ANSWER KEY. Chapter 5

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1 Chapter 5 Chapter 5 Project Worksheet 1 (p. 6) 1. Accept all reasonable responses. Madagascar is near Africa, and Tasmania is near Australia. 2. Accept all reasonable responses. The Hawaiian Islands and the Galapagos Islands are all far from any continent. 3. Answers may vary. A typical response might include several of the following: Birds could get to the island if carried over the ocean by a storm. Plant seeds could be carried in the birds digestive systems. Spores or small insects might be carried there by the wind. Ocean currents might carry tree trunks or branches, as well as fruits or seed pods, from the mainland. Small land animals, plants, and larger insects might hitch a ride on the trees. Human beings could also bring plants and animals to the island deliberately, or the animals could come as stowaways on boats. 4. Answers may vary. Students may correctly suggest that a larger island may have more species. Students may also notice that, with the exception of New Zealand, most of Earth s large islands are close to continents, so it would be easier for animals and plants to colonize them. Chapter 5 Project Worksheet 2 (p. 7) 1. The finches can be classified into two major groups based on their habitat: ground finches and tree finches. 2. Ground finches have curved beaks adapted for crushing food, although the cactus ground finch s beak is less curved than the beaks of the other ground finches. Tree finches have less curved beaks adapted for catching insects. The vegetarian tree finch has a blunt and curved, parrotlike beak. 3. The shape of each species beak is adapted to the type of food the bird eats. For example, ground finches with larger beaks eat larger seeds, those with smaller beaks eat smaller seeds. Tree finches have sharper beaks that help them catch insects. The cactus ground finch and the vegetarian tree finch both have beaks adapted to their particular foods. 4. Based on the patterns of adaptation in the table, students may correctly predict that the warbler finch probably eats insects and lives mainly in the trees. Most students will classify the warbler finch as a tree finch. In fact, scientists place the warbler finch on its own branch of the branching tree of Galapagos finches. Apparently, the warbler finch diverged from the other finches early in the evolution of the Galapagos finches. Section 5-1 Review and Reinforce (p. 11) 1. Charles Darwin was an English scientist of the 1800s. His job on the Beagle was to learn as much as he could about the living things he saw on the voyage. 2. Evolution is the gradual change in a species over time. 3. The shape of a finch s beak helps the finch eat the food that is available, and thus it helps the finch survive and reproduce. 4. They compete for food, water, and living space. 5. Food and other resources are limited, so many individuals of a species will not survive to reproduce. 6. If the variation makes the individual member better adapted to the environment, then it will more likely survive to reproduce offspring. 7. The environment selects organisms that are better adapted to their environment and thus have a better chance to survive and reproduce. 8. Helpful variations accumulate through natural selection, as the organisms that are better adapted to their environment reproduce offspring with the same variations. 9. Only genes are passed from parents to their offspring. 10. If a group is isolated from the rest of the species long enough to evolve different traits, a new species can evolve. 11. species 12. adaptation 13. theory 14. natural selection 15. variations 58 Unit 2 Resources Science Explorer Focus on Life Science

