Final answer:
Natural selection drives the increase of beneficial alleles in populations, as exemplified by the peppered moth, which underwent a color change due to industrial soot, showing the adaptation to the altered environment.
Step-by-step explanation:
Natural selection is a fundamental process in evolution where the environment acts on the population's heritable traits, favoring beneficial alleles that allow organisms to better adapt to their environment, and thus increasing their frequency in the population. Conversely, deleterious alleles are selected against, leading to a decrease in their frequency. An example of natural selection can be seen in the case of the peppered moth in 19th-century England. Before the Industrial Revolution, light-colored peppered moths were more common due to their camouflage against the lichen-covered trees. As the Industrial Revolution progressed, soot from factories blackened the trees, and dark-colored moths, which were initially rare and more visible, became better camouflaged. As a result, these dark-colored moths had higher survival rates and reproduced more, leading to an increase in their frequency in the population.