[Campbell Biology P.546] Based on the text, why do water snakes on islands still have banded... | Practice Question

Based on the text, why do water snakes on islands still have banded individuals despite natural selection favoring unbanded snakes for camouflage?

  • A: The unbanded trait is recessive and rarely expressed.
  • B: Predators on the islands prefer banded snakes, increasing their survival.
  • C: Gene flow from the mainland introduces banded alleles, counteracting the effects of natural selection on the islands.
  • D: The island environment is changing, making banded snakes more camouflaged.

Explanation

The passage explains that while unbanded snakes are favored on islands, gene flow from the mainland where banded snakes are common continuously introduces alleles for banded coloration into the island populations, preventing natural selection from completely eliminating them.