Name Class Date Chapter 15 Darwin s Theory of Evolution Enrichment Unique Islands Over 150 years ago, Charles Darwin visited a small cluster of islands the Galápagos Islands isolated in the Pacific Ocean. Darwin found no large mammals but some unusual reptiles. Some of the islands were barren, while others were mostly sparse cactus forest. Yet, what Darwin learned from these islands changed the way scientists thought about all living things. What is so special about the Galápagos Islands? Due to the climatic variation, the islands have four distinct zones of vegetation: dry lowlands, transition zone between lowlands and highlands, moist forest region of the highlands, and high upland zone. Each vegetation zone supports a different group of animal species. The question of how these plants and animals came to the Galápagos Islands has long puzzled scientists. At one time, scientists thought that a land bridge connected South America and the Galápagos Islands. However, no evidence has been found to support that idea, and scientists question why some species would have crossed the land bridge, whereas others did not. Today, scientists think that the plants and animals were carried to the islands on natural rafts of plant material and logs. Such rafts regularly float down South American rivers during heavy storms. Carried by the Humboldt Current, the rafts could have floated across the ocean and washed up on the shores of the Galápagos. These rafts, possibly as large as football fields, might have carried plants, seeds, insects, and animals. If the organisms found a way to survive and reproduce, they could have established populations on the islands. Of course, many of the organisms that arrived on the islands would not have survived to establish populations. After all, the Galápagos are not a very hospitable place, particularly for mammals. Scientists think that a successful colonization by a reptile or mammal species takes place only once every 100,000 years. However, over time, enough organisms would have survived to populate the Galápagos. The first plants and animals to colonize the Galápagos were not unique to these islands, because they had merely floated from the mainland of Central or South America. However, over time, these species changed. From one species of bird evolved many different species of birds. Different kinds of land tortoises evolved as well, each with a uniquely shaped shell. Of course, when Darwin arrived on the Galápagos, no one understood the origin of these different species. How such a variety of species had come to exist on a tiny group of isolated islands was a puzzling question a question Darwin eventually answered with his theory of evolution. Today, many of the Galápagos Islands are protected as biological reserves. Scientists are currently conducting research on the plants and animals and trying to find ways to protect them. Thanks to their dry, inhospitable climate, some of the islands remain untouched by human development. Essentially, they are the same Galápagos Islands that Darwin saw on his significant voyage so long ago. Evaluation Answer the following questions on a separate sheet of paper. 1. The Galapagos Islands are home to a species of penguin called the Galápagos penguin. Penguins are usually associated with cold climates. How might penguins be able to survive at the equator? 2. The Galápagos Islands support a variety of animal species. Darwin s finches, in particular, are a diverse and highly specialized group the beak of each finch species is particularly adapted to eating a certain food. How do you think the tiny Galápagos Islands can support this variety of animal species? 190 Teaching Resources /Chapter 15 Pearson Education, Inc. All rights reserved.
Name Class Date Chapter 15 Darwin s Theory of Evolution Comparing Adaptations of Birds Introduction When Charles Darwin explored the Galápagos Islands, he noted the great variety of beak shapes on the finches there. It was later determined that Darwin s finches made up 13 separate species. The similarities among the species suggested a common ancestor: A single species of finch that came from the mainland of South America. How did these birds evolve into genetically unique groups? With few native competitors and a wide variety of food sources, the newcomers were able to establish niches based on variations in beak shape and size. Finches with beaks that could exploit a particular food source insects in the bark of trees, for example established their own niche in the new habitat. Natural selection thus favored beak specialization because it enabled many birds to coexist within the same ecosystem. Many birds also show specialization of other body parts, including legs, feet, wings, and eyes. In this investigation, you will examine some bird characteristics. What are the survival benefits of each bird s adaptations? Problem What adaptations have evolved among modern birds that enable them to survive in diverse habitats? Pre-Lab Discussion Read the entire investigation. Then, work with a partner to answer the following questions. 1. What can you learn from observing and comparing specific physical traits of different birds? The physical traits constitute evidence that can be used to make inferences about the behaviors and habitats of the birds. 