Fossils — AQA GCSE Biology
Test yourself on Fossils with AQA GCSE practice questions.
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Fossils explained
While the earliest life forms were unicellular, many early multicellular organisms, such as simple worms and jellyfish-like animals, had soft bodies with no shells, bones or teeth.
Read the full explanation
Soft tissue decays quickly due to bacterial action and is rarely replaced by minerals, so it seldom fossilises. Hard parts resist decay and are much more likely to be preserved. This creates a gap in the fossil record: the further back in time we look, the fewer fossils we find, and the fossils we do find are biased towards organisms with hard parts. For example, a soft-bodied worm is far less likely to leave a fossil than a shelled mollusc living at the same time.
Your focus
- Explain why soft-bodied organisms rarely fossilise.
- Describe how the fossil record is biased towards organisms with hard parts.
- Account for gaps in the early fossil record.
Fossils exam tips
Marking Points
- States that many early multicellular life forms were soft-bodied.
- Explains that soft tissue decays quickly and is rarely preserved as fossils.
- Contrasts soft-bodied organisms with those having hard parts such as shells, bones or teeth which fossilise more easily.
- Concludes that early soft-bodied organisms left few traces, creating gaps in the fossil record.
- Uses an example, such as a soft-bodied worm compared with a shelled animal, to illustrate preservation bias.
Examiner Tips
- 💡Use the phrase ‘few traces’ rather than ‘no traces’ to stay accurate when discussing early soft-bodied life.
- 💡Link the lack of fossils to the decay of soft tissue by microorganisms.
Common Mistakes
- Claiming no early life existed because no fossils are found; correct this by explaining that absence of fossils is due to poor preservation, not absence of life.
- Thinking soft-bodied organisms never fossilise; correct this by saying they rarely fossilise, usually only in exceptional conditions where decay is prevented.
- Ignoring the role of hard parts; correct this by explaining that shells and bones fossilise more readily than soft tissue.