What does genetic drift affect within a population?

Genetic drift refers to the random fluctuations in the frequencies of alleles (gene variants) in a population from one generation to the next due to chance events. This phenomenon is particularly pronounced in small populations, where random events can significantly alter allele frequencies. Unlike natural selection, which involves differential survival and reproduction based on advantageous traits, genetic drift occurs independently of the fitness associated with specific alleles.

By affecting the frequency of existing gene variants, genetic drift can lead to a loss of genetic variation within the population, or it can result in certain alleles becoming fixed (reaching a frequency of 100%) purely by chance. This can have substantial evolutionary implications, potentially leading to differentiation between populations over time.

The other options relate to different aspects of biology or ecology that are not directly influenced by genetic drift. For instance, lifespan, food sources, and environmental adaptations are primarily influenced by factors such as natural selection, competition, and environmental pressures rather than the random processes associated with genetic drift.