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Answer 1

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A. Diversifying selection is also known as disruptive selection. It occurs where an environmental change may produce selection pressure that favours two extreme characteristics. For example, grass plant on welsh copper mines. Contaminated soil containing copper is lethal to normal grass plants but a chance mutation allowed one plant to grow. This plant prospered and reproduced but only on the contaminated soil. On normal soil, it grew more slowly than normal plants and was easily out competed.

B. Changing climate may isolate population on mountain peaks or in remnant lakes, or rare migrants may colonise new areas such as the Galapagos and Hawaiian islands. This geographic isolation is termed as allopatry and gives rise to allopatric speciation.

C. Adaptive radiation is a special evolutionary pattern characterised by rapid increase in the numbers of kinds of closely related species. It results in an evolutionary explosion of new species from a common ancestor. For example, Darwin's finches.

D. Directional selection occurs whenever the environment changes in a particular way and therefore, is a selective pressure for species to change in response to the environmental change. For example industrial melanism. Industrial melanism is a phenomenon shown by light coloured peppered moth (Biston betularia typica) and dark coloured moth (Biston betularia carbonaria). It is a evolutionary process in which darker individuals predominate over lighter individuals since the industrial revolution is a result of natural selection.

E. Convergent evolution is a process during which organisms with different evolutionary history evolve similar phenotypic adaptations in response to common environmental conditions. Hence, analogous organs are formed which have different basic structure but perform similar functions. For example, insect wings and birds wings.

Hence, when the organisms undergo changes to fill the new niches formed by changes in environment, the process is termed as adaptive radiation.