Question

Define adaptive radiation. How did Darwin explain adaptive radiation ?

Hint:

Adaptive radiation means many species arising from one ancestor, each adapted to a different niche. Darwin explained it using Galapagos finches and natural selection.

Answer 1

Step 1: Definition:
Adaptive radiation is an evolutionary process. In it, different species arise from one common ancestor in a geographical area.
The species spread out from that starting point and adapt to different habitats and ways of life (niches).

Step 2: Darwin's explanation, the setting:
Darwin studied small black birds, now called Darwin's finches, on the Galapagos Islands.
He saw that the finches on the islands looked alike in many ways but differed in their beaks.

Step 3: Darwin's explanation, the reasoning:
Darwin thought that all of them came from one original seed-eating finch that reached the islands.
Individuals showed variations in beak size and shape. Food and habitat differed from place to place.
Natural selection favoured the variants best suited to eat a particular food, so beaks changed.
Over time this gave insectivorous finches, vegetarian finches and seed-eating finches, each with its own beak.

Step 4: Another example:
Australian marsupials such as the koala, kangaroo and wombat arose from one ancestral stock in the same way.

Final Answer:
Adaptive radiation is the evolution of many species from one ancestor in an area, each adapted to a different habitat. Darwin explained it with the finches of the Galapagos, where natural selection shaped their beaks to suit different foods.