Q.By taking industrial melanism as one example, explain the concept of natural selection.

Step 1. Natural selection is the process by which better-adapted individuals, carrying favourable heritable variations, survive and reproduce more successfully than others, shifting the population's gene frequency over generations.

Step 2. Before industrialisation (around 1845) in Great Britain, the pale, lichen-camouflaged form of the peppered moth (Biston betularia) greatly outnumbered the dark form (Biston carbonaria), because the pale moths blended in well with lichen-covered tree trunks and escaped predatory birds, while the conspicuous dark moths were more often caught.

Step 3. As the industrial revolution progressed, factories released sooty smoke that killed the lichen and blackened tree trunks with pollution, reversing which colour form was camouflaged: the dark moth now blended in with the blackened bark, while the pale moth became conspicuous. …

Use the industrial-melanism case study to walk through how natural selection shifts a population's t …

• Describing industrial melanism as the pollution 'creating' the dark moths, rather than the pollution changing which pre-existing colour variant was favoured by predators. …