Pentadactyl forelimb of vertebrate function due to differences in environment is

1. Analyze the question The question asks which type of evidence (for evolution) is shown when the pentadactyl (five-digit) forelimb of vertebrates has different functions because of different environments. Examples are the human arm for grasping, the bat wing for flying, the whale flipper for swimming, and the horse leg for running.

2. Explain the concept

• The pentadactyl limb is a homologous structure. The animals have the same basic bone arrangement (humerus, radius, ulna, carpals, metacarpals, phalanges), but the limb has been modified for different functions.
• This is called adaptive radiation (divergent evolution), and it points to a common ancestor.
• Studying and comparing structures in different organisms is called comparative anatomy.

3. Check each option

• A. Comparative anatomy: compares body structures across species, including homologous organs such as the pentadactyl limb. This fits.
• B. Physiological evidence: compares body functions and biochemistry, such as blood proteins and hormones. It does not fit.
• C. Embryological evidence: compares the embryos of different animals, which look alike in early stages. It does not fit.
• D. Fossil records: uses preserved remains of ancient organisms. It does not fit.

4. Answer The pentadactyl limb with varied functions is a classic example of homologous structures, which is evidence from comparative anatomy.

5. Exam tip Remember this link: Homologous structures → same structure, different function → comparative anatomy → common ancestry. By contrast, analogous structures (such as a bird's wing and an insect's wing) have the same function but different origins.