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MOLLUSK NOTES Chapter 10, section 1 A. Characteristics of Mollusks 1. Body Structure a. Bilateral symmetry b. Digestive system with 2 openings 2. Circulatory System a. most have an open circulatory system 3. Obtaining Oxygen a. most have gills B. Classification of Mollusks Classification of Mollusks continued 1. usually classified by their physical appearance such as: a. Presence of a shell b. Type of shell c. Type of foot d. Presence of a nervous system Three major groups of mollusks a. gastropods 1.) Largest group of mollusks 2.) Have a single shell or no shell at all 3.) Include snails and slugs Gastropods continued… 4.) Obtaining Food a.) herbivores animals that eat only plants 5.) Radula – organ that flexible ribbon of tiny teeth used like sand paper to tear throuh plant tissue Mantle Part of the mollusk that makes a shell Picture of a gastropod’s radula Checkpoint Gastropods use their radula to… a. b. c. d. obtain food. move. protect themselves. clean their shell. ANSWER…. Obtain Food Gastropods continued 6.) Movement a.) has a muscular foot – secrets slime 1.) This helps it glide across the surface it’s moving on b. Bivalves 1.) these mollusks have 2 shells held together by strong muscles 2.) Obtaining Food a. filter feeders - capture food as water flows over their gills food particles stick to mucus that covers the gills Bivalves continued… 3.) Movement – don’t move quickly a.) young larvae can float or swim b.) adults stay put or use their foot to move slowly Mantle – just for review Part of the mollusk that makes the shell It’s the soft tissue of the mollusk In a squid it’s the outside of the squid – the part you eat if you eat calamari. Bivalves continued 4.) Protection a.) Grains of sand can get in and irritate the mantle b.) Mantle will produce a smooth, pearly coat over the sand and and this is what makes pearls Cephalopods Cephalopods Squid Nautilus – only cephalopo d with a shell C. Cephalopods 1.) ocean dwelling mollusk whose foot is adapted to form tentacles around its mouth 2.) 3.) most without shells only mollusks with a closed circulatory system Cephalopods continued 4.) Obtaining Food a.) carnivores – captures prey using tentacles 1.) tentacles have suckers sensitive to taste and touch Cephalopods continued 5.) Nervous System a.) most complex nervous system of any invertebrate b.) large eyes, good vision, large brains An octopus is pretty darn smart estimated to have 300,000,000 neurons. An octopus has a "good" memory and can also learn. Their eyes are similar to ours too… It has a cornea, lens, iris and retina. It can also focus and form images. It’s different from vertebrates in that it focuses light by moving the lens closer and further away from the retina. The vertebrate eye focuses by changing the shape of the lens. Another difference is that the eye of the octopus has NO blind spot since the nerve cells leave from the outside of the eyeball. Cephalopods continued 6.) Movement a.) swim by jet propulsion 1.)) squeeze a current of water out of the mantle cavity and through a tube called a siphon They are also very agile and can fit through spaces 1/10 the size of their bodies Type of mollusk Gastropod: Snails and slugs How they obtain How they move food Use radula – tongue like organ to scrape and tear plant or animal tissue Creep along on a muscular foot leaving a slime trail Type of mollusk How they obtain food How they move Bivalve: Filter Feeders Clams, oysters, scallops float or swim – some clap shells together to swim; muscular foot to bury themselves Type of mollusk Cephalopod: Octopus Squid Nautilis Cuttlefish How they obtain food Use tentacles to capture prey, crush prey in beaks, use radula to scrape and cut flesh How they move Swim using jet propulsion (water squirts out siphon) to propel backwards The foot of a cephalopod looks like a a. b. c. d. head. mouth. shovel. tentacle. Answer… Tentacles Which of the following is NOT true of ALL mollusks? A. They have shells. B. They have soft bodies. C. They have a mantle. D. They have a foot. Answer Not all mollusks have shells Cephalopods move by … A. B. C. D. using jet propulsion. moving their tentacles. crawling along on a muscular foot. gripping with their radula. Answer Using Jet Propulsion Don’t be like this dumbo octopus Use your… Study for Wednesday’s quiz and don’t forget your notes!