Question

State a reason for the increased population of dark coloured moths coinciding with the loss of lichen on the tree barks during industrialization period in England.

Answer 1

The colour of moths was light before industrialization and increased pollution levels led to the decrease in lichen numbers due to which the predators of the silk moth were easily identifying the light colour moths on tree barks.

Complete answer:
The moths used to feed on the lichens growing on the bark of the trees and originally they were having a dark colour so when they used to climb on the bark of the tree and feed on lichens their predators easily spotted them on the bark and ate them. So the moths adapted their body colour according to the lichen colour which made it difficult for the predators to identify the light colour moths so they started relying on the dark colour moths. By this the population of the light coloured moth started increasing and the dark moths population decreased.
But as told in the question about the industrialization, this resulted in the increased pollution levels of the water bodies and in the air which as a result affected the growth of lichens. Now due to this decreased growth the light colored moths were large in numbers and they were easily spotted on the bark of the tree because the bark of the tree is dark coloured. But on the other hand, now the dark coloured moths were in disguise due to matching colours with the bark nut it was not the case with light coloured ones. So the predators fed on the light coloured moths eventually decreasing the population.

Note: The phenomenon displayed by the moths by changing their colour according to nature and survival is known as the adaptive evolution and lots of other organisms have also adopted the adaptive evolution for their survival and keeping their species away from extinction. The development of the beaks of the different species of birds is a part of adaptive evolution and it was achieved according to the food habits of the birds.