What do the pictures A and B illustrate with reference to evolution? Explain.

Explanation

(A) Dark and grey-coloured varieties of Peppered Moth on the bark of a tree in unpolluted area.
(B) Dark and grey-coloured varieties of Peppered Moth on the bark of a tree in polluted area. The figures explain the phenomenon of industrial melanism or occurrence of more melanic forms of Moth in response to soot and pollution from industries. Prior to industrial revolution, England had abundant lichen flora on the bark of trees. The light grey form of Peppered Moth occurred their as it could hide itself among lichens. The dark-coloured moth was scarse as it could be easily spotted by insectivorous birds. However, due to industrial revolution, pollution resulted in disappearance of lichens. Soot from industries caused darkening of tree trunks. The dark-coloured form of Peppered Moth (Biston betularia carbonaria) could survive as they were not easily discernible. The grey form of Peppered Moth (Biston betularia typica) was easily picked up by the birds. Their population, therefore, declined.