Why can Hardy-Weinberg equilibrium happen only in populations that are large?

Answer 1

The force of genetic drift is much stronger in small versus large populations. This is because genetic drift is a change of allele frequencies as a result of random factors like natural disasters. In the smaller populations, genetic drift's force is much more powerful because each individual represents a greater % of the total genes in the population than it would be in a larger population. For instance, say you have a population of 10 lions, and 3 die, you lost 30% of the genes in that pool. Rather, if you have 100 lions and 3 die, you have only lost 3%. Therefore Hardy-Weinberg equilibrium is more likely to occur in large populations.