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12 terms

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adaptive radiation
process by which a single species or small group of species evolves into several different forms that live in different ways; rapid growth in the diversity of a group of organisms
allopatric speciation
the formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier.
directional selection
occurs when natural selection favors one of the extreme variations of a trait
disruptive selection
natural selection that favors individuals with either extreme of a trait; tends to eliminate intermediate phenotypes
founder effect
when a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool isn't reflective of the source population
genetic drift
The gradual changes in gene frequencies in a population due to random events
gradualism
a model of evolution in which gradual change over a long period of time leads to biological diversity
hardy weinberg principle
principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change.
punctuated equilibrium
evolutionary model suggesting species often diverge in spurts of relatively rapid change, followed by long periods of little change
sexual selection
A form of selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates (example: bigger antlers on a deer make that deer more likely to attract a mate)
spontaneous generation
hypothesis (disproven) stating that life could arise from nonliving matter
stabilizing selection
natural selection that favors intermediate variants by acting against extreme phenotypes