28.3 Reproduction Lesson Objectives Compare asexual and sexual reproduction. Contrast internal and external fertilization. Describe the different patterns of embryo development in animals. Explain how terrestrial vertebrates are adapted to reproduction on land. Lesson Summary Asexual and Sexual Reproduction Most animals reproduce sexually. Some animals are also able to reproduce asexually. Asexual reproduction requires only one parent allowing for rapid reproduction. Sexual reproduction requires two parents. This type of reproduction maintains genetic diversity in a population by creating individuals with new combinations of genes. Internal and External Fertilization In sexual reproduction, eggs and sperm meet either inside or outside the body of the egg-producing individual. During internal fertilization, eggs are fertilized inside the body of the egg-producing individual. In external fertilization, eggs are fertilized outside the body. Development and Growth Embryos develop either inside or outside the body of a parent in various ways. Oviparous species are those in which embryos develop in eggs outside the parents bodies. In ovoviviparous species, embryos develop within the mother s body, but they depend entirely on the yolk sac of their eggs. Viviparous species embryos obtain nutrients from the mother s body. Some mammals nourish their embryos by means of a placenta a specialized organ that enables exchange of respiratory gases, nutrients, and wastes between the mother and her developing young. As invertebrates, nonvertebrate chordates, fishes, and amphibians develop, they undergo metamorphosis, resulting in changes to their shape and form. Some insects undergo gradual or incomplete metamorphosis. Immature forms, or nymphs, resemble adults, but they lack functional sexual organs and some adult structures. Other insects undergo complete metamorphosis. Larvae change into a pupa, the stage in which an insect larva develops into an adult. Reproductive Diversity in Chordates Chordates had to adapt to reproduction on land. Most chordates need a wet or moist environment for their eggs. The eggs of most aquatic organisms must develop in water. Reptiles, birds, and a few mammals have evolved amniotic eggs in which an embryo can develop outside its mother s body, and out of water, without drying out. Mammals have various reproductive adaptations. But all mammalian young are nourished by milk produced by the mother s mammary glands. Lesson 28.3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 444
Asexual and Sexual Reproduction 1. What does asexual reproduction allow animals to do? It allows animals to increase their numbers rapidly. 2. What is an advantage of sexual reproduction? It helps a species maintain genetic diversity. 3. Shade the arrows showing haploid stage of the life cycle. Draw small dots in the arrows showing diploid stages. Female medusa Meiosis (dotted) (shaded) Sperm Male medusa Egg (dotted) Young medusa develops. Young medusa Fertilization Polyp Zygote Zygote grows into a larva. The larva attaches to a hard surface and develops into a polyp. Budding polyp (dotted) Internal and External Fertilization 4. What is the difference between external and internal fertilization? In external fertilization, eggs are fertilized outside the body of the egg-producing individual. In internal fertilization, eggs are fertilized inside the body of the eggproducing individual. Development and Growth Write the letter of the correct answer on the line at the left. B 5. In which mode of reproduction do the embryos develop inside the mother s body using the egg yolk for nourishment? A. oviparous C. viviparous B. ovoviviparous D. herbivorous C 6. Organisms that develop placentas are A. oviparous. C. viviparous. B. ovoviviparous. D. herbivorous. 7. Explain the difference between complete and incomplete metamorphosis. In complete metamorphosis, the insect goes through immature stages that do not look like the adult form. In incomplete metamorphosis, the immature form, the nymph, looks similar to the adult form. Lesson 28.3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 445
Reproductive Diversity in Chordates 8. Embryo Amnion Allantois Shell Chorion Yolk sac 9. Complete the table about mammal reproduction. Types of Mammalian Reproduction and Development Group How Are Young Born? How Are Young Fed? Monotremes Marsupials Placental mammals Young hatch from soft-shelled eggs laid outside the mother s body. Embryo is born at a very early stage of development and attaches to a nipple inside a pouch. Embryos develop inside the mother. Wastes and nutrients pass through the placenta. Young get milk from pores on the mother s abdomen. Young drink from a nipple inside the mother s pouch. Young are generally nursed by the mother. 10. How might the shape of an amniotic egg complement its function? SAMPLE ANSWER: The slightly elongated, pointed shape may help the mother lay the egg more easily. In addition, the shape keeps the egg from rolling far from a nest. Lesson 28.3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 446
