) pro = before; lact = milk (prolactin: a hormone produced by the anterior pituitary gland; it stimulates milk synthesis in mammals)

Relevant Song to Play in Class “Strong Enough,” Sheryl Crow

Answers to End-of-Chapter Questions The Process of Science

12. a. No. Blood sugar level goes too low. Diabetes would tend to make the blood sugar level go too high after a meal. b. No. Insulin is working, as seen by the homeostatic blood sugar response to feeding. c. Correct. Without glucagon, exercise and fasting lower blood sugar. The cells cannot mobilize any sugar reserves, and their blood sugar level drops. Insulin (which lowers blood sugar) has no effect. d. No. If this were true, blood sugar level would increase too much after a meal.

Biology and Society 13. Some issues and questions to consider: Why are parents concerned about their children’s height? Just because the hormone is available, does this mean that parents should request its use? What is the role of the physician in this situation? Would this kind of use be worth the risk? Is a child able to make an informed decision? How might the child feel in later years if the hormone has unintended side effects? In what ways would usage by an older adult be different? What are the pros and cons of adult use of HGH? At what age would it help the most or the least? Should athletes be allowed to use HGH if it can enhance their performance? How can people be prevented from misusing a legal drug? How are the distribution and use of these kinds of medications regulated?

14.Valid differences of opinion should be expected. Some students might say that parents need to be responsible for their children’s diet and exercise, but will acknowledge that this is more difficult today than it was 30 years ago. They might mention the elimination of physical education classes at school, the rise of fast-food restaurants, and that for many families, both parents work outside the home, making it more difficult to find time to cook 368

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nutritious meals and exercise. Other students might disagree and decide that the parents made the choice to feed their children fast food every day. They may also mention that fast-food restaurants frequently post nutrition information about their menu, so the information is available for parents to use. There are also socioeconomic reasons as well.

The government heavily subsidizes the corn industry—as a result, processed foods with lots of sugar and low nutritional value are often cheaper than more nutritious fruits and vegetables. How would this affect a parent’s choice of foods to buy? What else can be done as a society to reduce the obesity epidemic?

Additional Critical Thinking Questions The Process of Science 1. If all cells in the body contain the same DNA, why do some tissues have receptors for certain hormones, whereas others do not?

Suggested answer: Cells within an individual differ in their hormone receptors for the same reason they differ in any other respect, and that is differential gene expression. The different receptors are produced by the activation of certain genes in certain cells. This allows the cells to become even more differentiated as development proceeds.

2. Why do amine hormones generally require membrane receptors, whereas steroid hormones generally do not?

Suggested answer: Steroid hormones are generally relatively small, uncharged, and hydrophobic. Such molecules can pass through the hydrophobic core of the plasma membrane relatively easily. Amine hormones may be relatively large and usually contain amino acids that are charged and hydrophilic. Such molecules cannot easily pass through the hydrophobic core of the phospholipid bilayer. Therefore, membrane receptors are required outside the plasma membrane for signal transduction to occur inside the cell.

Biology and Society 3. Why is the incidence of type 2 diabetes so high compared to most other inheritable diseases? Why hasn’t this deleterious allele been eliminated by natural selection?

Some issues and questions to consider: Type 2 diabetes is typically a late-onset disease.

Therefore, it does not significantly affect the reproductive success of most individuals with the disease—so there is little reproductive selection against this trait, and selection will be largely ineffective in eliminating this allele. In addition, treatments are available that reduce the impact of the disease, thus allowing suboptimal genotypes to be passed to future generations. It is also possible that lifestyle and dietary choices associated with increased disease frequency may be a relatively recent development and evolution has not yet had time to reduce the frequency of what have become deleterious alleles. It should be noted that the selective value of an allele is always determined within an environmental context.

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CHAPTER

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Reproduction and Development

Why This Chapter Matters 1 All forms of life are products of reproduction. .

Understanding the basic structures and functions of the human reproductive system is important to maintaining good health and understanding disorders and disease.

2 .3. Sexually transmitted diseases can threaten fertility, lead to lifelong disease, and be fatal.

Chapter Objectives Biology and Society: Life after Death 1. Describe an example where society’s laws have not caught up to new reproductive technologies.

Unifying Concepts of Animal Reproduction 2. Describe the different forms of asexual reproduction. Explain the advantages and disadvantages of asexual reproduction.

3. Explain how hermaphrodites reproduce.

4. Distinguish between external and internal fertilization.

5. Describe the circumstances in which sexual reproduction is generally more adaptive than asexual reproduction.

Human Reproduction 6 Compare the structures and functions of the female and male human reproductive systems. .

Describe and compare the processes and products of oogenesis and spermatogenesis.

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Describe the events of the female reproductive cycle.

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Reproductive Health 89. Compare the most common methods of contraception. Note the effectiveness of each. . Describe the major types of sexually transmitted diseases and the organisms that cause 10. them. Explain why all sexually active people should be tested regularly for sexually transmitted diseases.

Human Development 11. Describe the events of fertilization. Explain how the structure of sperm matches its functions.

12. Describe the stages of development from the zygote to the gastrula. Explain the significance of the three layers produced in gastrulation.

13. Explain why induction and programmed cell death are significant parts of 14.

development.

Describe the structure of the embryo and its relationship to the uterus during and 15. soon 16. after implantation. Include the functions of the amnion, yolk sac, allantois, and chorion. Describe the developmental changes that occur in each of the three .

26 Reproduction and Development trimesters of pregnancy. Describe the functionsCHAPTER of oxytocin in pregnancy.

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17. Describe the main events of the three stages of labor.

Reproductive Technologies 18. Describe the common causes and treatments of infertility. Distinguish between infertility and impotency.

19. Describe the process of in vitro fertilization.

20. Describe some of the problems created by modern reproductive technologies.

Evolution Connection: The “Grandmother Hypothesis” 21. Explain how natural selection may have favored females who undergo menopause.

Lecture Outline I. Biology and Society: Life after Death 1. Infertility a. is the inability to conceive after at least one year of trying and b affects one in seven American couples.

2. .An infertile couple in New Jersey were using reproductive technologies to try to become pregnant 3. But during those efforts, the husband suddenly died of a heart attack 4. Within 6 hours of the death of her husband, the woman requested that a sample of her late husband’s sperm be removed 5. That sperm was used to fertilize the wife’s eggs and produce a child who is alive today 6. However, laws remain unclear regarding the rights of the child to death benefits

II. Unifying Concepts of Animal Reproduction 1. Reproduction is the creation of new individuals from existing ones A. Asexual Reproduction 1.Asexual reproduction a. is reproduction without sex and b. creates offspring that are genetically identical to the parent.

2. Budding a. is a type of asexual reproduction and b. produces offspring by the outgrowth and eventual splitting off of a new individual from the parent.

3. During the asexual process of fission, a parent separates into two or more offspring of about equal size 4. Fragmentation is the breaking of a parent body into several pieces 5. Regeneration a. typically follows fragmentation and b. is the regrowth of lost body parts.

6. Asexual reproduction a. eliminates the need to find a mate, b. allows a population to perpetuate itself if its individual members are isolated from one another, and c. permits organisms to multiply quickly without spending time or energy producing sperm and eggs.

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7. However, asexual reproduction produces genetically identical offspring, which limits a population’s chances of surviving periods of environmental change B. Sexual Reproduction 1.Sexual reproduction involves the a. fusion of two haploid sex cells called gametes (sperm and egg) and b. formation of azygote.

2. Sexual reproduction increases the a. genetic variability among offspring and b. chances that some of the varying offspring will survive and reproduce.

3. Some animals can reproduce a. sexually and b. asexually.

4. In some species, each individual is a hermaphrodite, with a. male and b. female reproductive systems.

5. Some hermaphrodites can fertilize their own eggs, while other species require a partner 6. The mechanics of fertilization play an important part in sexual reproduction 7. Many aquatic animals a. use external fertilization and b. discharge their gametes into the water.

8. In nearly all terrestrial animals, males deposit sperm directly into the female body

III. Human Reproduction 1. Both sexes of humans have a. a pair ofgonads that produce gametes, b. ducts to store and deliver the gametes, and c. structures that allow mating.

A. Male Reproductive Anatomy 1. The penis a. contains erectile tissue that fills with blood and b. becomes erect during sexual arousal.

2. A prepuce , or foreskin, a. covers the glans and b. may be removed surgically in a procedure known as circumcision.

3. The male gonads, the testes, a. are enclosed in a sac called the scrotum and b. produce sperm.

4. A testis and scrotum together are called a testicle 5. By keeping the sperm-forming cells away from the body, the scrotum keeps the testes cool enough for sperm to develop normally 6. Duringejaculation, sperm leave the epididymis and travel through a duct called the vas deferens, and

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7. The seminal vesicles and prostate gland add fluid that a. nourishes the sperm and b provides protection from the natural acidity of the vagina.

8 .Semen consists of these glandular fluids and sperm . The urethra conveys through the penis, at different times, both 9 a. semen and . b urine. .

B. Female Reproductive Anatomy 1. The outer features of the female reproductive tract are collectively called the vulva and consist of a. the vagina, or birth canal, b. the labia majora , fatty ridges that protect the entire genital region, c. the labia minora , inner folds bordering the openings, d. the hymen, partially covering the vaginal opening, and e. the clitoris, which becomes erect upon sexual arousal.

2. The ovaries a. are the sites of gamete production and b. containfolliclesconsisting of a single egg surrounded by cells that nourish and protect it.

3. The follicles also produce estrogen, the female sex hormone 4. Duringovulation, an immature egg a. is ejected from a follicle and b. enters theoviduct, where fertilization typically occurs.

5. The remains of the follicle grow to form a solid mass, the corpus luteum, which secretes hormones during the reproductive cycle 6. The uterus is a. the actual site of pregnancy and b. lined by a thick blood-rich layer of tissue, the endometrium, where an embryo implants and grows.

7. A developing human is called a. an embryo for the first nine weeks and b. a fetus from the 9th week until birth.

8. The cervix a. is the narrow neck at the bottom of the pear-shaped uterus and b. opens into the vagina.

9. Annual Pap smears a. sample cervical cells and b. can detect cervical cancer early, when treatment is more likely to be successful C. Gametogenesis 1. Gametogenesis a. uses meiosis and b. produces haploid cells called gametes.

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2. Humans have a. diploid cells with 46 chromosomes and b. haploid gametes with 23 chromosomes.

3. Spermatogenesis 4. Spermatogenesis a. is the formation of sperm cells and b. occurs in seminiferous tubules inside the testes.

5. Primary spermatocytes a. are diploid cells, b. undergo meiosis I, and c. produce secondary spermatocytes.

6. Secondary spermatocytes undergo meiosis II, each with the haploid number of chromosomes 7. Thus, spermatogenesis produces a total of four haploid cells from each primary spermatocyte D. Oogenesis 1. Oogenesis is the development of eggs within the ovaries 2. A primary oocyte a. is a diploid cell that pauses during prophase of meiosis I and b can be triggered to develop further by the hormone FSH to produce . i. a secondary oocyte and ii. a small polar body with almost no cytoplasm.

3. Meiosis II produces a. a mature ovum and b another polar body. oogenesis and spermatogenesis produce haploid gametes, but there are several .

4. Both important differences a. Human males create new sperm every day, from puberty through old age. b. Human females create primary oocytes only during fetal development. c. Spermatogenesis produces four gametes from each diploid parent cell, but oogenesis produces only one gamete from each diploid parent cell. d. Sperm are small and motile, while eggs are large and nonmotile.

E. The Female Reproductive Cycle 1. Human females have areproductive cycle , a recurring series of events that a. produces gametes, b. makes eggs available for fertilization, and c. prepares the body for pregnancy.

2. The female reproductive cycle is actually two cycles in one: a. the ovarian cycle controls the growth and release of an egg and b. the menstrual cycle prepares the uterus for possible implantation of an embryo.

3. Hormonal messages coordinate the ovarian and menstrual cycles 4. Menstruation is a. uterine bleeding b. caused by the breakdown of the endometrium. .

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IV. Reproductive Health 1. Two issues of human reproductive health are a. contraception , the deliberate prevention of pregnancy, and b.sexually transmitted diseases (STDs) .

A. Contraception 1.Contraception comes in many forms with varying degrees of effectiveness 2. Complete abstinence (avoiding intercourse) is the only totally effective method of contraception 3. Sterilization surgery prevents sperm from reaching an egg and is very reliable a a. The oviducts are cut and often tied off intubal ligation. b. The vas deferens are cut, preventing sperm from reaching the urethra, in a vasectomy.

4. Temporary abstinence a. is also called therhythm method or natural family planning and b. depends on refraining from intercourse during the days around ovulation.

5. Barrier methods prevent sperm from meeting an egg. These include a. diaphragms , dome-shaped rubber caps that cover the cervix, and b. condoms, sheaths usually made of latex, that fit i. over the penis or ii. within the vagina.

6. Barrier devices are usually used withspermicides , sperm-killing chemicals 7. Birth control hormones include a. oral contraceptives, orbirth control pills , b.morning-after pills (MAPs) , which are about 75% effective at preventing pregnancy when taken within three days of intercourse, and c. RU-486, which can induce an abortion.

B. Sexually Transmitted Diseases 1.Sexually transmitted diseases (STDs) are a. contagious diseases and b. spread by sexual contact.

2. Viral STDs a. cannot be cured but can be controlled by medications and b. include i. AIDS, ii. genital herpes , and genital warts. iii.

3. STDs caused by bacteria, protozoans, and fungi are generally curable with drugs 4. Chlamydia a. is the most common bacterial STD in the United States, b. poses a public health challenge because it is frequently “silent,” producing no visible symptoms, c. may lead to pelvic inflammatory disease (PID) and infertility, and d. can be easily treated with a single dose of an antibiotic.

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V. Human Development 1. Embryonic development begins with fertilization, the union of sperm and egg to form a zygote A. Fertilization 1. Sexual intercourse releases hundreds of millions of sperm into the vagina, but a. only a few thousand sperm survive the trip to the egg and b only one will fertilize it. . shape of a human sperm is streamlined, which helps it swim through fluids in the 2. The a. vagina, b. uterus, and c. oviduct.

3. Fertilization by a sperm involves many steps B. Basic Concepts of Embryonic Development 1. The key to development is that each stage of development takes place in a highly organized fashion 2. Development begins withcleavage, a series of rapid cell divisions that results in a multicellular ball 3. Cleavage continues as the embryo moves down the oviduct toward the uterus 4. A blastocyst a. forms about 6–7 days after fertilization and b. consists of a fluid-filled hollow ball with i. about 100 cells and ii. a small clump of inner cells called the inner cell mass, which eventually forms the fetus.

5. About 9 days after conception, the embryo a. undergoesgastrulation, an organized migration of cells, and b. changes to agastrula stage with three main tissue layers that establish the basic body plan: i. ectoderm, the outer layer that forms the nervous system and skin, ii. mesoderm, the middle layer that forms the heart, kidneys, and muscles, and iii. endoderm, the innermost layer that becomes the lining of the digestive tract.

6. Tissues and organs take shape in a developing embryo as a result of many different changes in the cells 7. In the process calledinduction, one group of cells influences the development of an adjacent group of cells 8.Programmed cell death a. selectively kills cells to reshape the embryo and b. is used to form fingers and toes.

C. Pregnancy and Early Development 1. Pregnancy, orgestation, a. is the carrying of developing young within the female reproductive tract and b. is measured as 40 weeks from the start of the last menstrual cycle in humans.

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2. The early stages of human development begin in the oviduct with a. fertilization and b. cleavage.

3. About 1 week after conception, a. the embryo has become a blastocyst, b the blastocyst contains an inner cell mass made of stem cells, which have the . potential to give rise to every type of cell in the body, c. the blastocyst implants in the uterine wall, and d. the outer embryonic cell layer, the trophoblast, starts to form part of the placenta, the organ that i. provides nourishment and oxygen to the embryo and ii. helps dispose of metabolic waste.

4. About a month after conception, four life-supporting pieces of equipment have formed: a. the amnion, a fluid-filled sac that encloses and protects the embryo, b. the yolk sac, which produces the first blood cells and first gamete-producing cells in the gonads, c. the allantois, which helps form the umbilical cord, and d. the chorion, which contributes to the placenta.

5. The placenta a. develops fingerlike chorionic villi that absorb nutrients and oxygen from the mother’s blood and pass these substances to the embryo and b. allows protective antibodies to pass from the mother to the fetus.

D. The Stages of Pregnancy 1. Pregnancy is divided into three trimesters of about 3 months each E. The First Trimester 1. About 5 weeks after fertilization, the embryo has developed a. a brain and spinal cord, b. four stumpy limb buds, and c. a short tail.

2. About 9 weeks after fertilization, a. the embryo is called a fetus, b. the embryo has all of its organs and major body parts, and c. the embryo’s limb buds have become tiny arms and legs with fingers and toes.

3. By the end of the first trimester, the sex of the fetus can be determined by an ultrasound 4. The Second Trimester 5. At about 14 weeks of development, the fetus a. is about 6 cm (2.4 inches) long and b. starts to look distinctly human.

6. At 20 weeks, the fetus a. is about 19 cm (7.6 inches) long, b. weighs about half a kilogram (1 lb), and c. has the face of an infant.

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8. The third trimester a. is a time of rapid growth and b includes many important physical changes. . birth, a typical baby 9. At a. is about 50 cm (20 inches) long and b weighs 3–4 kg (6–8 lb). .

F. Childbirth 1. The birth of a child is brought about by a series of strong, rhythmic contractions of the uterus called labor 2. Hormones such as oxytocin, a powerful stimulant of the smooth muscle walls in the uterus, play a key role in inducing labor 3. Labor involves three stages: a. dilation, the longest stage of labor, which increases the opening of the cervix, b. expulsion, which results in the delivery of the child, and c. delivery of the placenta usually within 15 minutes after the birth of the baby.

VII. Reproductive Technologies 1. Reproductive technologies can help solve problems related to the inability to conceive a child A. Infertility 1. Infertility is a. the inability to have children after one year of trying, b. most often due to problems in the man, such as underproduction of sperm or poor sperm quality, and c. sometimes caused byimpotence (erectile dysfunction), the inability to maintain an erection.

2. Female infertility can result from a. lack of eggs, b. failure to ovulate, or c. blocked oviducts.

3. There are technologies available to help treat the many forms of infertility B. In Vitro Fertilization 1.In vitro fertilization (IVF) begins with the administration of drugs that promote the development of multiple eggs followed by the, a. surgical removal of the eggs, b. collection of sperm, c. fertilization of the eggs with sperm in a petri dish, and d. injection of the resulting embryos into a uterus.

C. The Process of Science: Can Viable Embryos Be Identified?

1. Observation : Embryonic cells can be removed from the outer layer of a preimplantation blastocyst without any harm 2. Hypothesis: An analysis of gene activity within such cells could provide useful information about the chances of a successful pregnancy from each embryo 3. Prediction: Gene expression would differ between successful and unsuccessful embryos .

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4. Experiment: Genetic samples from embryos implanted in women were analyzed to identify genetic differences between successful embryos and those that did not develop fully 5. Results: A large number of differences were found between embryos that developed and those that did not. The results may help fertility researchers identify which embryos are most likely to develop when determining which embryos to implant D. The Ethics of IVF 1. IVF a. offers choices that nature does not and b raises many moral and legal issues. .

Connection: The “Grandmother Hypothesis” E. Evolution 1. Around age 50, human females undergo menopause, the cessation of ovulation and menstruation 2. How might menopause be adaptive?

