Biology · Evolution · NEET
No single moth changed colour. Both white and dark forms already existed in the population before industry (dark forms arose earlier by mutation). Industrialisation only changed which colour survived and reproduced more. So the POPULATION shifted towards dark, but no individual moth turned dark. This is the key NEET point: selection acts on variation that already exists, it does not create new colours on demand. This is Darwinian natural selection, not Lamarck's 'use and disuse' or inheritance of acquired characters.
Before factories, tree trunks were covered with light-coloured lichens. On this pale bark, white peppered moths were camouflaged and hard for birds to see, so more of them survived and left offspring. The dark moths stood out against the pale bark and were eaten by predatory birds. So in the pre-industrial environment, white was the 'fit' colour.
Soot and pollution from factories killed the lichens and blackened the tree bark. Now the dark moths matched the sooty bark and were hidden from birds, while the white moths were clearly visible and eaten more. So dark moths survived and bred more, and their proportion in the population rose. The bird predators are the selecting agent, and the changed environment decided which colour won.
It is an example of natural selection (Darwinism) acting on a population over generations. It is NOT an individual adapting during its life. NEET often frames it as 'evolution observed within human lifetime / anthropogenic (man-made) selection pressure' — proof that natural selection is a real, observable process, not just a fossil-age idea.
If pollution is reduced and lichens grow back so bark turns pale again, the white moths would again be better camouflaged and survive more, and the dark form would decline. This reversal (actually seen in Britain after clean-air laws) proves the environment, not the moth's 'will', controls which form is selected.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the increase of dark-coloured (melanic) peppered moths in polluted industrial areas because dark moths became better camouflaged on soot-blackened bark and survived bird predation more than light moths.
Biston betularia. Its light form is Biston betularia typica and the dark melanic form is Biston betularia carbonaria.
It shows directional selection, because the population shifted in one direction — from mostly light towards mostly dark — as the environment changed.
It is a real, observable example that natural selection happens in nature within a human lifetime, driven by an environmental change (pollution). It also cleanly separates Darwinism (selection of existing variation) from Lamarckism (acquired change).
Yes. The selection pressure (soot pollution) was created by human industrial activity, so it is often grouped with antibiotic and pesticide resistance as anthropogenic (man-made) evolution.
