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Chapter 11

The Evolution of Populations

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
Created by: harolds21
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