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Equilibrium where new mutations arise at the same rate that selection removes them.
Introduces genetic variation necessary for natural selection and adaptation.
Frequency-independent Selections
Directional, Stabilizing, Disruptive, Overdominance, Underdominance
Frequency Dependent Selections
Positive frequency and Negative frequency
Mice with dark fur are favored in lava-covered environments, showing directional selection due to predation pressure.
Positive assortative mating effect on genotypic frequencies?
Increases homozygosity and decreases heterozygosity.
Negative assortative mating effect on genotypic frequencies?
Increases heterozygosity, favoring mating between genetically different individuals.
Inbreeding relation to positive assortative mating?
Reduces genetic diversity, leading to lower fitness and increased disease susceptibility.
A large population (continent) supplies alleles to a smaller population (island), island allele frequencies converge to continent allele frequencies.
Migration occurs between multiple small populations, leading to convergence on mean of all islands allele frequencies.
Causes random changes, potentially leading to allele fixation or loss, especially in small populations.
Example of genetic drift in a real-world population.
Three ingredients for Natural Selection
Variation, trait heritability, selective reproductive success
Directional Selection
One allele is favored, leading to allele fixation (one replaces all)
Stabilizing Selection
Intermediate phenotypes are more fit than extreme ones, less diversity
Disruptive Selection
Two or more extreme phenotypes more fit than intermediate; more diversity
Overdominance Selection
heterozygote advantage; higher fitness
Underdominance Selection
heterozygote disadvantage; lower fitness
Positive Frequency Dependent Selection
phenotype fitness increases as more common
Negative Frequency Dependent Selection
phenotype fitness decreases as more common