Genetic drift Knowledge-Based Practice

Questions

1. 1.

   A sudden environmental catastrophe, such as a massive flood or disease outbreak, kills the majority of individuals in a population regardless of their genotypes. Which manifestation of genetic drift is characterized by this severe, non-selective reduction in population size?

   • A) Gene flow
   • B) Directional selection
   • C) The founder effect
   • D) A population bottleneck
2. 2.

   In the absence of gene flow, natural selection, and mutation, what is the primary long-term effect of genetic drift on two completely isolated populations derived from the same ancestral gene pool?

   • A) It causes both populations to converge genetically and maintain identical allele frequencies over time.
   • B) It increases genetic divergence between the populations as different alleles randomly drift toward fixation or loss.
   • C) It permanently preserves ancestral levels of heterozygosity and polymorphic diversity in both populations.
   • D) It systematically eliminates all deleterious recessive alleles from both populations to maximize average fitness.
3. 3.

   Which evolutionary phenomenon occurs when a small group of individuals separates from a larger population to establish a new colony, resulting in allele frequencies that differ substantially from the original parent population purely by chance?

   • A) Disruptive selection
   • B) Gene flow
   • C) Stabilizing selection
   • D) The founder effect
4. 4.

   In which of the following populations is genetic drift most likely to cause the rapid fixation or loss of an allele independently of its fitness value?

   • A) A large, continuously distributed population experiencing frequent gene flow with adjacent communities
   • B) A massive, panmictic continental population undergoing intense directional selection
   • C) An expansive aquatic population with random mating and low overall mutation rates
   • D) A very small, isolated population established on an offshore island by a few founding individuals
5. 5.

   Which of the following statements correctly describes genetic drift and its effect on biological populations?

   • A) It consistently increases genetic variation within a population by generating novel alleles through random mutations.
   • B) It causes random fluctuations in allele frequencies that have a much more pronounced effect in small populations than in large ones.
   • C) It drives directional adaptation by selectively eliminating deleterious alleles and promoting beneficial traits over generations.
   • D) It prevents the fixation or complete loss of neutral alleles by maintaining equal genotype proportions over time.

Answers and step-by-step solutions appear after you finish the test.