Answer:
3. It decreases genetic diversity via sampling error during mating.
Explanation:
Genetic drift is important in small population because it decreases genetic diversity via sampling error during mating from generation to generation.
Genetic drift is defined as a change in the allele frequency of a population as a result of sampling error across different generations.
For a small population that already has low number of alleles, genetic drift leads to the fixation of alleles within the population, increases inbreeding coefficients and increases the chance of homozygosity within the population thereby reducing the overall genetic diversity of the population.