Final answer:
Among the given options, 'A. Neutral variation' does not change phenotypes but increases the genetic variation, which can help a population adapt to environmental changes.
Step-by-step explanation:
Factors Influencing Genetic Variation
Genetic variation is crucial for the survival and evolution of a population. Within the options provided, A. Neutral variation is the one that will not typically change phenotypes but will increase genetic variation within a population. This increase in genetic variance allows a population to carry more alleles, potentially helping it to adapt to environmental changes. Neutral variations are mutations that have no effect on the organism's fitness. Unlike neutral mutations, deleterious mutations typically lower fitness and can be quickly removed from a population through natural selection. A point mutation can alter a phenotype if it occurs in a functional part of the genome, and it can be either detrimental, beneficial, or neutral. Lastly, chromosomal aberrations often have significant impacts on the phenotype and can be deleterious.