What is referred to as the gradual changes in gene frequencies in a population due to random events?

The correct choice is genetic drift, which refers to the gradual changes in gene frequencies in a population that occur due to random events. This phenomenon is particularly significant in small populations where chance events can have a more pronounced impact on the genetic makeup over time. For instance, if a natural disaster randomly eliminates a portion of a population, the gene frequencies in the survivors can differ markedly from the original population, altering the overall gene pool.

Genetic drift is distinct from other processes that influence gene frequencies. It does not involve the migration of individuals into or out of a population, which would be covered by gene flow. Additionally, while a population bottleneck refers to a sharp reduction in population size due to environmental events, leading to a loss of genetic diversity, genetic drift encompasses the broader scope of chance events impacting gene frequencies regardless of population size changes. The founder effect specifically relates to a scenario where a small group of individuals separates from a larger population to establish a new population, which can also lead to changes in gene frequencies but is a more specific instance of genetic drift rather than a general process.