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Mollusks Kingdom: Animalia Phylum: Mollusca Class: Gastropoda Class: Bivalvia Class: Cephlapoda Characteristics _______largest phylum 125,000 living species; 35,000 fossil species _____________________ Soft body Habitat ______________________(mostly marine, some freshwater), some moist terrestrial habitats Most are _____________________ and creep SLOWLY on a ventral muscular foot, some are free swimming Importance Food, pearls, cultivated plant damage, intermediate hosts for parasitic worms, ship damage (ex. wharves, pilinings) Body Structure _____________________ Coleom present _____________________ 2 body openings Structure _____________________: located in mouth, tongue-like organ with rows of teeth, used to scrap, drill, grate or cut food Bi-valves are filter feeders, (no radula) Digestion _____________________ digestive system (mouth stomach intestine anus) _____________________: filter feeders, burrow in sand & use cilia to beat water through incurrent siphon (gill-like structure) and push food to stomach Gastropods & Cephalopods are predators Nervous system _____________________ nervous system Brain & associate nerves Most have paired eyes Range from simple cups that detect light to complex eye (retina, pupils, irises) Circulatory System _____________________: blood flows through vessels into open spaces around body & over organs (most mollusks) _____________________: blood enclosed in vessels (squid & octopi) Heart has 2 chambers (one atrium and one ventricle Respiration Marine mollusks have one, to many, _____________________ Terrestrial mollusks have a “lung” (not a true lung) Gas exchange also takes place through epidermis (skin) Reproduction _____________________: most species have male & female, few are hermaphrodites Mollusk Classes Class: Gastropoda Examples: Snails, slugs, whelks, conks, abalone Most are marine, a few live in freshwater or on land Structure Conspicuous head with two pairs of retractile tentacles, a pair of eyes and a mouth Head joins directly to a long ventral muscular foot On top of foot there is a shell (one piece and is unchambered) Shell is spirally coiled and asymmetrical Soft parts can be drawn up into shell Class: Bi-valva Examples: Clams, mussles, scallops, oysters Mostly marine, a few fresh water species Structure Hard shell, symmetrical halves joined by an elastic hinge ligament Shell is secreted by mantle & is made of three parts o Periostracum – (top layer) horny covering that prevents parts underneath from being dissolved o Prismatic – (middle layer) layer of crystalline calcium carbonate o Nacre – (inner layer) mother of pearl, formed by thin layers of calcium carbonate Class: Cephalopoda (head-foot) Examples: Octopus, squid, cuttlefish, chambered nautilus Foot has evolved to have tentacles with suckers Grab food & use for movement Structure Most advanced invertebrates Cartilage “brain box”, vertebrate type eyes, separate pancreas Simple eyes (do little more than detect light and shape)