Q.State the essential postulates of Charles Darwin's theory of evolution by natural selection, as presented in 'On the Origin of Species' (1859).

Industrial melanism (the peppered moth, Biston betularia, turning darker in polluted industrial areas) is a classic demonstration of natural selection favouring the phenotype best camouflaged against predators.

Before the Industrial Revolution in England, the light-coloured (speckled) form of the peppered moth was common because it was well camouflaged on lichen-covered, light-coloured tree bark, while the rare dark (melanic) form was easily spotted and eaten by birds. As industrial pollution blackened tree trunks (soot killed the lichens), the dark form became better camouflaged and the light form became conspicuous:

• Predatory birds selectively ate the light-coloured moths that stood out against the sooty bark.
• The dark-coloured moths survived and reproduced more, so their frequency in the population increased dramatically.

This is not a new mutation causing the shift (the dark allele already existed in the population); rather, the environment (industrial pollution) changed which existing phenotype had a survival advantage. This differential survival/reproduction of better-adapted variants is precisely the definition of natural selection, making it a well-known example of evolution in action within a human lifetime.

The concept described — minute replicate particles from every body part — is the Theory of Pangenesis.

Pangenesis (proposed by Charles Darwin) held that every organ and tissue sheds tiny particles called gemmules ('pangenes'), which travel to the reproductive organs and are passed to offspring, supposedly transmitting the characters of each body part. It was later disproved but is historically important.

Why the others are wrong: 'fittest organism' and 'natural selection' describe survival and differential reproduction, not particle inheritance; polymorphism means the existence of several forms in a population.