MOLLUSKS AND SEGMENTED WORMS CHAPTER 35 MOLLUSKS AND SEGMENTED WORMS

MOLLUSKS-SOFT BODIED Three distinct parts: Visceral mass-houses the organs Muscular foot aids movement and secretes mucus (that’s the trail of slime snails leave behind) Mantle secretes the shell

DIGESTIVE SYSTEM REPRODUCTION NERVOUS SYSTEM Radula-tongue-like organ with rows of teeth used to scrape or cut food Bivalves are filter feeders. Gills used to filter food from water REPRODUCTION Most have separate sexes for external fertilization; land dwellers are hermaphrodites NERVOUS SYSTEM Brain and nerves that control movement and behavior Some have simple eyes that detect light; others have compound eyes that function as well as those in humans.

CIRCULATORY SYSTEM RESPIRATORY SYSTEM EXCRETORY SYSTEM- Three chambered heart Most have an Open circulatory system; there are no blood vessels that transport blood back to the heart. RESPIRATORY SYSTEM Aquatic mollusks have gills for gas exchange Land mollusks have lungs EXCRETORY SYSTEM- Wastes are removed from the body by nephridia

Classes of mollusks GASTROPODS-stomach-footed one shelled -snails, conch, periwinkle No shell-slugs; they are protected by mucus May be herbivores, predators, or parasites

BIVALVES-two shelled mollusks Clams, oysters, scallops No distinct head or radula Use muscular foot to burrow in sand ligament-hinge-like structure that connects the shells Filter feeders

CEPHALOPODS-head-footed Octopus, squid, chambered nautilus Foot has evolved into tentacles with suckers, hooks, and adhesive structures Jet propulsion to move and escape predators

SEGMENTED WORMS-ANNELIDS (“Little Rings”) Body plan resembles a tube within a tube. inner tube forms the digestive tract Bristles or setae on each segment which anchor worms into the soil Ringed segments are separated; have separate muscles, separate functions,

Closed circulatory system Simple nervous system Brain in some species attached to ganglia in each segment by nerve cord Closed circulatory system Carry blood throughout the body in vessels Can also breathe through their skin Complete digestive tract-includes mouth, pharynx, esophagus, crop, gizzard, intestines, and anus Reproductive system Earthworms and leeches are hermaphrodites Sperm is exchanged and fertilization takes place in a capsule which is shed and left behind in soil to hatch

CLASSES OF ANNELIDS OLIGOCHAETA POLYCHAETA HIRUNDINEA EARTHWORMS 100+ SEGMENTS CALLED FARMER’S HELPER CASTINGS (WORM POOP) ADDS NUTRIENTS TO THE SOIL POLYCHAETA BRISTLEWORMS, SANDWORMS HIRUNDINEA LEECHES PARASITIC; HAVE SUCKERS ON EACH END WITH ALLOW THEM TO ATTACH TO A HOST FOR FEEDING ONCE USED FOR MEDICINAL PURPOSES

EARTHWORM DISSECTION