Which of the following is true about alleles in a population?

Alleles can vary within a population is the correct understanding of genetic diversity. In any given population, individuals may possess different forms of a gene, which are known as alleles. This variation can arise due to mutations, genetic recombination during reproduction, and other evolutionary factors. The presence of multiple alleles contributes to the genetic diversity within a population, which is essential for adaptation and evolution, allowing populations to respond to environmental changes and pressures.

In contrast, the idea that there are always two alleles for a gene is not accurate, as some genes can have more than two alleles present in a population. The concept of alleles being identical in all individuals does not reflect the reality of genetic variation, as individuals often carry different alleles, leading to phenotypic diversity. Finally, alleles do influence traits; they determine the expression of physical characteristics and play a significant role in heredity, contradicting the notion that they do not influence traits. Thus, the assertion that alleles can vary within a population clearly highlights the importance of genetic diversity in biology.