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

10. 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

11. Tridacna Clam

13. Class Gastropoda Snails, sea slugs (nudibranchs), limpets, abalone
Gastropoda: one shell “univalve”
Shells are made of calcium carbonate and may have an operculum: covering of the shell opening that closes like a trap door over its foot.

14. Respiration
Gills take up oxygen from the water through the siphon tube. Absorbs O2 and releases CO2.

15. Feeding Styles
Snails use a radula (ribbon like toothed structure)to feed.
Herbivores- (ex. Periwinkle) graze on algae Scavenger-(mud snail) feed on dead or dying organisms. Use radula to tear and shred the dead matter into small pieces.

17. Feeding Styles Predator- actively hunt and kill their food.
Ex moon snail- feeds on live clams by secreting chemical to soften the shell and then eat the animal inside.
Ex. Cone snail-uses toxins from its harpoon-like radula to kill its prey.

18. Cone Snail

19. Circulation
Open circulatory system w/ a one chambered heart and tiny blood vessels.

20. Movement
Carried out by the nervous and muscular system working together. Signals sent from brain to motor nerves.

21. Reproduction Many different methods
Some have separate sexes; some are hermaphrodites
Fertilization is internal; development is external.
Many different methods: Welk has egg casings; moon snail has sand collar; mud snail has transparent jelly capsules.

22. Reproduction
Egg casing of welk 
Sand collar

23. Gastropod Diversity Abalone- produces mother of pearl used for jewelry
Slipper shell- live in intertidal zone attached to any hard substrate (even horshoe crab); change from male to female and stack themselves up. (Crepidula)

24. Gastropod Diversity
Limpet- intertidal zone of rocky coasts; looks like a flattened cone. (hole on top of shell for wastes to exit)

25. Gastropod Diversity
Nudibranch (sea slug)- lack or have a reduced shell; breathe through skin w/ tufts of gills on their backs; eat hydroids and anemones and use their stinging as part of their defense; very colorful to serve as a warning. Sea hare eat algae and some turn green from all the chlorophyll they consume.

26. California Sea Hare 75 cm in length= largest gastropod in ocean!!!!
Releases a dye when disturbed 

27. Pteropoda Important zooplankton Affected by rising CO2 in the oceans
This shells of calcium carbonate are eaten away by the carbonic acid formed because of too much CO2