Q.Taking the example of Peppered moth, explain the action of natural selection. What do you call the above phenomenon?

Step 1. Before industrialisation, tree trunks and building walls in England were pale-coloured, so the light-coloured form of Biston betularia was well camouflaged, while the rarer dark (melanic) form stood out and was more easily spotted and eaten by predatory birds.

Step 2. After industrialisation, soot and smoke from factories darkened tree bark, reversing the camouflage advantage: dark moths now blended into the sooty bark, while light moths became conspicuous.

Step 3. Predatory birds consequently caught proportionally more light moths than dark ones in industrial areas, so dark moths survived and reproduced at a higher rate than light moths. …

Trace the camouflage-advantage reversal before/after industrialisation through to differential predation and then …

• Describing only the 'before' or only the 'after' state without explaining the causal reversal in survival advantage. …