Term | Definition |
gene pool | collection of alleles found in all of the individuals of a population |
allele frequency | proportion of 1 allele, compared with all the alleles for that trait, in the gene pool |
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 1 more common |
stabilizing selection | natural selection where intermediate phenotypes are selected over phenotypes of both extremes |
disruptive selection | natural selection where 2 opposite, but equally uncommon, phenotypes are selected over the most common one |
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, results from an event that drastically reduces the size of a population |
founder effect | genetic drift, occurs after a small number of individuals colonize a new area |
sexual selection | certain traits enhance mating success , and are therefore passed on to offspring |
reproductive isolation | last stage in speciation where members of isolated populations are either no longer able to mate or no longer able to produce viable offspring |
speciation | evolution of 2 or more species from one ancestral species |
behavioral isolation | isolation between populations due to differences in courtship/mating behavior |
geographic isolation | isolation of populations die to the physical barriers between them |
temporal isolation | isolation between populations due to barriers related to time; such as differences in mating periods or time when individuals are most active |
convergent evolution | evolution towards similar characteristics in unrelated species, because of adaptations to similar environmental conditions |
divergent evolution | evolution of one or more closely related species into different species, because of adaptations to different environmetal conditions |
coevolution | process in which 2 or more species evolve in response to changes in each other |
punctuated equilibrium | the theory that speciation occurs suddenly and rapidly, followed by long periods of little evolutionary change |
adaptive radiation | 1 species evolves, gives rise to many descendant species that occupy different ecological niches |
index fossils | fossils of an organism that existed during only specific spans of geologic time across large geographic areas |
cyanobacteria | bacteria that can carry out photosynthesis |
endosymbiosis | ecological relationship in which one organism lives within the body of another |