3. Menopause might increase a woman’s fitness by allowing her to invest more time and energy in her children and grandchildren instead of having more children

Chapter Guide to Teaching Resources Unifying Concepts of Animal Reproduction Student Misconceptions and Concerns 1. Many students expect that hermaphroditic animals fertilize themselves. Although this may be common in some animals, exchanging gametes between hermaphrodites also occurs, as noted in the text.

2.Students do not often understand the costs and benefits of asexual and sexual reproduction.

Consider discussing the advantages and disadvantages of each of these forms of reproduction. Encourage students to focus on the compromises involved in any adaptation.

There is simply no one “best” way for all animals to reproduce.

Teaching Tips 1. Aphid life cycles usually alternate between asexual and sexual reproductive strategies during a single year. Consider challenging your class to explain why aphids (and other animals) do this. In general, sexual reproduction is most common in times of stress, and may be related to overpopulation or environmental change in which diversity may be favored.

2.Many salamander species use spermatophores to transfer sperm from the male to the female. Spermatophores are reproductive structures produced by males during courtship.

Sperm is deposited atop a gelatinous base, which is, in turn, attached to the substrate. The female moves over the spermatophore, removes some of the sperm from the cap, and stores the sperm in her reproductive tract until the time of egg deposition. Thus, sperm transfer is external but fertilization is internal. Many terrestrial salamander species use spermatophores, thus serving as one of the exceptions to the general rule that terrestrial animals reproduce by depositing sperm directly into the female’s body.

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Human Reproduction Student Misconceptions and Concerns 1. Student background knowledge of human reproductive biology is likely quite uneven.

What is well understood by some students is new to others. Further, the embarrassment frequently associated with related topics makes it difficult for teachers to fairly assess what students know. The best advice may be to not assume too much.

2. Student embarrassment with the subject of human reproductive biology may make open discussions uncomfortable for some students. Good clear textbook and media assignments that can be studied privately and opportunities to ask anonymous questions provide additional avenues to address sensitive content and questions.

Teaching Tips 1. Endometriosis is an inflammatory condition in which the endometrium spreads beyond the uterus. It can lead to painful menstrual cycles and infertility. The Endometriosis Association website at www.endometriosisassn.org/ is a good resource for additional 2. information.

Men in your class will be well aware of physiological changes in the scrotum associated with thermoregulation. When a man enters into cool water, the scrotum is pulled tight and the testes are held close to the body. During a warm shower or bath, the scrotum 3.

relaxes and the testes are held far away from the body. Women in your class may be much less aware of this common phenomenon.

In class, on a quiz, or on an exam, ask students to explain why polar bodies are produced at all, and why they have so little cytoplasm. Challenge them to explain why 4. polar bodies are not produced in spermatogenesis. (In general, oogenesis conserves cytoplasm while reducing the genetic composition of the forming ovum.)

Testicular cancer is the most common form of cancer in men between 15 and 35 years of 5. age. Students can find information about testicular cancer and how to perform a selfexam at the website for the American Cancer Society at www.cancer.org.

Students might wonder why a woman’s body goes through menstrual cycles. Why not just sustain the endometrium continuously? One hypothesis suggests that because the 6 uterus is a good environment in which bacteria can grow, menstrual cycles are a way to . “flush” the system and discourage microbial growth.

7 Many home pregnancy tests rely upon antibodies to HCG. . The Sexuality Information and Education Council of the United States (SIECUS) is a national, nonprofit organization, which affirms that sexuality is a natural and healthy Reproductive Health part of living. Its website, at www.siecus.org, is an excellent source of information Student Misconceptions related to this chapter. and Concerns 1. Students often mistakenly equate contraception with prevention of sexually transmitted diseases. As you review the forms of birth control, consider pointing out the strategies that provide little or no protection against STDs. The pill, for example, does nothing to prevent disease transmission. Consider noting that methods that greatly reduce the transmission of disease (condoms used with spermicides) are also effective forms of birth control. .

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2. Students often expect that drugs are available to cure most or all STDs. However, viral infections should be considered lifelong diseases. HIV, herpes, and HPV are examples of such STD viruses.

Teaching Tips 1. Although people infected with sexually transmitted diseases might have no apparent symptoms, they may still be capable of infecting partners. This important point is worth repeating to young college audiences who may be overly optimistic about the health of their partners.

2. Chlamydia is the most frequently reported bacterial STD in the United States (Source: CDC fact sheet at www.cdc.gov/std/chlamydia/STDFact-Chlamydia.htm).

Human Development Student Misconceptions and Concerns 1. Students often think that fetal blood and mother’s blood run together, one into the other.

Few students typically have a good understanding of the relationship of fetal and maternal blood in the placenta.

2. The extraembryonic membranes surrounding a human embryo are also not well understood by college students outside of the health sciences. These extraembryonic membranes can be viewed as analogous to the life-support systems used by astronauts.

Teaching Tips 1. Gastrulation establishes the basic body plan by positioning the future systems of the body in relationship to each other. This essential element of gastrulation is a crucial event that is a prerequisite for later developmental events (and thus is the basis of the quote directly below).

2. You might wish to reflect on the somewhat famous quote of Lewis Wolpert, who in 1986 said, “It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.” The development and arrangement of the basic embryonic layers (ectoderm: skin and nervous system; mesoderm: muscle and bone; and endoderm: digestive tract) establishes the basic body plan.

3. Ectopic pregnancies occur when an embryo implants anywhere other than the uterus. Most frequently, ectopic pregnancies occur in the oviducts. However, the structure of the oviduct cannot accommodate the growth of a fetus. Surgical removal of the ectopic pregnancy, resulting in an abortion, is thus required for the sake of the mother’s health. In the ongoing political and ethical debate about abortion, this circumstance is often noted as an acceptable exception, “to save the life of the mother.”

Programmed cell death in the formation of human hands is like carving. One begins with more “material” than is necessary and removes what is not needed to reveal the final shape.

All vertebrates develop in a fluid environment. Fish and amphibians typically lay their 5. eggs in water. Amniotes (reptiles, birds, and mammals) are defined by the presence of an amniotic sac, a self-contained aquatic system that surrounds the embryo with water inside the egg. The evolution of the amniotic egg removed the need to reproduce near water, freeing amniotes to reproduce underground, in deserts, and in trees!

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6.

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Morning sickness typically occurs during the first trimester and subsides during the second. However, a great deal of variation in the timing and degree of symptoms is known.

Unfortunately, the precise cause of morning sickness remains unknown.

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7. Most human babies weigh 3–4 kilograms (kg) at birth. Birth weights much larger or smaller than this are associated with increased mortality. This is an example of stabilizing selection, discussed in Chapter 13.

8. When discussing the dilation of the cervix as part of labor, it might be useful to note that cigarettes are 90–100 mm long. Thus, a fully dilated cervix is about as wide as a cigarette is long.

9. The descriptions of basic development address questions that students may have never thought to ask. How do we get so many cells (trillions!) in our adult bodies? How do basic tissues, organs, and organ systems form? What mechanisms permit the coordinated development of the body? Before beginning this chapter, consider challenging your students with some of these fundamental questions: How did you get a heart, a brain, and ears? What determined when you were ready to be born? How did you get nutrients and oxygen before you could eat or breathe?

10. The many benefits of breast-feeding are noted at the website of the U.S. Dept. of Health and Human Services, which can be found at www.womenshealth.gov/breastfeeding/.

Reproductive Technologies Student Misconceptions and Concerns 1. Students frequently confuse the terms infertility and impotency. Care should be used to distinguish these terms.

2. Few students understand that many STDs can lead to infertility. For example, chlamydia is the most frequently reported bacterial sexually transmitted disease, according to the CDC. Infertility is a common consequence of chlamydial infections.

Teaching Tips 1. Cardiovascular disease is often the cause of impotency (erectile dysfunction). Smoking, poor diet, and lack of exercise can therefore contribute to sexual problems.

2. The fate of surplus frozen embryos produced by in vitro fertilization is often debated.

Some have suggested that they be used as sources of stem cells. Others regard this as a form of unacceptable abortion. Students might enjoy researching and discussing the issues related to these embryos.

Key Terms asexual reproduction birth control pills budding cervix chlamydia chorion chorionic villi cleavage clitoris condoms contraception corpus luteum diaphragm

egg ejaculation embryo endometrium fertilization fetus fission follicles gametes gametogenesis gastrula gastrulation genital herpes

gestation gonads hermaphrodite hymen impotence in vitro fertilization (IVF) induction infertility labia majora labia minora labor menstrual cycle

menstruation morning-after pills (MAPs) natural family planning oogenesis ovarian cycle ovaries oviduct ovulation penis placenta prepuce primary oocyte

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primary spermatocytes secondary programmed cell death spermatocytes prostate gland semen reproduction seminal vesicles reproductive cycle seminiferous tubules rhythm method sexual reproduction scrotum sexually transmitted secondary oocyte diseases (STDs) sperm

spermatogenesis spermicides stem cells testes testicle trimesters trophoblast tubal ligation umbilical cord

urethra uterus vagina vas deferens vasectomy vulva zygote

Word Roots a = without (asexual reproduction: reproduction without sex) contra = against (contraception: the prevention of pregnancy) ectomy = cut out (vasectomy: the cutting of each vas deferens to prevent sperm from entering the urethra) fertil = fruitful (fertilization: the union of haploid gametes to produce a diploid zygote) gastro = stomach, belly (gastrulation: the formation of a gastrula from a blastula) in = without (infertility: the inability to reproduce sexually) labi = lip; major = larger (labia majora: a pair of thick, fatty ridges that enclose and protect the labia minora and vestibule) oo = egg; genesis = producing (oogenesis: the process in the ovary that results in the production of female gametes) ovi = egg (oviduct: the tube that carriers an egg from the ovary) tri = three (trimester: a three-month period) tropho = nourish; blast = bud (trophoblast: the outer epithelium of the blastocyst, which forms the fetal part of the placenta)

Relevant Songs to Play in Class “Miserable Bastard” (from the album Zygote), John Popper “Reproduction,” Grease 2 Soundtrack

“I Want Your Sex,” George Michael “Two Kinds of Seagulls,” Tom Chapin “Let’s Talk About Sex,” Salt N Pepa

Answers to End-of-Chapter Questions The Process of Science 12. Suggested answer: If some sperm can live 5 days, then there is a risk of pregnancy up to 5 days prior to ovulation (day 9), meaning that if the sperm are already present at ovulation, fertilization can occur. If the egg can survive up to 48 hours, there is a risk up to 2 days after ovulation (day 16) if sperm are present. Overall, this produces a potential 7-day fertility window.

13.Suggested answer: One of the first things to test would be temperature. At warmer temperatures, the sperm do not function properly. It would also be appropriate to test sperm numbers and shape. Men typically release 200,000,000 to 300,000,000 sperm per 384

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fertilization attempt. If the numbers were less, or the number of malformed sperm was unusually high, it could account for the problem. Finally, an analysis of the semen might determine if there were problems with the secretions from the seminal vesicles or prostate that may be causing the problem.

Biology and Society 14. Some issues and questions to consider: If it is technologically possible to save a baby, does that mean we have to do it? What would bring “the greatest good to the greatest number” of babies? If we diverted resources away from premature babies, would such resources really be used for prenatal care? Who pays for the treatment of premature babies? For prenatal care?

15. Some people will believe that using a surrogate mother is not acceptable under any circumstances and that other options, such as adoption, should be considered. Others may agree that surrogacy is an option but that the surrogate mother should be carefully selected and screened (for example, a family member who is not seeking financial gain). For those who believe that contracted surrogates are an option for infertile couples, their opinion

16.

on custody issues may be dependent on whether the surrogate mother was the donor of the egg. In any case, decisions on custody are extremely difficult to decide and many states

are attempting to prevent the use of contracted surrogates. Should a couple have the right to sue a surrogate who breached a contract and decided to keep the baby or undertook activities such as drug use that would harm the baby?

Some issues and questions to consider: What characteristics might parents prefer? If parents had the right to choose embryos based on these characteristics, what are some Additional Critical Thinking Questions possible benefits? What are potential pitfalls? Could an imbalance in the population result The Process of Science

by favoring one sex over another? Is it okay to keep an embryo disease-free, but choose 1. Why are egg cells usually much larger than sperm cells? one with certain genes for hair or eye color? Intelligence? (Providing we learn the Suggested answer: Eggs are usually much larger than sperm because the developing embryo genetic must have access to sufficient resources to allow it to develop to the point where it can basis thesenutrients traits.) from its environment. For example, in humans it can take 2 days to a obtainofmore week for the fertilized embryo to implant in the wall of the uterus. During this time, many cell divisions take place. If the egg were as small as the sperm, the embryo could never develop to the point where it could implant and begin to obtain nutrients from the mother.

The same is true of many other plants and animals. For this reason, at least one gamete is usually relatively large and immobile—usually the female. The other gamete—usually the male—is small and mobile. The sexual dichotomy ensures fertilization and sufficient nutrients for the developing embryo. Also, the egg typically is the source of mitochondria and other cellular organelles.

2.

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As a frog embryo develops, the neural tube forms from ectoderm along what will be the frog’s back, directly above the notochord. To study this process, a researcher carefully extracted a bit of notochord tissue and inserted it underneath the ectoderm, where the belly

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of the frog would normally develop. What can the researcher hope to learn from this experiment? Predict the possible outcomes. What experimental control would you suggest?

Suggested answer: The researcher might find out whether chemicals from the notochord stimulate the nearby ectoderm to become the neural tube, a process called induction.

Transplanted notochord tissue might cause ectoderm anywhere in the embryo to become neural tissue. Control: Transplant non-notochord tissue under the ectoderm of the belly area.

3. Variation in the length of the human menstrual cycle results mainly from individual differences in the preovulatory phase. The relatively uniform life span of the corpus luteum keeps the length of the postovulatory phase close to 14 days. A certain woman usually has 34-day cycles. If she last began menstruating on January 29 and it is now February 14, what is her reproductive status? Choose the best answer, and briefly explain why you chose it. a. Her endometrium has reached its peak development. b. An ovarian follicle has just started to grow. c. Unprotected intercourse now has a good chance of resulting in pregnancy. d. The LH concentration in her blood has surged upward, stopping menstruation.

Suggested answers: a. No. The endometrium reaches its peak development after ovulation. b. No. If menstruation started on January 29, it probably stopped around February 2, and the follicle started to grow then. By February 14, the follicle is very well developed. c. Correct. If the woman has 34-day cycles and we can assume that the postovulatory phase is 14 days, she has 20 days in her preovulatory phase. She started menstruating 17 days ago, so on February 14 it is probably 3 days before ovulation. Estrogen is rising rapidly, the follicle is about to ovulate, and (if recent data on the life span of sperm in the female reproductive tract are reliable) intercourse now could result in fertilization just after ovulation, in 3 days. d. No. Menstruation stopped about 5 days after it started, and the LH peak in the middle of the cycle has nothing to do with stopping it.

Biology and Society 4. New techniques for sorting sperm, combined with in vitro fertilization, make it possible for a couple to choose their baby’s sex. Would you want to do this if you had the chance?

Why or why not? What potential problems can you foresee if this procedure becomes widely available?

Some issues and questions to consider: Why might some people choose to have a girl?

A boy? Are these reasons important enough to go through the process of in vitro fertilization? Do you think more people would want to have a boy or a girl? Could an imbalance in the population result? What could be some problems to society with an imbalance of males or females? What problems could result if the procedure produced a baby of the opposite sex from what was planned?

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CHAPTER

27

Nervous, Sensory, and Locomotor Systems

Why This Chapter Matters 1. Nervous systems form a communication and coordination network in an animal’s body.

How we perceive, understand, and respond to our world are functions of this system.

2. The health and proper function of our senses greatly affects our ability to interact with our world.

3. The musculoskeletal system enables us to interact with our environment.

Chapter Objectives Biology and Society: The Seismic Sense of Elephants 1. Explain how echolocation, electroreception, and magnetoreception are used by animals with these systems.

An Overview of Animal Nervous Systems Describe 2. the structural and functional subdivisions of the nervous system.

Describe 3. the structure and functions of neurons.

Define 4. a resting potential and explain how it is generated.

Describe 5. the changes that are associated with an action potential.

Explain 6. how an action potential propagates itself along a neuron.

Compare 7. the structures and locations of electrical and chemical synapses.

Describe 8. the types of inputs a single neuron can receive and note the nature of the neuron’s response.

Describe 9. the types and functions of human neurotransmitters.

Explain 10. how drugs can alter chemical synapses.

The Human Nervous System: A Closer Look 11. Describe the general structure and functions of the brain and spinal cord.

12. Describe the functions of meninges and cerebrospinal fluid.

13. Compare the functions of the motor and autonomic divisions of the peripheral nervous system.

14. Compare the functions of the parasympathetic and sympathetic divisions of the peripheral nervous system.

15. Describe the three main regions of the human brain and note their parts and functions.

16. Note the detailed structures and functions of the cerebral cortex.

17. Describe the characteristics of major depression, bipolar disorder, and Alzheimer’s disease.

The Senses 18. Define sensory transduction, a receptor potential, and sensory adaptation. Illustrate each with examples.

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19. Describe the five general categories of sensory receptors found in animals. Note examples of each.

20. Describe the parts of the human eye and their functions.

21. Compare the structures, functions, distributions, and densities of rods and cones.

22. Explain the causes and symptoms of glaucoma, farsightedness, nearsightedness, and astigmatism.

23. List in order the structures of the ear involved in hearing. Describe the possible causes of hearing loss.

Locomotor Systems 24. Distinguish between the axial and appendicular skeletons. Describe three types of joints and provide examples of each.

25. Describe the complex structure of a bone, noting the major tissues that contribute to bones and their functions.

26. Describe the most common skeletal disorders. Explain why bones break and how we can help them heal.

27. Describe the structure and arrangement of the filaments found in a muscle cell.

28. Explain, in detail, how a muscle cell contracts.

29. Describe the structure and function of motor units.

30. Explain how a motor neuron signals a muscle fiber to contract.

31. Describe an example of a person using his or her sensory receptors, central nervous system, skeleton, and muscles to perform an activity.

Evolution Connection: Seeing UV 32. Explain how UV detection appears to have evolved in birds.

Lecture Outline I. Biology and Society: The Seismic Sense of Elephants 1. Many animals perceive the world in ways we cannot 2. Bats generate ultrasonic sounds in echolocation to a. detect echoes and b. determine the size, shape, location, speed, and direction of objects in the environment.

3. Many fish can detect prey by electroreception, detecting changes in electric fields 4. Many animals, including birds, fishes, turtles, and bees, navigate using magnetoreception, the ability to detect Earth’s magnetic fields 5. Elephants can communicate using low-rumbling infrasounds too low to be heard by human ears

II. An Overview of Animal Nervous Systems 1. The nervous system forms a communication and coordination network throughout an animal’s body 2. Neurons are nerve cells that carry electrical signals from one part of the body to another

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A. Organization of Nervous Systems 1. The nervous system of most animals has two main divisions a. The central nervous system (CNS) is made up of the brain and spinal cord (in vertebrates). b. The peripheral nervous system (PNS) is made up of mostly nerves that carry signals into and out of the CNS. 2. A nerve is a communication line made from cable-like bundles of neuron fibers tightly wrapped in connective tissue 3. The three interconnected functions of the nervous system are carried out by three types of neurons a. Sensory neurons function insensory input, sending signals from sensory receptors to the CNS. b. Interneurons integrate sensory signals and formulate appropriate responses. c. Motor neurons function inmotor output, the process of sending signals from integration centers to effector cells.

4. Effector cells perform the body’s responses to motor output B.

Neurons 1. Neurons a. are the functional units of the nervous system, b. vary widely in shape, and c. share some common features.

The 2. cell body houses a. the nucleus and b. other organelles.

