Comparative anatomy to study evidence for evolution depends on

Step 1: Analyze the question The question asks what comparative anatomy relies on as evidence for evolution. The options all refer to the number of fingers, so it is pointing to the pentadactyl limb.

Step 2: Explain the concept Comparative anatomy studies similarities and differences in the body structures of different organisms. A key example is homologous structures. These are structures that have the same basic anatomical plan and origin but may serve different functions.

The pentadactyl (five-fingered) limb is the classic example. It is found in:

• Humans, used for grasping
• Bats, used for flying (wing)
• Whales, used for swimming (flipper)
• Horses, used for running
• Frogs, lizards and birds, in modified forms

Although these limbs perform different jobs, they share the same bone arrangement: humerus, radius and ulna, carpals, metacarpals and phalanges. This suggests the animals share a common ancestor, and that the limb has been modified over time through adaptive radiation (divergent evolution).

Step 3: Solution

• Four-fingered, three-fingered and two-fingered limbs are modifications or reductions in particular animals. They are not the basic, universal plan.
• The five-fingered limb is the common ancestral pattern that comparative anatomy uses as evidence of evolution.

Step 4: Answer The correct option is D. five fingered.

Step 5: Exam tip Remember "Penta = Five". Whenever you see "homologous structures" or "adaptive radiation" in a JAMB question, think of the pentadactyl limb. Do not confuse it with analogous structures, such as the wings of a bird and an insect. These have the same function but different origins, and they are not evidence of common ancestry.