Final answer:
Population genetics is the study of how allele frequencies within a population change over time due to evolutionary forces such as natural selection, genetic drift, and gene flow.
Step-by-step explanation:
The part of evolutionary theory that focuses on studying the genetics of breeding populations is known as population genetics. This field of biology examines the dynamics of allele frequencies within a population and how they change over time. The foundational principle that states allele frequencies will remain constant in the absence of evolutionary forces is the Hardy-Weinberg equilibrium principle. Factors such as mutation, natural selection, genetic drift, and gene flow can lead to changes in allele frequencies, signaling that evolution is occurring within the population.