Other Evolutionary Forces

Mutations

Changes in DNA that can be beneficial, neutral, or detrimental

Beneficial mutation

A mutation that increases an organism’s fitness in its environment.

Neutral mutation

A mutation that has no significant effect on fitness.

Detrimental mutation

A mutation that decreases an organism’s fitness in its environment.

Black-footed Ferrets example

Reduction in prairie dog populations caused genetic drift to have a substantial effect on the ferrets’ gene pool.

Genetic Drift

Random change in allele frequencies over time

Example of Genetic Drift

Mexican Tetra (Cavefish): loss of skin color

Genetic Bottleneck

Drastic reduction in population size that alters the gene pool, e.g., cheetahs.

Founder Effect

Type of bottleneck where a small group leaves a larger population to colonize a new habitat, e.g., Pitcairn Island.

Nonrandom Mating

Mating patterns that are not random, can affect heterozygosity.

Positive Assortative Mating

Individuals mate with others like themselves, e.g., tall people marrying tall people

Negative Assortative Mating

Individuals mate with those unlike themselves, e.g., primrose heterostyly

Inbreeding Coefficient (F)

Probability that any two alleles are identical by descent