Adaptive radiation is illustrated in

1. Analyze the question Adaptive radiation is the diversification of a group of organisms from a common ancestor into many forms. Each form is adapted to a different niche, habit, or mode of life. The key idea is one ancestral structure → many modified forms.

2. Explain the concept

• Adaptive radiation (divergent evolution): a common ancestral structure becomes modified for different functions. Examples are the forelimbs of mammals (the pentadactyl limb) and the beaks of Darwin's finches.
• Convergent evolution: unrelated organisms develop similar structures for the same function. The wings of birds and bats are an example, and also of analogous structures.

3. Evaluate the options

• A. Modified insect mouthparts: All insects share the same basic mouthpart plan (labrum, mandibles, maxillae, labium). These are modified for biting and chewing (cockroach), piercing and sucking (mosquito), sponging (housefly), and siphoning (butterfly). This is a classic example of adaptive radiation: one basic structure diversified for different feeding habits.
• B. Dentition in mammals: Mammalian teeth also vary with diet (carnivores, herbivores, omnivores), so this could be argued. However, the standard textbook example in this context is insect mouthparts.
• C. Wings in birds and bats: These are analogous structures, which illustrate convergent evolution, not adaptive radiation. (Their forelimbs are homologous, but the wings as flight structures evolved independently.)
• D. Appendages in insects: This is too general, and it is not the usual textbook illustration.

4. Answer

5. Exam tip

• Adaptive radiation = Divergent evolution = Homologous structures (same origin, different functions).
• Convergent evolution = Analogous structures (different origin, same function). Wings of birds, bats, and insects are the common example.

Whenever you see "wings of birds and insects" or "bats and birds" in an option, think convergent, not adaptive radiation.