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