Question

Use the appropriate equations for effective populatoin size to determine which of the

following populations will lose heterozygosity more quickly: a population (starting at

generation 0) with a 9:1 sex ratio that remains constant at 240 individuals for four

additional generations, or a population with a 1:1 sex ratio that starts at 240 individuals in

generation 0, crashes to 20 for one generation, and recovers to 240 for the second, third,

and fourth generations. Explain how you got your answer.

Answer 1

Effective population size represents the number of individuals present in a given population who can contribute offsprings to the next generation. It is calculated by the following formula,

Ne = (4 Nm Nf) / (Nm + Nf)

Where, Ne is effective size of population, Nm and Nf representing number of breeding males and females respectively.

From the formula, we can easily ascertain that the effective population will be more when the number of males and females are equal (sex ratio of 1:1). When the sex ratio becomes skewed in either of the sexes, the effective population size decreases.

Heterozygosity depends upon the effective population size as large effective population ensures different permutations and combinations in mating. So, there will be loss of heterozygosity in the population which has a sex ratio of 9:1 than in the population which has the sex ratio of 1:1.