plz explain :
When more than one adaptive radiation appeared to have occured in an isolated geographical area (representing diffwerent habitats) , one can call this convergent evolution.
Adaptive radiation refers to an evolutionary process in which different species evolve from a common ancestor, on inhabiting new areas as they successfully adapt to their environment; while convergent evolution is an evolutionary process in which different structures of different species are evolved for the same function.
So, we can say that during adaptive radiation the changes are governed by the environment. The organism evolves to survive in the particular environment. Therefore, if two different adaptive radiation occur in an area, then it is most likely that both the evolved species will have similar adaptations to survive in that particular area. Hence, they will develop similar structures to perform similar functions.
For example: In case of Australian marsupials like Kangaroo, Marsupial rat etc; each marsupial is different from the other but has evolved from the same ancestor and all co-exist in a common geographical area i.e. Australia. This is one adaptive radiation. Another adaptive radiation is there in the case of placental mammals. Now, if we look at the evolved organisms from both the lineages, we can see that they have similar characteristics and look similar.