What are fossils?

Fossils are defined as the remains or traces of ancient organisms that have been preserved in the Earth's crust. This includes a wide variety of forms, such as bones, shells, and plant material, as well as traces like footprints or burrows that provide evidence of an organism's existence and behavior from long ago.

The study of fossils allows scientists to understand past life forms, their environments, and how they have changed over time, contributing to our knowledge of evolution and the history of Earth. Fossils form through processes such as mineralization, where organic material is replaced by minerals, or through the imprint of an organism in sediment that later hardens into rock. This context emphasizes their importance in paleontology and geology.

In contrast, the other choices do not accurately represent fossils in their entirety. For instance, while remains of living organisms may be part of the fossil record, the definition is broader as it encompasses traces and impressions that inform us about ancient life that is no longer living.