Bottleneck and founder effects Knowledge-Based Practice

Questions

1. 1.

   During a brief and severe population bottleneck, which measure of genetic variation typically undergoes the most rapid and substantial loss?

   • A) The average expected heterozygosity across polymorphic loci
   • B) The spontaneous mutation rate per nucleotide across the genome
   • C) The frequency of the most common adaptive allele
   • D) The total number of unique alleles per locus (allelic richness)
2. 2.

   Even when a population's census size rapidly rebounds following a severe bottleneck event, its overall genetic diversity typically remains depleted for many generations. Which factor primarily accounts for this prolonged lag in the recovery of genetic diversity?

   • A) High rates of gene flow from neighboring populations consistently counteract the generation of novel alleles.
   • B) Natural selection actively purges all non-deleterious alleles that survived the initial demographic crash.
   • C) The restoration of lost alleles depends largely on new mutations, which occur at very low rates per generation.
   • D) Elevated inbreeding immediately halts all chromosomal crossing over during meiotic cell division.
3. 3.

   Which statement best explains why a rare, deleterious recessive allele can reach an unusually high frequency in a population established via the founder effect?

   • A) The allele confers a distinct adaptive advantage that is favored by natural selection in the new habitat.
   • B) The physiological stress of colonizing a new environment triggers targeted mutations at that gene locus.
   • C) The allele was present by chance in one of the few founding individuals and increased in frequency through genetic drift.
   • D) Natural selection actively promotes homozygosity to eliminate genetic variation in small isolated groups.
4. 4.

   Which statement correctly describes a major genetic consequence shared by both the bottleneck effect and the founder effect?

   • A) They systematically increase overall heterozygosity by promoting novel gene combinations.
   • B) They direct allele frequencies toward phenotypes that maximize individual reproductive fitness.
   • C) They prevent random fluctuations in allele frequencies across subsequent generations.
   • D) They reduce overall genetic variation and can cause rare or non-adaptive alleles to become fixed purely by chance.
5. 5.

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

   • A) A small group of birds is blown off course during a storm and colonizes an uninhabited oceanic island.
   • B) A severe drought kills the majority of a plant population in its native grassland habitat.
   • C) An outbreak of a novel viral disease destroys over 90% of a native amphibian population.
   • D) Overhunting by humans drastically reduces the census size of an elephant herd across its historic territory.

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