Teacher sheet · Ages 10–11 · about 45–50 minutes
How fossils form
Lesson page: echoesof.science/school/fossils/ages-10-11/ · Pupil worksheet: echoesof.science/school/fossils/ages-10-11/print/
Learning aims
- Distinguish body fossils from trace fossils.
- Explain the conditions needed for fossilisation and why it is rare.
- Describe permineralisation, moulds and casts.
- Plan and carry out a fair test.
- Know Mary Anning's contribution to palaeontology.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: show a fossil shell, a footprint photo and an insect in amber. How are they different? |
| 10 min | Read the text; sequence picture cards of fossil formation. |
| 15 min | Fair test: best 'fossil mud' (plaster cast prepared by the teacher, checked next lesson). |
| 5 min | Play Body or trace? |
| 10 min | Quiz and discussion: why so few fossils? |
Materials for the experiment
- 3 small trays or pots
- Dry sand, damp sand and play dough or modelling clay
- The same shell for every test
- A heavy book (to press with the same force)
- A magnifying glass
- Optional, for the teacher: plaster of Paris, a plastic cup and a stirrer
Safety: Only the teacher mixes and pours plaster; avoid breathing the powder, and never put hands into setting plaster because it gets warm. Do not eat play dough. Wash hands afterwards.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Fossils are the original bones. | Most fossil bones have been filled or replaced by minerals and turned to stone. |
| Mould and cast mean the same thing. | The mould is the hollow; the cast is what fills it. |
| The fossil record shows every animal that ever lived. | Very few organisms become fossils, and soft-bodied and land animals are rarer. |
Worksheet answers
- 1. The animal dies in the sea; 2. it sinks and is quickly buried by mud or sand; 3. more layers pile up and turn to rock while minerals fill the shell or bones; 4. millions of years later the rock is lifted and worn away and the fossil is found.
- Usually the play dough or damp sand; fair: same shell, same force (the book), same time, only the material changed.
- Jellyfish and worms are soft and usually rot before they can be buried and preserved; shells are hard and durable.
- False: the hollow is a mould; the cast is what fills the mould.
Quiz answers
- Why must remains be buried quickly to become a fossil? Burial protects them from rotting and scavengers. Quick burial prevents decay, weathering and scavenging.[4]
- In which kind of rock are fossils usually found? Sedimentary rock. Fossils are typically found in sedimentary rocks.[3]
- Which of these is a trace fossil? A dinosaur footprint. Trace fossils are signs of activity, like footprints.[5]
- What is a mould fossil? A hollow left where a buried shell or bone dissolved. A mould is the space left in the shape of the original.[1]
- About what share of the fossils found are of sea animals? About 99%. Sea animals were often quickly buried by sand or mud.[1]
- What did Mary Anning find that had never been found complete before? A plesiosaur skeleton. She found the first complete plesiosaur skeleton.[2]
Going further
Find out about the Jurassic Coast and plan a safe, responsible fossil hunt: beaches only, away from cliffs, with an adult, checking tide times.
Sources used in this lesson
- [1] How are fossils formed? (Natural History Museum, London): reliability High
- [2] Mary Anning: the fossil hunter (Natural History Museum, London): reliability High
- [3] Fossils (British Geological Survey (BGS)): reliability High
- [4] How Fossils Form (US National Park Service (NPS)): reliability High
- [5] What is a Fossil? (US National Park Service (NPS)): reliability High
- [6] How do fossils form? (Australian Museum): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/fossils/sources/
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