___T______ 1. An adaptation is an inherited trait that helps an organism survive. ____F_____ 2. Each branch of a cladogram represents the same evolutionary paths. Different. ____T____ 3. Species that share more similarities on their DNA are more closely related than those that that share fewer similarities. _____F___ 4. Darwin concluded that the mechanism for evolution is artificial selection. Natural selection. ___T______ 5. If variations are lacking in a population, then evolution will not occur. ____F____ 6. When a population becomes divided by an event, the event creates differentiation. Isolation Completion. Complete each statement. 7. The process of how organisms acquire adaptations over time is called evolution. 8. An organism from others have descended is an ancestor. 9. Scientists believe the Earth is about 4.6 billion years old. 10. Another word for a branching diagram is a cladogram. 11. The rock layers from which most fossils are dug are sedimentary. 12. DNA is used as evidence for evolution because species with more similarities in their base sequences are more closely related than those with fewer similarities. 13. By studying the embryos of a fish, calf, and rabbit, scientists can conclude that they all come from a common ancestor. 14. A hummingbird’s long beak helps it get nectar from a flower. This is an example of an adaptation. 15. Darwin hypothesized that the different finches on the Galapagos Islands all had a common ancestor. 16. The scientist who argued that food shortages lead to a “struggle for existence” in humans was Thomas Malthus. 17. When breeders produce changes in a species on purpose, they are using artificial selection. 18. Without variation in a population evolution could never occur. 19. Increased competition with other species, newly introduced predators, loss of habitat, and catastrophes all may lead to extinction of a species. 20. When the ground finches could no longer interbreed, differentiation had occurred among the populations. 21. An organism’s body is quickly covered in sediments. Over time, more and more sediments cover the remains, burying the body parts that do not rot under layers of sediments. Chemicals in the body parts are replaced with minerals, resulting in a rock-like copy of the original organism. 22. That the two species share a common ancestor. 23. Artificial selection is used by breeders of greyhounds or racehorses while natural selection is determines the traits in crows or whitetail deer. 24. Mutations occur randomly in genes and produce variation of traits in a population. 25. When a population gets divided by an event, the original population gets divided. Since the populations are physically separated from each other they can no longer reproduce. When species are isolated, the environments that each lives in may also be different, leading to eventual adaptation and differentiation. 26. Populations with a greater number of variations have a better chance of survival when there is a change in the environment. 27. There are several islands in the Galapagos. He observed that finches on the islands were slightly different from those found on the mainland. He also noted slight differences in finches from island to island. The difference that he found most notable was the differences in beak shape. It appeared to be different based on the type of food eaten, and therefore Darwin concluded that the finches were adapted for the type of food they ate. From his observations, Darwin hypothesized that an ancestral species of finch from the mainland ended up on the Galapagos, and the finches were scattered to different environments. Then, they had to adapt to different conditions, and over many generations evolved into new species. 28. The 4 steps in the process of natural selection are: 1) Populations over-reproduce. All organisms produce more offspring than can survive to adulthood and reproduce. Survivors that are able to reproduce pass their traits on to their offspring. 2) 3) 4) Individuals in a population vary. There is random variation in traits among individuals in a population of a species. Even though the variations are by chance, they are then passed on to their offspring. Favorable adaptations are selected. When an environment changes, selection of favorable traits occurs. Adaptations that fit well with the environment are passed to the offspring. Favorable adaptations accumulate. Over many generations, favorable adaptations accumulate. This may eventually lead to a new species. 29. Because of the change in the tree color, dark-colored moths would not be as visible as lighter-colored moths. Consequently by natural selection, the dark-colored moths population would increase and the light-colored moth population would decrease. 30. a. b. The earlier species became extinct. Correct answers include: The changing environments on Earth causing loss of habitat, increased competition, new predators, or catastrophes. Lack of genetic variation within a species.