Question

How does the process of Natural Selection affect the Hardy-Weinberg equilibrium? Explain with the help of graphs.

Answer 1

The Hardy-Weinberg equilibrium, which holds that allele and genotype frequencies in a population stay constant over generations in the absence of evolutionary forces, is upset by natural selection. Over time, their frequencies fluctuate as a result of natural selection favouring particular features.

The following diagrams assist in explaining how natural selection affects the Hardy-Weinberg equilibrium.

1. Stabilising Selection: It reduces population variation by favoring the average phenotype. The distribution curve around the mean narrows in a graph that illustrates this.
2. Directional Selection: It favours one extreme phenotype, which, over time, causes the distribution of traits in the population to change. This would be shown graphically as the curve moving toward one end of the spectrum.
3. Disruptive Selection: The selection against the average phenotype favours both extreme phenotypes, which could result in a bimodal distribution. There would be a dip in the middle of the graph, with peaks at either extreme of the phenotypic range.