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Chapter 11
The Evolution of Populations
Term | Definition |
---|---|
gene pool | collection of alleles found in all of the individuals of a population |
allele frequency | proportion of one allele, compared with all the allele for that trait, in the gene pool |
normal distribution | distribution in a population in which allele frequency is higher near the mean range value and decreases progressively toward extreme end |
microevolution | observable change in the allele frequencies of a population over a few generations |
directional selection | pathway of natural selection in which one uncommon phenotype is selected over a more common phenotype |
stabilizing selection | pathway of natural selection in which intermediate phenotypes are selected over phenotypes at both extremes |
disruptive selection | pathway of natural selection in which two opposite, but equally uncommon, phenotypes are selected over the most common phenotype |
gene flow | physical movement of alleles from one population to another |
genetic drift | change in allele frequencies due to chance alone, occurring most commonly in small populations |
bottleneck effect | genetic drift that results from an event that drastically reduces the size of a population |
founder effect | genetic drift that occurs after a small number of individuals colonize a new area |
sexual selection | selection in which certain traits enhance mating success; traits are passed on to offspring |
Hardy-Weinberg equilibrium | condition in which a population's allele frequencies for a given trait do not change from generation to generation |
reproductive isolation | final stage in speciation, in which members of isolated populations are either no longer able to mate or no longer able to produce viable offspring |
speciation | evolution of two or more species from one ancestral species |
behavioral isolation | isolation between population due to differences in courtship or mating behavior |
geographic isolation | isolation between populations due to physical barriers |
temporal isolation | isolation between populations due to barriers related to time, such as differences in mating periods or differences in the time of day that individuals are most active |
convergent evolution | evolution toward similar characteristics in unrelated species, resulting from adaptations to similar environmental conditions |
divergent evolution | evolution of one or more closely related species into a different species; resulting from adaptations to different environmental conditions |
coevolution | process in which two or more species evolve in response to changes in each other |
extinction | elimination of a species from Earth |
punctuated equilibrium | theory that states that speciation occurs suddenly and rapidly followed by long periods of little evolutionary change |
adaptive radiation | process by which one species evolves and gives rise to many descendant species that occupy different ecological niches |