Final answer:
Evolution at the genetic level occurs when there is a change in allele frequency of a gene within a population, which can be influenced by natural selection, genetic drift, or gene flow.
Step-by-step explanation:
A change in the frequency of a particular gene in one direction in a population is known as evolution at the genetic level. This change in allele frequency can result from various processes such as natural selection, genetic drift, and gene flow. In the context of natural selection, an allele that provides a survival or reproductive advantage will increase in frequency over time because the traits it confers are more likely to be passed down to subsequent generations. Genetic drift refers to changes in allele frequencies due to random chance events, which can have significant effects in small populations. Lastly, gene flow involves the introduction or removal of alleles from a population due to the migration of individuals or their gametes (e.g., pollen).