2. What are some terms you can use to describe the size and shape of a bird s beak? You may want to refer students to Section 15 3 in the textbook for a discussion of adaptations. Time required: 50 minutes Size can be described using terms such as long, short, large, or small. Shape can be described using Prentice-Hall, Inc. straight, curved, hooked, pointed, flat, narrow, or broad. 3. How does a bird s beak help you identify its habitat? The size and shape indicate the types of foods the bird eats. The bird must live, or at least hunt, in a habitat that includes those foods. 4. A certain bird ordinarily lives in or near water and spends much of its time swimming. Based on Data Table 1, what type of feet would you expect this bird to have? Webbed and paddlelike feet that enable the bird to swim well. Biology Laboratory Manual A/Chapter 15 131
5. Birds that spend much time perching have three front toes and one back toe. Based on Data Table 1, how is this different from the feet of birds that are better adapted for climbing than for perching? The feet of climbing birds have two front toes and two back toes. The back toes help keep the bird from falling when climbing upward. Materials (per group) specimens or illustrations of birds detailing their physical adaptations, field guides to birds Procedure 1. Look carefully at the diagrams of birds in Figure 1. Notice the details of each bird s feet and beak. Using the diagrams, complete Data Table 1 by filling in one or more examples of birds that exhibit each of the beak and foot adaptations described. 2. Inferring In Data Table 2 on page 134 consider the adaptations of the birds listed and then describe their likely habitat. Check your answers using a field guide. Cardinal It might be helpful to have several different types of field guides for students to use as references if they are having difficulty with the lab or wish to check their responses. Mounted specimens may be available on loan from local nature centers, museums, or colleges. If time permits, suggest that students use field guides or other sources to compare wing length and shape, and have students discuss the adaptive benefit of these features. Woodpecker Great horned owl Common snipe Purple martin Osprey Prentice-Hall, Inc. Figure 1 (Diagrams are drawn in approximate, not exact, scale.) 132 Biology Laboratory Manual A/Chapter 15
Name Class Date Mallard duck Great blue heron Hummingbird Prentice-Hall, Inc. Figure 1 continued Pelican Ostrich Biology Laboratory Manual A/Chapter 15 133
Make sure students understand that a particular bird may be listed more than once in Data Table 1. Data Table 1 Body structure Adaptation for Type of bird Short, wide, pointed beak cracking seeds and nuts cardinal Medium-length, chisel-shaped beak breaking into tree bark for insects woodpecker Long spear-shaped beak with wide base spearing fish heron Sharply hooked beak tearing animal tissue osprey/owl Beak with pouch holding fish pelican Long, very narrow beak probing flowers for nectar hummingbird Long, straight, medium-wide beak probing for soft-ground food common snipe Very short, slightly curved beak catching insects in midair purple martin Large, forward-looking eyes binocular and night vision for spotting prey Long, thick, powerful legs and two thick toes running; defense (kicking) ostrich 2 front toes/2 back toes holding onto side of tree without falling back owl woodpecker 3 short front toes/1 back toe without claws or webbing perching on branches cardinal/purple martin Long foot with 3 front toes/ wading; walking on mud; 1 back toe walking on sand heron/common snipe 3 front webbed toes/1 back toe swimming mallard/pelican 3 front clawed toes/ catching, grasping, and 1 back clawed toe carrying prey over distances osprey/owl Prentice-Hall, Inc. 134 Biology Laboratory Manual A/Chapter 15
Name Class Date Accept inferences that students can justify with evidence and logic. Data Table 2 Bird Osprey Great horned owl Woodpecker Purple martin Great blue heron Common snipe Mallard duck Pelican Cardinal Hummingbird Ostrich Habitat shorelines coniferous woods near open fields forests; parks; suburban areas fields near streams/rivers marshes; shores of lakes, ponds, and rivers bogs; marshes; shorelines creeks; rivers; ponds; lakes shorelines; estuaries wooded and suburban areas wherever appropriate plants are found, including suburban areas savanna; grassy plain Analysis and Conclusions 1. Comparing and Contrasting Each pair of birds mentioned below shares some characteristics. Yet they each have their own niche; they do not compete directly for the same resources. For each pair, describe how the birds are similar and how they are different. How might their differences enable them to occupy different niches? a. osprey and great horned owl Both have similar beaks and claws adapted for hunting; the owl has large eyes that enable it to hunt at night. Prentice-Hall, Inc. b. woodpecker and purple martin Both eat insects. The woodpecker has a longer beak that can probe. The purple martin s beak helps it catch and trap insects as it flies. c. great blue heron and common snipe Both have feet adapted for wading; the heron has longer legs, enabling it to wade more deeply. Biology Laboratory Manual A/Chapter 15 135
