1. Stop 6: Phylum mollusca

2. Characteristics
Soft-bodied invertebrate covered with protective mantle that may or may not form a hard, calcium carbonate shell
Includes chitons, snails, slugs, clams, oysters, squid, octopus, & nautilus
Second largest animal phylum to Arthropoda
Have a muscular foot for movement which is modified into tentacles for squid & octopus
Complete, one-way digestive tract with a mouth & anus

3. Characteristics Have a fully-lined coelom
Cephalization - have a distinct head with sense organs & brain
Have a scraping, mouth-like structure called the radula
Go through free-swimming larval stage called trochophore

4. Characteristics Body organs called visceral mass lie below mantle
Have circulatory, respiratory, digestive, excretory, nervous, & reproductive systems
Bilaterally symmetrical
Most have separate sexes that cross-fertilize eggs
Gills between the mantle & visceral mass are used for gas exchange

5. Includes 4 classes Polyplacophora (chitons)
Gastropoda (snails, slugs, nudibranchs, conchs & abalone)
Pelecypoda or Bivalvia (clams, oysters, & mussels)
Cephalopoda (squid, octopus, & nautilus)

6. Class Cephalopoda or Amphineura
Includes octopus, squid, cuttlefish, & chambered nautilus  
All marine

7. Class Cephalopoda Most intelligent mollusk Well developed head
Active, free swimming predators
Foot divided into tentacles with suckers
Use  their radula & beak to feed

8. Class Cephalopoda Use their radula & beak to feed
Closed circulatory system
Lack an external shell
Highly developed nervous system with vertebrate-like eyes
Separate sexes with internal fertilization

9. Squid
Largest invertebrate is the Giant Squid * Large, complex brain * Ten tentacles with longest pair to catch prey * Use jet propulsion to move by forcing water out their excurrent siphon * Chromatophores in the skin can help change squid color for camouflage

10. Squid
* Can squirt an inky substance into water to temporarily blind predators * Have internal shell called pen * Female lays eggs in jellylike material & protects them until hatching

11. Octopus
Eight tentacles * Similar to squid * Crawls along bottom looking for prey

12. Chambered Nautilus
Has an exterior shell * Lives in the outer chamber of the shell * Secretes gas into the other chambers to adjust buoyancy

13. 2) Class Polyplacophora
All marine
Have a shell divided into 8 over-lapping plates
Live on rocks along seashore feeding on algae

14. 3) Class Gastropoda
Head has a pair of retractable tentacles with eyes located at the ends
Have a single shell or valve (snails) or none (slugs)
Known as univalves

15. Snails May be marine, freshwater, or terrestrial
Aquatic snails breathe through gills & use their radula to scrape algae for food 
Terrestrial snails use their mantle cavity as a modified lung & saw off leaves
Retreat into shell in dry periods & seals opening with mucus

16. Snails
Have open circulatory system * Secrete mucus & use muscular foot to move * Land snails are hermaphrodites * Aquatic snails have separate sexes * Use internal fertilization

17. Pteropods Called "sea butterflies“ Marine
Have a wing-like flap for swimming

18. Oyster Drills
Radula modified to drill into oyster shells

19. Nudibranchs
Marine slug
Lacks shell

20. Class Bivalvia or Pelecypoda
Sessile or sedentary
Includes marine clams, oysters, shipworms, & scallops and freshwater mussels
Filter feeders
Have two-part, hinged shell (2 valves)

21. Class Bivalvia Have muscular foot that extends from shell for movement
Scallops clap valves together to move
Shell secreted by mantle & made of 3 layers --- outer horny layer protects against acids, middle prismatic layer made of calcium carbonate for strength, & inner pearly layer next to soft body
Mantle secretes substance called "mother of pearl" to surround irritants like grains of sand
Oldest, raised part of shell called umbo

22. Class Bivalvia
Powerful anterior & posterior adductor muscles open & close shell
Lack a distinct head
Have an incurrent & excurrent siphon that circulate water over the gills to remove food & oxygen

23. Class Bivalvia Have heart & open circulatory system
Nervous system made of 3 pairs of ganglia, nerve cords, & sensory cells that detect light, chemicals, & touch
Separate sexes with external fertilization of eggs

24. Economic Importance of Mollusks
Used  by humans for food
Pearls from oysters
Shells used for jewelry
Do crop & garden damage
Serve as intermediate hosts for some parasites such as flukes