1. Chitons, Snails, Slugs, Mussels, Oysters, Clams, Squid, Octopus
Phylum Mollusca
Chitons, Snails, Slugs, Mussels, Oysters, Clams, Squid, Octopus

2. Phylum Mollusca Characteristics
50,000 living species
“soft body”
Bilateral symmetry
First coelomates
All organs present and well developed
Gills or lungs
Open circulatory system with heart

3. More Characteristics
First coelomates: space lined with mesoderm; and organs suspended by mesodermal membranes called mesenteries
Gives support and protection to organs

4. More Characteristics
Gills or lungs in addition to exchange through body surfaces
Respiration and circulation are advanced enough to permit large size
Largest invertebrates at 18 m. and 450 kg.

5. More Characteristics
Mantle: secretes a shell in most cases; is a sheath of skin that is often a pair of folds
Radula: a rasping tongue-like organ with tiny teeth
Foot: muscular sole mostly for locomotion
Sensory organs including touch, smell, taste, equilibrium, and vision
Vision is especially keen in cephalopods

7. Snail Radula
radula

8. Classification

9. The Major Classes

10. Gastropods Snails (shell) Slugs
Only terrestrial mollusks are in this class
Freshwater and marine

11. More Gastropods

12. Class Pelecypoda Bivalves No terrestrial Freshwater and marine
Filters small organic particles from the water
Scallop

13. More Bivalves

15. Class Polyplacophora Chitons Flattened, elongated Graze on algae
7 or 8 dorsal shell plates

16. Class Cephalopoda Squid, Octopus, nautilus, cuttlefish
Fastest, most intelligent invertebrates
Closed circulation
Predators

17. More Cephalopods

18. Cuttlefish
Nautilus

19. Baby Octopus