1. Phylum Mollusca

2. Phylum Mollusca Soft bodied Bilateral symmetry
Head, foot, and coiled visceral mass
Most have external or internal shell
Brain
Coelom: fluid filled cavity
Over 100,000 species

3. Class Bivalvia (Bivalves)
Two shells hinged together by adductor muscles
Prey to sea stars, predatory snails and humans

4. Shell Lines on shells represent age (like tree rings)
Made of calcium carbonate
Produced by mantle-thin membrane inside shell
Mantle also makes pearls by reacting to a grain of sand.

5. Siphon Tube Protrudes through gap btwn the clam’s shell
Used for breathing and feeding
Two openings
Incurrent siphon allows water containing food and O2 in
Excurrent siphon allows water containing wastes and CO2 out

6. Respiration Gills- membranes that take in O2 and give off CO2
Microscopic cilia beat to create a current on gills.

7. Feeding and Digestion
Filter feeding: currents of water that contain plankton and organic debris pass into the clam through it’s incurrent siphon, propelled by the ciliary action of gill surfaces. Cilia move the food into the clam’s mouth and into a one-way digestive tract.

8. Circulation
Open circulatory system: nutrients and O2 transported by a colorless blood.

9. Movement
Mussels: live in turbulent intertidal zone w/ constant wave action. Attach with fibrous protein secreted by foot
Oysters: bottom shell secretes a cement like substance
Use muscular foot to dig in sand
Contract and relax adductor muscles
Scallops

10. Reproduction Separate sexes External fertilization
Young are part of plankton community

11. Tridacna Clam