1. mantle- tissue that surrounds the internal organs, and secretes the shell in shelled mollusks. 2. radula- raspy tongue-like structure that is used for feeding 3. nervous systems- simple nervous system, but some are advanced enough to have a brain and complex eyes (octopus is capable of solving simple problems) A. General Body structure; Bilateral symmetry, coelom and complete digestive tract. VI. Mollusks;

4. circulation a. open- blood travels through open body cavities b. closed- blood travels through a series of blood vessels 5. excretion- nephridia remove wastes from the body 6. respiration a. ctenidia – filament gill system found in most mollusks (all aquatic species) b. primitive lung- formed in the mantle cavity of land snails and slugs

7. Reproduction- sexual repro. with separate sexes in most species. Fertilization may be external in aquatic species and is usually internal in terrestrial species. B. Classes; 1. Gastropoda (Stomach footed); includes land, and aquatic species. May have one external shell, or no external shell. Includes snails, slugs, and nudibranch Gastropods may be predatory or grazing feeders.

The checkered cone snail has one of the top 10 deadliest toxins of all animals. Gastropods-

nudibranch

2. Pelecypoda, also called bivalves (Two shells); all aquatic, mostly marine, but some are found in fresh water Most are filter feeders. Includes clams, scallops, oysters, and mussels

Eyes around the edge of a scallop shell

3. Cephalopoda (Head footed); Marine Only the nautilus has an external shell. Includes squid, octopus, cuttlefish and nautilus Cephalopods are carnivorous predators.

squid

octopus

cuttlefish