Question

Name the phenomenon by which dark coloured moth originated from grey coloured moths.

Answer 1

Hint: An orderly change from one condition to another is referred to as evolution. Evolution helps in unfolding or revealing the hidden potentials in living organisms. The mode of evolution has been put forward by four theories namely Lamarckism, Darwinism, Hugo de Vries’ mutation theory, and the Modern concept of evolution.

Complete answer:
Dark coloured moths originated from grey coloured moths by a phenomenon referred to as industrial melanism.
William Bateson, a geneticist first noticed industrial melanism. The phenomenon did not suggest polymorphism. Instead, the fact that the colour morphs were inherited was observed by Bateson.
In 1850 (before industrialization set in), it was seen that the number of grey coloured moths were more than black coloured moths. However, in 1920 (after industrialization), the numbers were reversed. There were more black coloured moths.
The industrial smoke and soots made the tree trunks dark. Hence, the predators could easily recognize the grey coloured moths. This led to the survival of black coloured moths.
In the pre-industrialization era, trees used to be covered with white-coloured lichens, and hence white ones could camouflage and escape from predators.
But, with the trees becoming darker, the scenario reversed because it is easier for the predators to spot a moth against a contrasting background.

Hence, the correct answer is option (B).

Note: Thus, industrial melanism supports evolution by Natural Selection. The salient features of Darwin’s Theory of Natural Selection are
a) Overproduction,
b) Limited food and space,
c) Struggle for existence,
d) Variations,
e) Survival of the fittest.
It is evident that those who have the potential to adapt can survive and increase in population size.