The primary purpose of natural selection in evolution is to drive adaptation in populations. It enables organisms with advantageous traits to survive and reproduce more successfully than those without these traits. Over time, these favorable traits become more common in the population, leading to evolutionary change. Natural selection acts on existing genetic variation within a population, influencing which individuals are more likely to pass on their genes to the next generation. This process is fundamental in shaping the biodiversity we see in nature and provides a mechanism for species to adapt to changing environments.