| A | B |
|---|
| gene pool | The total aggregate of genes in a population at any one time |
| relative frequency | number of times that allele occours in a gene pool |
| single-gene trait | trait controlled by a single gene that has two alleles |
| polygenic trait | An additive effect of two or more gene loci on a single phenotypic character |
| directional selection | Natural selection that favors individuals on one end of the phenotypic range |
| stabilizing selection | form of natural selection by which thecenter of the curve remains in its current position |
| disruptive selection | form of a natural selection in which a single curve splits into two |
| genetic drift | Changes in the gene pool of a small population due to chance |
| founder effect | A cause of genetic drift attributable to colonization by a limited number of individuals from a parent population |
| hardy-weinberg principle | The steady-state relationship between relative frequencies of two or more alleles in an idealized population; both the allele frequencies and the genotype frequencies will remain constant from generation to generation in a population breeding at random in the absence of evolutionary forces |
| genetic equilibrium | situation in which allele frequencies remain constant |
| speciation | The origin of new species in evolution |
| reproductive isolation | Two populations of organisms are isolated if their members are unable to interbreed and produce fertile offspring. Various structural, behavioral, and biochemical features can prevent interbreeding and thus reproductively isolate populations as distinct species |
| behavioral isolation | form of reproductive isolation in which two populations have differances in courtship rituals |
| geographic isolation | form of reproductive isolation in which two populations are seperated physically by geographic barriers |
| temporal isolation | form of reproductive isolation in which two populations reproduce at different times |
