- Genetic variation occurs mainly through DNA mutation, gene flow (movement of genes from one population to another) and sexual reproduction. Due to the fact that environments are unstable, populations that are genetically variable will be able to adapt to changing situations better than those that do not contain genetic variations.
- Sexual reproduction allows for genetic variations to occur through genetic recombination. Recombination occurs during meiosis and provides a way for producing new combinations of alleles on a single chromosome. Independent assortment during meiosis allows for an indefinite number of combinations of genes.
- Sexual reproduction makes it possible to assemble favorable gene combinations in a population or to remove unfavorable gene combinations from a population.
- Populations with more favorable genetic combinations will survive in their environment and reproduce more offspring than those with less favorable genetic combinations.