Vocabulary

1. theory that evolution occurs in small gradual steps over time
5. anatomically similar structure inherited from a common ancestor
6. shift of a population toward an extreme version of a beneficial trait
8. amount of time required for half of a radioactive isotope to decay
9. Darwin's term for the selective breeding of organisms selected for certain traits in order to produce offspring having those traits
12. process in which individuals with average traits are removed; creates two populations with extreme traits
15. most common form of natural selection in thich organisms with extreme expressions of a trait are removed
18. structure that has the same function but different construction; not inherited by a common ancestor
19. process in which a large population declines in number then rebounds
20. preserved evidence of an organism found in sedimentary rock
21. diversification of a species into a number of different species

2. method used to determine the age of rocks by comparing
3. explains that eukaryotic cells may have evolved from prokaryotic cells
4. theory that evolution occurs with relatively sudden periods of speciation followed by long periods of stability
7. change in the frequency of a trait based on competition for a mate
10. states that the oldest layers of rock are found at the bottom and the youngest layers are found at the top
11. hereditary changes in groups of living organisms over time
13. reduced form of a funtional structure that indicates shared ancestry
14. theory of evolution developed by Darwin based on four ideas
16. random change allelic frequencies in a population
17. random effect that can occur when a small population settles in an area separated from the rest of the population and interbreeds