Question

How can adaptive radiation occur on an island chain?

Answer 1

Hint: Adaptive radiation is defined as a process by which organisms show diverse variation as compared to the ancestral species and develop into a new form. It happens due to environmental changes, availability of new resources and the interaction in the ecosystem. The best example of adaptive radiation is the Darwin finches in Galapagos island.

Complete answer:
Adaptive radiation is the outcome of ecological changes or a new adaptive region. The loss of competitors or predators is the main trigger for evolution. This results in the increase in the population and leads to a stable population. The increased population will be more genetically diverse as compared to the ancestral populations. The phenotypic variations also increase in a stabilizing population. This results in intraspecific competition for mates, food etc. It leads to divergent selection. This results in adaptive radiation.

The adaptive radiation is mostly seen in the isolated areas like the area formed after volcanic eruption, isolated island chains, lakes.

The islands show evolutionary explosion as it is not intruded by exotic species which gives freedom from competition and access to a variety of habitats.
The islands offer directional selection of species and can rapidly yield morphologically diverse species which is adapted to its own ecological niche.

Note: Darwin proposed the Finches theory which is based on adaptive radiation. He observed the beak shape varied in the finches. He proposed that the beak of the ancestors have undergone adaptations so as to adapt with the various food sources. This theory holds good in explaining evolution, adaptation and multiplication of species.