Bottleneck and founder effects Knowledge-Based Download PDF

Questions

1. 1.

   In population genetics, which statement accurately distinguishes the demographic event causing a founder effect from that causing a population bottleneck?

   • A) A founder effect is driven primarily by directional natural selection, whereas a population bottleneck results strictly from non-random mating within an undisturbed habitat.
   • B) A founder effect requires the complete demographic collapse of the ancestral population, whereas a population bottleneck leaves the original gene pool fully intact.
   • C) A founder effect occurs when a small subgroup separates to colonize a new geographic area, whereas a population bottleneck results from a severe mortality-driven collapse of an existing population.
   • D) A founder effect systematically increases heterozygosity across the genome, whereas a population bottleneck uniformly purges all deleterious recessive alleles from survivors.
2. 2.

   A population experiences a severe bottleneck and then rapidly rebounds to its original census size. What is the primary reason this recovered population remains genetically vulnerable despite its large number of individuals?

   • A) Deleterious recessive alleles are completely purged from the gene pool during the demographic contraction.
   • B) Novel allelic diversity relies on spontaneous mutations, which accumulate over timescales far slower than demographic rebound.
   • C) High reproductive rates immediately restore the lost ancestral heterozygosity across all genetic loci.
   • D) Natural selection systematically reverses the stochastic allele frequency shifts caused by the bottleneck event.
3. 3.

   Certain rare autosomal recessive disorders occur at markedly higher frequencies in isolated founder populations than in the general ancestral population. Which evolutionary mechanism primarily accounts for this elevated prevalence?

   • A) An elevated rate of germline mutation is triggered across recessive loci by environmental stress in the new territory.
   • B) Random sampling error caused the rare allele to be disproportionately represented among the small group of founders.
   • C) Directional natural selection favored the expression of recessive alleles over dominant alleles in the new habitat.
   • D) Continuous gene flow from neighboring communities introduced the deleterious allele into the expanding gene pool.
4. 4.

   Which of the following genetic consequences is typically shared by both a population bottleneck and the founder effect?

   • A) A significant reduction in overall genetic variation and random fluctuations in allele frequencies
   • B) A substantial increase in average heterozygosity resulting from the spontaneous creation of novel alleles
   • C) Directional adaptation toward optimal fitness driven primarily by environmental natural selection
   • D) The rapid establishment of Hardy-Weinberg equilibrium across all loci in the resulting population
5. 5.

   Which of the following scenarios best exemplifies the founder effect rather than a population bottleneck?

   • A) A severe wildfire destroys over 95% of a forest, leaving only a few surviving rodents to rebuild the local population.
   • B) A novel infectious disease wipes out most individuals in a marine mammal colony, drastically reducing its genetic variation.
   • C) Overhunting by humans reduces an isolated animal population to twenty individuals, resulting in widespread allele fixation.
   • D) A small flock of storm-blown finches arrives on a remote archipelago and establishes a thriving community with limited genetic diversity.