Allopatric speciation Knowledge-Based Practice

Questions

1. 1.

   Why does allopatric speciation typically occur more rapidly when a small population becomes isolated from a large parental population than when two large populations are separated by a geographic barrier?

   • A) Small isolated populations possess higher initial genetic diversity, providing more raw material for adaptive radiation.
   • B) Gene flow between the parental population and the isolated group increases as the population size decreases.
   • C) Spontaneous mutation rates increase automatically in smaller populations due to localized environmental stress.
   • D) Genetic drift exerts a much stronger effect in small populations, accelerating allele frequency changes alongside natural selection.
2. 2.

   Allopatric speciation typically occurs via either dispersal or vicariance. Which of the following scenarios describes allopatric speciation initiated specifically through vicariance?

   • A) A small flock of songbirds is carried by storm winds to an isolated volcanic island and establishes a new breeding population.
   • B) Marine invertebrate larvae drift across a wide ocean current on floating debris to colonize a previously unoccupied coral reef.
   • C) The gradual uplift of an impassable mountain range divides a continuous population of lowland salamanders into two separated groups.
   • D) A subgroup of herbivorous insects within a continuous meadow shifts to mating exclusively on an introduced host plant.
3. 3.

   Once a geographic barrier interrupts gene flow between two separated populations, which evolutionary mechanisms primarily drive their genetic divergence over time?

   • A) Persistent gene flow and stabilizing selection that maintain identical allele frequencies
   • B) Independent mutations, divergent natural selection, and genetic drift acting within each population
   • C) Assortative mating that actively promotes gamete exchange across the physical barrier
   • D) Balanced polymorphisms maintained by identical environmental pressures across both regions
4. 4.

   Following an extended period of geographic separation between two populations of an animal species, the physical barrier disappears and the populations come into secondary contact. Which of the following observations provides the most definitive evidence that allopatric speciation has successfully occurred?

   • A) The two populations occupy completely different ecological niches within the shared territory.
   • B) Morphological differences between individuals of the two populations can be readily distinguished.
   • C) Overall genetic diversity within each population has decreased compared to the ancestral population.
   • D) Individuals from the two populations are unable to interbreed and produce viable, fertile offspring.
5. 5.

   Which of the following events is the essential initial requirement for allopatric speciation to occur between two populations of a species?

   • A) Development of behavioral courtship differences within a continuous shared territory
   • B) Geographic separation that physically prevents gene flow between the populations
   • C) Polyploidy that immediately establishes postzygotic isolation in a single generation
   • D) Rapid sexual selection that divides individuals into distinct ecological niches locally

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