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Bio Unit 11
Term | Definition |
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gene pool | collection of alleles found in all of the individuals of a population. |
allele frequency | proportion of one allele, compared with all the alleles for that trait, in the gene pool. |
normal distribution | distribution in a population in which allele frequency is highest near the mean range value and decreases progressively toward each 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, therefore, 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 populations 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 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. |
adaptive radiation | process by which one species evolves and gives rise to many descendant species that occupy different ecological niches. |
punctuated equilibrium | theory that states that speciation occurs suddenly and rapidly followed by long periods of little evolutionary change. |