3. Two types of extensions project from the cell body: a. dendrites i. receive incoming messages from other cells and

ii. convey the information toward the cell body, and b. axons transmit signals toward another neuron or toward an effector cell.

4. Supporting cells a. outnumber neurons by as many as 50 to 1 and b. protect, insulate, and reinforce the neurons.

5. myelin sheath The a. forms an insulating material around an axon and b. helps speed electrical transmission along an axon.

6. An axon ends in a cluster of branches, each with a bulb-like synaptic terminal that relays signals to a. another neuron or b. an effector cell.

C. Sending a Signal through a Neuron 1. A resting neuron has potential energy that can be put to work to send nerve signals from one part of the body to another 2. This difference in charge (voltage) across the plasma membrane of a resting neuron is the resting potential .

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3. The Action Potential 4. A stimulus is any factor that causes a nerve signal to be generated 5. A stimulusof sufficient strength can trigger an action potential, a nerve signal that carries information along a neuron 6. If the stimulus is strong enough, a sufficient number of channels open to reach the threshold , the minimum change in a membrane’s voltage that must occur to trigger the action potential 7. Propagationof the Signal 8. An action potential is a localized electrical event 9. To function as a long-distance signal, this local event must be passed along the neuron 10. Action potential propagation is like a “domino effect” along a neuron 11. Action potentials are a. all-or-none events and b. the same no matter how strong or weak the stimulus that triggers them.

D. Passing a Signal from a Neuron to a Receiving Cell is a relay point 1. A synapse a. between two neurons or b. between a neuron and an effector cell.

2. Synapses come in two varieties: a. electrical and b. chemical.

3. Chemical synapses a. have a narrow gap, thesynaptic cleft, separating a synaptic terminal of the sending neuron from the receiving cell and b. rely on neurotransmitters , chemicals that carry information from one nerve cell to another kind of cell.

4. Chemical synapses can process extremely complex information 5. A neuron may receive input from hundreds of other neurons via thousands of synaptic terminals 6. Neurotransmitters 7. A variety of small molecules can act as neurotransmitters, including amines and peptides a. Amines i. are derived from amino acids and ii. affect sleep, mood, attention, and learning. b. Peptides i. are short chains of amino acids and ii. include endorphins, which decrease our perception of pain.

8. Drugs and the Brain 9. Many drugs, such as caffeine, nicotine, and alcohol, act at synapses by increasing or decreasing the normal effect of neurotransmitters 10. Prescription drugs used to treat psychological disorders alter the effects of neurotransmitters

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III. The Human Nervous System: A Closer Look 1. Although there is remarkable uniformity in the way nerve cells function, there is great variety in how nervous systems as a whole are organized 2. Vertebrate nervous systems are diverse in a. structure and b. level of sophistication.

A. The Central Nervous System 1. Vertebrate central nervous systems a. integrate information coming from the senses, b. transmit signals that produce responses, and c. consist of the i. brain , the master control center of the nervous system, and ii. spinal cord , a jellylike bundle of nerve fibers inside the spine.

2. The brain and spinal cord a. contain spaces and b. are filled withcerebrospinal fluid , a liquid that i. cushions theCNS and ii. helps supply the CNS with nutrients, hormones, and white blood cells.

3. Also protecting the brain and spinal cord are layers of connective tissues called meninges B. The Peripheral Nervous System 1. The vertebrate peripheral nervous system is divided into two functional components, the a. motor system and b. autonomic nervous system.

The 2. motor system a. carries signals to and from skeletal muscles and b. mainly responds to external stimuli.

3. The autonomic nervous system a. regulates the internal environment and b. controls i. smooth and cardiac muscles and ii. organs and glands of the digestive, cardiovascular, excretory, and

endocrine systems.

4. The autonomic nervous system contains two sets of neurons with opposing effects on most organs a. The parasympathetic division primes the body for digesting food and resting. b. The sympathetic divisionprepares the body for intense, energy-consuming activities.

C. The Human Brain 1. The human brain is more powerful than the most sophisticated computer and consists of a. up to 100 billion intricately organized neurons and b. many more supporting cells.

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2. The brain is divided structurally into three regions, the a. hindbrain, b. midbrain, and c. forebrain 3. The brainstem a. consists of the hindbrain (medulla oblongata and pons) and the midbrain and b. serves as a sensory filter, selecting which information to pass on.

4. Thecerebellum , another part of the hindbrain, is a planning center for body movements 5. The forebrain contains the most sophisticated integrating centers in the brain a. The thalamus relays information to the cerebral cortex. b. The hypothalamus has many regulatory functions.

6. The Cerebral Cortex 7. The cerebrum a. is the largest and most complex part of the brain and b. consists of the right and left cerebral hemispheres.

8. The corpus callosum connects the cerebral hemispheres, enabling them to process information together 9. The cerebral cortex a. is a highly folded layer of tissue that forms the surface of the cerebrum, b. accounts for over 80% of the total brain mass, c. contains about 10 billion neurons, and d. helps produce our most distinctive human traits.

10. The right and left cerebral hemispheres have four lobes, each named for a nearby skull bone 11. Higher mental activities occur in association areas of the brain 12. Brain Trauma 13. Evidence from brain surgery indicates that patterns of lateralization are not fixed 14. Neurologists sometimes gain insight into how the brain works from people who have suffered brain trauma 15. In 1848, a railroad accident involving a man named Phineas Gage a. propelled a three-foot-long spike through his head and b. caused significant changes in his personality.

16. Neurological Disorders 17. Neurological disorders can also affect brain function a. Major depression may be associated with extreme and persistent sadness and loss of interest in pleasurable activities. b. Bipolar disorder , or manic-depressive disorder, involves extreme mood swings. c. Alzheimer’s disease is a form of mental deterioration, or dementia, characterized by i. confusion, ii. memory loss, and iii. a variety of other symptoms.

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IV. The Senses 1. Sensory structures a. gather information and b. pass it on to the CNS. A. Sensory Input 1. Sensory input is the process of using receptors to a. sense the environment and b. send information about it to the CNS to be integrated and acted upon.

2. Sensory transduction is the conversion of a stimulus signal to an electrical signal by a sensory receptor cell 3. Sensory Transduction 4. Receptor potentials a. are changes in membrane potentials caused by sensory stimuli and b. vary in intensity, depending on the strength of the stimulus.

5. Sensory adaptation a. causes some sensory receptors to be less sensitive when they are stimulated repeatedly and b. keeps the body from continuously reacting to normal background stimuli.

6. Types of Sensory Receptors 7. Sensory receptors can be grouped into five categories, which work in various combinations to produce the five human senses 8. A section of human skin reveals why the surface of our body is sensitive to such a variety of stimuli 9. Pain receptors sense stimuli that may indicate tissue damage 10. Thermoreceptors detect heat or cold 11. Mechanoreceptors are stimulated by various forms of mechanical energy 12. Chemoreceptors respond to chemicals in the external environment or body fluids 13. Electromagnetic receptorsrespond to electricity, magnetism, or light (photoreceptors) B. Vision 1. Human eyes are able to a. detect a multitude of colors, b. form images of faraway objects, and c. respond to minute amounts of light energy.

2. Structure of the Human Eye 3. The human eye consists of a. a tough outer covering, the sclera, b. a transparentcornea in front of the lens, c. an iris with a center opening, the pupil, and d. the retina , at the back of the eyeball, where photoreceptors respond to light.

4. The optic nerve connects the retina to the brain 5. Two fluid-filled chambers make up the bulk of the eye a. The large chamber behind the lens is filled with jellylike vitreous humor. b. The much smaller chamber in front of the lens contains a thinner fluid called the aqueous humor. .

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6. Function of the Human Eye 7. The cornea lets light into the eye and helps focus light 8. The iris a. regulates the size of the pupil and b. lets light shine onto the lens.

9. The lens of the eye changes shape and focuses light onto the retina 10. Photoreceptors 11. The human retina contains two types of photoreceptors a. Rods i. are extremely sensitive to light, ii. perceive only shades of gray, and iii. are distributedat the outer edges of the retina. b. Cones i. are less sensitive to light, ii. can distinguish color, and iii. are distributedat the retina’s center of focus.

12. Rods and cones a. detect light using an array of disks containing light-absorbing pigments and b. convert a stimulus to an electrical signal.

13. Other retinal neurons a. integrate these receptor potentials and b. generate action potentials that travel along the optic nerve to the brain.

14. Vision Problems and Corrections 15. The most common visual problems are a. nearsightedness, the inability to focus well on distant objects, b. farsightedness , the inability to focus well on near objects, and c. astigmatism , blurred vision caused by a misshapen lens or cornea.

C. Hearing 1. The Structure of the Human Ear 2. The ear is composed of a. the outer ear, b. the middle ear, and c. the inner ear.

3. The outer ear a. consists of the flap-like pinna and the auditory canal, b. collects sound waves, and c. passes sound waves to the eardrum, a sheet of tissue that separates the outer ear from the middle ear.

4. In the middle ear , the vibrating eardrum passes the sound waves to three small bones that relay the sound to the inner ear 5. The Eustachian tube a. conducts air between the middle ear and back of the throat and b. allows air pressure to stay equal on either side of the eardrum.

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6. The inner ear consists of fluid-filled channels in the bones of the skull 7. One of the channels, the cochlea, is a long coiled tube 8. The cochlea contains the organ of Corti, which a. is the actual hearing organ and b. includes hair cells, the receptor cells of the ear.

9. Function of the Human Ear 10. When we hear, sound waves are a. collected by the pinna and the auditory canal, b. channeled to the eardrum, making it vibrate, c. passed through the middle ear bones, and d. transmitted to the cochlea.

11. The waves generated in the cochlear fluid move hair cells of the organ of Corti against an overlying membrane, triggering receptor potentials and sending nerve signals to 12. the brain Louder sounds of cause a. greater movement the hair cells and b. more action potentials.

13. Hearing Problems 14. Deafness, the loss of hearing, can be caused by a. middle ear infections, b. injury, such as a ruptured eardrum, c. stiffening of the middle-ear bones (a common age-related problem), or d. overexposure to loud noises.

V. Locomotor Systems 1. Movement a. is one of the most distinctive features of animals and b. relies upon an interplay of organ systems 2. The nervous system issues commands to the muscular system 3. The muscular system exerts the forces that make animals move by acting on the skeletal system A. The Skeletal System 1. The skeletal system provides a. anchoring, b. support, and c. protection of internal organs.

2. Organization of the Human Skeleton 3. All vertebrates have an endoskeleton, situated among soft tissues, and consisting of a. bones, hard supporting elements, and b. cartilage at points of flexibility.

4. The axial skeleton a. supports the axis of the body and b. includes the skull, vertebral column, and ribs.

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5. The appendicular skeleton is made up of the bones of the a. limbs, b. shoulders, and c. pelvis.

6. The bones of the skeleton are held together at movable joints by strong fibrous tissues called ligaments 7. Much of the versatility of our skeleton comes from three types of movable joints: a. ball-and-socket joints in the shoulder and hip, b. hinge joints that permit movement in a single plane, and c. pivot joints that allow rotation.

8. The Structure of Bones 9. Bones a. are covered with a sheet of fibrous connective tissue, b. have cartilage at their ends that cushions the joints, and c. are supported by blood vessels.

10. The central cavity of a long bone contains yellow bone marrow, which is mostly stored fat 11. The end of a long bone contains red bone marrow, a specialized tissue that produces blood cells 12. Skeletal Diseases and Injuries 13. The human skeleton is a. quite strong and provides reliable support, but b. susceptible to disease and injury.

14. Arthritis a. is an inflammation of the joints and b. affects one out of every seven people in the United States.

15. Rheumatoid arthritis a. is an autoimmune disease, b. usually begins between ages 40 and 50, and c. affects more women than men.

16. Osteoporosis a. makes bones thinner and more porous and b. is most common in women after menopause.

17. Bones are rigid but not inflexible 18. If a force exceeds a bone’s capacity to bend, the result is a broken bone, or fracture 19. The treatment of a fracture involves a. putting the bone back into its natural shape and b. immobilizing it until the body’s natural bone-building cells can repair the fracture.

B. The Muscular System 1. The muscular system is made of all the skeletal muscles in the body 2. Skeletal muscles a. are attached to the skeleton and b. produce body movement by interacting with the skeleton.

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3. Tendons connect muscles to bones 4. Antagonistic pairs of muscles produce opposite movements 5. The Cellular Basis of Muscle Contraction 6. Skeletal muscle is made up of a hierarchy of smaller and smaller parallel strands 7. Each skeletal muscle cell, or fiber, a. contains bundles of myofibrils and b. is called striated, because the myofibrils exhibit alternating light and dark bands when viewed with a light microscope.

8. A sarcomere is a. the region between two dark, narrow lines in the myofibril and b. the functional unit of muscle contraction.

9. A myofibril is composed of regular arrangements of two kinds of filaments a. Thin filaments are made mostly of the protein actin. b. Thick filaments are made mostly of the protein myosin.

10. A sarcomere contracts (shortens) when its thin filaments slide past its thick filaments 11. In the sliding-filament model, the key events are the binding between a. parts (called heads) of the myosin molecules in the thick filaments and b. specific sites on actin molecules in the thin filaments.

12. Contraction requires energy supplied by ATP 13. Motor Neurons: Control of Muscle Contraction 14. Motor neurons a. are part of the central nervous system, b. release neurotransmitters that cause muscle fibers to contract, and c. can branch to a number of muscle fibers.

15. A motor unit consists of a. a neuron and b. all the muscle fibers it controls.

16. Motor units may consist of a. just one muscle fiber or b. up to several hundred muscle fibers.

17. The strength of a muscle contraction depends on the number of motor units activated C. The Process of Science: How Do New Senses Arise?

1. Observation: Two species of electric fish use special ion channel proteins in muscle cells to generate electric fields 2. Question: Did different ion channel proteins evolve in these two species?

3. Hypothesis: Ion channel genes of the two electric species had mutated in unique ways 4. Experiment : The DNA sequence of the genes in the two electric fish was determined and compared to a closely related but nonelectric South American fish 5. Results: A single ion channel gene duplicated in the common ancestor, into forms a and b a. The aform mutated differently in the two electric fish species. b. The bform retained its muscle functions in electric and non electric fishes.

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D. Stimulus and Response: Putting It All Together 1. An animal’s nervous system connects sensations derived from environmental stimuli to responses carried out by its muscles E. Evolution Connection: Seeing UV 1. Many birds can see ultraviolet light, which seems to be important in a. social communication and b. food gathering.

2. Researchers have discovered that a single amino acid change in the pigment protein rhodopsin converted it to a UV-detecting form 3. This is another example of a large-scale change that can be traced to a small change: a single mutation

Chapter Guide to Teaching Resources An Overview of Animal Nervous Systems Student Misconceptions and Concerns 1. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. The limited permeability of membranes, charges of ions, and natural electrical attractions may be unfamiliar assumptions. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).

2. As additional details are added, students often forget the fundamental functions of the nervous system. In short, they “miss the forest for the trees.” Regularly relate the three fundamental functions of the nervous system—sensory input, integration, and motor output—to an image of the PNS and CNS, noting where these functions occur (for example, Figure 27.1). Returning to this same diagram throughout the lectures on the nervous system reminds students of these fundamental functions in a familiar figure.

Consider presenting the diverse actions of neurotransmitters and related drugs in a table, 3. for quick and easy reference during lecture. Many students will have a particular interest in a drug, but soon forget the related action if it was discussed earlier. A table will enable easy reference to check an action of a drug.

Teaching Tips 1. A nerve is like a bundle of wires (axons) encased in insulation (myelination). Consider bringing a piece of stereo wire or other electronic cable to show the many copper wires inside. Later, when myelin is addressed, you can make an analogy between the function of myelin and the insulation.

2. Here is another analogy to represent myelin sheaths and nodes of Ranvier. Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. For those who really want to make the point, you could find a fake hot dog–like item and bring along three hot dog buns.

3. Students might require a review of the basic concept of potential energy. A simple demonstration in class, holding an object, and then letting it plummet to the floor, might make a quick, clear demonstration. As noted in the text, potential electrical energy can be stored in a battery.

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4. Challenge your students to find examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that sense aspects of engine performance, interpret the signals, and then send signals to make adjustments.

5. The authors compare the changes in a cell membrane associated with an action potential to the fall of a series of dominoes. This process is similar to a “wave” that sports fans generate, which travels around a stadium.

6. Challenge students to explain how the intensity of a signal can be expressed when the strength of an action potential signal is steady. As noted in the text, signal intensity is communicated by the frequency of the signals. This is like knocking on a door again and again to communicate urgency.

Students may better comprehend the idea of the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person can reach a “threshold” where he or she is stimulated enough to get up and turn it off.

Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an 8. “automatic” response to a stimulus?

The transmission of a signal across a chemical synapse is like driving along a road to a 9. river, then taking a ferry across the river, and driving away on a road on the other side. The transportation of you (or the signal) continues, but via different mechanisms along the way (an automobile and a ferry).

Drugs that block a receptor act like someone who has parked in your parking space. Your 10. vehicle cannot “bind” to your “receptor.”

Recycling, as noted with the breakdown of neurotransmitters in a synapse, is a common 11. feature of cell physiology. Students should already be familiar with the recycling of ADP and P to form ATP. Remind them of the efficiency of reusing monomers to build polymers. Recycling of aluminum and other waste products has this same advantage.

An analogy to the diverse signal input to a neuron might be helpful, if not amusing.

12.

A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd, cheering for and against them. A similar situation often arises during a game show, as a player’s decision is influenced by the loud suggestions of the audience.

Here is a bit of logic you might share with your students. Ask your students if they would 13. avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why? A likely response will be that one might not trust a criminal pharmacist to carefully provide one’s medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell illegal drugs on the street?

Students may have heard about “chemical imbalances” in the brain, but not known 14. specifically what this means. Unusual levels of neurotransmitters in the central nervous system, resulting from disease or chemical exposure, can change our ability to perceive and respond to our world. Illegal drugs risk toxic disruption of this imbalance with potentially disastrous consequences.

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The Human Nervous System: A Closer Look Student Misconceptions and Concerns 1. Popular media often suggests that certain people are “left-brained,” whereas others are “right-brained.” Students might therefore expect that they are one or the other. As the text notes, and as biology frequently reveals, little about life is this clear and distinct. The traits associated with each side of the brain are matters of degree. Surgical procedures, disease, and injury reveal considerable plasticity.

2. Students may think of the human brain as completely unique. Yet, the anatomical components of the human brain mirror the basic components found in many other vertebrates. These similarities are so extensive that sheep brains are often studied in biology laboratories to better understand human anatomy.

Students often confuse the terms spinal column, spinal cord, spine, and backbone. They 3. may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Consider a little extra attention to avoid these sorts of confusion.

Students often think of the motor system as “voluntary” and directed by conscious 4. thoughts. You might point out to your students that they are not likely concentrating on contracting the various muscles needed to maintain their posture as they sit in class.

Teaching Tips 1. Tables such as 27.1, which provide summaries of structures and functions, can relieve lectures from the repetition of tedious detail. Instead, more class time can be spent on more interesting and meaningful aspects of the topic. Such tables also facilitate the creation of matching questions on exams!

2. Challenge your students to explain what we mean by a “head” in an animal. Why are heads concentrated on one end of the body? Why is the mouth usually, but not always, associated with the head? (The opening to the digestive tract of a planarian is in the middle of the body.) An analogy might be made to an airplane, whose pilot sits inside the cockpit at the front of the plane, gathering and processing information about where the plane is 3. headed.

Why are all six of our major senses (taste, smell, sight, touch, sound, and balance) all centered in our heads?

