Unit 4 Chapter Chapter 15

3. theory that evolution occurs with relatively sudden periods of speciation followed by long periods of stability
4. theory that evolution occurs in small gradual steps over time
6. factor that prevents a hybrid zygote from developing, or prevents hybrid offspring from reproduction; operates after fertilization
7. heredity changes in groups of living organisms over time
8. theory of evolution developed by Darwin, based on four ideas; excess reproduction, variations, inheritance, and the advantages of specific traits in an environment
11. shift of a population toward an extreme vision of a beneficial trait
13. states that the allelic frequencies in populations stay the same unless they are affected by a factor that causes change
14. anatomically similar structure inherited from a common ancestor
15. Darwin's term for the selective breeding of organisms selected for certain traits in order to produce offspring having those traits
16. study of the distribution of plants and animals on Earth
17. morphological adaptation in which one species evolves to resemble another species for protection or other advantages
19. structure that has the same function but different construction and was not inherited from a common ancestor
20. change in the frequency of a trait based on competition for a mate

1. most common factor of natural selection in which organisms with extreme expressions of a trait are removed
2. factor that prevents individuals from different species from mating; operates before fertilization
5. process in which individuals with average traits are removed, creating two populations with extreme traits
9. random effect that can occur when a small population settles in an area separated from the rest of the population and interbreeds, producing unique allelic variations
10. random change in allelic frequencies in a population
12. reduced form of a functional structure that indicates shared ancestry
18. organism's early prebirth stage of development