Darwin's finches and Australian marsupials are an example of:

The correct answer is Option (3) → Adaptive Radiation

Option (1) Divergent Evolution — Incorrect. NCERT uses divergent evolution for homologous organs: the same basic structure that developed in different directions, like the forelimbs of whales, bats, cheetahs and humans. Divergence does take place in the finches too, but the name the book gives to these two examples is adaptive radiation.

Option (2) Convergent Evolution — Incorrect. Convergent evolution gives similar forms in groups that are not closely related, as in analogous organs like the wings of a butterfly and a bird. Australian marsupials and the placental mammals that look like them show convergence, but the marsupials among themselves show radiation from one ancestor.

Option (3) Adaptive Radiation — Correct. Adaptive radiation is the evolution of different species in one geographical area from one starting point, spreading out into different habitats. The finches arose from seed-eating ancestors with altered beaks, and the marsupials from one ancestral stock, all within Australia.

Option (4) Natural Selection — Incorrect. Natural selection is the mechanism that favours the fittest variations. It drives adaptive radiation, but it is not the name of the pattern these examples show.

Note: A similar question was also asked in CUET (UG) 2023 on 07-06-2023 (Slot 3).

NCERT Extract:
What Is Adaptive Radiation? – “… During his journey Darwin went to Galapagos Islands. There he observed an amazing diversity of creatures. Of particular interest, small black birds later called Darwin’s Finches amazed him. He realised that there were many varieties of finches in the same island. All the varieties, he conjectured, evolved on the island itself. From the original seed-eating features, many other forms with altered beaks arose, enabling them to become insectivorous and vegetarian finches (Figure 6.5). This process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats) is called adaptive radiation. Darwin’s finches represent one of the best examples of this phenomenon. Another example is Australian marsupials. A number of marsupials, each different from the other (Figure 6.6) evolved from an ancestral stock, but all within the Australian island continent.”

Figure 6.5 Variety of beaks of finches that Darwin found in Galapagos Island

Figure 6.6 Adaptive radiation of marsupials of Australia