Fossils
Biology: AQA GCSE Higher, topic 6.3.8
Fossils
Fossils are the remains or traces of ancient life. Fossils are found in rocks and have been preserved by natural processes. There are 3 different ways of forming fossils:
Hardening soft materials
- The hardening of soft materials can produce casts or impressions, such as footprints.
- For example, clay hardens around an organism that is buried within it. This organism then decays, leaving behind a cast of itself.
Preservation when decay is not possible
- Where decomposers cannot act, preservation is possible.
- Decomposers cannot operate in glaciers (extreme, low temperatures) and peat bogs (extreme acidity).
Mineral replacement
- Hard parts of organisms are gradually replaced by minerals as they decay slowly, creating a rock-like substance.
- When the surrounding sediment turns to rock, the teeth-shaped mineral structure remains distinct (different).
Test yourself on Fossils
Why can't decomposers act in peat bogs?
Why do both peat bogs and glaciers help preserve organisms as fossils?
Which of the following are correct regarding fossils?
How does fossil formation by mineral replacement differ from the formation of a cast?