Evolution Week 9 - Fitness& Pleiotropy Flashcards
Define fitness
The survival and reproductive success of an individual with a particular phenotype.
What are 3 components of fitness?
Survival to reproductive age
Mating success
Fecundity
Define relative fitness (w).
Contribution of individuals with one genotype compared with the average contribution of all individuals in the population.
Define pleiotropy.
Mutation in a single gene affects more than one phenotypic trait.
Define antagonistic pleiotropy.
Beneficial effects for one trait but detrimental effects for other traits.
The net effect on fitness determines what?
The outcome of selection.
Alleles may have pleiotropic effects when…
Fitness effects oppose each other and when the environment determines direction of selection.
Define negative selection.
Alleles that lower fitness
experience.
Define positive selection.
Alleles that increase fitness
experience.
Define additive alleles.
Homozygous condition yields twice the phenotypic effect for the gene as compared with heterozygotes.
Define dominance.
Dominant allele masks presence
of recessive in heterozygote.
Which alleles are especially vulnerable to the action of selection? Why?
Additive alleles.
Define negative frequency-dependent selection. Give an example.
Common phenotypes are selected
against, and rare phenotypes are favored. Ex. Female guppies prefer to mate with males that have rare phenotypes.
Define heterozygote advantage. Give an example.
Heterozygosity confers greater fitness than homozygotes.
What are two balancing selections?
Negative frequency-dependent and heterozygote advantage.
