CK-12 Biology 10.3: Microevolution and the Genetics of Populations

allele frequency

how often an allele occurs in a gene pool relative to the other alleles for that gene

gene pool

all the genes of all the members of a population

gene flow

change in allele frequencies that occurs when individuals move into or out of a population

sexual dimorphism

differences between the phenotypes of males and females of the same species

microevolution

evolutionary change that occurs over a relatively short period of time within a population or species

macroevolution

evolutionary change that occurs over geologic time above the level of the species

Hardy-Weinberg theorem

founding principle of population genetics that proves allele and genotype frequencies do not change in a population that meets the conditions of no mutation, no migration, large population size, random mating, and no natural selection

population genetics

science focusing on evolution within populations that is the area of overlap between evolutionary theory and Mendelian genetics

directional selection

type of natural selection for a polygenic trait in which one of two extreme phenotypes is selected for, resulting in a shift of the phenotypic distribution toward that extreme

genetic drift

a random change in allele frequencies that occurs in a small population

stabilizing selection

type of natural selection for a polygenic trait in which phenotypes at both extremes of the phenotypic distribution are selected against, resulting in a narrowing of the range of phenotypic variation

disruptive selection

type of natural selection for a polygenic trait in which phenotypes in the middle of the phenotypic distribution are selected against, resulting in two overlapping phenotypes, one at each end of the distribution