The environment of England was unpolluted before the industrial revolution. The lichens on the bark of the trees were pale and white winged moths were numerous which could easily camouflage on the trees. The dark winged moths were less as they could not camouflage and were thus, easily spotted by birds for food. After industrial revolution, the lichens became dark due to deposition of soot. This, in turn, favored the dark-winged moths while the white-winged were picked by birds. The population of the former which was naturally selected increased.
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