Question

In the case of peppered moth, the black coloured form (Biston carbonaria) became dominant over the light coloured form (Biston betularia) in England after the industrial revolution. This was the result of

• A. deposition of soot on the moths from the atmosphere
• B. natural selection whereby the darker forms were selected
• C. appearance of the black coloured individuals due to poor sunlight
• D. protective mimicry

Answer 1

The correct option is B natural selection whereby the darker forms were selected

Natural selection is the process of selection of organisms by nature whereby organisms better adapted to their environment tend to survive and produce more offspring.

Before industrialisation in England, it was observed that there were more light-winged moths on trees than dark-winged or melanised moths. The light colour conferred a survival advantage to the moths by camouflaging them in the light coloured background of lichens. However, after industrialization, more dark winged moths were spotted than light ones in the same area. In post industrialization, the tree trunks became dark due to industrial smoke and soot. The pollution in the prevailing environment did not offer a suitable condition for the survival of lichens. The white lichens, which are pollution indicators, stopped growing on the trees. Hence, light colour winged moths were easily spotted in the contrasting background by the predators. The dark coloured moth survived because they could camouflage with the dark background or tree trunk. With time, the dark coloured form could survive in the industrial area as compared to the white coloured form. The dark coloured moths were selected by nature and their numbers started increasing in the population. This is an example of natural selection.


Protective mimicry is a defence mechanism where the organisms are able to avoid harmful encounters by deceiving enemies. For example - an owl butterfly mimics an owl to escape from the predators.