4. Students often are surprised to learn that their brain is hollow, although some students may know that the central nervous system is surrounded by cerebrospinal fluid. The 5. basic development of the brain and spinal cord arise from an embryonic tube.

Students often remember the functions of the autonomic nervous system better by thinking of them as “automatic.”

Many of the sympathetic division responses are the products of hormones released into 6.

the bloodstream.

These responses cannot be quickly reversed. You might want to encourage students to think of how long it usually takes for them or others to calm down after

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. having become extremely nervous or upset. Time and separation from the source of stress are usually required. For example, those who take a long walk to calm down often find, in

the mild exercise and the retreat from the situation, an emotional comfort that also makes biological sense.

Students may remember the functions of the sympathetic division as “sympathetic” to

7. As students learn about the structure and function of the cerebral cortex, they are actually using these sets of cells to think about these cells. As student understanding grows, these sets of cells become increasingly aware of their own properties, in a process that is like looking in a mirror!

8. Sleep seems to be involved in learning and memory. Study strategies that involve cramming large amounts of information into the memory in a short period of time may not permit enough sleep and review for deeper understanding. Students who engage in such practices may easily be confused on an exam. The strategy of processing smaller amounts of information over a longer period of time, allowing for rest and frequent review, is likely to result in the retention of a better-integrated body of information.

Moving information from short-term memory to long-term memory requires frequent 9. rehearsal. Using note cards to create questions and answers based upon the information for an exam is one form of rehearsal that can be very effective when studying basic information. This chapter helps students understand the underlying physiological basis of many successful study techniques.

10.

The text notes that nearly 20 million American adults are affected by depression. However, many students have little idea of the population of the United States. Does 20 million represent a large or small fraction of the people in our country? Consider checking your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population is estimated at the website www.census.gov/main/www/popclock.html. At the time of the writing of this book, the U.S. population was nearly 315 million people.

The frequent occurrence of the neurological disorders discussed in this chapter makes it 11. likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class.

Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and 12. cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure.

The Senses Student Misconceptions and Concerns 1. We tend to think the world is that which we perceive. These modules on the sensory systems provide hints of the world that other organisms detect. From sounds and wavelengths above and below our spectrum to concentrations of scents beyond our detection, other organisms may perceive the world very differently from us. Consider encouraging your students to imagine the world as other organisms perceive it and thereby gain insight into their existence.

2. The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help make a connection. For example, digital cameras and DVD recordings rely on electronic storage and signal conversions to store and generate sounds and images.

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3. Lectures on the sensory systems of humans present numerous opportunities to relate new information to familiar student experiences. For example, the functions of the pinna of the ear can be exaggerated by cupping one hand around the pinna and noticing an increased ability to detect sound. Consider other simple demonstrations and explanations relating common experiences to the structure and function of the senses. (See the Teaching Tips below for examples.)

Teaching Tips 1. The natural tendency to wonder about our world seems sadly to fade with increasing education. Discussions of the human sensory systems can rekindle that curiosity in your students, if time is available to field their questions to help explain their experiences.

Perhaps you might have your class ask questions about their sensory experiences on 3 × 5 cards, which you can selectively answer later, and as time permits. The following tips include some examples.

2. As noted in the text, the brain does not have pain receptors. Challenge your class to explain what causes the pain of a headache. Muscle tension, sinus congestion, a toothache, and eyestrain can all cause headache pain beyond the brain. However, when our brain “hurts,” it is likely from pain receptors in the blood vessels supplying the brain.

3. You might want to ask your students to consider the uneven distribution of sensory receptors in the human body. Sensory receptors may be concentrated in regions where environmental inputs are focused, such as the eyes and ears, or spread more generally, such as skin or the walls of the digestive tract.

Students can better understand sensory adaptation by thinking about events in their lives.

4.

Perhaps they notice a distinct smell in the hallways and laboratories of the science facilities at your school. However, after a few minutes, we tend not to notice the smells as much. These experiences illustrate sensory adaptation.

Bits of cellular debris can drift within the vitreous humor and temporarily distort our 5. image. These bits are commonly called “floaters.”

Some students might recognize the test for glaucoma in which a puff of air is shot at the 6. eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball or squeezing a tennis ball are examples of other tests of internal pressure of a sphere.

The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses 7. might run when we cry because tears drain into our nose.

Challenge students to explain why an image appears clearer as we move closer to it. In 8. general, it has to do with the concentration of rods and cones in the retina. When we see an object at a distance, perhaps using only 1% of our field of vision, we use a proportional amount of rods and cones to form the image (about 1%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like computer monitors and newspaper photographs, the image is formed by a series of dots: the more dots to paint the picture, the clearer the image.

Cataracts, a clouding of the lens of the eye, are a common vision problem. Extensive 9. exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce exposure to UV light.

10.

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Why are albino eyes red and human eyes, in some photographs, red too? A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor

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cells. This pigment prevents reflected light from interfering with the detection of new light.

Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by this pigment layer, and instead reflects off of red blood cells in the choroid layer of the eye. Flash photography in a dimly lit room (in which pupils are large) can overwhelm the pigment layer, reflect unabsorbed light off red-colored blood, and make the pupils appear red.

11. Ciliary muscles of the eye can become fatigued if one focuses closely for long periods.

Students who spend hours reading, especially at the end of a long day, might find it difficult to focus closely. Staring off into the distance is relaxing in part because the ciliary muscles can relax.

12. Many optical illusions reveal the mental gymnastics of our mind to make sense of our visual world. Consider searching “optical illusions” in a Google search to identify many examples to share with your class.

13. Challenge students to explain why two eyes are better than one. Some of your athletes may have been given advice to turn their head as far as possible to spot a ball they hope to catch. Two eyes provide greater depth perception than one. Your students may not understand the concept of triangulation.

The lumping together of hearing and balance in the five senses learned in elementary school may result in a decreased appreciation for the sense of balance. Yet, hearing and balance are clearly separate senses. (Hearing-impaired people can still walk!) Consider asking your students to close their eyes and tilt their heads in different directions. How can they tell the position of their heads? In addition to the semicircular canals, stretch receptors in the neck provide positional information.

Consider asking your students why each of us has two ears. In general, it helps us locate 15. the source of a sound. If a sound is louder in one ear, then that ear is probably closer to the source. In general, when sound is of equal volume in both ears, we are facing the source.

Of course, there are exceptions.

Ask your class to consider the hypothesis that motion sickness results from mixed sensory 16. inputs from the eyes and balance organs. For example, do students agree that they might be able to read while traveling down a straight highway, but become sick if they read on a winding road? How might standing on the outside of a boat be different from standing deep inside a boat, unable to see the horizon? Considering the causes of motion sickness affords an opportunity to practice informed critical thinking.

Students might wonder why their voice played back from a recording sounds different 17. from what they hear when they speak. When we hear our own voice, many of the vibrations are transferred from our throat to our ear via bones, cartilage, and soft tissues.

These materials transfer the sound differently and thus do not sound the same as our voice transmitted through air.

14.

The range of human hearing and the effect of age can be demonstrated by a popular high18. pitched ringtone. Searching “high-pitched ringtone” on a Google search will reveal multiple sites where the pitch can be heard and downloaded. (It might also be called a “mosquito” ringtone.) Typically, people over the age of 30 have more difficulty detecting this pitch. This might also offer the opportunity to discuss the potential damage of loud noises on the delicate structure of the ear.

MP3 players and other players have increased our ability to damage our hearing. In 19. addition, listening to loud music while actively exercising outdoors can interfere with the

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detection of danger or vital communication. Consider discussing these important safety concerns with your class.

20. Students that have sampled colognes or perfumes may have noticed that after an initial sniff, the scent tends to linger. Assuming that the scented liquid was not touched to the nose region, the lingering smell may result from its persistence in the mucus covering the sensory cells. Without the cilia of the olfactory region to sweep away the mucus containing the scent, the smell might last much longer.

Locomotor Systems

Student Misconceptions and Concerns 1. The actual cellular mechanism of movement of skeletal muscle during contraction, the bending of myosin heads, is not well understood by most students. Consider focusing on this fundamental question as an introduction, exploring the answer as the detail of muscle structure is explored.

2. Muscle cells are only able to contract. None can actively relengthen. Challenge your students to explain how muscle cells return to their extended length. (Answer: Opposing muscles or other forces, such as gravity, act in opposition to relengthen muscle cells when they relax.)

3. Students often think of bones as static structures that provide support. The continuous remodeling of bone, adding or detracting in specific ways, is a nonstop sculpting process that enables our bones to accommodate the effects of mass and motion.

Teaching Tips 1. Most vertebrate skulls do much more than house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.

2. The structure of a tendon is very similar to that of a steel cable. In a tendon, collagen fibers are neatly arranged and slightly twisted together. Steel wire in a cable has a similar design.

The twist in both structures permits a limited degree of stretching to avoid snapping when a strong force is suddenly applied.

3. Students may have encountered hyaline cartilage at the ends of chicken bones during a meal. If the ends of bones are exposed during cooking, the cartilage dehydrates and does not appear white and glossy. However, if a joint is separated after cooking, such as dislocating a thigh from the leg of a chicken hindquarter, the glossy nature of the white cartilage can be appreciated for its ability to reduce friction in joints.

4. People do not often consume the nutritious elements inside of bone (although these tissues provide flavoring in soups that include a soup bone). However, in times and places with limited nutritional resources, boiling bones and/or breaking them open allows access to these additional nutrients.

5.

6.

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Astronauts typically suffer from bone loss. After months of time in the microgravity of space, the problem can become significant. Biomedical researchers working with NASA are trying to better understand the causes and methods that can limit this loss of bone mass.

Students may need help understanding how the contraction of sarcomeres over microscopic distances results in the perceptible motions of our body. Consider explaining it like this: Imagine we have a train with 100 cars that are all 20 feet long. If we shorten

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each car by 1 foot, how much shorter will the train be? (Answer: 100 feet.) The collective contraction of sarcomeres adds up to much larger movements.

7. One way to help explain motor units is to provide an analogy with the controls for the sets of lights in your classroom (if you are so equipped). Each set of lights is controlled by its own switch. The lights in one set all turn on or off (or perhaps dim) together. The total amount of light in the room depends upon how many sets of lights are turned on. Just as in 8. muscles, if a room requires more refined lighting, more switches (more motor units) will control fewer lights each (fewer muscle cells per motor unit).

Students might wonder why skeletal muscle cells have many nuclei. One of the limits of cell size is the ability of a nucleus to control the cytoplasm. As the cytoplasmic volume increases,

9. additional nuclei have been adaptive. A general analogy is to a daycare. At some point, as additional children are accepted into a daycare, more supervisors are required. There is a limit to the number of children that can be responsibly supervised by a single person, just as there is a limit to the amount of cytoplasm that can be controlled by one nucleus.

Key Terms The differences between dark meat and white meat in chickens and turkeys reflect differences in types of skeletal muscle fibers. Unlike humans, these birds have muscles action potential cones motor output retina made up primarily of just one of these types of muscle fibers. Dark meat in birds has Alzheimer’s disease cornea motor system rheumatoid arthritis higher amounts of myoglobin, fat, and capillaries associated with sustained contractions. appendicular skeleton corpus callosum motor units rods White meat, with less fat, less myoglobin, and fewer capillaries, is associated with quick aqueous humor dendrites muscular system sarcomeres contractions of the pectoral muscles to generate lift during takeoff. arthritisbursts, such as the eardrum myelin sheath sclera Artificial selection has resulted in variations on these basic differences. association areas effector cells myofibrils sensory adaptation astigmatism electromagnetic nearsightedness sensory input auditory canal receptors nerve sensory neurons autonomic nervous endoskeleton nervous system sensory transduction system Eustachian tube neurons skeletal muscles axial skeleton farsightedness neurotransmitter skeletal system axon hinge joint optic nerve spinal cord ball-and-socket joints hypothalamus osteoporosis stimulus bipolar disorder inner ear outer ear supporting cells brain integration pain receptors sympathetic division brainstem interneurons parasympathetic synapse cell body iris division synaptic cleft central nervous system lens peripheral nervous synaptic terminal system (PNS) tendons (CNS) ligaments photoreceptors thermoreceptors cerebellum major depression pinna thick filaments cerebral cortex mechanoreceptors pivot joint thin filaments cerebrospinal fluid medulla oblongata pupil threshold cerebrum meninges receptor potential vitreous humor chemoreceptors middle ear resting potential cochlea motor neurons .

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Word Roots aqua = water; humor = fluid (aqueous humor: a thin watery fluid in front of the lens of the eye) arthro = joint; itis = inflammation (arthritis: inflammation of the joints of the skeleton) audi = hear (auditory canal: the tube that channels sound to the eardrum) auto = self (autonomic nervous system: a subdivision of the motor system of vertebrates that regulates the internal environment) bi = two (bipolar disorder: a manic-depressive disorder in which a person switches between two extremes) cerebro = brain (cerebrum: the largest and most sophisticated part of the human brain) chemo = chemical (chemoreceptors: sensory cells that respond to chemicals) dendro = tree (dendrite: one of usually numerous, short, highly branched processes of a neuron that conveys nerve impulses toward the cell body) endo = inner (endoskeleton: a skeleton inside the body) hypo = below (hypothalamus: the master control center of the endocrine system, located below the thalamus in the brain) inter = between (interneurons: an association neuron; a nerve cell within the central nervous system that forms synapses with sensory and motor neurons and integrates sensory input and motor output) myo = muscle (myofibril: a contractile thread in a muscle cell) neuro = nerve; trans = across (neurotransmitter: a chemical messenger released from the synaptic terminal of a neuron at a chemical synapse that diffuses across the synaptic cleft and binds to and stimulates the postsynaptic cell) osteo = bone; pori = a hole (osteoporosis: a disease of thinning and porous bones) para = near (parasympathetic division: one of two divisions of the autonomic nervous system) photo = light (photopsin: a light-sensing pigment found in cones) syn = together (synapse: the locus where a neuron communicates with a postsynaptic cell in a neural pathway) thermo = heat (thermoreceptors: sensory receptors that detect heat)

Relevant Songs to Play in Class “Think,” Aretha Franklin “Insane in the Brain,” Cypress Hill “Check My Brain,” Alice in Chains

“19th Nervous Breakdown,” The Rolling Stones “Nervous Breakdown,” Rise Against “Brain Stew,” Green Day

Answers to End-of-Chapter Questions The Process of Science 13. Suggested answer: The corpus callosum allows communication between the two cerebral hemispheres. This structure allows for the integration of information. This must be the damaged structure that accounts for the patient’s problems.

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14. Suggested answer: Students could suggest experiments that test the ability of a person to either have a better depth perception with two eyes or better location of a source of sound with two ears.

Biology and Society 15. Some issues and questions to consider: Some people might be against the use of embryonic stem cells for any disorder. This may be related to religious or moral beliefs, or the belief that people are attempting to clone people. Potentially, some people may not be aware of the source of these stem cells and may be against their use if they believe that the cells come from elective abortions. It is important to discuss where scientists get stem cells for research. Other people may agree with the use of stem cells in research due to the potential to cure diseases that currently can lead to a fatal outcome. Some people who may have a neutral opinion on the issue might be swayed by the thought of a loved one who might be helped by stem cell therapy.

16. Some issues and questions to consider: What is the role of alcohol in crime? What are its effects on families and in the workplace? In what ways is an individual responsible for alcohol abuse? The family? Society? Who is affected by alcohol abuse? How effective are treatment and punishment in curbing alcohol abuse? Who pays for alcohol abuse and consequent treatment or punishment? Is it possible to enjoy alcohol without abusing it?

17.

Some issues and questions to consider: As with any known health risk, there is debate regarding how many and what type of warnings should be provided and what limits should be imposed on personal choices. Students might also debate whether warnings will be headed, and what else could be done to limit hearing damage.

Additional Critical Thinking Questions The Process of Science 1. Sixty degrees Fahrenheit at the end of a hot summer feels cold, whereas the same temperature at the end of a cold winter feels hot. How is it that the same stimulus produces two different sensations? Can you think of another stimulus, besides temperature, that produces this effect?

Suggested answer: Perception is always relative. The brain compares present experiences with previous ones and makes judgments based on that analysis. Therefore, at the end of a cold winter, 60°F is warm compared to 30°F, whereas at the end of a hot summer it is cold compared to 100°F. Also, hormone levels in our body such as thyroxine can alter our metabolism, which will also affect the way we perceive temperature. Another example that shows the same effect is taste. It is difficult to taste the sweetness of mildly sweet food after eating a candy bar.

2.

When a person dies, muscles become rigid and fixed in position, a condition known as rigor mortis. Rigor mortis occurs because muscle cells are no longer supplied with ATP. Also, calcium flows freely into dying cells. Explain, in terms of the mechanism of muscle contraction described in this chapter, why the presence of calcium and the lack of ATP would cause muscles to become rigid, instead of limp, after death.

Suggested answer: ATP causes the myosin heads of the thick filaments to detach from the thin filaments. If there is no ATP present, the myosin heads remain attached to the thin filaments, and the muscle fiber remains fixed in position.

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Biology and Society 3. Athletes sometimes take anabolic steroids illegally to increase the muscle size that occurs with training. In young people, whose bones are still growing, steroids also act to speed up the conversion of cartilage to bone. With regard to bone growth, what might be some negative consequences of steroid use by young athletes? Does steroid use seem to you to be worth the risks? Why or why not? As a competing athlete, would you use anabolic steroids if you knew you could get away with it? Why or why not?

Some issues and questions to consider: The major negative consequence is that the bones will become completely hardened before they have grown to their full size. This means that the steroid user will be shorter than he or she would otherwise have been. Do steroid users know this? Do they think the effects of steroids are temporary or reversible? Why is such emphasis placed on appearance and athletic prowess? Will steroid users later regret their use? Even if steroid use were not against the rules, would it be acceptable? What are the long-term effects of steroid use? If athletes use steroids and they break a record, should that record be counted?

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CHAPTER

28

The Life of a Flowering Plant

Why This Chapter Matters 1. Plants provide humans with food, lumber, fabric, paper, industrial chemicals, and medicines.

2. Plants provide shelter, food, and breeding areas for animals, fungi, and microorganisms.

3. The human diet consists almost entirely of plants and animals that ate plants.

4. Humans could not survive without the oxygen produced by plant photosynthesis.

Chapter Objectives Biology and Society: The Buzz on Coffee Plants 1. Describe the history of coffee cultivation.

The Structure and Function of a Flowering Plant 2 Compare the structures of monocots and dicots. .

Compare the structures and functions of root and shoot systems. Explain how “pinching back” a plant helps make the plant more bushy.

3 .4. Describe and compare the structures and functions of a taproot, runner, rhizome, tuber, and tendril.

5. Compare the structure and function of xylem and phloem.

6. Describe the structures, functions, and arrangements of the dermal tissue system, vascular tissue system, and ground tissue system in roots, shoots, and leaves.

7. Compare the structure and function of parenchyma cells, collenchyma cells, sclerenchyma cells, tracheids, vessel elements, water-conducting cells, and food-conducting cells.

Plant Growth 8. Compare indeterminate and determinate growth. Distinguish between annuals, biennials, and perennials.

9. Distinguish between primary and secondary growth.

The Life Cycle of a Flowering Plant 10. Describe the parts of a flower and their functions. Relate this structure to the life cycle of an angiosperm.

11. Describe the processes and events that lead to double fertilization.

12. Explain how a seed forms and describe the advantages of seed dormancy.

13. Describe the structure, formation, and functions of fruit.

14. Describe the general process of germination in a pea plant.

Evolution Connection: The Problem of the Disappearing Bees 15. Explain how flowering plants and land animals each gain from their mutually beneficial relationship.

