Final answer:
A population in biology is a group of interbreeding individuals with a common set of genes, and population genetics studies the genetic variations within such a group. The gene pool refers to all genes and alleles within that population.
Step-by-step explanation:
A population in biology refers to a group of interbreeding, sexually reproducing individuals that have a common set of genes. This concept is fundamental in population genetics, where biologists study the changes in allele and genotypic frequencies within a population due to selective forces. It is important to recognize that a gene pool includes all the genes of all the members of a population, and for each gene, it encompasses all the different alleles that exist within the population.
Furthermore, individuals within a species can interbreed and produce viable, fertile offspring. In the context of evolutionary biology, the term population is assumed to be a relatively closed group, implying that most mating occurs within the population. This is distinct from a wider definition of species, which encompasses populations that are capable of interbreeding to produce fertile offspring but are reproductively isolated from other such groups.