| A | B |
|---|
| gene pool | combined genetic information of all the members of a particular population |
| relative frequency | number of times an allele occurs in a gene pool compared with the number of times other alleles occur |
| single-gene trait | trait controlled by a single gene that has two alleles |
| polygenic trait | trait controlled by two or more genes |
| directional selection | form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve |
| stabilizing selection | form of natural selection in which the center of the curve remains in its current position; occurs when individuals near the center of a distrubution curve have higher fitness than individuals at either end |
| disruptive selection | form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle |
| genetic drift | random change in allele frequencies that occurs in small populations |
| founder effect | change in allele frequencies as a result of the migration of a small subgroup of a population |
| Hardy-Weinberg principle | principle that the allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change |
| genetic equilibrium | situation in which allele frequencies remain constant |
| speciation | formation of a new species |
| reproductive isolation | separation of a species or populations so that they cannot interbreed and produce fertile offspring |
| behavioral isolation | form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding |
| geographic isolation | form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water |
| temporal isolation | form of reproductive isolation in which two populations reproduce at different times |