2 Section 5-1 Enrich (p. 12) 1. Some ancestral giraffes stretched their necks to reach leaves higher in trees. They passed this trait to their offspring. 2. Some ancestral giraffes had longer necks than others. These giraffes were better able to eat the leaves higher in trees, and thus survived. They passed this trait to their offspring. 3. In Theory 1, the offspring could not have, because stretching a neck does not change the organism s genes. Only genes are passed from parents to offspring. In Theory 2, the offspring could have, because the ancestral giraffes naturally had longer necks. Students should infer that this trait was a gene-controlled variation within the species. Thus, the gene could be passed from parent to offspring. 4. Theory 2 matches Darwin s theory since it includes all the factors that affect natural selection, including overproduction, variation, and selection. Section 5-2 Review and Reinforce (p. 15) 1. gradualism 2. punctuated equilibria 3. punctuated equilibria 4. gradualism 5. gradualism 6. punctuated equilibria 7. Most fossils form when organisms that die become buried in sediments. Over millions of years, the sediments harden into sedimentary rock. The hard parts of the dead organisms become fossils, including molds, casts, and petrified fossils. 8. a 9. c 10. b Section 5-2 Enrich (p. 16) million years 2. The forefeet became larger, changed from a foot with four toes to a foot with one toe, and changed from a padded foot to a hoofed foot. 3. The skull became larger and longer. 4. Answers will vary. A typical answer might suggest that as the environment changed from a dense forest to a prairie, the diet and habits of the horse adapted to fit the new conditions. These changes included an improved ability to move around a vast prairie and an ability to eat grasses instead of forest plants and animals. Section 5-3 Review and Reinforce (p. 19) 1. Both have essentially the same bones, though in somewhat different shapes. 2. They infer that the two species had a common ancestor. 3. homologous structures 4. Scientists could compare the DNA of the two species to confirm an evolutionary relationship. 5. Scientists compare body structures, development before birth, and DNA sequences to determine the evolutionary relationships among organisms. 6. Similarities in early development suggest that species are related and have a common ancestor. 7. homologous 8. branching tree Section 5-3 Enrich (p. 20) 1. It is a branching tree, which shows how scientists think different groups of organisms are related. 2. Evidence includes fossils as well as similarities in body structure, early development, and DNA sequences among modern-day organisms. 3. First reptiles, Thecodonts, Large dinosaurs, Archaeopteryx, Modern birds 4. Crocodilians did not evolve from dinosaurs; both dinosaurs and crocodilians evolved from a common ancestor, thecodonts. 5. First reptiles 6. Any new information might cause a change, including newly discovered fossils and DNA evidence. Science Explorer Focus on Life Science Unit 2 Resources 59

3 Chapter 5 Skills Lab (pp ) For answers, see Teacher s Edition, p Chapter 5 Skills Lab (pp ) For answers, see Teacher s Edition, pp Chapter 6 Chapter 6 Project Worksheet 1 (p. 30) Student answers will vary. Chapter 6 Project Worksheet 2 (p. 31) Student answers will vary. Section 6-1 Review and Reinforce (p. 35) 1. minerals 2. Mold 3. Cast 4. carbon 5. activities 6. Preserved remains 7. A mold is an empty space in rock in the shape of an organism or part of an organism. If water carrying dissolved minerals and sediment seeps into the mold and deposits those minerals and sediments there, the result is a cast in the shape of the organism. 8. Fossil footprints can provide clues about the dinosaur s size and behavior. 9. sedimentary rock 10. paleontologist Section 6-1 Enrich (p. 36) 1. Trace fossils are fossils that provide evidence of activities of ancient organisms. 2. The soil must have been moist to hold the shape of the print. 3. The prints became trace fossils when the sediment hardened into rock. 4. The dinosaur came from the upper left; the mammal came from the lower left. 5. The dinosaur began at a walk and then started to run, as evidenced by the sudden difference in stride length. 6. The dinosaur s prints lead away from the meeting. 7. Answers may vary. A typical answer might describe how the dinosaur saw the mammal, attacked, killed and devoured the mammal, and then walked away. Section 6-2 Review and Reinforce (p. 39) 1. Layer C is the youngest, because the law of superposition says that a layer is younger than the layers below it. 2. The extrusion is younger, because extrusions are always younger than the rock layers below them. 3. The fault is younger than layer A, because rock layers are always older than the faults they contain. 4. The fossil might be able to be used as an index fossil. Geologists can use index fossils to match up rock layers at locations that are far apart. 5. b 6. h 7. g 8. e 9. c 10. d 11. a 12. f Section 6-2 Enrich (p. 40) 1. Sedimentary rock layers form when sediment is deposited in flat layers one on top of the other. Over years, the sediment hardens and changes into sedimentary rock. 2. They weathered and eroded away. 3. When the first sedimentary layers eroded away, new layers formed on top of the eroded surface. The boundary where the eroded and new layers make contact is an unconformity. 4. The Grand Canyon formed when the Colorado River cut down through the rock layers. 60 Unit 2 Resources Science Explorer Focus on Life Science

