Australian marsupials show the phenomena of:

Adaptive radiation

The correct answer is Option (2)- Adaptive radiation

The 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.

In the realm of evolutionary biology, adaptive radiation refers to the swift diversification of organisms from a common ancestor into numerous new forms. This typically occurs when environmental changes introduce fresh resources, present novel challenges, or unveil previously unoccupied ecological niches. Conversely, convergent evolution describes organisms lacking close genetic relationships independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

A number of marsupials, each different from the other evolved from an ancestral stock, but all within the Australian island continent. When more than one adaptive radiation appeared to have occurred in an isolated geographical area (representingdifferent habitats), one can call this convergent evolution. Placental mammals in Australia also exhibit adaptive radiation in evolving into varieties of such placental mammals each of which appears to be ‘similar’ to a corresponding marsupial (e.g., Placental wolf and Tasmanian wolf-marsupial).