Which term refers to similarity of structure due to shared ancestry?

• A. Vestigial organs
• B. Analogy
• C. Homology
• D. Embryology

Answer: (C)

Homology is similarity of structure due to shared ancestry. When different species inherit a common anatomical blueprint, their body parts can look alike and follow the same basic organization even if their functions diverge. A classic example is the forelimbs of humans, cats, whales, and bats: all have a similar arrangement of bones (humerus, radius, ulna, carpals, metacarpals, phalanges), reflecting descent from a common ancestor, while each limb adapts to a different lifestyle.

In contrast, features that look similar because they serve the same function but evolved independently are called analogous structures, not homologous. Vestigial organs are remnant structures that have lost their original function, not evidence of shared structural similarity through ancestry. Embryology is the study of development and, while it can help reveal homologous relationships, the term itself does not denote similarity due to shared ancestry.