Natural selection

Definition

The process by which heritable traits that enhance survival and reproduction become more common in a population over successive generations, while disadvantageous traits diminish. Natural selection acts on phenotypic variation that arises from genetic mutation, recombination, and other sources; it requires heritability, variation in fitness, and differential survival or reproduction. Unlike artificial selection, it operates without intention or foresight, driven solely by environmental pressures including predation, resource availability, climate, and competition.

Etymology

Coined by Charles Darwin in "On the Origin of Species" (1859), contrasting with "artificial selection" practiced by animal and plant breeders.

Example

Industrial melanism in the peppered moth (Biston betularia): in soot-covered industrial regions of 19th-century England, the dark carbonaria morph rose from rarity to predominance because it was less visible to bird predators against blackened tree bark, while the typical pale morph suffered higher predation. As air quality improved and lichens recolonized bark, selection reversed and the pale morph rebounded.

Synonyms

• Darwinian selection

Related Terms

• Artificial selection
• Sexual selection
• fitness
• adaptation
• Phenotypic plasticity
• Directional selection
• Stabilizing selection
• Disruptive selection
• gene flow
• Genetic drift

Usage Notes

Distinguished from sexual selection (selection for mating success) and artificial selection (human-directed breeding). Often mischaracterized as "survival of the fittest," which conflates fitness (reproductive success) with mere survival strength. In arthropods, natural selection operates rapidly due to short generation times and large populations, producing observable evolutionary change within decades—examples include insecticide resistance in mosquitoes and mites, and host-race formation in fruit flies.