| A | B |
|---|
| gene pool | all the genes, including all the different alleles for each gene, that are present in a population at any one time |
| allele frequency | number of times that an allele occurs in a gene poo compared with the number of alleles in that pool compared with the number of alleles in that pool for the same gene |
| single-gene trait | trait controlled by one gene that has two alleles |
| polygenic trait | trait controlled by two or more genes |
| directional selection | form of natural selection in which individuals at one end of a distibution curve have higher fitness thatn individuals in the middle or at the other end of the curve |
| stabilizing selection | form of natural selection in which individuals near the center of a distribution curve have higher fitness than individuals at either end of the curve |
| disruptive selection | natural selection inw hich individual at the upper and lower ends of the curve have higher fitness than individuals near the middle of the curve |
| genetic drift | random change in allele frequency caused by a series of chance occurrences that cause an allele to become more or less common in a population |
| bottleneck effect | a change in allele frequency follwoing a dramatic reduction in the size of a population |
| founder effect | change in allele frequencies as a result of the migration of a small subgroup of a population |
| genetic equilibrium | situation in which allele frequencies in a population remain the same |
| Hardy-Weinberg principle | principle that states that allele frequencies in a population remain constant unless one or more factors cause those frequencies to change |
| sexual selection | when individuals select mates based on hertiable traits |
| species | a group of similar organisms that can breed and produce fertile offspring |
| speciation | formation of a new species |
| reproductive isolation | separation of a species or population so that they no longer interbreed and evolve into two separate species |
| behavioral isolation | form of reproductive isolation in which two populations deveop differences in courtship rituals or other behaviors that prevent them from breeding |
| geographic isolation | form of reproductive isolation in which two populations are separated by geographic barriers such as rivers, mountains, or bodies of water, leading to the formation of two separate subspecies |
| temporal isolation | form of reproductive isolation in which two or more species reproduces at different times |
| molecular clock | method used by researchers that uses mutation rates in DNA to estimate the length of time that two species have been evolving independently |