16. Describe the latest threat to bees. .

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Lecture Outline I. Biology and Society: The Buzz on Coffee Plants 1. Human progress has always depended upon expanding our use of plants for a. food, b. fuel, c. clothing, and d. other trappings of modern life.

2. Coffee is one of the most important agricultural products in the world today 3. Ground coffee is made from the seeds of plants belonging to several species in the genus Coffea 4. Coffee was discovered in Ethiopia during the 1200s 5. By the 1700s, imported coffee plants were an important crop in the Americas 6. People love coffee because of the jolt we get from caffeine, which a. is naturally produced by the coffee plant as a self-defense against herbivores and b. stimulates the nervous system of those who consume it.

II. The Structure and Function of a Flowering Plant 1. Angiosperms a. have dominated the land for over 100 million years and b. account for about 250,000 species alive today.

2. Most of our foods come from 100 or so species of domesticated flowering plants including a. roots such as beets and carrots, b. fruits of trees and vines such as apples, nuts, berries, and squash, c. fruits and seeds of legumes, such as peas, peanuts, and beans, and d. grains, fruits of grasses, such as wheat, rice, and corn.

A. Monocots and Dicots 1. On the basis of several structural differences, angiosperms are classified into two groups: a. monocots and b. dicots.

2. The names of the groups refer to cotyledons, the first leaves to emerge from a growing seedling a.

A monocot embryo has one seed leaf.

A dicot embryo has two seed leaves. b.

The 3. largest group of dicots is the eudicots Most flowering plants are eudicots 4.

B. Plant Organs: Roots, Stems, and Leaves 1. Plants have a. organs made up of different tissues and b. tissues made up of one or more types of cells.

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2. The evolution of plants onto land around 475 million years ago required a. structures for absorbing water and minerals from the soil, b. a large light-collecting surface, c. the ability to take in carbon dioxide from the air for photosynthesis, and d. adaptations for surviving dry conditions.

3. In a land plant, these vital functions are performed by a. roots (below ground) and b. shoots (above ground), including i. stems, ii. leaves, and iii. flowers.

4. Roots 5. A plant’s roots a. anchor it in the soil, b. absorb and transport minerals and water, and c. store food.

6. All of a plant’s roots make up its root system 7. Root hairs a. are tiny projections near the root tips and b. increase the surface area of the root, providing an extensive outer layer for absorption of water and minerals.

8. Large taproots a. occur in plants such as carrots, turnips, sugar beets, and sweet potatoes and b. store food in the form of carbohydrates such as starch.

9. Other types of modified roots include buttress roots, aerial roots that a. look like buttresses and b. support the tall trunks of the trees that produce them.

10. Stems 11. The shoot system of a plant is made up of a. stems, b. leaves, and c. structures for reproduction (flowers).

12. Stems generally a. grow above the ground and b. support the leaves and flowers.

13. A stem has a. nodes, the points at which leaves are attached, and b. internodes, the portions of the stem between nodes.

14. When a plant stem is growing in length, the terminal bud, at the apex (tip) of the stem, has a. developing leaves and b. a compact series of nodes and internodes.

The 15. axillary buds , one in each of the crooks formed by a leaf and the stem, are usually dormant .

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16. In many plants, the terminal bud produces hormones that inhibit growth of the axillary buds, a phenomenon calledapical dominance 17. Removing the terminal bud can make a plant bushier 18. Stems can take many forms a. Strawberry plants have horizontal stems, or runners, that i. grow along the ground surface and ii. serve as a form of asexual reproduction. b. Iris or ginger plants have horizontal underground stems called rhizomes. c. A potato plant has rhizomes ending in enlarged structures called tubers. d. The “eyes” of a potato are axillary buds, which can grow into new plants, allowing potatoes to be easily propagated.

19. Leaves 20. Leaves are the primary sites of photosynthesis in most plants and consist of a. a flattenedblade and b. a stalk, orpetiole, which joins the leaf to the stem.

21. Leaves are highly varied a. Leaves can be either simple or compound. b. Grasses and most other monocots have long leaves without petioles. c. A modified leaf called a tendril can help plants such as sweet peas or grapes climb up their supports. d. The spines of the cactus are modified leaf parts.

C. Plant Tissues and Tissue Systems 1. Tissues are a group of cells that together perform a specialized function 2. A tissue system consists of one or more tissues organized into a functional unit within a plant. For example, vascular tissue called a. xylem conveys water and dissolved minerals upward from the roots to the stems and leaves and b. phloem tissue transports sugars from leaves or storage tissues to other parts of the plant.

3. Plant organs a. include roots, stems, and leaves, and b. are made up of three tissue systems: i. the dermal tissue system, ii. the vascular tissue system, and iii. the ground tissue system.

4. Each tissue system is a. continuous throughout the entire plant body but b. arranged differently in leaves, stems, and roots.

5. The dermal tissue system forms an outer protective covering and a. forms a first line of defense against physical damage and infectious organisms. b.

6. On leaves and on most stems, dermal cells secrete a waxy coating called the cuticle, which helps prevent water loss

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7. The vascular tissue system a. provides support and long-distance transport and b. includes xylem and phloem.

8. The ground tissue system a. accounts for most of the bulk of a plant and b. has diverse functions, including i. photosynthesis,

ii. storage, and iii. support.

9. A cross section of a eudicot root illustrates the three tissue systems a. The epidermis (the outer layer of the dermal system) is a single layer of tightly packed cells covering the entire root. b. In the center of the root, the vascular tissue system forms a cylinder, with i. xylem cells that radiate from the center and ii. phloem cells that fill in the wedges between the spokes. c. The ground tissue system forms the cortex, where cells i. store food and ii. take up water and minerals. iii. The innermost layer of cortex is the endodermis, a thin cylinder one cell thick that is a selective barrier that regulates the passage of substances between the cortex and the vascular tissue.

10. All plant stems have vascular tissue systems arranged in numerous vascular bundles a. The location and arrangement of these bundles differ between monocots and eudicots. b. In eudicots, another part of the ground tissue system, known as the pith, i. fills the center of the stem and ii. is often important in food storage.

11. The three tissue systems occur in eudicot leaves a. The epidermis containsstomata, tiny pores between two specialized guard cells, which regulate the opening and closing of the stomata. b. The ground tissue system of a leaf contains the mesophyll, the main site of photosynthesis. c. The leaf’s vascular tissue system is made up of a network of veins.

D. Plant Cells 1. Most plant cells have three unique structures a. Chloroplasts are the sites of photosynthesis. b. A largecentral vacuole containing fluid helps maintain the cell’s firmness (turgor). c. A protectivecell wall i. surrounds the plasma membrane and ii. consists largely of the carbohydrate cellulose.

2. Parenchyma cells a. are the most abundant type of cell in most plants and b. perform a variety of functions, such as i. food storage and ii. photosynthesis. .

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3. Collenchyma cells a. resemble parenchyma cells in lacking secondary walls, but they have unevenly thickened primary walls and b. provide support in parts of the plant that are actively growing.

4. Sclerenchyma cells a. have thick secondary cell walls usually strengthened with lignin, the main chemical in wood, and b. provide support to the plant.

5. Angiosperms have two types of water-conducting cells: a. tracheids , long, thin cells with tapered ends, and b. vessel elements , wider, shorter cells that are less tapered.

6. Water-conducting cells a. are arranged in chains of hollow tubes with overlapping ends and b. form a system of water-carrying tubes.

7. Food-conducting cells a. are also arranged end to end, forming tubes, but b. unlike water-conducting cells, remain alive at maturity.

III. Plant Growth 1. Most animals are characterized by determinate growth, ending growth after reaching a certain size 2. Most species of plants have indeterminate growth, the ability to grow for as long as they live 3. The life span of plants varies greatly a. Annuals live for only a single year or growing season. b. Biennials i. live for two years and ii. typically produce flowers and seeds in their second year. c. Perennials may live for many years.

A. Primary Growth: Lengthening 1. Growth in all plants is made possible by tissues called meristems, undifferentiated (unspecialized) cells that divide when conditions permit, generating new cells and tissues 2. Apical meristems a. occur at the tips of roots and in the buds of shoots and b. enable primary growth, growth in length.

3. A growing root a. is pushed through the soil by primary growth and b. contains a root cap that protects the actively dividing cells.

4. Primary growth in a root is achieved by a. cell division and b. cell elongation, mainly by taking up water.

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B. Secondary Growth: Thickening 1. The stems and roots of many plant species also thicken by a process called secondary growth a. Such thickening is most evident in woody plants, including trees, shrubs, and vines. b. The stems of woody plants last from year to year and consist mainly of thick layers of mature, mostly dead xylem tissue called wood.

2. The vascular cambium is a cylinder of actively dividing cells between the primary xylem and primary phloem 3. Secondary growth adds cells on either side of the vascular cambium 4. Annual growth rings result from the layering of secondary xylem 5. The layers are visible as rings because of uneven activity of the vascular cambium during the year 6. When secondary growth begins, the epidermis is shed a. It is replaced with a new outer layer called cork, produced by a meristem tissue called the cork cambium .

7. Mature cork cells a. are dead and b. have thick, waxy walls, which protect the underlying tissues of the stem.

8. Bark consists of everything external to the vascular cambium, including the a. secondary phloem, b. cork cambium, and c. cork.

C. The Process of Science: What Happened to the Lost Colony of Roanoke?

1. In 1587, 121 English settlers landed on Roanoke Island, in present-day North Carolina 2. Three years later they were gone and the settlement was deserted 3. There were no signs of struggle, and all the buildings had been dismantled 4. Observation: A large number of very old bald cypress trees around Roanoke Island could provide a reliable record of the climate over the past 800 years 5. Question: Could the tree ring data provide insight into the colony’s mysterious disappearance?

6. Hypothesis: The loss of the colony corresponded to a period of drought 7. Prediction : Tree ring data would show abnormal growth during the years after settlement 8. Experiment : Dozens of trees that covered the period 1185 to 1984 were analyzed 9. Results: a. The colonists arrived at the start of the worst three-year drought in the southeastern United States in 800 years. b. The drought and the resulting inability of the colonists to cultivate plants could have forced them to abandon the settlement.

IV. The Life Cycle of a Flowering Plant 1. Many flowering plants can reproduce sexually and asexually 2. Asexual reproduction allows a single plant to produce many offspring quickly and efficiently 3. Sexual reproduction in plants involves fertilization, the union of gametes from two parents, to produce genetically distinct offspring .

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A. The Flower 1. In angiosperms, the structure specific to sexual reproduction is the flower 2. The main parts of a flower are modified leaves: a. sepals enclose and protect the flower bud, b. petals are often colorful and fragrant, which may serve to advertise the flower to insects and other pollinators, c. stamen,and

d. carpel.

3. The flower’s reproductive organs are the stamen and the carpel anther, where meiosis occurs and pollen 4. A stamen consists of a stalk tipped by an grains develop 5. A carpel has a long slender neck (the style) with a sticky stigma where pollen grains land 6. The base of the carpel is theovary 7. Within the ovary areovules, each containing a. one developing egg and b. the cells that support it.

8. The term pistil is sometimes used to refer to a single carpel or a group of fused carpels B. Overview of the Flowering Plant Life Cycle 1. The life cycles of all plants include alternation of a a. haploid generation and b. diploid generation.

The diploid plant body is the 2. sporophyte 3. The haploid plant is thegametophyte 4. The sexual life cycle of an angiosperm involves a. fertilization,

b. the ovuleof a flower maturing into a seed containing the embryo, c. the ovarydeveloping into a fruit, d. the seed germinating in a suitable habitat, e. the embryo developing into a seedling, and f. the seedling growing into a mature plant.

C. Pollination and Fertilization 1. Fertilization requires gametes, which are produced by gametophytes a. The male gametophyte is thepollen grain, which i. is essential for pollination and ii. produces sperm. b. The female gametophyte is a multicellular structure called the embryo sac, which produces the egg.

2. The first step leading to fertilization is pollination, the delivery of pollen grains from anther to stigma 3. Many angiosperms are dependent on insects, birds, or other animals to transfer their pollen

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4. Double fertilization occurs as a. one sperm fertilizes the egg, forming the diploid zygote, and b. the other sperm i. contributes its haploid nucleus to the large diploid central cell of the embryo sac and ii. produces a triploid cell that will give rise to the food-storing tissue called endosperm .

D. Seed Formation 1. After fertilization, the ovule, containing the zygote and the triploid central cell, begins developing into a seed 2. The zygote a. divides via mitosis and b. forms a ball of cells that becomes the embryo.

3. The triploid cell a. divides via mitosis and b. develops into the endosperm.

4. The result of embryonic development in the ovule is a mature seed, a plant embryo and endosperm packaged within a tough protective covering called a seed coat E. Fruit Formation 1. A fruit is a mature ovary that acts as a vessel, a. housing and protecting seeds and b. helping disperse seeds from the parent plant.

2. Fruits include a. corn kernels, b. peaches c. tomatoes, and d. pea pods.

3. Mature fruits can be either a. fleshy or b. dry.

F. Seed Germination 1. Germination of a seed usually begins when the seed takes up water 2. The hydrated seed expands, bursting its coat, and the embryo resumes the growth and development that was temporarily suspended during seed dormancy G. Evolution Connection: The Problem of the Disappearing Bees 1. Flowering plants and land animals have had mutually beneficial relationships throughout their evolutionary history a. Angiosperms depend on insects, birds, or mammals for i. pollination or ii. seed dispersal. b. Most land animals depend on angiosperms for food and shelter.

2. In late 2006, U.S. beekeepers noticed a sudden and drastic die-off in their bee colonies 3. The next year, similar problems were reported in Europe 4. Bees pollinate $15 billion worth of crops each year, which is about one-third of our food supply .

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5. The cause of the die-off has not yet been explained, but several biological agents have been implicated, including mites or their pathogens

Chapter Guide to Teaching Resources The Structure and Function of a Flowering Plant Student Misconceptions and Concerns 1. Students often fail to see the applications of fundamental principles in biology. For example, many structural adaptations increase the surface-to-volume ratio in plants and animals. The divisions within the human lung, microvilli, leaves, and root hairs are examples. Increased surface areas are typically found where something is exchanged: gases exchanged at respiratory surfaces, nutrients absorbed by microvilli, light absorbed by leaves, and water and minerals absorbed by root hairs. If this chapter is one of the final topics addressed in your course, illustrating these broad principles from a variety of subjects can be a unifying review.

2. Students may not understand turgor, although they encounter it in their lives. The shape of a water balloon is different from the shape of an uninflated balloon due to internal fluid pressure (turgor). A plant in need of water may have drooping leaves, a consequence of decreased turgor.

Teaching Tips

1. Table 28.1 is a visually simple and important comparison of monocots and dicots.

Consider showing this table when comparing these two groups.

2. The impact of the green revolution and the continued improvement of agricultural techniques and crops may be little appreciated by your students. Yet, from 1940 to 1980, wheat production doubled while the cost of production was cut in half. Consider

3.

sharing and discussing the importance of these developments as they relate to modern economies and world population.

4. Consider bringing living examples of monocots and dicots to class or using a short trip outside during a related lab to quickly compare examples.

5. Challenge your students to suggest circumstances when apical growth is more adaptive for 6. a plant, and other situations in which branching would be more favorable.

Cellulose is the most abundant organic compound on Earth. Students often find this 7.

fact worth remembering.

Students might remember the function of phloem if you point out the “F” sound

8. common to phloem and food.

The modifications of the three plant organs reveal the remodeling nature of evolution.

As 28 TheJacob Life of anoted, Floweringevolution Plant François works more like a tinkerer 418 CHAPTER . and not an engineer. The common ancestry of eudicots is revealed by the diverse modifications of three basic plant organs derived from the shared ancestors. Your students’ appreciation of the enormous evidence of evolution will grow with frequent examples noted throughout your course.

The functions of human epidermis have some similarities in plants. Like plants, our epidermis is a defense against physical damage and infectious organisms. In addition,

Plant Growth Student Misconceptions and Concerns 1. Students often expect determinate growth in plants, because it is characteristic of humans.

However, most plant species show indeterminate growth, capable of growing as long as they can live.

2. Students typically expect that as a tree grows taller, the length of the trunk stretches upward. This expectation naturally arises from our own human experiences. However, as a tree grows, the trunk does not stretch upward. Instead, growth occurs at the upper ends and through expansion of the trunk. Therefore, initials carved into the trunk of a tree will be Teaching Tipsto remain at that height as long as the tree is upright and healthy. expected 1 Lobsters are one of the few animals that show indeterminate growth. . Students may not realize that the cork used to seal a wine bottle is the same cork that is 2 discussed above. Cork can come from a variety of trees.

3 . . Students may not appreciate the many important functions of tree bark. Carving into bark, or peeling it away from a trunk, exposes the inner tissues to pathogens. In many ways, the functions of human skin and bark are similar.

The Life Cycle of a Flowering Plant Student Misconceptions and Concerns 1. Students’ knowledge of sexual reproduction in animals often results in an expectation of similar processes in plants. The double fertilization typical of angiosperms requires extra time and attention to distinguish it from processes seen in animals.

2. The distinctions between fruits and vegetables are often debated in public discussions of plants. Consider discussing the use and significance of the terms fruit and vegetable.

Teaching Tips 1. The four main parts of a flower, which are modified leaves, represent additional examples of evolutionary remodeling.

2. Students may better remember that stamens are the male organs because they remember sta-“mens.”

3. Plants that produce light windborne pollen are the major sources of allergies, because the pollen remains in the air longer than heavier pollen grains.

4. Coconut “milk” is an example of liquid endosperm. Coconut “meat” is solid endosperm.

5. Seed dispersal mechanisms are diverse and reflect specific adaptive strategies. The inventor of Velcro was inspired by the seed dispersal mechanisms of the common burdock plant.

6. Seed production in most plants clearly illustrates the ability of organisms to produce more offspring than can survive, a premise of natural selection. While discussing seed production, consider reminding students of this important principal well illustrated in plants.

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Key Terms annuals anther apical dominance apical meristem asexual reproduction axillary buds bark biennials blade carpel cell wall central vacuole chloroplasts collenchyma cells cork cork cambium cortex cotyledons cuticle dermal tissue system determinate growth

Word Roots

dicot double fertilization embryo sac endodermis endosperm eudicots fertilization flower fruit gametophyte germinates ground tissue system guard cells indeterminate growth internodes leaves lignin meristem mesophyll monocot nodes

organ ovary ovules parenchyma cells perennials petals petiole phloem pith pollen grain pollination primary growth rhizomes roots root cap root hairs root system sclerenchyma cells secondary growth seed seed coat

sepals sexual reproduction shoot system sporophyte stamen stems stigma stomata terminal bud tissue tissue system tracheids tubers vascular cambium vascular tissue system vessel elements wood xylem

a = without (asexual reproduction: reproduction without sex) apic = the tip; meristo = divided (apical meristems: embryonic plant tissue on the tips of roots and in the buds of shoots that supplies cells for the plant to grow) bienn = every two years (biennial: a plant that requires two years to complete its life cycle) chloro = green (chloroplasts: the green, photosynthetic organelle common in plants) coll = glue; enchyma = an infusion (collenchyma cells: a flexible plant cell type that occurs in strands or cylinders that support young parts of the plant without restraining growth) di = two (dicot: a flowering plant whose embryos have two seed leaves) endo = inner; derm = skin (endodermis: the innermost layer of the cortex in plant roots) epi = over (epidermis: the dermal tissue system in plants; the outer covering of animals) gamet = a wife or husband (gametophyte: the multicellular haploid form in organisms undergoing alternation of generations, which mitotically produces haploid gametes that unite and grow into the sporophyte generation) inter = between (internode: the segment of a plant stem between the points where leaves are attached) meso = middle; phyll = a leaf (mesophyll: the ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis) mono = one (monocot: a flowering plant whose embryos have a single seed leaf) perenni = through the year (perennial: a plant that lives for many years)

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phloe = the bark of a tree (phloem: the portion of the vascular system in plants consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant) sclero = hard (sclerenchyma cells: a supportive cell with a very rigid secondary wall) sporo = a seed; phyto = a plant (sporophyte: the multicellular diploid form in organisms undergoing alternation of generations that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation) stam = standing upright (stamen: the pollen-producing male reproductive organ of a flower, consisting of an anther and filament) stoma = mouth (stomata: a hole in plant leaves through which water, oxygen, and carbon dioxide pass) vascular = little tube (vascular tissue system: a transport system of tubes for water and nutrients in plants) xyl = wood (xylem: the tube-shaped, nonliving portion of the vascular system in plants that carries water and minerals from the roots to the rest of the plant)

Relevant Songs to Play in Class “Send Me On My Way,” Rusted Root “The Dreaming Tree,” Dave Matthews Band “Seed to a Tree,” Blind Melon

“High Hopes (Rubber Tree Plant),” Doris Day “Autumn Leaves,” Tony Bennett

Answers to End-of-Chapter Questions The Process of Science 11. Suggested answer: The botanist would need to look at a cross section of the tree trunks. By counting annual growth rings, the approximate age of the tree should be apparent. The annual growth rings are produced in the vascular cambium each year. The rings result from the interruption of secondary growth in the winter and the resumption of growth in the spring.

