Microevolution & Modes of Selection

Vocabulary flashcards based on lecture notes for Microevolution & Modes of Selection.

Genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

Gene flow

The transfer of genetic variation from one population to another.

Mutation

A change in the nucleotide sequence of an organism's DNA.

Directional selection

A mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.

Disruptive selection

A mode of natural selection in which extreme values for a trait are favored over intermediate values.

Stabilizing selection

A type of natural selection in which the population mean stabilizes on a particular non-extreme trait value.

Balancing selection

Natural selection that maintains two or more phenotypic forms in a population.

Sexual selection

A mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection).

Intersexual selection

Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from the other sex; also called mate choice.

Intrasexual selection

A direct competition among individuals of one sex (usually the males) for mates of the opposite sex.

Sexual dimorphism

A difference in secondary sexual characteristics between males and females of the same species.

Frequency-dependent selection

The fitness of a phenotype depends on how common it is in the population.

Heterozygote advantage

Occurs when heterozygotes have a higher fitness than do both homozygotes.