Question

There are multiple color phenotypes in a hypothetical population of beetles living in a New England forest, matching the various colors of the bark of the trees on which they live and hide from predators.
The diagrams below show four possible changes to the population of beetles after air pollution from a coal-burning power plant darkens the bark of the trees in the forest.
Which of the following diagrams represents the most probable change in the coloration of the beetle population in response to the effects of the air pollution?

• A. The observed phenotypes are shown in Diagram 4. The darker flies became easier for predators to find.
• B. The coloration is shown in Diagram 2. Predators no longer recognized the lighter colored beetles as a food source, and the darker colored beetles were better able to camouflage themselves against the darker colored bark.
• C. The coloration shown in Diagram 3. Predators could find both the lighter and darker colored beetles more easily.
• D. The coloration shown in Diagram 1. Predators were able to find the lighter colored beetles more easily than the darker colored beetles. Selective pressure towards the dark phenotype results in a population of mostly dark-colored beetles.

Answer 1

Answer: (D)

The coloration shown in Diagram 1. Predators were able to find the lighter colored beetles more easily than the darker colored beetles. Selective pressure towards the dark phenotype results in a population of mostly dark-colored beetles.

Diagram 1 represents the most probable change in the coloration of the beetle population in response to the effects of the air pollution. Earlier, both dark and light colored beetles were present. After coal-burning, the bark of the trees in the forest were darkened. Hence, predators were able to find the lighter colored beetles more easily than the darker colored beetles on dark bark. Selective pressure results in a population of mostly dark-colored beetles.

Thus, the correct answer is 'The coloration shown in Diagram 1. Predators were able to find the lighter colored beetles more easily than the darker colored beetles. Selective pressure towards the dark phenotype results in a population of mostly dark-colored beetles.'