Mollusks Bivalves-scallops Cephalopod Chambered Nautilus & Squid Polyplacophora-Chitin

General Characteristics Mollusca 1. Phylum Mollusca 2. Meaning: Soft-bodied 3. Body plan: Coelomates 4. Reproduction: Sexual 5. Internal or external shell made of calcium carbonate Bilateral Symmetry 6. Bilateral Symmetry –2 body openings 7. Respiration: Gills or Skin 8. Habitat: Marine, freshwater, land 9. Muscular Foot for moving 10. Food source for many animals

Four Basic Mollusk Parts Mantle 1. Mantle – thin membrane surrounding the organs that secretes shell in those that have them externally. Radula 2. Radula-tongue-like organ used to scrape food Visceral Mass 3. Visceral Mass-found beneath the mantle; contains internal organs Shell 4. Shell- external or reduced or lost in some terrrestrial & aquatic organisms.

Class Gastropoda: Class Gastropoda: “Stomach Foot”or “Univalve” 1. No shell or one 2. Nervous System – small brain Open Circulatory System 3. Open Circulatory System 4. Respiration –diffusion through moist skin 5. Habitat: terrestrial, freshwater, marine 6. Examples: Snails, Slugs, Sea Slugs 7.Radula present 8. Reproduction- sexual hermaphrodites hermaphrodites

Class Bivalvia- the “Hatchet footed” 1. “Two Shells” ganglia 2. Simple Nervous System- several small ganglia throughout body 3. Open circulatory system 4. Respiration: Gills Sedentary 5. Lifestyle: Sedentary (don’t move much) 6. Ex: Clams, oysters, scallops, and mussels 7. Habitat: freshwater, marine 8. Filter Feeders 9. Reproduction: sexual; hermaphrodites clamsoystersscallop

Class Cephalopoda- Class Cephalopoda- “Head Footed” 1. Shell #: none except chambered nautilus 2.Nervous System: a. most complex and most active mollusk b. large brain c. good eyesight d. tentacles very sensitive to touch 3. Circulatory system: closed 4. Respiration: Gills 5. Habitat: Marine 6. Ex: octopus, squid, cuttlefish, & nautilus 7. Radula present 8. Head is attached to a foot that is divided up into tentacles 9. Reproduction: Sexual & internal; eggs laid outside body Nautilus

Defense - can change colors for camouflage & communication - can expel ink if threatened Lion fish Mimic octopus 10

Polyplacophora Most primitive 8 dorsal plates Marine herbivores Ex. Chiton

Importance of Mollusks 1. Food source for animals & people 2. Clams filter water –can be indicators of water pollution problems when their populations decrease. 3. Snails/slugs pests on farms. 4. Host for disease causing organisms (ex: Flukes)

QUIZ # 1. Which animal listed below belongs to class cephalopoda? A. Clamb. Snailc. squid 2. The radula is for: a. Reproductionb. Feedingc. respiration 3. Cephalopods have____ circulation while gastropods and bivalves have _____ circulation. a. Open, closedb. Closed, open 4. Which of the following is NOT true about mollusks? a. They can be used to monitor water quality because they are filter feeders. b. They have radial symmetry. c. They all have a mantle that surrounds their internal organs. d. They are a source of food for animals as well as people. 5. Clams and octopus breathe ______, snails breathe ___. a. By diffusion, with gillsb. with gills, by diffusion c. with gills, sunlight 12