Answer:
a. Genetic drift is a random process that can reduce the genetic variation within a population. It occurs when specific individuals in a population contribute more offspring to the next generation purely by chance. As a result, the frequency of specific alleles may increase or decrease in the population, while others may be lost altogether. Over time, this can lead to a decrease in the overall genetic diversity within the population.
b. Genetic drift is most likely to occur under certain conditions. These conditions include small population size, random fluctuations in reproductive success, and lack of gene flow (migration of individuals between populations). When a population is small, the effects of genetic drift are more pronounced because the chances of random fluctuations in allele frequencies are higher. Similarly, when there is limited gene flow, the genetic makeup of a population becomes more susceptible to the random changes brought about by genetic drift.
c. The situation described with the migrating birds blown off course and ending up on a small island with only three survivors represents a founder effect. The founder effect occurs when a small group of individuals establishes a new population in a new location, leading to a loss of genetic variation compared to the original population. In this case, the three birds that survived the storm became the founders of the new population on the island. Since they represent only a tiny fraction of the genetic diversity of the original population, the genetic variation in the population on the island is reduced compared to the larger population they originated from.
Step-by-step explanation: