1. Invertebrate Phylum
Mollusca
(Mollusks)

2. Vocabulary
visceral mass = contains internal organs of digestion, excretion, and reproduction
mantle = thin membrane that surrounds internal organs

3. Vocabulary
Radula = tongue-like structure with teeth used to grate, cut, and scrape
Torsion = visceral mass twists 180* in relation to head
Siphon = fleshy tubes for movement of water in a mollusk

4. Characteristics true coelm * bilateral symmetry * two body openings
* 3 body parts: head, muscular foot, visceral mass
* most have shell secreted by mantle
* gills for gas exchange with water
* some have a radula for feeding

5. Three Major Classes

6. Gastropoda: "stomach foot"
* single shell - snails, abalone, conch
* no shell - nudibrachs, slugs
* move by muscular contractions of foot
* open circulatory system

10. Bivalvia: shell with "two valves”
* clams, oysters, scallops
* strong muscle for pulling shell and burrowing
* no head or radula
* filter food from water via gills; cilia move food to stomach

11. Cephalopoda: "head-foot”
* octopuses, squid, nautilus
* free swimming; predatory; tentacles with suckers
* radula and sharp beak
* large brain and advanced nervous system
* closed circulatory system