Color in peppered moths is controlled by genes. A light-colored variety and a dark-colored variety of a peppered moth species exist in nature. The moths often rest on tree trunks, and several different species of birds are predators of this moth.
Before industrialization in England, the light-colored variety was much more abundant than the dark-colored variety and evidence indicates that many tree trunks at that time were covered with light-colored lichens.
Later, industrialization developed and brought pollution which killed the lichens leaving the tree trunks covered with dark colored soot. The results of a study made in England are shown in the graph below.
State one possible reason that the light-colored variety was not completely eliminated from the polluted environment. Be sure your reason can be supported by the evidence shown.
Answer in at least 3 complete sentences.
