Fundamentals exam3 Pt 2

Directional selection

A mode of selection in which one extreme phenotype has the highest fitness.

Stabilizing selection

A mode of selection in which the intermediate phenotype is most fit.

Disruptive selection

A mode of selection in which two or more phenotypes are more fit than the intermediates.

Absolute fitness

The per capita growth rate of each phenotype.

Relative fitness

The fitness of a genotype relative to that of a reference genotype.

Mean fitness

The average fitness of individuals in a population relative to the fittest genotype.

Coefficient of selection

The amount by which the fitness of a genotype is different from the reference genotype.

Purifying selection

Selection that lowers the frequency of or eliminates a selectively disadvantageous allele.

Balancing selection

Maintenance of polymorphism by natural selection.

Heterozygote advantage

When a heterozygote has higher fitness than either homozygote.

Heterozygote disadvantage

Occurs when the heterozygote has lower fitness than either homozygote.

Antagonistic selection

Opposing selective forces that may or may not maintain polymorphism.

Extended phenotype

A phenotype that is not limited to the individual body in which a gene is housed.

Frequency-dependent selection

A type of balancing selection where the fitness of a phenotype depends on its frequency.

Inverse frequency-dependent selection

The rarer a phenotype, the greater its fitness.

Positive frequency-dependent selection

The fitness of a genotype is greater the more frequent it is in a population.

Adaptive landscape

A metaphor for the relationship between mean fitness of a population and allele frequencies.

Adaptive peak

The allele frequency at which mean fitness of a population has a local maximum.

Adaptive valley

A set of allele frequencies at which mean fitness is at a minimum.

Shifting balance theory

Adaptive evolution may proceed quickly when a population divides into subpopulations.