Populations have gene-frequency changes {microevolution}. Microevolution includes gene flow, mutation pressure, and segregation distortion.
natural selection
Natural selection causes most gene-frequency changes. Natural selection can cause adaptations in constant environments or make new genes in fluctuating environments. Natural selection typically stabilizes gene frequencies and decreases homozygote percentage. New species arise from microevolutionary changes by accumulated changes in one direction {progressive evolution}.
drift
Random gene-splicing errors can cause heterozygosity loss by genetic drift, but this factor only affects small populations with inbreeding and consanguinity.
Biological Sciences>Biology>Evolution>Variation
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Date Modified: 2022.0224