The Four Evolutionary Forces Flashcards
Mutation
Mutations are the source of all new alleles in a population - they are random, may be beneficial or harmful, and the mutation itself will not change allele frequencies dramatically, it is selection on the mutation that causes it to increase in frequency in the population
Gene Flow (migration)
The flow of alleles into or out of a population due to migration if individuals - can increase variation and can make two populations less distinct
Genetic Drift
Random changes in allele frequencies due to sampling error, particularly in small population - leads to loss of variation and gain or loss of alleles from a population by chance
Genetic Drift: Founder Effect
May occur after a subset of a population migrates to a new habitat
Genetic Drift: Bottleneck
Typically occurs after a catastrophic event, drastically reduces the population size
Disruptive Selection
Extreme phenotypes are favored over intermediate phenotypes; ex: beak size of Santa Cruz Finches in the Galapagos
Directional Selection
Selection that favors one phenotype over another; ex: selection for increasing body size in horses over time
Stabilizing Selection
Selection against either extreme stabilizes an intermediate phenotype; ex: Human birth weight
Sexual Selection
Selection that favors traits that increase mating success; ex: birds of paradise do elaborate mating displays
Positive Frequency-Dependent Selection
Favors traits that are common; ex: warning coloration in butterflies
Negative Frequency-Dependent Selection
Favors traits that are rare
Kin Selection
Favors altruistic behavior toward kin, these behaviors decrease the individual’s chance of own reproduction but increase their kin’s chance of reproduction
Fitness
A measure of how likely an organism with a particular genotype is to pass its genes onto the next generation