28.4 Homeostasis Lesson Objectives Explain how homeostasis is maintained in animals. Describe the importance of body temperature control in animals. Lesson Summary Interrelationship of Body Systems Homeostasis is the maintenance of a relatively stable internal environment. All body systems work together to maintain homeostasis. Fighting disease-causing agents is a large part of maintaining homeostasis. Most animals have an immune system that attacks pathogens. Vertebrates and many invertebrates regulate many body processes using a system of chemical controls. Endocrine glands, which produce and release hormones, regulate body activities by releasing hormones into the blood. Body Temperature Control Control of body temperature is important for maintaining homeostasis, particularly in areas where temperature varies widely with time of day and with season. An ectotherm is an animal whose regulation of body temperature depends mostly on its relationship to sources of heat outside its body. Most reptiles, invertebrates, fishes, and amphibians are ectothermic. An endotherm is an animal whose body temperature is regulated, at least in part, using heat generated by its body. Birds and mammals are endothermic. Interrelationship of Body Systems 1. Complete the graphic organizer about body systems working together. Circulatory System Respiratory System The Main Organ Systems Contributing to the Delivery of Oxygen and Nutrients to Cells. Digestive System Lesson 28.4 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 447
2. What is homeostasis? Homeostasis is the ability of an animal to maintain a stable internal environment. 3. Name the body system that helps protect mammals from disease and describe how it accomplishes this task. The immune system protects mammalian bodies from disease. It does this by distinguishing between self and other. Once the immune system discovers others in the body, it attacks the invaders. 4. What are endocrine glands? Endocrine glands are part of the body system that regulates many body processes using chemical controls. Endocrine glands release chemicals called hormones that affect other organs and tissues. Body Temperature Control 5. List three features that animals need in order to control their body temperature. Animals need a way to generate heat, a way to conserve heat, and a way to eliminate excess heat. 6. How do ectotherms control their body temperature? They rely on interactions with the environment. 7. Explain how the human body cools itself. Humans sweat to help reduce their body temperature. As sweat evaporates, it removes heat from the skin and the blood in capillaries just under the surface of the skin. Thus, as warm blood flows through the cooled capillaries, it loses heat. 8. Name one advantage and one disadvantage of endothermy. One advantage is that endotherms can move around easily during cool nights or in cold weather. One disadvantage is that endotherms require a lot of fuel in the form of food in order to generate body heat. For Questions 9 15, complete each statement by writing the correct word or words. 9. Control of body temperature is important for maintaining homeostasis. 10. Cold muscles contract more slowly than warm muscles. 11. An animal that must absorb most of its heat from the environment is a(n) ectotherm. Lesson 28.4 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 448
12. An animal that uses heat generated by its own body to maintain its body temperature is a(n) endotherm. 13. Endotherms have a higher metabolic rate than ectotherms. after 14. Endothermy evolved ectothermy. 15. Mammals use body fat and hair as insulation in order to stay warm. Match each organism with the method of controlling body heat. Methods may be used more than once. Organism Body Heating Method B A 16. mammals 17. fish A. Ectothermy B. Endothermy A A B A 18. amphibian 19. invertebrate 20. birds 21. reptiles For Questions 22 25, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. True 22. The first land vertebrates were ectotherms. True 23. Some scientists hypothesize that some dinosaurs were endotherms. twice 24. Current evidence suggests that endothermy evolved at least four times. endotherms 25. Most animals living in polar regions are ectotherms. 26. Explain how an organism s circulatory, digestive, or excretory system helps the organism maintain homeostasis. SAMPLE ANSWER: The excretory system of an organism helps it maintain homeostasis by regulating water balance and getting rid of toxic waste products. For example, the kidneys excrete or retain excess liquid, but they filter waste products out of the bloodstream so that the waste products will not poison cells. Lesson 28.4 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 449
Chapter Vocabulary Review 1. In the box below, draw a picture of the arrangement of a joint, including at least one ligament and at least one tendon. Label your picture. Students drawings should show the articulation point of two bones. This point should be labeled as a joint. Connective tissues should be drawn connecting the two bones. This tissue should be labeled as a ligament. Another connective tissue should connect a bone to a muscle. This tissue should be labeled as a tendon. For Questions 2 7, complete each statement by writing the correct word or words. 2. A single, specific reaction to a stimulus is a(n) response. 3. A structure called a(n) placenta forms when an embryo s tissues join with the tissues from the mother s body. 4. One of the most important adaptations to life on land is the amniotic egg, which protects the growing embryo and keeps it from drying out. 5. In ovoviviparous animals, the eggs develop inside the mother s body, and the embryo uses the yolk for nourishment. 6. A(n) exoskeleton is a tough external covering of the body. 7. A(n) endoskeleton is an internal skeleton. For Questions 8 11, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. True 8. A stimulus is any kind of signal that carries information and can be detected. viviparous 9. In oviparous animals, the embryos develop inside the mother s body and obtain their nourishment from their mother, not the egg. pupa 10. In complete metamorphosis, the stage in which an insect changes from larva to adult is called a(n) nymph. True 11. A group of nerve cells that control the nervous system in many invertebrates is called a(n) ganglion. Write the letter of the correct answer on the line at the left. C 12. Mammals are characterized by hair and A. lungs. C. mammary glands. B. prehensile tails. D. four-chambered hearts. B 13. Animals that can generate their own body heat are known as A. ectotherms. C. chordates. B. endotherms. D. invertebrates. Chapter 28 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 450
