Scientists have studied, in detail, the evolution of the peppered moth, Biston betularia, over the last two hundred years. The peppered moths rest on tree trunks and are a tempting treat for birds in the area. In the mid-1800s the trees in their England habitat were covered with lichens, which are a light, grayish-green color. Although color variations occurred, the vast majority of the moths were light-colored. Because their light coloration effectively camouflaged them against the lichens-covered trees, they were not as easily seen by birds as darker colored moths. The light colored moths flourished.The environment changed, as the Industrial Revolution progressed. By 1900, the lichens had died and trees were coated with soot due to industrial pollution. The lighter colored moths were

Question

no longer "hidden" in their environment, and in fact, were easily seen by their predators. Their numbers dwindled. At the same time, the darker-colored moths flourished because of their ability to hide on the soot-covered trees.a. What type of selection is this?b. What is the agent of selection?c. What alleles were favored in the clean environment? The polluted environment?

What will be an ideal response?

Answer 1

a. This is an example of directional selection.
b. The agent of selection was birds who preyed on the light colored moths in the clean environment and the dark colored moths in the polluted environment.
c. In the clean environment, the light alleles were favored and in the polluted environment, alleles coding for the darker color were favored.