Arthropoda, Mollusca, Echinodermata
These are three of the most successful and diverse invertebrate phyla:
- Arthropoda
- Mollusca
- Echinodermata
Comparison Table
| Feature | Arthropoda | Mollusca | Echinodermata |
|---|---|---|---|
| Body symmetry | Bilateral | Bilateral | Radial (adults), Bilateral (larvae) |
| Body cavity | Haemocoel | Haemocoel + reduced coelom | True coelom (large) |
| Segmentation | Present (tagmosis) | Absent | Absent |
| Skeleton | Exoskeleton (chitin) | Shell (calcium carbonate) – often | Endoskeleton (calcareous plates) |
| Locomotion | Jointed appendages | Muscular foot / jet propulsion | Tube feet (water vascular system) |
| Circulatory system | Open | Open (except cephalopods) | Water vascular + haemal |
| Respiration | Gills / tracheae / book lungs | Ctenidia (gills) / mantle | Dermal gills & tube feet |
| Examples | Insect, Spider, Crab, Centipede | Snail, Octopus, Clam, Squid | Starfish, Sea urchin, Sea cucumber |
3. Phylum Arthropoda
Largest & most successful phylum – ~80% of all known animals
- Jointed legs
- Exoskeleton
- Tagmosis
- Open circulation
- Advanced sense organs
🦗 Grasshopper Anatomy - Interactive Learning
🦗 Grasshopper External Anatomy
📚 Function Information
Click on any label to see its function and characteristics!
4. Phylum Mollusca
Second largest phylum – very diverse body forms
- Mantle & shell
- Muscular foot
- Radula present
- Mostly open circulation
- Very diverse
🐌 Snail Anatomy - Interactive Learning
🐌 Snail Structure
📚 Function Information
Click on any label to see its function and characteristics!
5. Phylum Echinodermata
Marine animals with unique water vascular system
- Spiny skin
- Water vascular system
- Pentamerous radial symmetry
- Excellent regeneration
- Marine only
⭐ Starfish (Asterias) Anatomy - Interactive Learning
⭐ Asterias Structure
📚 Function Information
Click on any label to see its function and characteristics!
📝 Quick Quiz (8 Questions)
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