Term | Definition |
population genetics | the study of the frequency and interaction of alleles and genes in populations |
microevolution | a change in the collective genetic material of a population |
bell curve | a symmetrical frequency curve |
gene pool | all of the genes of the reproductively active members of a population |
allele frequency | the proportion of gene copies in a population that are a given allele, expressed as a percentage |
phenotype frequency | the ratio if individuals with a particular phenotype to the total number of individuals in a population |
Hardy-Weinberg genetic equilibrium | the principle that states that the frequency of alleles in a population does not change unless evolutionary forces act on the population |
immigration | the movement of an individual or a group to a new community or region |
emigration | the movement of an individual or group out of its native area |
gene flow | the movement of genes into or out of a population due to interbreeding |
genetic drift | the random change in allele frequency in a population |
sexual selection | an evolutionary mechanism by which traits that increase the ability of individuals to attract or acquire mates appear with increasing frequency in a population; selection in which a mate is chosen on the basis of a particular trait or traits |
stabilizing selection | a type of natural selection in which the average form of a trait is favored and becomes more common |
disruptive selection | a type of natural selection in which two extreme forms of a trait are selected |
directional selection | a natural selection process in which one genetic variation is selected and that causes a change in the overall genetic composition of the population |
speciation | the formation of new species as a result of evolution |
morphology | the study of the structure and form of an organism |
biological species concept | the principle that defines a species as a group of organisms whose members can interbreed to produce offspring |
geographic isolation | the physical separation of populations due to geographic barriers that prevent interbreeding |
allopatric speciation | species that arise as a result of geographic isolation |
reproductive isolation | the inability of members of a population to successfully interbreed with members of another population of the same or a related species |
prezygotic isolation | type of reproductive isolation that occurs before fertilization |
sympatric speciation | occurs when two subpopulations become reproductively isolated within the same geographic area. |
gradualism | a model of evolution in which gradual change over a long period of time leads to biological diversity |
punctuated equilibrium | a model of evolution in which short periods of drastic change in species, including mass extinctions and rapid speciation, are separated by long periods of little or no change |
postzygotic isolation | type of reproductive isolation that occurs after fertilization |