AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
As preserved traces of organisms, such as footprints, burrows and rootlet…
Full specification wording
Fossils: as preserved traces of organisms, such as footprints, burrows and rootlet traces.
Not every fossil is a body fossil.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 5 of 8
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Not every fossil is a body fossil. Sometimes the organism itself is absent and what survives is a trace of its activity, preserved in rock. A dinosaur footprint forms when a foot presses into soft mud; if that mud later hardens and is buried, the impression can survive as sedimentary rock. A burrow shows where an animal tunnelled through sediment, and a rootlet trace records where a plant root once grew, leaving a cast or impression after the root decayed. These are called trace fossils. They form only when the sediment sets before the trace is destroyed, and they are later exposed by erosion or quarrying. Trace fossils reveal behaviour and movement, which body fossils often cannot, so they add evidence about how organisms lived.
What earns the marks
- Trace fossils are preserved evidence of an organism's activity rather than its body parts.
- A footprint forms when a foot deforms soft sediment that later lithifies, preserving the impression.
- A burrow is a tunnel or hole made in sediment by an animal and later filled or cast by mineral material.
- Rootlet traces record the position and branching pattern of plant roots after the root tissue has decayed.
- Trace fossils can indicate behaviour such as walking, burrowing or anchoring, which body fossils may not show.
- Preservation requires the sediment to harden before the trace is eroded, disturbed or destroyed.
Common mistakes and how to put them right
Thinking a footprint is part of the animal's body.
Put it right by stressing that the body has gone and only the impression or cast remains.
Assuming any mark in a rock is a fossil.
Put it right by requiring evidence that a once-living organism produced the trace.
Confusing a burrow with a rootlet trace.
Put it right by linking burrows to animal activity and rootlet traces to plant roots.
Exam tips
- Name the type of trace and the organism group that made it, for example an animal footprint or a plant rootlet trace.
- Describe the sequence: soft sediment is disturbed, then hardens and is buried, then is exposed by erosion.
- Contrast trace fossils with body fossils in one sentence to show you understand the difference.
Try the lesson
The start of the Fossils: as preserved traces of organisms, such as footprints, burrows and rootlet traces. lesson, made from checked teaching notes for this specification point.
Have a go first
A student finds a rock containing a preserved footprint of an animal. Which type of fossil is this?
Listen
Not every fossil is a body fossil. Sometimes the organism itself is absent and what survives is a trace of its activity, preserved in rock. A dinosaur footprint forms when a foot presses into soft mud; if that mud later hardens and is buried, the impression can survive as sedimentary rock. A burrow shows where an animal tunnelled through sediment, and a rootlet trace records where a plant root once grew, leaving a cast or impression after the root decayed. These are called trace fossils. They form only when the sediment sets before the trace is destroyed, and they are later exposed by erosion or quarrying. Trace fossils reveal behaviour and movement, which body fossils often cannot, so they add evidence about how organisms lived. A strong answer earns marks for these points. Trace fossils are preserved evidence of an organism's activity rather than its body parts. A footprint forms when a foot deforms soft sediment that later lithifies, preserving the impression. A burrow is a tunnel or hole made in sediment by an animal and later filled or cast by mineral material. Rootlet traces record the position and branching pattern of plant roots after the root tissue has decayed. A common slip: Thinking a footprint is part of the animal's body. Instead, stressing that the body has gone and only the impression or cast remains. Exam tip: Name the type of trace and the organism group that made it, for example an animal footprint or a plant rootlet trace.
See it
Put it in order
Put these steps in the order they happen.
- 1. Trace fossil found: footprint, burrow or rootlet trace
- 2. Exposed by erosion or quarrying
- 3. Sediment sets before the trace is destroyed
- 4. Trace preserved in sedimentary rock
- 5. Organism activity: foot presses into soft mud, animal tunnels through sediment, or plant root grows
- 6. Trace formed in soft sediment
- 7. Sediment hardens and is buried
Key words
Say what each word means before you turn the card.
Trace fossils
Try answering aloud or in your head before turning the card.
Preservation in sedimentary rock
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Behaviour recorded by traces
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Interpreting fossil evidence
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See every definition
- Trace fossils
- Preserved traces of organisms, such as footprints, burrows and rootlet traces, rather than the organism's body parts.
- Preservation in sedimentary rock
- A trace survives when the sediment sets before the trace is destroyed, and is later exposed by erosion or quarrying.
- Behaviour recorded by traces
- Trace fossils reveal behaviour and movement, which body fossils often cannot, adding evidence about how organisms lived.
- Interpreting fossil evidence
- Trace fossils show behaviour such as walking, burrowing or anchoring, which body fossils may not show.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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