Given below are two stages in the evolution of man. Study them and answer the questions that follow: Given below are two stages in the evolution of man. Study them and answer the questions that follow:
Name the organism used as an example to explain ‘Industrial Melanism’.
Topic: Industrial melanism
Answer
The PEPPERED MOTH, Biston betularia.
Before industrialisation, English tree trunks were pale with lichen. The light peppered moths were camouflaged there and the dark (melanic) forms were conspicuous and easily eaten by birds.
Soot from the factories killed the lichen and blackened the trunks, reversing the advantage. Within a few decades the dark form had become the common one in industrial areas.
THE POINT THE EXAMPLE MAKES: the moths did not CHANGE to suit their surroundings. BOTH forms already existed, and the changed environment altered WHICH ONE SURVIVED to breed. That is precisely what natural selection means.
It is valuable because it happened fast enough to be OBSERVED — evolution witnessed within a human lifetime.