What does the term "genetic variation" refer to?

The term "genetic variation" refers to the diversity of alleles within a population's gene pool. This diversity is crucial for the adaptability and survival of a species, as it provides the raw material for evolution through natural selection. When there are multiple alleles for a given gene within a population, it allows for a range of phenotypes, or physical traits, which can be beneficial in varying environmental conditions.

This variation arises from mutations, gene flow (the transfer of alleles between populations), and sexual reproduction, which mixes genetic material. Understanding genetic variation is fundamental in fields like conservation biology, genetics, and evolution, as it underpins the resilience of populations to changing environments, diseases, and other selective pressures.

The other options provided, while related to genetics, describe different concepts. Differences in physical characteristics pertain more to phenotypic variation rather than the genetic basis for those differences. The degree of genetic divergence between populations relates to genetic distance, which can indicate how distinct two populations are but does not encapsulate the total variation within a single population. The mutation rate refers specifically to the frequency of mutations occurring in a genome, which is just one source of genetic variation rather than a comprehensive definition.