chapter 23 the evolution of populations

conditions of hardy weinberg equilibrium

no mutations, random mating, no natural selection, very large population size, no gene flow

bottleneck effect

a sudden change in the environment that drastically reduces the population size

founder effect

individuals are isolated from the large population creating a gene pool difference

gene flow

the transfer of genes into or out of a population due to the movement of fertile organisms

genetic drift

chance event that causes allele frequencies to spread from one generation to the next

directional selection

favors individuals of one extreme phenotypic range

disruptive selection

favors individuals of both extreme phenotypic ranges rather than those with intermediate ranges

stabalizing selection

favors individuals intermediate phenotypic ranges rather than those with extreme phenotypic ranges