Question

When more than one adaptive radiation appeared to have occurred in an isolated geographical area, it is called
A. Divergent evolution
B. Convergent evolution
C. Anthropogenic evolution
D. Saltation

Answer 1

Hint: An organism is said to have evolved when they acquire new characteristics that can be passed on from parents to offspring. In evolution, adaptive radiation refers to the diversification of a species into different forms under the influence of environmental factors. Adaptive radiation can lead to speciation.

Complete answer:
Option (a) is incorrect. Divergent evolution occurs when an ancestor species evolves into new species. The accumulation of new characters can be under the influence of abiotic factors such as physical isolation that eventually results in reproductive isolation.
Option (b) is correct. Convergent evolution occurs when species of different origin evolve to have similar characteristics because they share the same geographical habitat. Convergent evolution results in the formation of analogous structures. For example, the fins of fishes and whales. Both these species, though belong to different groups, and do not have a common ancestry, have evolved to develop fins. This evolution is because of the fact that they share a common habitat – water. Adaptive radiation, if occurs twice in a geographically isolated area will have a similar result, that is the evolved species will have similar adaptations suitable for the area. Hence, it will be a case of convergent evolution.
Option (c) is incorrect. Anthropogenic evolution is evolution of a new species due to human activities. The most common example of anthropogenic evolution is industrial melanism. This is prominent in white winged moths that lived in areas covered with lichens. The white lichens helped the moths to remain camouflaged to avoid predation. During the industrial revolution, Sulphur dioxide pollution occurred and soot from industries caused blackening of the tree barks. The white winged moths were prominent on the white background that resulted in excessive predation. This resulted in the formation of a new species of moth that were black in colour. The new species was naturally selected and increased in numbers.
Option (d) is incorrect. Saltation is a rapid mutation that forms a new species in successive generations. It is a process where a lineage abruptly ends through genetic mutations. Polyploidy is thought to be a type of speciation by Saltation.

Hence, the correct answer is option (B).

Note: Adaptive radiation results in evolution of similar features in species of different ancestry. The changes in characteristics occur in order to adapt to a new environment. It can be in structures that serve the same function. Adaptive radiation is a convergent pattern of evolution and results in the formation of analogous structures like the fins of whales and fishes.