Question

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

Hint:

Natural selection causes changes in allele frequencies over time by favoring individuals with advantageous traits. This disrupts Hardy-Weinberg equilibrium and leads to evolution in a population.

Answer 1

The Hardy-Weinberg equilibrium is a theoretical concept in population genetics that describes the genetic variation in a population at equilibrium, assuming no evolutionary influences. The equilibrium occurs when allele frequencies remain constant from generation to generation. The five conditions required for Hardy-Weinberg equilibrium are:
1. No mutation.
2. No natural selection.
3. Random mating.
4. Large population size.
5. No gene flow (migration).

Effect of Natural Selection on Hardy-Weinberg equilibrium:
Natural selection is one of the key evolutionary forces that can disrupt Hardy-Weinberg equilibrium. It acts on individuals in a population by favoring those with advantageous traits, which leads to changes in allele frequencies over time. This is not in accordance with the assumption of no natural selection in Hardy-Weinberg equilibrium.
In a population where natural selection is acting:
- Alleles that provide a survival advantage increase in frequency over time.
- Alleles that reduce fitness decrease in frequency.
- This results in a change in genotype and allele frequencies, which causes the population to evolve, thereby deviating from Hardy-Weinberg equilibrium.
Graphical Explanation: 
1. Graph 1: Hardy-Weinberg equilibrium (no selection) 
When there is no natural selection, allele frequencies remain constant over generations, represented as a straight line. The population is at equilibrium.
2. Graph 2: Effect of natural selection 
When natural selection is introduced, the advantageous allele increases in frequency over time, while the disadvantageous allele decreases in frequency, leading to evolution. This is represented by a curve showing the change in allele frequency.
The graph demonstrates that, with natural selection, the population will evolve, and the allele frequencies will shift, causing the population to deviate from Hardy-Weinberg equilibrium.