Go to Section: Interest Grabber A Trip Around the World While on his voyage around the world aboard the H.M.S. Beagle, Charles Darwin spent about one month observing life on the Galápagos Islands. There, he encountered some unique animals, such as finches and tortoises. Section On a sheet of paper, list five animals that you have encountered in the past two days. 2. How do these animals differ from the finches and tortoises of the Galápagos Islands? (Examine Figures 15–3 and 15–4 in your textbook.) 3. Propose a hypothesis to account for the differences between the animals that you observed and the finches and tortoises of the Galápagos Islands.

Go to Section: Section Outline 15–1The Puzzle of Life’s Diversity A.Voyage of the Beagle B.Darwin’s Observations 1.Patterns of Diversity 2.Living Organisms and Fossils 3.The Galápagos Islands C.The Journey Home Section 15-1

Go to Section: Pinta Island Intermediate shell Pinta Isabela Island Dome-shaped shell Hood Island Saddle-backed shell Hood Floreana Santa Fe Santa Cruz James Marchena Fernandina Isabela Tower Giant Tortoises of the Galápagos Islands Section 15-1

Go to Section: Section 15-1 Figure 15–1 Darwin’s Voyage

Go to Section: Interest Grabber My, How You’ve Changed! Prior to the 1800s, life scientists knew that living things changed over generations. They just didn’t know how these changes were brought about. Section Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair. 2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument. 3. Which of the items in your lists do you think you might pass on to your children? Explain your answer.

Go to Section: Section Outline 15–2Ideas That Shaped Darwin’s Thinking A.An Ancient, Changing Earth 1.Hutton and Geological Change 2.Lyell’s Principles of Geology B.Lamarck’s Evolution Hypotheses 1.Tendency Toward Perfection 2.Use and Disuse 3.Inheritance of Acquired Traits 4.Evaluating Lamarck’s Hypotheses C.Population Growth Section 15-2

Go to Section: Sea level Sedimentary rocks form in horizontal layers. When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers. As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed. New sediment is then deposited above the exposed older rock surface. Movement of Earth’s Crust Section 15-2 Sea level

Go to Section: Figure 15–7 Lamarck’s Theory of Evolution Section 15-2

Go to Section: Interest Grabber When Is a Flipper a Wing? All living things are related. Some relationships are easy to see— your pet cat may not roar like a lion, but it clearly resembles one. Other relationships are less obvious. Section 15-3

Go to Section: Interest Grabber continued 1.On a sheet of paper, construct a table that has five columns and six rows. In the columns, write the following heads: Animal Group, Example, Legs, Fins, and Tail. Then, place the following animal groups in their own row: Mammal, Bird, Fish, Amphibian, Reptile, and Insect. 2.Give one example for each group, and then fill in the information for that example. For Legs, write in the number of legs that each animal has. Do animals with fins have legs? Do animals with wings have legs? If so, how many? 3.Can you tell from your table if a fish is more closely related to a bird or to an amphibian? Explain your answer. Section 15-3

Go to Section: Section Outline 15–3Darwin Presents His Case A.Publication of On the Origin of Species B.Inherited Variation and Artificial Selection C.Evolution by Natural Selection 1.The Struggle for Existence 2.Survival of the Fittest 3.Descent With Modification D.Evidence of Evolution 1.The Fossil Record 2.Geographic Distribution of Living Species 3.Homologous Body Structures 4.Similarities in Embryology E.Summary of Darwin’s Theory F.Evolutionary Theory Since Darwin Section 15-3

Go to Section: Concept Map Section 15-3 includes Evidence of Evolution Physical remains of organisms Common ancestral species Similar genes which is composed ofwhich indicateswhich implies The fossil record Geographic distribution of living species Homologous body structures Similarities in early development

Go to Section: Beaver NORTH AMERICA Muskrat Capybara SOUTH AMERICA Coypu Figure 15–14Geographic Distribution of Living Species Section 15-3 Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara

Go to Section: TurtleAlligatorBirdMammal Ancient lobe-finned fish Figure 15–15 Homologous Body Structures Section 15-3

Internet The latest discoveries in evolution Interactive test Articles on evolution For links on evolution, go to and enter the Web Code as follows: cbn For links on Darwin, go to and enter the Web Code as follows: cbn For links on natural selection, go to and enter the Web Code as follows: cbn Go Online

Section 1 Answers Interest Grabber Answers 1. On a sheet of paper, list five animals that you have encountered in the past two days. Sample answers: dogs, cats, insects, snakes, birds, and so on. 2. How do these animals differ from the finches and tortoises of the Galápagos Islands? (Examine Figures 15–3 and 15–4 in your textbook.) Students may not see a noticeable difference between birds in their area and finches. However, the land tortoises, which are very large, would be very different from any turtles that students may have on their lists. 3. Propose a hypothesis to account for the differences between the animals that you observed and the finches and tortoises of the Galápagos Islands. Sample hypothesis: Animals become well suited to their surroundings.

Section 2 Answers Interest Grabber Answers 1. Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair. Students should list traits that are genetically influenced. 2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument. Remind students that many features, including skills, appearance, and athletic ability, can be changed to some degree by effort. 3. Which of the items in your lists do you think you might pass on to your children? Explain your answer. Genetically influenced traits are passed on. Some items, such as musical or athletic talent, may have both inherited and learned components.

Section 3 Answers Interest Grabber Answers 1.On a sheet of paper, construct a table that has five columns and six rows. In the columns, write the following heads: Animal Group, Example, Legs, Fins, and Tail. Then, place the following animal groups in their own row: Mammal, Bird, Fish, Amphibian, Reptile, and Insect. 2.Give one example for each group, and then fill in the information for that example. For Legs, write in the number of legs that each animal has. Do animals with fins have legs? Do animals with wings have legs? If so, how many? Fish do not have legs. Birds have two legs, while insects have six legs (three pairs). 3.Can you tell from your table if a fish is more closely related to a bird or to an amphibian? Explain your answer. It is difficult to tell from the table that a fish is more closely related to an amphibian than to a bird. Accept all reasonable explanations. Students may say that the fish is more closely related to the amphibian than to the bird because an amphibian and a fish spend time in the water.

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