Snails, slugs, oysters, clams, Scallops & squids.

• includes snails, clams, octopi and slugs

All mollusks share 6 Characteristics

Body Cavity

They have a true coelom, Though it is a small space

Near the heart.

Most mollusks have Bilateral symmetry.

They also have a 3 part body plan.

These parts are the visceralMass, mantle and foot.

All mollusks have organ systemsFor excretion, circulation, Respiration, digestion and

Reproduction.

Many mollusks have 1 or 2 shellsThat act as an exoskeleton.

The shells are made of Calcium carbonate.

All mollusks, except for oysters,Have a radula.

The radula is a tongue like organThat has thousands of teeth.

Mollusks are the only coelomatesWithout segmented bodies.

Mollusks are the first to have Developed an efficient

Excretory system.

The nephridia is used to remove Liquid wastes.

Most mollusks have a 3 chambered heart and

An open circulatory system.

Many mollusks have gills thatAre used for respiration,

Snails have a primitive lung.

Reproduction

• Sexual• External fertilization

• Some hermaphrodites• Some oysters can switch sex

Mollusk Classes

A. Class Gastropoda: Snails & Slugs– single shell (slugs lost it)– large foot on ventral side

Class Bivalvia: Clams, Mussels & Oysters

• two hinged shells

• filter feeders and benthic

• foot used to burrow and anchor

• scallops “clap”

C. Class Cephalopoda: Squid & Octopus

• foot evolved into tentacles with suckers

• active marine predators

• jet propulsion

• radula is a beak

Segmented Worms

Annelid fossils have been found That are 530 million years old!

Scientists think that annelids Evolved from the sea, where

Most annelids are found.

Their size varies from 1mm to More than 3m long!

No matter how long,All segments contain digestive,

Excretory, circulatory, And muscles.

There is a cerebral ganglion,Or primitive brain, in one

Of the first segments and isConnected to a nerve cord

That runs along the bottom Of the worm.

They have septa, which are bodyWalls that separate segments.

They also haveSetae, which are

Bristles thatHelp traction as

They crawl along.

Habitat

• Soil, saltwater and freshwater

• Closed circulatory system

Respiratory System

• Gas exchange through body wall

Cuticle

Digestive System

• “Tube within a tube” digestive system

• Mouth• Pharynx• Esophagus• Crop• Gizzard• Intestines • Anus

Reproduction

•Hermaphrodites

•Sexual

• Clitellum -- cocoon