The document discusses the phylum Mollusca, including their body plans and three main classes. Molluscs are soft-bodied animals that live in various aquatic and moist environments. They have a mantle that secretes a shell in most species and organs like gills. The three classes are bivalves like clams that have two hinged shells, gastropods like snails that have a muscular foot and often a single coiled shell, and cephalopods like octopuses and squid that have tentacles surrounding their head and well-developed eyes and nervous systems.

1. Phylum: Mollusca Common name: Molluscs or Mollusks Members of this Phylum include the snail, oyster, slug, clam, squid and octopus. Molluscs live in oceans, streams, ponds and even moist soil.

2. Body Plan of Molluscs Molluscs are soft bodied animals with bilateral symmetry. Their bodies are covered by a thin tissue called a mantle . In most molluscs the mantle produces a hard, protective shell. Molluscs have a digestive system with two openings and a circulatory system. Molluscs also have gills , these are special organs for absorbing oxygen from water.

3. Three Classes of Molluscs Hatchet-Footed Molluscs Clams, oysters and scallops are Hatchet-footed molluscs. Named for the type of foot that it has - their foot is shaped like a hatchet. The shape of this foot helps these animals to dig quickly into the sand. All three of these molluscs are bivalves - two shells that are hinged together.

4. Stomach-Footed Molluscs These Molluscs are called Gastropods - means “stomach-footed. Gastropods - are molluscs that have a muscular foot along their ventral surface. Common Gastropods are snails, conches and slugs. Most gastropods have a single shell. However, slugs have none. Have a flat muscular foot for crawling, and a raspy tongue for scraping food.

5. Head-Footed Molluscs Named - Cephalopods - they are molluscs that have a foot divided into tentacles. Members of this class have tentacles that extend from the head. Octopus and squids are examples of cephalopods The squid has a shell inside of its body and an octopus has no shell these molluscs have distinct head and mouth parts and large eyes.

6. Cephalopods