a localized group of individuals of the same species that can interbreed, producing fertile offspring
Genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. Typically, the surviving population is no longer genetically representative of the original population.
Natural selection that favors intermediate variants by acting against extreme phenotypes
natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals
natural selection that favors individuals with either extreme of a trait; tends to eliminate intermediate phenotypes