Question

(a) Explain adaptive radiation with the help of a suitable example.
(b) Cite an example where more than one adaptive radiation has occurred in an isolated geographical area. Name the type of evolution your example depicts and state why it is named so.

Answer 1

Hint: Adaptive radiation is the process where there is evolution of different species from a single common ancestor which happens when there is natural environmental change.

Complete answer:
(a) Adaptive radiation is a process which refers to the adaptations of the organisms which diversify from an ancestral species into new forms which happens when there is change in the environment as it creates new challenges.
Example of adaptive radiation is Darwin finches. This is the best example for adaptive radiation. About two million years ago, the common ancestor of Darwin finches arrived in Galapagos and after the time has passed, the Darwin finches evolved into 15 species and these 15 species were having different body size, beak shape, feeding behaviour, etc. and due to the changes in the size and the form of beak they have, it enabled them to adapt according to the different food resources like insects, seeds.
(b) Australian Marsupials are an example where there is more than one adaptive radiation which has occurred in an isolated geographical area. There are so many different marsupials which are evolved from an ancestral stock within the isolated Australian island but all of these are adapted to different habitats, for instance, Tasmanian wolf is marsupial and a placental wolf is placental mammal.
The type of evolution it depicts is Convergent evolution because these marsupials are evolved independently from each other and they have lived in geographical isolation from mammals for around 100 million years, they also show the development of similar adaptive functional structures in unrelated groups of organisms.

Note:
Adaptive radiation refers to the evolution of different species from ancestral one, for example, Darwin finches were developed from their common ancestors in Galapagos and they were evolved in 15 species. There is more than one adaptive radiation which has occurred in an isolated geographical area and the example is Australian marsupials. This type of evolution is called Convergent evolution.