12. Suggested answer: Though closing may seem like a disadvantage because it limits the carbon dioxide that can enter the plant, when the stomata are left open, the plant loses water. When temperatures are very hot, as at noon in the summer, this dehydration can be damaging. Experiments varying the temperature and/or moisture levels of the environment would test this explanation.

Biology and Society 13. Some issues and questions to consider: Why are forests cut when preserving them is more beneficial for the future? Why are the developing nations not creating new forest products themselves? Should developing and developed nations share in the profits from the forests? What incentive is there for a company to create a new product if it cannot keep the profits? Should companies pay an exploration fee for exclusive rights to take plants from a certain area? Should the developing country get a percentage of the profits from new products? Are there reasons to preserve the forests, other than profits and beneficial new products? Do people or corporations in less industrialized nations (or any nation) have the right to cut down tropical forests for profit? .

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14. Some issues and questions to consider: Most people are not as concerned about the cloning of plants as they are about the cloning of animals. The natural occurrence of plant cloning and the long history of human culturing of cloned plants may make some people more comfortable with plant cloning. The issue of cloning plants actually brings about some of the same concerns as animal cloning. These concerns might include lack of diversity in the population.

Additional Critical Thinking Questions The Process of Science 1. Why does thinning a forest by logging increase the diversity of the plants in the undergrowth?

Suggested answer: Thinning trees allows more light to penetrate the upper canopy. As more light reaches the ground, the greater the number of plants that can grow under the trees. Thinning creates a disturbance and increases the types of habitat in a forest, allowing more species to grow.

2 Since plants can make their own food through photosynthesis, why does a seed need stored nutrients for the plant embryo?

Suggested answer: As the embryo emerges from the seed, the embryonic shoot must push through the soil before it comes in contact with sunlight and can begin photosynthesis. The stored nutrients sustain the embryonic plant long enough to begin the photosynthetic process.

Biology and Society 3. Plant scientists are searching Peru, Mexico, and the Middle East for the wild ancestors of potatoes, corn, and wheat. Why is this search important?

Some issues and questions to consider: Modern methods of plant breeding and propagation have increased crop yields but have decreased genetic variability, so plants become more vulnerable to epidemics. Primitive varieties of crop plants could contribute to gene banks and be used for breeding new strains.

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CHAPTER

29

The Working Plant

Why This Chapter Matters 1. The human diet consists almost entirely of plants and animals that ate plants.

2. Plants provide humans with lumber, fabric, paper, industrial chemicals, and medicines.

3. The ability to control and direct the mass production of plants and plant products is therefore essential to the welfare of humanity.

4. Understanding plant nutrition, growth, and reproduction is an essential part of modern agriculture.

Chapter Objectives Biology and Society: Planting Hope in the Wake of Disaster 1. Explain how phytoremediation is helping to address the damage caused by Hurricane Katrina and the 2011 earthquake disaster that struck Japan.

How Plants Acquire and Transport Nutrients 2. Explain where and how a plant obtains all the materials necessary to construct all the organic materials it needs.

3. Distinguish between micronutrients and macronutrients, noting examples of each.

4. Describe the advantages of organic farming.

5. Describe the structure and function of root hairs.

6. Explain how mycorrhizae help plants absorb nutrients from the soil.

7. Explain how and why most plants depend on bacteria to supply nitrogen.

8. Describe the special relationship between legumes and nitrogen-fixing bacteria.

9. Explain the transpiration-cohesion-tension mechanism responsible for the ascent of sap in xylem.

Explain how and when guard cells control transpiration.

10.

Explain how, when, and where phloem conducts sap.

11.

Plant Hormones 12. Describe the general roles and properties of plant hormones.

13. Describe the roles of the five major types of plant hormones.

14. Explain how plant hormones are used to manipulate agricultural crops.

Response to Stimuli 15. Define phototropism, gravitropism, and thigmotropism and explain their significance in plants.

16. Distinguish between short-night plants and long-night plants.

Evolution Connection: Plants, Mantises, and People 17. Explain how life is interrelated.

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Lecture Outline I. Biology and Society: Planting Hope in the Wake of Disaster 1. On March 11, 2011 a magnitude 9.0 earthquake originated beneath the Pacific Ocean.

This earthquake a. was one of the five strongest earthquakes ever recorded, b. produced a tsunami that swept six miles into northeastern Japan, c. killed more than 15,000 people, d. damaged or destroyed at least 125,000 buildings, and e. flooded the Fukushima Nuclear Power plant, leading to a core meltdown.

2. Cleanup of this disaster will take decades 3. Bioremediation a. is the use of living organisms to detoxify polluted sites and b. includes phytoremediation, the use of plants to help clean up polluted soil and groundwater.

4. Sunflowers and other domestic plant species are being used to help clean up after a. the Hurricane Katrina disaster of 2005 and b. this recent disaster in Japan.

II. How Plants Acquire and Transport Nutrients 1. About 96% of a plant’s dry weight is organic material synthesized from inorganic nutrients extracted from the surroundings 2. Plants obtain a. carbon dioxide (CO2) from the air and b. water (H2O) and minerals (inorganic ions) from the soil.

3. Plants produce sugars via photosynthesis using a. CO2 and b. H2O 4. A plant constructs all the other organic materials it needs using these sugars and minerals A. Plant Nutrition 1. A plant’s essential elements are chemical elements, a. obtained from its environment and b. needed to complete its life cycle.

2. Of the 17 essential elements, a. 9 are macronutrients, required in relatively large amounts, and b. 8 are micronutrients, which plants require in relatively small amounts.

3. Macronutrients 4. Six of the nine macronutrients, carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus, make up almost 98% of a plant’s dry weight 5. The other three macronutrients, calcium, potassium, and magnesium, make up another 1.5% of a plant’s dry weight

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6. What does a plant do with macronutrients? a. Carbon, oxygen, and hydrogen are the basic ingredients of a plant’s organic compounds. b. Nitrogen is a component of i. all nucleic acids, ii. all proteins, iii. ATP, iv. chlorophyll, and v. many plant hormones. c. Sulfur is a component of most proteins. d. Phosphorus is a major component of i. nucleic acids, ii. phospholipids, and iii. ATP. 7. Micronutrients 8. Eight micronutrients a. are required by all plants and b. make up the remaining 0.5% of a plant’s dry weight.

9. Micronutrients are a. recycled and therefore b. needed in small amounts.

10. Fertilizers 11. The quality of soil affects a. the health of plants and b. their nutritional value to organisms that eat them.

12. Nitrogen shortage is the most common nutritional problem for plants 13. Fertilizers are compounds given to plants via the soil to promote the plants’ growth 14. There are two basic types of fertilizers a. Inorganic fertilizers contain simple, inorganic minerals. b. Organic fertilizers are composed of chemically complex organic matter, such as compost, a soil-like mixture of decomposed organic matter.

15. Organic farming a. uses compost and other organic fertilizers, b. uses no (or few) synthetic pesticides, c. maintains and replenishes soil quality, d. avoids genetically modified organisms, e. conserves water, and f. is one of the fastest-growing segments of agriculture.

B. From the Soil into the Roots 1. A plant uses its roots to absorb water and essential nutrients from the soil 2. Root hairs a. are extensions of epidermal cells and b. dramatically increase the surface area available for absorption.

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3. All substances that enter a plant root are dissolved in water 4. To reach the xylem, the solution must pass through the selectively permeable plasma membranes of root cells 5. Many plants formmycorrhizae , mutually beneficial associations with fungi that a. increase the absorptive surface area of the roots and b. nourish the fungus.

C. The Role of Bacteria in Nitrogen Nutrition 1. Most plants rely on bacteria to supply them with usable nitrogen in the form of or a. ammonium (NH+) 4 b. nitrate (NO–).

3 2. Soil Bacteria and Nitrogen 3. Three types of soil bacteria play an essential role in supplying plants with nitrogen a. Nitrogen-fixing bacteria convert atmospheric N2 to ammonium, a process called nitrogen fixation. b.

Ammonifying bacteria add to the soil’s supply of ammonium by decomposing c. organic matter.

Nitrifying soil ammonium to nitrate.

Nodulebacteria Bacteriaconvert and Nitrogen 4. Root 5. Legumes a. include peas, beans, peanuts, and other plants that produce their seeds in pods and b. have their own nitrogen-fixing bacteria in root nodules that produce ammonium.

D. The Transport of Water 1. To thrive, a plant must be able to transport a. water and b. dissolved ions from its roots to the rest of the plant.

2. Xylem sap, a. is a solution of water and inorganic nutrients and b. is transported from the roots to the tips of the leaves through vertical xylem tubes.

3. The Ascent of Xylem Sap 4. Transpiration , the loss of water vapor from the leaves of a plant by evaporation, a. mostly occurs through the stomata of leaves and b. pulls xylem sap up the plant against gravity.

5. Transpiration relies on two special properties of water a. Adhesion is the sticking together of molecules of different kinds. b. Cohesion is the sticking together of molecules of the same kind.

6. Together, adhesion and cohesion create a continuous string of water molecules that stick a. to each other and b. to the inside walls of the xylem tubes. c. The ascent of xylem sap is called the transpiration-cohesion-tension mechanism.

7. The Regulation of Transpiration by Stomata 8. Transpiration a. helps to distribute water within a plant but b. can cause plants to lose large amounts of water.

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9. Plants adjust their transpiration rates to changing environmental conditions 10. In many plants, stomata are open during the day, which a. allows CO2 to enter the leaf from the atmosphere and b. keeps photosynthesis going when sunlight is available.

11. At night, when there is no light for photosynthesis, and therefore no need for CO2, many plants close their stomata 12. Stomata are opened and closed by changes in the shape of the two guard cells flanking each stoma E. The Transport of Sugars 1. Phloem sap contains a. inorganic ions, b. amino acids, c. hormones, and d. the disaccharide sugar sucrose a plant makes by photosynthesis.

2. Phloem sap moves in various directions, a. from a sugar source , where sugar is produced, b. to a sugar sink , where sugar is stored or consumed.

3. Phloem sap moves from a sugar source to a sugar sink by the pressure-flow mechanism 4. Plant Hormones 5. A hormone is a chemical signal that a. is produced in one part of an organism, b. is transported to other parts, and c. acts on target cells to change their functions.

6. Hormones in plants control growth and development by affecting the a. division, b. elongation, and c. differentiation of cells.

7. Plant biologists have identified five major types of plant hormones F. Auxins 1. Auxins a. are group of related hormones and b. are responsible for a wide range of growth and development effects in plants.

2. Phototropism and Cell Elongation 3. Phototropism a. is the directional growth of a plant shoot in response to light and b. is caused by the elongation of cells on the side of the stem that gets the least amount of light.

G. The Process of Science: Do Chemical Signals Affect Plant Growth?

1. Charles Darwin and his son Francis performed some of the earliest experiments on phototropism 2. Observation: Grass seedlings bend toward light only if the tips of their shoots are present 3. Question: Do the tips of the seedlings produce some kind of growth signal? .

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4. Hypothesis: Plant tips sensed light and produced a growth signal in response 5. Prediction : Removing a shoot tip or blocking its access to light will prevent phototropism 6. Experiments : The Darwins performed several experiments to test their hypotheses 7. Results: a. Growth toward light was prevented by i. removing the tip of a grass shoot or ii. preventing the cap of a shoot from receiving light. b. Growth toward light occurred when placing i. a transparent cap on the tip of a grass shoot or ii. an opaque shield around its base.

8. Conclusions: a. The tip of the shoot was responsible for sensing light. b. The growth response, the bending of the shoot, occurred below the tip. c. Some unknown growth signal was transmitted downward from the tip to the growing region of the shoot.

9. The Action of Auxins 10. The hormones responsible for the phototropism observed by the Darwins are auxins produced by the apical meristem at the tip of the shoot 11. An uneven distribution of auxin on each side of a shoot causes a. higher auxin concentrations in the cells on the dark side, b. cells on the dark side to elongate, and c. the shoot to bend.

12. Auxins demonstrate that a. different concentrations of the same hormone may have different effects in the same target cell and b. the same concentration of a hormone may have different effects on different target cells.

13. Agricultural Applications 14. The use of synthetic plant hormones allows more food to be produced at lower cost 15. One widely used herbicide is a weed killer that a. is a synthetic auxin that disrupts the normal balance of hormones that regulate plant growth and b. affects monocots more than dicots.

H. Ethylene 1. Ethylene is a hormone that is released as a gas that triggers a variety of aging responses in plants, including a. fruit ripening and b. dropping of leaves.

2. Fruit Ripening 3. Fruit ripening is a. triggered by a burst of ethylene production in the fruit and b. spread from fruit to fruit by ethylene gas.

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5. Stored apples are often flushed with CO2, which inhibits the action of 6. ethylene Leaf Drop The loss of leaves in autumn is affected by ethylene 7. Leaf drop is triggered by environmental stimuli that 8. a. cause a change in the balance of ethylene and auxin and b. weaken cell walls in a layer of cells at the base of the leaf stalk.

I. Cytokinins 1. Cytokinins a. are a group of closely related hormones that act as growth regulators that promote cell division, b. are produced in actively growing tissues, and c. counter the inhibitory effects of auxin, resulting in complex growth patterns in most plants J. Gibberellins 1. Gibberellins a. are growth-regulating plant hormones and b. stimulate cell elongation and division in stems and leaves.

2. A combination of gibberellins and auxins can a. influence fruit development, b. make apples, currants, and eggplants develop without pollination and seed production, and c. make seedless grapes grow larger and farther apart in a cluster.

K. Abscisic Acid 1. Abscisic acid a. slows growth and b. can inhibit seed germination, allowing seeds to go dormant.

2. Some desert plants remain dormant until a downpour of rain a. washes out abscisic acid and b. allows the seeds to germinate when water is available.

III. Response to Stimuli 1. Plants can respond to physical stimuli from the environment, including a. light, b. touch, and c. gravity.

A. Tropisms 1. Tropisms are directed growth responses that cause parts of a plant to grow a. toward or b. away from a stimulus.

2. Phototropism is the directional growth of a plant shoot in response to light 3. Thigmotropism a. is a response to touch and b. occurs when a pea plant tendril coils around a string or wire it touches for support.

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4. Gravitropism a. is the directional growth of a plant organ in response to gravity and b. occurs when c. shoots grow upward and d. roots grow downward.

B. Photoperiod 1. Light a. provides energy for photosynthesis, b. directs growth, and c. regulates a plant’s life cycle, including i. flowering, ii. seed germination, and iii. the onset and ending of dormancy.

2. A photoperiod a. is the relative lengths of day and night and b. the environmental stimulus that plants most often use to detect the time of year.

3. Plants whose flowering is triggered by photoperiod fall into two groups: a. long-night plants and b. short-night plants.

4. Florists apply knowledge of the photoperiod of particular plants to bring us flowers out of season C. Evolution Connection: Plants, Mantises, and People 1. Plants rely on organisms from two other kingdoms to help acquire nutrients: a. soil bacteria and b. the fungi of mycorrhizae.

2. Nearly all land animals depend on plants or animals that ate plants for food 3. Consider the African mega mantis on the cover of the textbook a. The mantis depends on protists, plants, and animals for food. b. In turn, the mantis is eaten by other animals.

4. One of biology’s overarching themes is the interrelatedness of organisms a. Animals depend on other animals and plants. b. Plants depend on animals, fungi, and protists. c. All eukaryotic life depends on prokaryotes.

5. This interdependency reminds us once again that it is impossible to separate ourselves from all of the living creatures that share the biosphere

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Chapter Guide to Teaching Resources How Plants Acquire and Transport Nutrients Student Misconceptions and Concerns 1. Although analogies are often useful, some similarities can be misleading. The vascular tissues and movement of fluid through plants is in many ways unlike the circulatory system of animals, especially vertebrates. Vertebrates have one-way flow of fluids propelled by a contracting heart. Tissues in phloem can move in either direction, propelled instead by a pressure-flow mechanism.

2. It is important to distinguish between the acquisition of nutrients and the acquisition of food. Plants, unlike animals, do not obtain their food from the environment. Instead, plants are autotrophs that generate their own food. The essential elements required by plants are not sources of calories.

Students might assume that macronutrients are large in size and micronutrients are small.

3.

Instead, the word roots “macro” and “micro” refer to the quantities of nutrients required in each category.

4. Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the “win-win” nature of mutualism.

Teaching Tips 1. Cohesion of water enables some insects to walk or stand on a liquid water surface.

Cohesion and adhesion of water is also the reason why we need to dry ourselves off when we leave a shower—with water still clinging to our skin and hair.

2. Demonstrate or ask students to recall that when they use a soda straw and lift the straw out of the beverage, some of the beverage still sticks to the straw. This is an example of adhesion.

3. Many saps other than maple syrup are used commercially. For example, sap from rubber trees native to the Brazilian Amazon was once the major source of rubber. Now most rubber is synthetic, except for some specialized uses. Pine oil, derived from pine tree resin, is the active ingredient of Pine Sol. 4. With the exception of small amounts of glycogen from meat and lactose from dairy products, we get our dietary carbohydrates from plants.

5. Root hairs exhibit yet another example of an adaptation to increase the surface area of an organism. Alveoli within the human lung, microvilli, and plant leaves are other examples.

Increased surface areas are typically found where something is exchanged: gases exchanged at respiratory surfaces, nutrients absorbed by microvilli, light absorbed by leaves, and water and minerals absorbed by root hairs. If this chapter is one of the final topics addressed in your course, illustrating these broad principles from a variety of subjects can be a unifying review.

6. The change in shape of guard cells is due to turgor, internal fluid pressure, important in many other organisms. Turgor helps maintain the shape of plant cells, gives structure to the hydrostatic skeletons of sea anemones and earthworms, and causes a penis to become firm on erection. Before addressing guard cells, you may challenge your class to explain what leaves, sea anemones and earthworms have in common. The answer is turgor.

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Plant Hormones Student Misconceptions and Concerns 1. Students may think of plants as static, inert objects that passively interact with their environments. Without careful study and consideration, it can be challenging to explain how plants respond to their surroundings. This section on plant hormones reveals some of the significant mechanisms used by plants to respond appropriately to changing environmental conditions.

