Final answer:
Sampling error, which is synonymous with genetic drift, increases as population size decreases because each individual's genetic contribution has a much bigger impact in smaller populations. The correct answer is option 3.
Step-by-step explanation:
Genetic drift refers to the random fluctuations in allele frequencies within a population due to chance events. One form of genetic drift is sampling error, which occurs when the individuals chosen to reproduce become the genetic representatives of the next generation by chance, leading to fluctuations in allele frequencies over generations.
In smaller populations, genetic drift becomes more pronounced. With fewer individuals, each generation's genetic composition is more susceptible to chance events, such as the random selection of alleles in reproduction. As a result, sampling error, or the impact of chance events on allele frequencies, increases in smaller populations.
Conversely, larger populations experience reduced sampling error. With a larger pool of individuals, random fluctuations in allele frequencies have less impact on the overall genetic composition of subsequent generations. The effects of chance events become diluted in larger populations due to the larger number of reproducing individuals, resulting in decreased sampling error or reduced genetic drift.
Therefore, as population size decreases, the impact of sampling error (genetic drift) becomes more significant, leading to greater fluctuations in allele frequencies over time.