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Natural Selection: Industrial Melanism
Concepts tested here
- Selection acts on existing variation
All Questions
2007 AIPMT-PRE 1 question
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Industrial melanism as observed in peppered moth proves thatBefore industrialisation in England, the light-coloured form of the peppered moth (Biston betularia) was common, and the dark melanic form was rare.
During the Industrial Revolution, soot from coal-burning factories killed the lichens and darkened the tree trunks. The melanic moths were now camouflaged and escaped predation by birds, while the light moths were picked out; the frequency of the melanic form rose to over 90 percent in polluted areas.
The important point is that the dark form was not created by pollution. It was already present in the population, arising again and again by a random mutation.
Pollution only changed the direction of natural selection, so that the already existing melanic variant was favoured.
So the melanic form does have a selective advantage in industrial areas, the light form has an advantage in non-polluted areas, and melanism is not a pollution-generated feature; those three statements are wrong.
Industrial melanism thus proves that the true black melanic forms arise by a recurring random mutation.