Microevolution

Microevolution is a change in allele frequencies within a population across generations. Mutation, natural selection, genetic drift, and gene flow can produce these changes.

Natural selection: Differential survival and reproduction cause heritable variants to become more or less common in a population. Selection changes allele frequencies when inherited traits affect reproductive success.
Allele: One of the alternative forms of a genetic sequence at a particular locus. Microevolution tracks how common particular alleles become.
Peppered moth evolution: A change in the frequency of dark and light peppered moth forms associated with industrial pollution and predation. The case illustrates selection shifting a heritable trait's frequency as environments change.
Adaptation: An inherited trait or evolutionary process that improves performance in a particular environment. Selection can increase alleles that contribute to adaptation in a population.
Macroevolution: Evolutionary patterns and processes at or above the level of species, including speciation and extinction. It describes larger-scale patterns that can emerge from population-level change.
Genetic drift: Random sampling of individuals causes allele frequencies to fluctuate, especially in small populations. Chance alone can shift frequencies, even when alleles do not affect fitness.
Gene pool: The total collection of alleles present in a population at a given time. Allele-frequency change describes a shift in the population's gene pool.
Antibiotic resistance: The ability of microbes to survive and reproduce despite exposure to drugs that once inhibited them. Resistance alleles can rise rapidly under strong selection from antibiotic use.
Genetic variation: Differences in genetic material among individuals or populations. Microevolution changes the amount and distribution of genetic variation.
Phenotypic plasticity: The capacity of one genotype to produce different phenotypes in different environments. A trait can change across environments without a corresponding allele-frequency shift.

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