Sympatric speciation Knowledge-Based Practice

Questions

1. 1.

   When disruptive natural selection favors two extreme phenotypes in a sympatric population, which evolutionary factor is necessary to prevent recombination and gene flow from homogenizing the diverging gene pools?

   • A) Positive assortative mating between individuals with matching adaptive phenotypes
   • B) Negative assortative mating that encourages hybridization between different morphs
   • C) Stabilizing selection that favors intermediate phenotypes over extreme morphs
   • D) Random mating that maintains broad recombination across the entire population
2. 2.

   Which of the following genetic events is required for an initially sterile interspecific plant hybrid to restore fertility and establish a new allopolyploid species in sympatry?

   • A) Recurrent backcrossing to the parental species to dilute divergent alleles from the hybrid genome
   • B) Extensive reciprocal translocation between non-homologous chromosomes during embryonic mitosis
   • C) A chromosome doubling event that provides each chromosome with a homologous partner for meiotic synapsis
   • D) Complete epigenetic silencing of one parental chromosome set to reestablish a functional haploid state
3. 3.

   During sympatric speciation through autopolyploidy, why are hybrid offspring produced by matings between newly formed tetraploid individuals and ancestral diploid individuals typically sterile?

   • A) Mitotic spindle failure during early cleavage divisions causes immediate developmental arrest of the hybrid embryo.
   • B) Unequal segregation of homologous chromosomes during meiosis disrupts normal gamete formation.
   • C) Prezygotic mechanical incompatibilities prevent successful transfer of gametes between ploidy levels.
   • D) Rapid degradation of sex chromosomes in triploid germline cells prevents organogenesis of reproductive structures.
4. 4.

   Which of the following scenarios best illustrates the initiation of sympatric speciation through ecological niche differentiation?

   • A) Subpopulations of an herbivorous insect specialize on different host plants within the same orchard and mate exclusively on their preferred host.
   • B) A newly formed mountain range separates a mainland rodent population into two geographically isolated groups.
   • C) Rising sea levels isolate a lizard subpopulation on an offshore island where it adapts to novel predators.
   • D) A severe drought divides a large lake into two disjunct ponds located several kilometers apart.
5. 5.

   Which of the following processes can lead directly to sympatric speciation within a shared geographic area without physical isolation?

   • A) Formation of an impassable mountain range dividing a population into two separate ranges
   • B) Gradual sea-level rise that isolates mainland individuals on an offshore island
   • C) Migration of a small founding group across an ocean to an uninhabited archipelago
   • D) Instantaneous reproductive isolation caused by an autopolyploid error during plant meiosis

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