The seven insects establish a new population on the island that increases in number significantly over several generations. The color is controlled by the interaction of two genes, one with two alleles, the other with three alleles.Ī piece of driftwood carrying two green insects and five red insects floats in the ocean for several days and washes up on a small island where the insect species did not previously live. This theory holds good in explaining evolution, adaptation and multiplication of species.Ī continental population of insects has blue, red, green, and black variations. He proposed that the beak of the ancestors have undergone adaptations so as to adapt with the various food sources. He observed the beak shape varied in the finches. Note: Darwin proposed the Finches theory which is based on adaptive radiation. The islands offer directional selection of species and can rapidly yield morphologically diverse species which is adapted to its own ecological niche. 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 adaptive radiation is mostly seen in the isolated areas like the area formed after volcanic eruption, isolated island chains, lakes. This results in intraspecific competition for mates, food etc. The phenotypic variations also increase in a stabilizing population. The increased population will be more genetically diverse as compared to the ancestral populations. This results in the increase in the population and leads to a stable population. The loss of competitors or predators is the main trigger for evolution. The best example of adaptive radiation is the Darwin finches in Galapagos island.Īdaptive radiation is the outcome of ecological changes or a new adaptive region. It happens due to environmental changes, availability of new resources and the interaction in the ecosystem. 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.
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