Which term would you use to describe fossils that show an organism's activities such as footprints?

• A. Trace Fossils
• B. Petrified Fossils
• C. Cast
• D. Homologous Structures

Answer: (A)

Fossils that capture what an organism did, such as walking or digging, are called trace fossils. They preserve evidence of behavior rather than the organism’s body itself. Footprints are a classic example because they record movement and how the animal interacted with its environment, including direction and stride. Trace fossils (also known as ichnofossils) form when an organism leaves an imprint or track that hardens into rock, capturing that act of activity.

This differs from petrified fossils, where the organic material is replaced by minerals to make a stone-like replica of the organism’s body, preserving anatomy. A cast is a replica that fills a mold to reproduce the external shape, again showing form rather than action. Homologous structures refer to similar body parts across species because of shared ancestry, not to fossils that show behavior. So trace fossils are the best term for fossils that show activities like footprints.