Shared ancestry of a body part is called what?

• A. Descent with modification
• B. Analogy
• C. Homology
• D. Embryology

Answer: (C)

Homology is the pattern where a body part is shared due to common ancestry. When two species have structures that come from the same original feature in a distant ancestor, those parts are homologous. Evolution can modify their function over time, so the parts may look and work differently today, but the underlying bone arrangement or developmental origin stays linked. For example, the forelimbs of humans, cats, whales, and bats all derive from the same set of bones, even though they’re used for grasping, walking, swimming, or flying.

Choosing analogy would be mistaking similarity from function instead of origin—wings of bats and insects look similar and serve flight, but they don’t come from the same ancestral structure. Embryology is the study of development and can reveal homologous relationships, but it’s not the term for shared ancestry itself. Descent with modification is the broader evolutionary process that explains how traits arise and diverge, not the specific label for a shared ancestral relationship of a body part.