Final answer:
Genetic drift can increase genetic differences between populations due to random events that alter allele frequencies, potentially leading to fixation or loss of alleles in distinct populations.
Step-by-step explanation:
Genetic drift refers to the random changes in allele frequencies within a population, particularly in small populations. It can occur due to various chance events, such as natural disasters, which may lead to some alleles becoming fixed in one population while being completely lost in another. These changes are not related to the fitness of individuals but rather to randomness. For instance, if a natural event causes the death of the only organisms carrying a particular allele, like white rabbits in a storm, that allele might significantly diminish or disappear from the gene pool. Additionally, the founder effect and bottleneck effect are examples of how genetic drift can result in significant changes in the genetic makeup of a population.
In a small population, the impact of losing an individual with a rare allele is much greater as it represents a larger fraction of the gene pool. Over time, without any selective pressure, genetic drift can lead to complete elimination of an allele, or alternatively, it can cause previously rare alleles to become predominant within the population. This process shows how populations can diverge genetically over time, even in the absence of natural selection.