Evolution: How Populations Evolve

Vocabulary flashcards covering the units of evolution, causes of microevolution, modes of natural selection, and mechanisms of speciation based on the Honors Biology lecture notes.

Population

A group of individuals of the same species living in the same place at the same time.

Gene pool

The total collection of genes in a population at any one time.

Microevolution

A change in the relative frequencies of alleles in a gene pool.

Convergent evolution

Process where species that are not closely related independently evolve similar adaptations and share similar features.

Analogous structures

Similar structures in organisms without shared ancestry that evolved independently to serve the same purpose, such as the wings of birds, insects, and bats.

Divergent evolution

Process where species with a recent common ancestor develop different features and evolve different adaptations.

Homologous structures

Features that share a similar structure but have different functions, resulting from divergent evolution from a common ancestor, such as rat and bat limbs.

Genetic drift

A random change in the frequency of an allele in a population that has a greater effect on small populations.

Bottleneck effect

A type of genetic drift where an event drastically reduces population size, such as the reduction of elephant seals after being hunted in the 1890s.

Founder effect

A type of genetic drift that occurs when a new population is established by a few individuals from an initially larger population.

Gene flow

The gain or loss of alleles from a population due to the movement of individuals (immigration/emigration) or gametes; it tends to have a homogenizing effect by reducing genetic differences between populations.

Mutation

A random change in an organism’s nucleotide sequence; it is the ultimate source of the genetic variation that initiates evolution.

Nonrandom mating

Occurs when males and females with similar phenotypic traits mate, or when individuals mate with neighbors rather than more distant members of the population.

Sexual dimorphism

Distinct physical differences between males and females of a species, often produced by sexual selection.

Stabilizing selection

A mode of natural selection that favors intermediate phenotypes.

Directional selection

A mode of natural selection that acts against individuals at one of the phenotypic extremes, moving the population toward the other extreme.

Disruptive selection

A mode of natural selection that favors individuals at both extremes of the phenotypic range.

Species

A group of populations whose individuals can interbreed and produce fertile offspring.

Speciation

A process where populations become isolated and evolve independently into new species through geographic or reproductive isolation.

Allopatric speciation

Speciation that occurs when geographic separation restricts gene flow; the term means "other country."

Sympatric speciation

Speciation that occurs when a reproductive barrier develops while populations live in the same area ("same country"), caused by behavioral differences, temporal differences, or sexual selection.

Temporal isolation

A reproductive barrier where species mate at different times, such as the eastern spotted skunk mating in late winter and the western spotted skunk mating in late summer.