Final answer:
The Hardy-Weinberg principle posits that allele frequencies in a population remain constant across generations in the absence of evolutionary pressures, encapsulated by a mathematical equation assessing genetic stability. Deviations from Hardy-Weinberg equilibrium signal evolutionary processes at work, allowing scientists to study the underlying causes of genetic change.
Step-by-step explanation:
The Hardy-Weinberg principle of equilibrium theory illustrates how, under certain conditions, allele frequencies in a population remain constant from generation to generation. These conditions include no mutations, random mating, no gene flow (migration into or out of the population), immensely large population size, and no natural selection. If all of these conditions are met, the population is said to be in Hardy-Weinberg equilibrium, meaning the genetic structure of the population does not change over time, illustrating a state of genetic stability. The principle is encapsulated by the equation p² + 2pq + q² = 1, where ‘p’ and ‘q’ represents the frequencies of the dominant and recessive alleles, respectively.
When evolutionary forces such as mutation, genetic drift, non-random mating or selection pressure act upon a population, it can cause the allele frequencies to vary, signifying evolution is taking place. For example, the frequency of alleles for pesticide resistance in an insect population may shift after continued use of the pesticide, indicating an evolutionary response to the selective pressure. This departure from equilibrium enables scientists to understand and measure the evolutionary processes affecting a population.