4 5. The rock layers are older, because they formed before the river cut the canyon. Section 6-3 Review and Reinforce (p. 43) 1. They cannot use radioactive dating because sedimentary rock layers are made of particles from other rocks. Dating would provide the ages of those particles, not the rock. 2. They can use radioactive dating, because extrusions and intrusions are made of igneous rock. 3. Rock layer C is at least 80 million years old, because it is older than the intrusion that cuts partway across it. 4. element 5. half-life 6. atoms 7. radioactive decay Section 6-3 Enrich (p. 44) 1. Potassium-40, 100%; argon-40, 0% billion years 3. Each amounts to 50%. 4. More argon Potassium-40, 12.5%; argon-40, 87.5% 6. No, a geologist would not have to wait because the potassium-40 immediately begins to decay into argon-40 when the rock is formed. Section 6-4 Review and Reinforce (p. 47) Geologists subdivide eras into periods and periods into epochs. 6. Geologists use the geologic time scale to show Earth s history because the time span of Earth s past is so great. 7. They studied rock layers and index fossils worldwide. With that information, they placed Earth s rock layers in order by relative age. 8. The divisions of the geologic time scale depend on events in the history of life on Earth. 9. invertebrates 10. geologic time scale Section 6-4 Enrich (p. 48) 1. The bottom slanted rock layers formed in Precambrian Time, which was before the Paleozoic Era. 2. Carboniferous Period 3. Cambrian Period 4. Permian Period 5. The rock layers end with the Permian Period, which is before the Mesozoic Era began. 6. Neither the Ordovician nor the Silurian periods are represented by rock layers. It could be that no sediment was deposited during those periods, or layers formed but were later eroded away. Section 6-5 Review and Reinforce (p. 51) 1. Paleozoic 2. Paleozoic 3. Cenozoic 4. Mesozoic 5. Precambrian 6. Paleozoic 7. Paleozoic 8. Mesozoic (or Cenozoic) 9. Precambrian 10. Mesozoic 11. They were like present-day bacteria. 12. The Cambrian Explosion occurred at the beginning of the Paleozoic, when a great number of different kinds of organisms evolved in a relatively short time period. 13. The probable cause of the mass extinction at the end of the Paleozoic Era was a climate change that occurred when Pangaea formed. The probable cause of the mass extinction at the end of the Mesozoic Era was that an asteroid struck Earth. 14. Dinosaurs or Reptiles 15. The extinction of the dinosaurs created an opportunity for mammals. 16. Ice ages occurred, as thick continental glaciers advanced and retreated over parts of Europe and North America. 17. b 18. c 19. a 20. d Science Explorer Focus on Life Science Unit 2 Resources 61

5 Section 6-5 Enrich (p. 52) 1. Evidence includes the fossil record, which shows many organisms died out 65 million years ago, an impact crater near the Yucatán Peninsula, and a layer of rock around Earth that is enriched with iridium. 2. Evidence includes the fossil record, which shows many organisms died out 65 million years ago, a huge area of volcanic rock on the Indian subcontinent from 65 million years ago, and a layer of rock around Earth that is enriched with iridium. 3. In each theory, a dust cloud blocks the energy of the sun from reaching Earth s surface for months or longer. This causes plants, which use energy from the sun to make food, to die, and then animals die. 4. Answers may vary. A typical answer might suggest that there is no evidence that could prove absolutely that one or the other of these theories is true. 5. Answers may vary. A typical answer might suggest that the asteroid theory makes more sense because volcanic eruptions in recent times have not caused similar extinctions. Chapter 6 Real-World Lab (pp ) For answers, see Teacher s Edition, p Chapter 6 Skills Lab (pp ) For answers, see Teacher s Edition, p Unit 2 Resources Science Explorer Focus on Life Science