Final answer:
Population genetics is the field within evolutionary biology that studies changes in allele frequencies in populations. It evaluates how evolutionary processes such as natural selection and genetic drift drive these changes, leading to evolution.
Step-by-step explanation:
The discipline within evolutionary biology that studies changes in allele frequencies is known as population genetics. This science focuses on the forces of evolution at the level of allele frequencies in populations, taking into account the impacts of factors such as natural selection, genetic drift, gene flow, mutation, nonrandom mating, and environmental variances. Studies in population genetics might look at allele frequencies in various genes, like pesticide resistance in mosquitoes or the ABO blood group system, to understand how these frequencies shift over time - indicating evolutionary changes.
For instance, an increase in a beneficial allele due to natural selection can cause it to become more common over generations, which demonstrates evolution taking place. Conversely, if allele frequencies remain constant over time, the population conforms to the Hardy-Weinberg equilibrium, which describes a non-evolving state. Hence, tracking changes in allele frequencies helps scientists to decipher the evolutionary history and current evolutionary pressures on a population.