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

Answer the following.

(a) What name has been given to this phenomenon?

(b) Give the common name and the scientific name of the insect involved in this phenomenon.

(c) Briefly mention why the changes shown in the two figures appeared.

(d) The following phenomenon provides a classical explanation of a scientific theory given by a certain scientist.

(i) Name and explain the said theory.

(ii) Give the name of the scientist who gave this theory.

(a) Industrial Melanism

(b) Common name — Peppered moth

Scientific name — Biston betularia

(c) Biston betularia, this moth with its light coloured wings dotted with spots blended well with the lichens growing on the houses and tree trunks on which it rested. After the Industrial Revolution, pollution resulted in a decline in the growth of lichens. The tree bark got exposed due to the absence of lichens. As a result, dark-coloured moths now got an advantage of a dark background, were camouflaged and survived, while the light-coloured moths were easily picked by predators. This showed that in a mixed population, those moths which could adapt to the changing environment after the Industrial Revolution survived and increased in number, while the ones which could not adapt were slowly wiped out from the population.

(d) The theory explaining Industrial Melanism and the name of the scientist who gave it is given below:

1. Natural selection — During the struggle for existence, only those individuals which have advantageous variations survive while the ones which lack these variations are wiped out. Nature selects only those variations which are suitable for existence. This process is called natural selection.
2. Charles Darwin