Fossils are the ‘remains’ of organisms from millions of years ago, which…

The idea

A fossil is any preserved evidence of an organism that lived millions of years ago, typically discovered within sedimentary rock. The word ‘remains’ is deliberately broad: it covers actual body parts, mineral-replaced tissue and traces such as footprints. Fossils matter because they provide the direct evidence used to reconstruct how life on Earth has changed over geological time.

For example: A dinosaur leg bone embedded in layered sandstone, or a fossilised ammonite shell in limestone, counts as a fossil because it is ancient biological material or its impression locked in rock.

What earns the marks

• States that fossils are evidence of organisms that lived millions of years ago.
• States that fossils are found in rocks, commonly sedimentary rock.
• Recognises that ‘remains’ includes body parts, mineral-replaced material and preserved traces.
• Gives a valid example, such as a fossilised bone, shell, footprint or leaf impression.
• Links a fossil to the organism that produced it and to the rock layer containing it.

Common mistakes and how to put them right

• Thinking a fossil must always be the actual unchanged body of an organism.

  Put it right by explaining that mineral replacement and traces also count.

• Confusing fossils with modern bones or shells lying on the ground.

  Put it right by stressing the millions-of-years timescale and burial in rock.

• Assuming all fossils are dinosaurs.

  Put it right by giving plant, shell and trace examples.

Exam tips

• Define the term using both key ideas: ancient organism and found in rock.
• Use a named example to make the definition concrete.
• If asked to identify a fossil, justify your choice by referring to its age and its location in rock.