SHE S JUST LIKE HER MOTHER After the incredible birth of the bonnethead shark at the Doorly Zoo, the zoo s public relations department was probably working overtime. The birth of this shark provided a perfect opportunity to promote the zoo. Learning Promoting Zoo Births Zoos work responsibly to foster the reproduction of animals. The birth of a zoo animal is something to be celebrated and promoted, especially when it involves an endangered or threatened animal. Zoo births are helpful to zoos in many ways. For example, they can bring in additional visitors and encourage donations to the zoo. A zoo s public relations department can find many ways to promote the birth of an animal. They may create and issue press releases, posters, pamphlets, commercials, and billboards. Their efforts may lead local television and radio stations to cover the animal birth in news reports. The following is an example of what a transcript of a live report by a local television station might have been like after a Sumatran tiger gave birth to triplets at the San Francisco Zoo. Live at 5 - San Francisco News REPORTING LIVE FROM THE SAN FRANCISCO ZOO March 14, 2008 - I m reporting live from the San Francisco Zoo. Zookeepers were in for a couple of surprises today at the San Francisco Zoo. The zoo has been buzzing with excitement and activity since their 230-pound Sumatran tiger, Leanne, gave birth to one cub on March 6. But just this week, the zoo revealed that Leanne actually had triplets! The zoo s chief veterinarian did not suspect that there was more than one cub until 6 days ago. How could this be? Well, Leanne had decided to take a tiger-size lick of the camera that was monitoring her, fogging up part of the lens. The birthing box was not completely visible, either. It was not until the thirsty new mom left the box to get a drink that the zookeeper noticed the two other cubs. Zookeepers do not want to disturb the mother and her young yet. Leanne is doing a great job of taking care of her babies even protecting them from the camera lens. Sumatran tigers are an endangered species, with only about 600 remaining in the wild. Zoo officials hope that these web-footed cubs will soon be swimming just as fast as other Sumatran tigers. Continued on next page Chapter 28 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 451
Themes Science and Global Awareness 1. What is the tone of this television report, and how is it intended to make you feel? SAMPLE ANSWER: The tone is one of excitement. It is probably intended to make the viewer want to visit the zoo to see the tiger triplets. 2. Suppose you were giving this report. What information would you add to the report? Explain your answer. SAMPLE ANSWER: I would give more information about the cubs, which is the main focus of the story, and thus the reason people are watching the report. I would give details about how big they were when they were born, when they will be moving about, and how healthy they are. 3. What do you think is the purpose of this television report? SAMPLE ANSWER: I think the purpose is to get viewers excited. They left out just enough information to keep viewers interested, which may serve to encourage viewers to visit the zoo. 4. What are some words and phrases in the broadcast that appeal to listeners emotions and make them want to visit the zoo? Examples of words and phrases in this report that appeal to a listener s emotions include surprises, buzzing with excitement, and new mom. These words and phrases are all emotionally charged. 5. What are two facts you learned about Sumatran tigers from this report? SAMPLE ANSWER: Sumatran tigers have webbed feet and can swim fast. There are only about 600 left in the wild. Promote Zoo News The skills used in this activity include information and media literacy, creativity and intellectual curiosity. Find out about the latest news at a zoo close to your town or in your area by calling the zoo and asking to speak with its public relations department, visiting the zoo, or looking at the zoo s Web site. Choose an event, such as the recent birth or acquisition of an animal, that you can promote to encourage more people to visit the zoo. After researching the event, create a poster to promote it. Your poster should include persuasive text, photographs or illustrations, contact information, and how to visit the zoo. Display copies of your poster around your school. You may also want to contact the zoo and encourage them to use your poster. Evaluate students posters based on the organization of the text and art, the appeal of the art as an enticement to visit the zoo, the succinctness and completeness of the text, and the information it contains. Chapter 28 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 452