2. Inferring Birds have hollow bones. Explain how this is adaptive. It is a structural adaptation that lessens their weight and enables them to fly. 3. Observing The hummingbird s beak is adapted to getting its food. Describe another adaptation of the hummingbird that enables it to get the food it needs. Its tiny, lightweight body and its ability to beat its wings rapidly for hovering over flowers assist the hummingbird in obtaining nectar. 4. Inferring Birds such as Darwin s finches are adapted to occupy highly specific niches. Would this adaptation make it easy or difficult for such birds to adapt to environmental change? Explain your answer. It would be difficult for them to adapt because they are so specialized. For example, they might not be able to adjust to an environmental change such as loss of a food source. 5. Formulating Hypotheses Why might a particular bird be found in more than one habitat? Birds might hunt or feed in one habitat but nest or seek shelter in another. 6. Inferring Birds are well-adapted to their habitats, yet some birds are considered members of endangered species. Infer why certain birds are endangered. Students may infer that certain birds are now endangered because their habitats are being destroyed. Going Further Based on the results of this investigation, develop a hypothesis about the physical characteristics and habitat requirements of birds that live in hot, dry climates such as the desert. When developing a hypothesis, consider sources of food, water, shelter, nesting materials, and other factors. To test your hypothesis, with your teacher s permission, use various resources to learn about the physical characteristics and the habitat of one or more desert-dwelling birds. Prentice-Hall, Inc. 136 Biology Laboratory Manual A/Chapter 15
Name Class Date Chapter 15 Darwin s Theory of Evolution Graphic Organizer Concept Map Using information from the chapter, complete the concept map below. If there is not enough room in the concept map to write your answers, write them on a separate sheet of paper. Darwin s Theory of Evolution includes includes In nature, organisms differ from one another. Some of this variation is inherited. 1. causes causes 2. results in Members of the same species must compete for limited resources. Pearson Education, Inc. All rights reserved. 3. leads to Species change over time. New species arise, and other species disappear. Teaching Resources /Chapter 15 191
Name Class Date Chapter 15 Darwin s Theory of Evolution Chapter Vocabulary Review Matching On the line provided, write the letter of the definition that best matches each term on the left. 1. evolution a. change over time 2. fossil b. differences among individuals within a species 3. natural variation c. preserved remains of an ancient organism 4. struggle for existence d. survival of the fittest 5. fitness e. all species are derived from common ancestors 6. adaptation f. structures that develop from the same embryonic 7. natural selection tissues, but have different mature forms 8. common descent g. ability of an individual to survive and reproduce in a specific environment 9. homologous structures h. organ with little or no function 10. vestigial organ i. competition for food, space, and other resources among members of a species j. inherited characteristic that increases an organism s chance of survival Defining Terms On the lines provided, write a definition for each of the following terms. 11. theory 12. artificial selection 13. survival of the fittest 14. descent with modification Multiple Choice On the line provided, write the letter of the answer that best completes the sentence. 15. Cows that give more milk than other cows are an example of a. natural variation. c. survival of the fittest. b. natural selection. d. struggle for existence. 16. The practice of breeding dogs to produce offspring with specific traits is an example of a. natural variation. c. common descent. b. natural selection. d. artificial selection. Pearson Education, Inc. All rights reserved. 188 Teaching Resources /Chapter 15
Name Class Date 17. Natural selection is the same as a. struggle for existence. c. artificial selection. b. survival of the fittest. d. descent with modification. 18. The diagrams of the limbs below show evidence of a. natural variation. c. common descent. b. natural selection. d. artificial selection. Turtle Alligator Bird Mammals 19. The bones in the diagram above are examples of a. homologous structures. c. adaptation. b. fitness. d. struggle for existence. 20. A human s appendix and a skink s legs are examples of a. vestigial organs. c. natural selection. b. fitness. d. artificial selection. Short Answer On the lines provided, answer the following questions. 21. How did Darwin interpret the fossil record? Pearson Education, Inc. All rights reserved. 22. What conditions force organisms to compete in a struggle for existence? 23. How do successful adaptations improve an organism s fitness? 24. What does descent with modification imply about the relationships among the different species on Earth today? Teaching Resources /Chapter 15 189