Question

Prior to industrialization there were far more white-winged moths on trees than melanised moths in England. However, after industrialization the distribution pattern of these two kinds of moths reversed. What does the above observation indicate? Explain giving reasons.

Answer 1

The observation indicates the phenomenon of industrial melanism, which demonstrates the action of natural selection.

Before industrialization, tree trunks were covered with light-colored lichens that camouflaged the grey-coloured moths, making them less visible to predators, while the black (melanic) moths were more conspicuous and were preyed upon more, so grey moths were more abundant. After industrialization, soot and smoke from factories blackened the tree trunks, making grey moths conspicuous and black moths camouflaged. Consequently, predation reduced the melanised moth population and increased the grey moth population. This led to a reversal in the distribution pattern of the two moth forms.