<p> Mollusks</p><p>A. Mollusks - soft bodied invertebrates that have a mantle and a muscular foot.</p><p>1. Mantle - tissue that covers a mollusk’s body. </p><p>2. Have lungs or gills that exchange carbon dioxide for oxygen. </p><p>3. Have a radula or a scratchy tongue-like organ to help them eat. </p><p>B. Three Groups of Mollusks</p><p>1.Gastropods - most have a shell and are the largest group. </p><p> a. Live in land or water</p><p> b. Move by gliding their large muscular foot across a trail of mucus.</p><p> c. Have a radula to help them get food.</p><p> d. Snails, slugs, and conchs are examples.</p><p>2. Bivalves - have two shell halves held together by a muscle. </p><p> a. Are filter feeders that take food out of the water. </p><p> b. Have gills that take oxygen out of the water. </p><p> c. Have an open circulatory system where blood splashes over organs. </p><p> c. Clams, oysters, and scallops are examples.</p><p>3. Cephalopods - have no shell and are the most complex group. </p><p> a. Developed foot is divided into tentacles with suckers.</p><p> b. Have a closed circulatory system that contains blood vessels. </p><p> c. Adapted for quick movement in the ocean. </p><p> d. Octopuses, squids, and nautilus are examples. </p>