Final answer:
Changes in allele frequencies, or microevolution, can be highly variable and occur on short timescales. This is evident in the study of Darwin's finches by the Grants, demonstrating rapid evolution within a population due to factors like natural selection, genetic drift, and changes in the environment.
Step-by-step explanation:
Changes in allele frequencies within species can be highly variable and occur on relatively short scales of time. This concept is known as microevolution, which refers to the changes in a population's genetic structure, particularly in allele frequency, over generations. Microevolution can be observed through various mechanisms such as natural selection, genetic drift, and gene flow, and is influenced by factors like nonrandom mating, mutation, and environmental changes.
One compelling example of microevolution is the observation made by the Grants in Darwin's finches, where notable evolutionary changes occurred over just a few generations. Studies like these underscore the dynamic nature of population genetics and the importance of tracking how selective forces change the allele frequencies in a population over time. An allele conferring a beneficial phenotype may become more common very quickly, while a detrimental allele may be swiftly eliminated from the gene pool.