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 the industrial pollution. The lighter colored moths

Question

were 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 darkened trees. Describe what the initial normal population curve would look like before pollution. Describe what the population curve would look like after the Industrial Revolution and indicate what phenotype was favored.

What will be an ideal response?

Answer 1

The initial curve would have a higher peak towards the lighter side of the population spectrum. After time as the environment changes the curve would shift towards the darker side of the population spectrum.
  
The darker phenotype is selected for in the polluted environment.