Final answer:
A population at Hardy-Weinberg equilibrium is not evolving regarding a particular gene. This concept provides a baseline to detect evolution in populations by comparing actual allele frequencies to expected values under equilibrium conditions.
Step-by-step explanation:
A population at equilibrium according to the Hardy-Weinberg law is not evolving concerning a given gene. The Hardy-Weinberg equilibrium symbolizes a state where allele frequencies in a population's gene pool remain constant from generation to generation, suggesting no evolution. This is described by the mathematical equation p² + 2pq + q² = 1, which holds under certain conditions: no mutations, no gene flow, random mating, no genetic drift, and no selection. However, because these conditions are rarely fully met in nature, the principle serves more as a baseline for scientists to compare real population changes and detect evolutionary forces should allele frequencies deviate from the expected values.