Evaluating the Statements

(1) Loss of genetic variation occurs within a small population due to genetic drift.
This statement is correct. Genetic drift, especially in small populations, leads to the random loss of alleles and a reduction in genetic diversity. Over time, this makes populations less adaptable and more vulnerable to extinction.

(2) The number of deleterious alleles present in the gene pool of a population is called the genetic load.
This statement is correct. Genetic load refers to the presence and frequency of deleterious alleles in a population’s gene pool, which can reduce the average fitness of individuals.

(3) Genetic erosion is a reduction in levels of homozygosity.
This statement is incorrect. Genetic erosion refers to the loss of genetic diversity—that is, the loss of alleles from the gene pool, leading to increased homozygosity and decreased heterozygosity. A reduction in homozygosity would mean more genetic diversity, which is the opposite of genetic erosion.

(4) Inbreeding depression results from increased homozygosity for deleterious alleles.
This statement is correct. Inbreeding depression occurs because inbreeding increases the chance that individuals will be homozygous for harmful recessive alleles, reducing population fitness.

Correct Answer

The incorrect statement is:

(3) Genetic erosion is a reduction in levels of homozygosity.

In reality, genetic erosion leads to a reduction in genetic diversity and an increase in homozygosity, not a reduction.