Pentadactyl plan of the fore limbs of frog, bird, horse, whale and man is a proof of?

1. Analyze the question The question asks what the pentadactyl (five-digit) limb plan, found in frogs, birds, horses, whales and humans, is evidence of.

2. Explain the concept "Pentadactyl" means having five digits (fingers or toes). The forelimbs of these animals have the same basic bone structure:

• Humerus (upper arm)
• Radius and ulna (lower arm)
• Carpals (wrist bones)
• Metacarpals (palm bones)
• Phalanges (digits)

Each limb has been modified for a different function:

• Frog: swimming and jumping
• Bird: flying (wing)
• Horse: running (the digits are reduced)
• Whale: swimming (flipper)
• Man: grasping and handling objects

Structures with the same basic structure and origin but different functions are called homologous structures. This is the idea of adaptive radiation (divergent evolution). It shows that these animals descended from a common ancestor, and their limbs were modified over time to suit different environments.

3. Solution

• A. Spontaneous generation is the old idea that living things arise from non-living matter. It is not related to limb structure.
• B. Evolution is correct. Homologous structures point to a common ancestry and gradual modification.
• C. Locomotion is movement. The limbs have different functions, so the shared plan is not about locomotion itself.
• D. Creation is a belief, not scientific evidence from comparative anatomy.

4. Answer The pentadactyl limb is evidence of evolution, which is option B.

5. Exam tip Remember: Homologous structures → common ancestor → evolution (for example, a human arm, a bat's wing and a whale's flipper). Analogous structures have the same function but different origins (for example, a bird's wing and an insect's wing). They show convergent evolution, not common ancestry.