2. Students are unlikely to know about the many manipulations of plants in modern agriculture. Learning about them reveals the usefulness and importance of knowledge. In addition, some students will recognize the potential financial gains that come with the manipulation of plants and their products.

Teaching Tips 1. So much biology in courses answers questions, which students might have never thought to ask. Consider posing these questions before discussing plant hormones with your class.

What keeps seeds dispersed in autumn from sprouting in the winter? What keeps seeds in fruit from germinating immediately? As we explore biology, it is useful to wonder first, to prepare the mind for the explanation.

2. Although the analogies are limited, students might be challenged to identify human hormones that have effects similar to the plant hormones discussed in this chapter. For example, gibberellins and human growth hormone both promote growth.

3. Consider bringing a plant from someone’s office or greenhouse that distinctly shows a plant’s orientation in one direction. Before discussing phototropism, ask students to explain why the plant may have this orientation.

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Before explaining the answer, ask your students to explain how some seedless fruits are produced. It is often an amusing question to consider when you do not know how it is done!

In the nineteenth century when coal gas was used to power streetlights, the leakage of gas from pipes caused nearby trees to drop their leaves prematurely.

Special bags that are made of a material that absorbs ethylene gas are now commercially available. They can extend the life of fruits and vegetables stored within each bag.

Biology and modern agriculture represent compromise. Modern agriculture and society 7. must balance cost, quality, and environmental risks associated with our food supply. Share with your students the importance of science and education, to inform the decisions regarding these important issues regarding our food and the environment.

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Response to Stimuli Student Misconceptions and Concerns 1. As noted just above, students struggle to see plants as active responders to their environments. In addition to internal changes in physiology produced by hormones, plants can move in response to environmental stimuli.

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Teaching Tips 1. Photographs or living examples of a germinating seed and a climbing vine are very useful for demonstrating gravitropism and thigmotropism, respectively.

2. Short video clips on plant tropisms can be found by searching “tropisms video” in Google.

Such short clips can quickly illustrate these activities.

3. You might challenge your students to predict what would happen to North American longnight plants that typically bloom in the fall, if we moved them to Australia. We would expect that in Australia, long-night plants would bloom in the spring, compared to North America.

Key Terms abscisic acid adhesion auxins cohesion compost cytokinins essential element ethylene

fertilizers gibberellins gravitropism hormones macronutrients micronutrients minerals mycorrhiza

nitrogen fixation organic farming phloem sap photoperiod phototropism pressure-flow mechanism sugar sink

sugar source thigmotropism transpiration transpirationcohesion-tension mechanism tropisms xylem sap

Word Roots aux = grow, enlarge (auxins: a class of plant hormones that promote cell elongation, stimulate secondary growth, and promote the development of leaf traces and fruit) co = together; hesita = stick fast (cohesion: the sticking together of molecules of the same kind) cyto = cell; kine = moving (cytokinins: a class of related plant hormones that retard aging and act in concert with auxins to stimulate cell division, influence the pathway of differentiation, and control apical dominance) gibb = humped (gibberellins: a class of related plant hormones that stimulate growth in the stem and leaves, trigger the germination of seeds and breaking of bud dormancy, and stimulate fruit development with auxin) gravi = heavy; trop = turn, change (gravitropism: directional growth of plants in response to gravity) macro = large (macronutrients: elements required by plants and animals in relatively large amounts) micro = small (micronutrients: elements required by plants and animals in very small amounts) myco = a fungus (mycorrhizae: mutualistic associations of plant roots and fungi) photo = light (phototropism: growth of a plant shoot toward or away from light) thigmo = touch (thigmotropism: growth of a plant in response to touch)

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Relevant Songs to Play in Class “Send Me On My Way,” Rusted Root “The Dreaming Tree,” Dave Matthews Band “Seed to a Tree,” Blind Melon

“High Hopes (Rubber Tree Plant),” Doris Day “Autumn Leaves,” Tony Bennett

Answers to End-of-Chapter Questions The Process of Science

11. Suggested answer: Hypothesis: When fixed nitrogen levels increase to a certain level in the soil, genes coding for nitrogen-fixing enzymes in nitrogen-fixing bacteria are switched off. Test: Expose cultures of nitrogen-fixing bacteria (symbiotic and nonsymbiotic ones found in soil) to solutions of different concentrations of fixed nitrogen. Determine the concentrations of nitrogen-fixing enzymes produced by the bacteria in each sample. Prediction: If your hypothesis is correct, and the fixed nitrogen concentration is high enough in some of the samples, you would expect the enzyme concentration to be measurably lower in samples whose fixed nitrogen concentration is above the level that causes negative feedback.

Biology and Society 12. Some issues and questions to consider: How were the farmers assigned or sold “rights” to the water? How is the price established when a farmer buys or sells water rights? Is there enough water for everyone who “owns” it? What kinds of crops are these farmers growing? What will the water be used for in the city? Are there other users without rights, such as wildlife? Is any effort being made to curb urban growth and conserve water?

Should millions of people be living in what is essentially a desert? What are the reasons for farming desert land? What kind of crops are the farmers growing? Do they require a lot of water? Are the crops sold locally in cities, thus reducing the need to transport crops a long distance, or are the crops (for example, alfalfa) used to feed horses and cattle?

13. Some issues and questions to consider: Do traces of the hormone or its breakdown products remain with the apples when they come to market? If so, is the hormone safe for human consumption? What are its effects in the environment? Could its production produce impurities or wastes that might be harmful? What kinds of tests need to be done to demonstrate its safety? How much does it cost to make and use? Are the benefits worth the costs and risks? Is it worth using an artificial chemical on food simply to improve its appearance? A scientist could seek answers by studying the stability of the hormone in a variety of laboratory simulations of natural conditions. The toxicity of the hormone, of the materials used to produce it, and of its breakdown products could be determined in laboratory tests.

Additional Critical Thinking Questions The Process of Science 1. Since gravity and light affect plants through auxin production, predict the effect on a seed planted upside down with a light source from below the plant.

Suggested answer: The shoot will emerge from the soil and the roots will grow into the soil.

Once the shoot emerges from the soil, it will begin to grow toward the light below the pot.

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2. Jon just started a new job as night watchman at a plant nursery. His boss told him to stay out of a room where chrysanthemums (which are long-night plants) were about to flower.

Around midnight, looking for the restroom, Jon accidentally opened the door to the chrysanthemum room and turned on the lights for a moment. How might this affect the chrysanthemums? What could Jon do to correct his mistake?

Suggested answer: The red wavelengths in the room lights quickly convert the phytochrome in the mums to the Pfr form, which inhibits flowering in a long-night plant.

The mums will not flower unless Jon can rig up some far-red lights. Exposure to a burst of far-red light would convert the phytochrome to the Pr form, allowing flowering to occur.

Biology and Society 3. The clear-cutting of the tropical rain forest has global effects, which can be seen in carbon dioxide buildup and a drop in rainfall totals. The land created for farming becomes useless quickly because of depleted nutrients. Do we have any right to tell other countries how to manage their lands, such as rain forests? If we explain the consequences of clear-cutting the rain forests but that government decides to continue with the process, should we interfere?

Some issues and questions to consider: Our government has a responsibility to us to protect our environment but we also value freedom and cannot take that from other countries. Education and agricultural assistance may be our best means of preserving the rain forests. Can other countries interfere if one country’s actions affect nearby countries?

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APPENDIX

Great Ideas for Teaching Biology In the following pages you will find ideas and strategies submitted by instructors on a variety of topics ranging from freshening lectures to helping students retain information. These articles were originally published in the Pearson newsletter for science instructors, Strategies for Success. Past issues of the newsletter are available at http://www.pearsonhighered.com/strategies.

Popular Music Can Enliven Your Classroom Eric J. Simon, New England College esimon@nec.edu No subject in the science curriculum intersects with today’s popular culture more than biology. As teachers, we can take advantage of the current “golden age of biology” by em- phasizing the myriad ways that curricular content relates to students’ lives outside the class- room. Biology abounds in movies (travel to the Galapagos Islands with Russell Crowe in Master and Commander or consider a near-future society where genetic makeup determines social status in GATTACA), television shows (CSI reigns as the most popular show in Ameri- ca, and medical-themed shows can be seen nightly on the Discovery Channel), and music. Most students today are popular culture sponges; it is what they think about during their free time. By making references to these media, we can remind our students that biology exists outside the four classroom walls. We can also entertain and enliven the teaching/learning en- vironment—benefits of particular importance in the non-majors introductory course, where gaining and holding students’ attention can be half the battle.

One easy way to bring popular culture into the classroom is to play music before class. In my introductory courses (one for science majors and one for nonscience majors), I play a song relevant to each day’s lesson before the period starts. I then ask the same set of questions: Who can name the song and artist? Why am I playing this particular song today? Students enjoy the brain teaser of making the connection between the song and the subject under discussion. As a teacher, it is always gratifying to realize that students are thinking about the course material before the opening bell. This technique also allows you to create a loose, interactive atmosphere without sacrificing any actual class time.

During my lecture, I add the song (at half volume) to the PowerPoint slide that most closely relates to the song’s significance. The recurrence of the song can provide an “Aha!” moment for students, and some have said that the aural connection helps them remember the topic.

There are popular songs that intersect (often frivolously) with almost every topic in the introductory biology curriculum, either through the song title, the content of the song, or the name of the artist. Some are fairly obvious (“Do the Evolution” by Pearl Jam), others require a bit more thought (“More Than Words” by Extreme, used when discussing archaea), and a few induce groans (“I’ve Got You Under My Skin” by Frank Sinatra when discussing anatomy, or “Tiny Bubbles” by Don Ho when discussing protists). Here are a few more: • Introduction to Science: “She Blinded Me With Science” (Thomas Dolby), “Weird Science” (OingoBoingo), “The Sounds of Science” (Beastie Boys) • Introduction to Biology: “Wonderful World” (aka “Don’t Know Much Biology” by Sam Cooke), “Alive” (P.O.D.) .

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• Nutrition and Digestion: “Sugar Sugar” (The Archies), “Eat It” (Weird Al Yankovich), “The Middle” (Jimmy Eat World) • The Cell: “Tainted Love” (Soft Cell), “Golgi Apparatus” (Phish) • Photosynthesis: “Don’t Turn Off the Lights” (Enrique Iglesias), “Walking on Sunshine” (Katrina and the Waves) •

Reproduction: “Reproduction” (Grease 2 soundtrack), “Let’s Talk About Sex” (Salt N Pepa)

• Cloning: “I Think I’m a Clone Now” (Weird Al Yankovich), “Hello Dolly” (Broadway musical soundtrack) For a list of over 60 relevant songs that I have compiled (with the help of many colleagues)—or to contribute your own suggestion to this list—please e-mail me at esimon@nec.edu.

If you are not familiar with popular music yourself, you can easily turn this idea into an active learning exercise for your students. After you’ve played a few songs in class, you can offer your students one bonus point for each relevant song they suggest. Few professors would begrudge a student extra credit for actually thinking about biology during their free time!

One easy (and free and legal) way to play music in a computer-equipped classroom is to access music sites like itunes.com or amazon.com. There, you can play free samples of songs (typically 30 seconds). These sites also provide search engines that can find song titles or artist names containing relevant keywords (try entering “cell” into the iTunes search engine for a lot of interesting band names!).

While popular music is unlikely to impart content knowledge to your students, it can help grab and retain their attention, show the relevancy of the subject matter to the world around them, and perhaps even cause them to engage the subject matter outside the classroom.

Among introductory students, such small victories can be significant.

Freshen Lectures by Connecting Unrelated Concepts David Eakin, Eastern Kentucky University david.eakin@eku.edu For most students, the concept of “lively lectures” is as meaningful as the thunderous silence we experience at the end of most lectures. It is an oxymoron. Unfortunately, some in- structors still approach the act of teaching using the Middle English concept of lecture —“the act of reading.” Worse are those who have adopted Webster’s second definition, “a lengthy rebuke or scolding.” We fare no better when we investigate the synonyms for the word “live- ly”—and there are many: vigorous, full of spirit, marked by animated intelligence, invigorat- ing, refreshing, sparkling, effervescent, dynamic, full of life and energy. Need I continue? Each of these words suggests the single ominous antonym for the word, namely DULL! Following my own advice to communicators, I will address my remarks to the audience for whom this newsletter is written: those who are willing to work to become better at their craft! When I die, “dull as a doorknob” would not be my preferred epitaph! And while technology has added the possibility of innovation and freshness to the classroom, a bad teacher will be a bad teacher whether they have a piece of chalk or a laser pointer in their hand.

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I will use Darwin’s Concept of Natural Selection to illustrate one way to freshen your lectures. We all know what needs to be presented, and even how and where it is covered in our text. But sometimes a change of place and context will add a refreshing element of interest to our presentations. Why not put this essential concept in the context of the equally important concepts of biotic potential and population growth curves? And then add a dash of information on Darwin’s ability to do lateral thinking? Do I have your attention now?

Let’s see how this can apply to the five essential parts of Darwin’s thinking.

1. Populations tend to increase at an exponential rate.

2. Over time, populations tend to remain remarkably constant.

These are obviously ideas Darwin gleaned from the famous essays on human populations penned by Thomas Malthus. In modern terms, number one above is the J-shaped curve for biotic potential, while number two is the S-shaped curve for normal population growth and stabilization. Hence, we have a curve representing potential growth and one representing real growth. For me, cockroaches work well here, but you can use whatever great example of exponential growth excites you. In each case, there is the potential for billions in a short period of time, yet the reality is far less than the potential. The difference between the two curves is best explained by individual competition for limited resources. Thus Darwin’s third idea: 3. Competition exists between individuals of a species.

The beauty of this approach is that we can add the concept of lateral thinking. Leaving the ideas of Malthus, Darwin shifts to his experience with the artificial selection techniques used by breeders. From this experience he deduces his fourth idea and conclusion: 4. No two individuals in a population are exactly the same genetically, thus: 5. Those individuals with the most favored genetic characteristics will survive, passing these characteristics to their offspring, and subsequently changing the genetic makeup of the population.

And what is the importance of adding lateral thinking to the process? Most of us just keep digging deeper in the same hole when stymied by some difficult problem. What characterizes the genius of Darwin and others like him is their ability to dig a new hole and then connect seemingly unrelated concepts. When a World War II bomber crew lost their hydraulic fluid to flak, they were saved because someone shifted their thinking and suggested that the hydraulic system be filled with urine instead—something they could produce themselves. Darwin was able to connect seemingly unrelated concepts from genetics and population studies to develop his now famous concept of natural selection!

Perhaps this strategy will stimulate you to consider new approaches, ideas, and technologies in your lectures—things that bring to the classroom and your students your passion and excitement for the subject!

What Freshmen Don’t Know William J. Higgins, University of Maryland wh16@umailsrv0.umd.edu About five years ago I returned from a detour into administration to teaching. I was so enthralled with the idea of returning to teaching, that I assigned myself an introductory biology course for new freshmen. While I have not regretted my decision, I have wrestled with a question faced by many faculty: why do so many freshmen do so poorly in introductory science courses? .

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During the first semester with my freshmen, I was rolling along until the first lecture examination. Disastrous! Shameful! Just plain ugly! Over 50% of this brilliant group of students scored less than 65% on an easy, straightforward test. What went wrong? Who messed up, teacher or students or both? I decided to get some answers.

First, I asked for an early anonymous written evaluation from each student. According to my class, I was THE MAN. After reading notes full of superlatives, I realized that my freshmen were judging the quality of the class and the instruction by my enthusiasm and humor.

They were unable to identify problems with the learning process. They too were frustrated by their performances on an examination they judged to be “fair,” “on material they expected,” and “really fairly easy in hindsight.” I resolved to dig deeper into this mystery.

I got my first glimpse of the problem while I was attempting to answer a student’s question after class by referring to her lecture notes. I couldn’t find the section of her notes that covered the topic in question. I knew that she had attended every lecture and wrote frenetically as I spoke. But where in her notes was the stuff I wanted to show her? I hurriedly grabbed notebooks from every other student still in the lecture hall and frantically turned pages. The difficulty became obvious. During my lecture, students were accurately capturing less than 60% of the information and actually hearing and processing much less than that. Then they dutifully put the notebooks away until the next class, never revisiting those notes until the week of the test.

The root of the problem was apparent to me: my freshmen came to me with a collection of facts learned in high school, solid SAT scores that predicted brilliant academic careers, but no tools or strategies for handling college-level work. They needed a plan, an organized set of guidelines and strategies to help them survive until they evolved into mature, sophisticated learners.

How to generate this? I assembled a group of “volunteers” in my laboratory late one afternoon. Together we drafted the first version of what is now known to Maryland’s freshmen as the “Higgins Plan”—eight strategies for academic success.

Strategies for Academic Success The plan is simple, straight-forward things each student should do to insure success in difficult courses. Rule 1: Go to class, sit up front, and speak to the professor. Hey, you may be physically present, but it doesn’t mean you’re there! Rules 2 and 3: Form a study group of 3 or 4 students and recopy your lecture notes using the double column method after each class. This yields a complete set of notes rephrased in a student’s own words. The adjacent column of extra notes indicates corresponding pages in the text (highlights the important material and focuses the study effort), identifies material given special emphasis by the lecturer, and refers students to specific review questions in exams from previous semesters. Rule 4: Always have the examinations from previous semesters and use them to test your understanding. Rules 5 through 7: Practice, get help early, and manage your time well! My favorite, Rule 8: Things to do and behaviors to avoid on the day of the examination. The students have summarized this rule as, “Keep your cool so you don’t lose your . . . buttocks.”

Experienced seniors employ these or other similar strategies. They have figured out that you really know or understand something when you can explain or teach it. Hence, they study in groups. I now incorporate these learning strategies into my freshman lectures. Most listen to my message only after the first exam.

I, too, had to learn new things. I now put my lecture notes on the Web so everyone has the outline and knows where we are going. No, I don’t worry about students skipping class. I do want them to be relaxed listeners, confident that they’ll mentally replay the lecture, and fill in the gaps in their study group session. I generate tons of sample questions and post old examinations on the Web. I look at the notebooks of every student who comes to speak with me. I play 440

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matchmaker, banding strangers together into study teams. As a class we discuss strategies for learning, the value of group learning activities, and the importance of doing well.

Each fall I speak to Maryland’s incoming freshmen about the details of the Higgins Plan in special seminars in the residence halls. I put an abbreviated version on the Web at www.life.umd.edu/classroom/bsci230/higgins/. But, the most effective and influential presen- tation of these concepts comes as part of a class. Most freshmen are willing to work long and hard to be successful, but often do not because they simply don’t know what to do. We, the faculty, must give them the methods along with the information.

Exams with a Group Component Thomas Terry, University of Connecticut thomas.terry@uconn.edu When we think of the function of an exam, we usually think of assessing student learning and providing a grade that (hopefully) is a valid measure of that learning. We rarely give much thought to making the exam a learning experience in itself. As I went through my own learning curve as a teacher, I discovered that my students were very interested in learning what the correct answers to exam questions were, but the longer the time lag before they got this information, the less they cared. If I held a review class to “go over the exam” a few days or a week later, almost no one came. On the other hand, if I posted detailed answer keys online immediately after the exam, over 90% of students checked them within 8 hours. I wished I had some way to get them to look over the exam immediately after taking it, so they could see what they had done wrong and learn from their mistakes, but I couldn’t think of a mechanism to do this.

