Body Sort: Who Gets to Be a Fossil?
Goals
- Identify and sort organisms by body type: soft-bodied, exoskeleton, or endoskeleton.
- Understand how different body types affect fossilization.
- Build vocabulary to prepare for lessons on types of fossils.
Vocabulary
- Exoskeleton – A hard, outer shell that supports and protects the body (like a trilobite).
- Endoskeleton – A hard skeleton inside the body (like ours!).
- Soft-bodied – Animals with no bones or shells (like jellyfish or worms).
- Fossil – Remains or impressions of ancient life preserved in rock.
Background
During the Cambrian Period, life in the oceans became wildly diverse. Scientists call it the Cambrian Explosion because it seems like so many new body types showed up in a short time! Some creatures had soft squishy bodies, others had hard shells or spiky armor, and a few had skeletons inside.
But only some of these creatures left fossils behind and that has everything to do with their body structure.
- Picture cards of Cambrian creatures
- Three category cards: “Soft-Bodied,” “Exoskeleton,” and “Endoskeleton”
- Optional: printable in lesson resources
1. Introduce the Three Body Types
- Show photos or drawings: a jellyfish, a trilobite, and a fish.
- Discuss: What’s different about how their bodies are made?
- Lay out a group of creature cards.
- Learners sort them into categories based on what kind of body they have.
- Ask: Which ones might leave a fossil behind? Why?
Explain that hard parts fossilize best, so soft-bodied animals rarely leave fossils unless conditions are just right.
Optional Add-Ons
- Draw-a-Creature Challenge: Have learners invent a new Cambrian creature and decide if it has an exoskeleton, endoskeleton, or soft body.
- Look at real fossil photos and predict what kind of body it had.
Transition into Fossils
End the lesson with a question:
“If soft-bodied animals don’t fossilize well, how do we know they were ever here?”