[Campbell Biology P.545] Refer to the 'WHAT IF?' question in Figure 23.12. If a severe weath... | Practice Question

Refer to the 'WHAT IF?' question in Figure 23.12. If a severe weather event caused island water snake populations to decrease significantly in size, but did not affect mainland populations, what would be the immediate effect of gene flow from the mainland on the color patterns in island populations?

  • A: The frequency of unbanded snakes (Pattern D) would increase, as they are better adapted to island environments.
  • B: The frequency of banded snakes (Patterns A, B, C) would increase in island populations due to gene flow from the mainland, potentially hindering their local adaptation.
  • C: Genetic drift would cause a rapid increase in the most advantageous allele for island survival, regardless of gene flow.
  • D: Both banded and unbanded patterns would quickly disappear from island populations due to the reduced population size.

Explanation

The text states that mainland snakes are strongly banded, and gene flow from the mainland causes banding to persist in island populations, even though unbanded is advantageous on islands. If island populations decrease in size making them more susceptible to gene flow's effects , the influx of banded alleles from the mainland would have a more pronounced immediate effect, increasing the frequency of banded patterns and hindering local adaptation to the unbanded form.