Question

Given below are two figures (A and B) showing a phenomenon that was first observed in Manchester before and after the year 1850.

Answer the following:

1. What name has been given to this phenomenon?
2. Give the common name and the scientific name of the insect involved in this phenomenon.
3. Briefly mention why the changes shown in the two figures appeared.
4. The following phenomenon provides a classical explanation of a scientific theory given by a certain scientist.
   1. Name and explain the said theory.
   2. Give the name of the scientist who gave this theory.

Answer 1

1. Industrial melanism.
2. 1. Common name: peppered moth.
   2. Scientific name: Biston betularia.
3. The changes shown in the figure appear because:
   • Before the Industrial Revolution in England, light-coloured moths were more common because tree trunks were light-coloured and covered with lichens.
   • On these light backgrounds, light-coloured moths were well camouflaged, while dark-coloured moths were easily seen and eaten by predators.
   • After industrialisation, soot and smoke darkened the tree trunks and destroyed the lichens.
   • Dark-coloured moths then became better camouflaged, while light-coloured moths became more visible to predators.
   • Therefore, dark-coloured moths survived and reproduced in greater numbers. This is an example of natural selection.
4. 1. Natural selection: During the struggle for existence, organisms possessing favourable variations have a better chance of surviving and reproducing. Nature selects the variations best suited to the environment. This process is called natural selection.
   2. The theory of natural selection was proposed by Charles Darwin.