∞ generated and posted on 2016.09.11 ∞

Changes in allele frequencies as they occur within populations or species versus evolution as it occurs above the level of the species.

Microevolution consists of all of those forces that can result in changes in the allele frequencies associated with a single population/species; the underlying microevolutionary forces are mutation, migration, natural selection, and genetic drift.

Microevolutionary forces include especially mutation, sampling error (i.e., genetic drift), genetic migration, and natural selection.

Microevolution is ongoing all the time in all populations unless those populations are very large (i.e., infinite), sustain no mutations, experience no out migration nor in migration, and are not subject to differential reproductive success (natural selection, though see also simply selection).

The following video provides a gorgeous illustration of microevolution in action. Note the stochasticity (i.e., randomness of mutation) as well as how adaptations build on adaptations. Literally evolution in action.

Microevolutionary forces can lead to speciation events and this conversion of one species into one or more additional species is considered to represent the dividing line between microevolutionary phenomena and macroevolution.

See also Hardy-Weinberg equilibrium.

Video (Introductory lecture covering the rise of the ideas of evolution and microevolution)