The Group Exam Technique Several years ago, a colleague at a teaching conference described a group exam technique he used. He gave exams that were shorter than the time available, and used the last part of the exam period for students to retake the same exam in small groups. Most of each student’s grade still came from their first, individual, performance, but he allowed a small addition to each student’s grade if the group outperformed its highest scorer. This sounded promising, and I tried it out in a large microbiology class. It worked surprisingly well, and I’ve used it ever since. My students spend the first 40 minutes of the 75-minute period taking the exam individually and recording their answers on a cover sheet that is handed in (students keep the exam). Then they reassemble into previously formed groups of 3–4 students, and each group is given the remaining half hour to move to its own space in the classroom, discuss the exam, and fill out a single group answer sheet. Watching the classroom during this group exam is an educator’s dream! In each group, students argue passionately for their answer, and occasionally laugh or even moan when they discover some of their mental follies. They walk out of the classroom having processed the exam thoroughly, and having taught each other.

Grading Rules Grades are the motivator for students to participate, so I spell out the grading rules very carefully. A group has to score higher than its best individual performer for the group to earn any bonus points. For example, if the group scores 95 out of 100, and its individual members scored 60, 70, 80, and 90, the group bonus is 5 points. I add that bonus to each member’s grade, so their final grades are 65, 75, 85, and 95. I disallow any group bonus greater than 5 points, even if the group scores 10 or even 25 points higher that its highest member (this does happen occasionally). If the group scores lower than its highest performer, the group bonus is zero—I don’t subtract points. In my experience, roughly 2/3 of groups earn a bonus on any given exam. .

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The same groups don’t always earn bonus points, but over three exams, less than 5% of groups fail to earn a bonus at least once. The average bonus over many semesters has consistently been about 3.6 points. It’s important that the bonus not be so large that groups who fail to earn it feel penalized. I’ve encountered situations where a group included someone who scored so high (e.g., 98 or 100) that the group could not earn bonus points. To prevent this from being a problem, I use a maximum grade of 95 for all individual scores, so every group has the potential to earn a 5 point bonus, but I restrict the maximum grade to 100.

Challenges Any procedure involving groups is bound to involve some challenges. I’ve tried various strategies for forming groups, and I’ve settled on letting students form their own groups with my prodding during earlier classes. I use group activities for other purposes, so by exam time most groups have had some experience working together. I allow students to change groups after each exam, but seldom find the need. Students who rarely come to class are the biggest problem, since they often miss periods when groups form and learn to work together before exams.

Time is the other main challenge. I have not used this format in classes with 50-minute periods—it always takes at least five minutes to collect individual exam papers (even with several proctors), cajole the slower students into handing in their papers, get the groups together and working, hand out the group answer sheet, and deal with problems (students who don’t know their group, groups missing too many members to function effectively, etc.). I find a 75-minute class period to be workable, but students must be able to complete the exam in less than 40 minutes in order for the exam to be a useful measure of accomplishment.

This format allows an exam to function both as an assessment tool and a learning experience, and over 90% of students rank it as adding value to their course. As one student said “The only thing I don’t like about the group exam is that I used to have the luxury of several days after taking an exam when I could sustain the illusion that I’d done better than I had— now I walk out of the exam knowing all the mistakes I made.”

Modeling Exercises Improve Understanding Jean Heitz, University of Wisconsin jgheitz@wisc.edu When I began my career, I thought that my students would learn more if I were a better teacher or if my presentations were better. However, as my presentations improved, student learning didn’t. I worked harder to increase student understanding— using PowerPoint and searching for color photos, diagrams, and animations. For one lecture presentation I selected the best animation of protein translation I could find. After the animation I projected slides recapping the steps in the process. I explained what each slide illustrated, and later asked the 200+students in the class if they understood. Many nodded, andTwenty-two no students admitted they students didn’t. went to their discussion section immediately after the of those same lecture. Their teaching assistant gave them each five minutes to either write a brief description of translation or diagram it. None of the students in the class could do this. What was the problem?

I later attended a colleague’s lecture where he showed an animation of DNA replication.

The animation included a recent discovery on how the RNA primers on Okasaki fragments are removed. I left the lecture feeling that “I really understood how it worked,” but when I tried to explain it to another colleague, I discovered that I couldn’t. Finally, the light dawned.

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My students didn’t understand for the same reason as I—neither of us had translated what was “obvious” in the animations into something that could be retained. How could I solve this problem and get my students to learn more? I needed to concentrate on how to help my students learn, rather than focusing on my knowledge and how I could do better.

Now I approach teaching differently. I still use animations in class to give my students a good feeling for the dynamic nature of processes that they otherwise couldn’t see. However, I have learned that after showing an animation, I need to work through my own interpretation of it on the blackboard. I’m not an artist. (Both Grandma Moses’s work and cave drawings would beat mine in any contest.) I use annotated stick figures, simple symbols, and line drawings to do the interpretation. For students to understand my drawings, I need to explain what each symbol or stick figure is supposed to represent. In the long run, however, my artistic shortcomings prove advantageous for two reasons.

First, after seeing my drawings, students never worry that their drawing ability is inadequate. Second, translating the animation into a very simple model helps them put all the associated terms and ideas into context. It also makes it easy for them to take notes. As a result, the process makes more sense and is easier to understand and remember.

Modeling to Learn and Retain To help insure that my students really understand the process, I don’t give them a copy of my diagram to memorize. I have them draw, diagram, or model the process themselves. For example, as a discussion exercise, I give the students a list of the different organelles, structures, and components that are required for translation. Using this list I have them work in groups of three to develop a model or diagram that they could use to teach translation.

The rules are simple: • Each group has to include all the listed items in their model or diagram. They can use their notes and textbooks while doing this.

• The model has to be simple. Drawings have to be in the form of stick-figure-type drawings or cartoon characters.

• For domino-effect processes (e.g., step 1 triggers 2 which leads to 3), I recommend they use play dough and develop “claymation” models. They can also diagram these as “Rube Goldberg” systems. I give students the following clip art and remind them of the board game “Mouse Trap®” as examples of this type of system.

• Each member of the group has to understand the process because, when they are done, I will randomly select one member of each group to teach a part of the process.

As the student groups develop their models, I move from group to group and ask questions to help direct their efforts. When their models are completed, each group is asked to explain theirs to another group. With ten minutes left in the period, I call on a student from each group to teach a specific part of the process of translation.

The following week, when I quiz the students on translation, almost all of them demonstrate a solid understanding of the process.

This type of modeling exercise will help students understand any kind of structure or process that is otherwise hard to view directly, which includes structures and processes that oc.

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cur at the molecular, and cellular, as well as global levels. For example, I have asked students to draw an annotated flow diagram (or Rube Goldberg type handout) to explain how the various components of the ear interact to produce the sensation of sound in the brain. In another exercise, I asked them to diagram and explain the interactions among B and T cells in immune responses. At the other end of the spectrum, I have asked students to diagram and explain global air circulation patterns.

To make sure they understand the processes I add a few “what if” questions. For example: AIDS targets T4 cells and kills them. What effect would this have on a person’s ability to fight off bacterial infections? What will happen to rainfall in the tropics as more and more of the tropical rainforests are destroyed? How could this affect weather patterns in Wisconsin?

These types of questions not only test their understanding of the process, they give students a reason for knowing the process. They also help students see how this new knowledge fits in with what they already know about the rest of the world. As a result they are more likely to retain that knowledge.

Doing Science Collaboratively with Investigative Case-Based Learning Margaret Waterman, Southeast Missouri State University, mwaterman@semo.edu, and

Ethel Stanley, BioQUEST Curriculum Consortium, Beloit College, stanleye@beloit.edu

Investigative case-based learning (ICBL) is a type of problem-based learning that is especially good for structuring collaborative work. ICBL uses realistic cases to engage students in a science topic, turning one of humanity’s oldest teaching strategies—telling stories—into a tool for collaborative science learning. Students frequently work as part of a group while they analyze the case and raise questions, as they conduct related scientific investigations, and as they prepare and present their findings. ICBL requires students to develop teamwork, communication, and information management skills—precisely the abilities needed for the workplace and for lifelong learning!

The story that follows is a composite of our own experience with ICBL and that of several biology instructors who have been in our ICBL workshops over the last five years. “Bob Powers” is a fictional instructor using an ICBL case with a general biology class.

Bob Powers Uses ICBL After years of teaching the macromolecules section of introductory biology, Bob Powers was still dissatisfied with how this part of the course went. The text was fine, the lectures well organized, and the labs were appropriate with students doing exercises in groups. The problem was that the students never seemed to get really interested and the group work seemed artificial.

Bob decided to use an ICBL case he found online (see expanded article for references) to try to hook the students and have them see that the information about macromolecules applied outside the classroom. He had read a little about cases and problem-based learning and thought it might be a way to use groups for more realistic science problem solving.

During lecture, Bob told his class that they would be using an ICBL case. Very few of his students had used cases before, so he assured them that he would show them how to do this.

He then passed out a single sheet that had a short case on one side and a case analysis sheet 444

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with room for notes on the other (see below). He asked a student volunteer to read the case out loud.

How Now Mad Cow

Stacy Kiser, Lane Community College, www.bioquest.org/lifelines My mother and I were driving to a nursery to buy plants for Mother’s Day when I asked her for a breath mint. She offered me some gum, but said, “I don’t have any breath mints after the big scare.”

I said, “Oh give me a break! What big scare?”

She said, “Well, I read on the Internet that you can get Mad Cow Disease from those mints made in England. After all, they’re made in Great Britain and they do have gelatin in them.”

And sure enough: (a picture of the mint box with “contains gelatin” and “Made in Great Britain” circled in yellow).

Case Analysis Sheet 1. Recognize potential issues and identify major topics. Working individually, underline or list terms or phrases that seem to be important for understanding what the case is about. Then discuss these with your group.

2. Pose specific questions.

By yourself, or better yet, in a group, think about what you know that is related to the case and its topics. Keep track of questions that arise with the Know/Need to Know chart below.

What do we know?

What do we need to know?

Identify 1–3 questions or issues from the “need to know” list that you or your group wants to explore.

3. Obtain additional references or resources to help answer or explore questions.

List four different resources you think would be helpful.

“Wow. Is that really true?” a student asked aloud.

“We’ll see,” Bob said. “So what do you all think this case is about?” Several students raised their hands. “Mad cow disease.” “Gelatin and getting sick from it.” “Wild rumors on the Internet.” “Regulation of foods.”

Next, Bob asked the whole class if any of them had any experience with some element of the case. How has Mad Cow Disease affected them? Do they ever use gelatin? Has anyone been in the UK lately? By asking these questions Bob was modeling the kinds of questions the students should be asking each other.

Bob next asked the class to work together in small groups discussing the case and raising questions for a few minutes. He asked them to use the case analysis sheet to structure their discussion and, particularly, the Know/Need to Know chart as a way for them to keep track of their ideas. He asked one volunteer from each group to take notes for the group on the Know/Need to Know chart.

Bedlam broke out momentarily as students rearranged themselves and their chairs. Then, quiet conversation began as students began to ask each other questions and to share what they knew about Mad Cow Disease, breath mints, and gelatin. “Gelatin is what???? Cow skins and hooves? Yuck!” “But it’s good for fingernails because it’s protein.” “What is Mad Cow Dis.

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ease?” “It’s a problem with the brain.” “Can people get it?” “How?” “Do we have it in the US?” “Is it over or still going on, ’cause we’re going to Europe next summer . . .”

Every group worked intently for 10 minutes or so. When they seemed to be slowing down, Bob called the class back together to hear a sampling of the ideas and questions that the groups had. Here are some ideas the students felt they knew: • Gelatin comes from boiled cow parts.

•

Gelatin contains protein.

• Enzymes are proteins.

• Hair is protein.

• Eggs contain protein. When you boil eggs, you are changing the structure of the proteins; that’s what makes them harden.

• Mad cow disease affects the brain. People can get it, and there’s no cure. If you’re worried, don’t eat beef.

• They slaughtered thousands of cows and sheep (?) a couple of years ago in Europe.

• The disease is something you can “catch.” It might be caused by a virus.

Students wanted to know: • What causes Mad Cow Disease?

•

If gelatin is a possible source, is the disease caused by a protein?

• How can a protein cause a disease? What do proteins do?

• Can you really get the disease from breath mints?

After this brief discussion, Bob had a pretty good idea of student background knowledge on proteins. Some students had learned quite a bit already. Just hearing each others’ ideas showed the students that no one person knew all the answers. They also learned that their fellow students were worth listening to.

The rest of that week the topic was proteins. In lecture, they learned about prions and Mad Cow Disease, as well as protein structure and enzyme function. Students worked in pairs with molecular models to see how amino acids are put together. In lab, Bob used activities he had done before, but now students seemed to have specific questions about proteins.

Students formed research teams in lab to examine the effects of pH, enzymes, or heat on protein structure. Bob set out some materials to work with: gelatin (hardened), egg whites (runny), a variety of fruits (including kiwi and fresh pineapple), vinegar, water, bleach, and a heat source, but encouraged groups to design and conduct their own investigations. Each group made posters to persuade their peers of their experimental methodologies and interpretations of results. The groups also used a computer simulation of an enzyme lab, varying parameters such as enzyme concentration, substrate, and inhibitors to explore enzyme function.

They had to run at least two simulations and explain their results.

For extra credit, individual students could use an Internet resource that Bob had identified for the class to complete—a personal risk analysis of getting Mad Cow Disease.

While students worked on their research designs, Bob observed the groups in action. He noticed what types of resources students consulted, how they worked together in groups, if they were posing questions, presenting results, and generating ideas. Such informal observations are a type of assessment that Bob used to help groups stay on task and work effectively.

In addition to these informal observations, the students produced a variety of products that Bob could choose to grade: the Know/Want to Know sheets, the group research designs, the posters, outputs from the simulations, and the risk analyses.

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After using “How Now Mad Cow,” Bob asked his students to answer a short survey about learning with cases. (He modified it from one available at www.bioquest.org/ lifelines/studentsurvey.doc.) The response was positive.

Given these data and his own impressions, Bob felt that the chemistry section went better this time and that he was able to accomplish several goals. First, his students were intrigued by the case, and he and they kept trying to connect their questions to new information discussed during the section on proteins. Second, Bob used collaborative methods in a lecture setting as students analyzed the case. Their analysis served as an informal assessment of what the class as whole already knew about proteins. Third, the case also raised interest in subsequent lectures and lab investigations. In effect, the case and case analysis discussion set a context that made lab and lectures more meaningful. An unintended outcome was that one student shared, “Hey, this is just like what my cousin is doing in med school—working on a case to learn how to use medical information!”

ICBL Is Based on Scientific Inquiry As we developed ICBL teaching strategies, we found the BioQUEST 3Ps to be helpful as a framework for instruction: Problem Posing, Problem Solving, and Peer Persuasion are based on the actions taken by practicing scientists. Students who learn with investigative cases utilize a similar three-phase approach.

I. Problem Posing: Analyzing a Case •

Introduce the case

•

Recognize potential issues and major concepts

•

Pose specific questions via Know/Need to Know analysis

II. Problem Solving: Investigating the Questions •

Obtain additional references/resources

•

Define problems more by sharing views and concerns

•

Design and conduct scientific investigations

III. Peer Persuasion: Supporting Methods and Reasoning •

Produce materials that support understanding of conclusions

Learn More About ICBL Getting started with any new teaching approach such as ICBL is easier if you are working with other faculty who are also learning to use this new tool. The expanded version of this article, available on the Strategies for Success website at www. pearsonhighered.com/strategies, includes information on the many ways ICBL can be used, preparing students for ICBL, assessing ICBL learning, and a wealth of cases and online resources for ICBL in biology.

Critical Analysis in the Laboratory

Cathy Switzer, Tomball College cathy.switzer@nhmccd.edu Keeping students engaged makes teaching and learning more fun for everyone, but the quality of student engagement is critical in determining the amount of actual learning taking place. Students can be engaged in laboratory activities that require memorization, but still have no ability to apply the knowledge to their daily lives. Most of all, students can be so immersed in the details of biology that they fail to see the beauty of its interconnectedness. Biology becomes a series of disjointed facts memorized and regurgitated on an exam—bulimic biology. .

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To help students with retention and problem-solving skills, I assign a current event article for each laboratory subject covered. Students are asked to read their articles and individually prepare a 1–2 page report, which will be discussed in class.

Reporting on the Article The report must include the following information: Title, author, bibliographic information.Students are asked to provide this information in MLA format. This reinforces the need to understand the value of bibliographic information as it appears in texts, journals, and other sources of scientific information.

Brief summary.The length of this summary should be relative to the length of the article.

As a general rule of thumb, I ask students to write one sentence for every one or two paragraphs. This is an excellent way to challenge their critical reading and writing skills as well as their ability to rephrase the thoughts of others.

Connections to the textbook.This challenges students to use the textbook as a resource and to venture outside the current chapter to look for other information related to this assignment. This helps students see that biology is not a series of categories to be covered, but rather a large, interconnected field of knowledge.

Connections to the lab exercise. This carries the connections just a little further to make sure that the students have read their lab exercise and know how it relates to the text and the article.

Scientific vocabulary.Reinforcing vocabulary is important in biology; therefore, students must list scientific words and their definitions. We often forget that this truly is a foreign lan- guage to most students, and requiring definitions helps dispel confusion.

Evidence of faulty reasoning.Students have a tendency to believe that everything written about a scientific topic must be true—it’s science. This activity helps students to become more critical readers, not just in science, but in all subjects. This is the hardest section for most students, and it will require some patience on the part of the instructor. However, the goal is for the student to show progress over the course of the semester. I provide my students with a handout that summarizes the following errors in reasoning: • Ad hominem: Criticism of the person rather than the argument. (Also known as “thought stoppers” because they evoke emotional rather than rational responses.)

• Appeal to authority: Acceptance as fact based upon the power or position of the person making the claim. (Obvious when no supporting data is offered.)

• Begging the question: Making something appear true when it is not. (Can be accomplished with visual aids as well as statements.)

• Equivocation: Introduction of words with multiple meanings to confuse the reader.

(Beware of slang terminology that derives meaning from context and voice inflection.)

• False dichotomy: Providing only two alternatives and inferring there are no other choices. (Either/or statements that corner readers into making a choice.)

• Red herring: Excessive information that detracts from the focus of the argument. (Information is off-track and might be more appropriate elsewhere.)

• Slippery slope: Conclusion of a cause-effect relationship between two events or actions. (May be in the form of a generalization.)

Using the Article in Lab Sessions Using the report in class is the next step. For example, prior to our first laboratory assignment on bacteria, students were assigned a reading from a common news magazine on a recent bacterial outbreak. After completing the assignment, I asked students to divide up 448

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based upon who thought it was a scientifically sound article and those who did not. Each side described their rationale based upon their search for faulty reasoning. Although I limited the discussion to ten minutes, this exercise became the key to development of critical reasoning.

As students explained their positions, quality discussion followed. Students who were less adept at analyzing articles learned quickly from their classmates, performed much better on subsequent analyses, and participated more in later discussions.

The most exciting results occurred during the actual laboratory exercise. Students remained engaged in both the execution of their lab exercises and in meaningful discussion during the entire lab period. Questions changed from hollow inquiries like, “Do I have to know this for the practical?” to more thoughtful questions like, “How does this organism evade the human immune system as compared to the one we read about?” The quality of answers to essay questions has improved, and student feedback on these assignments has been very positive. Many have returned to tell me how they have applied these analytical skills in other courses and at work.

This format can be adapted in a number of ways to fit most any science course. I have used it to focus on organisms in the news, bioethics, and environmental issues. It can be expanded into a large project or compressed into a smaller exercise done in class. It can also be done individually or in groups. It can even be done effectively online. My preference is to make the written portion of the assignment an individual responsibility to encourage freedom of expression. The classroom discussion allows immediate feedback and assistance for those who struggle with the critical analyses.

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