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 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 towards 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 common, 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. |
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. |