Question

figure 2. map of the island following the 1832 earthquake
the island was surveyed again in 2015, and scientists determined that the giant kangaroo rats originally in population a are now to be considered as a new species.
which of the following best explains the mechanism that caused this speciation event in the giant kangaroo rats of population a?
a the animals in population a were exposed to different predators and had to modify their fur color to be better camouflaged.
b the animals in population a were reproductively isolated from those in populations b, c, and d.
c the animals in population a accumulated fewer genetic mutations, adapting to their microclimate.
d the animals in population a mate at different times of year, causing their gametes to be incompatible with those from animals in populations b, c, and d.

Explanation:

• Option A: Organisms can't "modify" fur color consciously; adaptations are genetic, so A is wrong.
• Option B: Speciation often requires reproductive isolation (pre - or post - zygotic) to prevent gene flow. If population A is reproductively isolated from B, C, D, genetic divergence can occur, leading to new species.
• Option C: Speciation usually involves genetic changes (mutations, etc.), and "fewer mutations" is not a typical mechanism for speciation; in fact, genetic variation from mutations is important, so C is wrong.
• Option D: The question doesn't mention different mating times, and this is a less likely default mechanism without evidence, while reproductive isolation (option B) is a more fundamental mechanism for speciation.

Answer:

B. The animals in population A were reproductively isolated from those in populations B, C, and D.