Question

A population of a certain size (say, 500 individuals) is more likely to go extinct if it has suffered a bottleneck effect in the recent past than if it has maintained a similar population size for many generations. Why?

Answer 1

Bottleneck effect means a drastic reduction in the number of individuals in a particular population, due to some catastrophic or sudden event such as flood or fire. This decreases the population to a very less number. So, if a population is of only 500 individuals, and has undergone a bottleneck effect in the past, only a few individuals with a limited gene pool may be left and with each passing generation, the population has a higher risk to get completely extinct.

But if a population of 500 individuals, does not suffer due to the bottleneck effect, then, its population will stay similar in size as per the Hardy Weinberg equilibrium, for several genrations. Other conditions include absence of any migration, genetic drift, and mutation in the population. So, the gene pool will remain same in every generation with same or similar allelic and genotypic frequencies for each generation. Hence, a population of 500 individuals can survive for many generations.