Question

How does the creation of variations in a species promote survival?

"In the early part of the nineteenth century, the common form of Biston betularia, called typica, had a peppered appearance. Its wings were flecked with black and white, and it was well camouflaged in its favourite resting place, the pale and lichen-covered barks of trees in rural England. A dark, or melanistic, form of the moth, called carbonaria, was first recorded in about 1848, and presumably had existed in very small numbers before then. But by the middle of the twentieth century, the melanistic form of the moth had come to represent over 95 percent of the Biston betularia population, especially in such industrial centers as Manchester and Liverpool. This is among the most rapid of all recorded evolutionary changes. Why was there such a dramatic change in fortunes of the peppered typica and the melanistic carbonaria ? With rapid industrialisation, soot came to cover the barks of trees, making them black instead of pale, and also killed the lichens. Now the melanistic form was better camouflaged on the darkened bark, while the peppered form became increasingly less camouflaged and hence more easily detected and eaten by birds. The birds, which had kept the melanistic form at a very low frequency before industrialisation, now concentrated their attention on the peppered form. Natural selection, in the form of bird predation, favoured the peppered form earlier and the melanistic form later." Where did the variations seen in the appearance of the moth most likely come from?

In 1956, strict anti-pollution laws were enacted in England, which led to the countryside becoming relatively less polluted and free of smoke. One of the following was observed in 20 years from this event and is believed to be linked to this event. Which one could it be?

Select the option that correctly summarises the given observations in the passage.