Flatworms (Platyhelminthes) are the simplest types of worms.

Parasitic animals live in the body of another animal for food.

MOLLUSKS are animals with soft bodies that live oceans, streams, and moist soil.

Animals that are not parasitic are called FREE-LIVING animals.

Hermaphroditic is having both male and female reproductive organs.

Worms are invertebrates with long, soft, usually cylindrical bodies, and without legs

Flatworms have a simple brain called GANGLIA, which is a bundle of nerves.

The three types of mollusks are UNIVALVES, BIVALVES, and CEPHALOPODS.

UNIVALVES have one shell. BIVALVES are hinged together. Squid and octopus are examples of CEPHALOPODS. The squid have highly reduced internal shell.

GILLS are special organs that help animals absorb oxygen from the water.

Roundworms (nematodes) have TWO POINTED ENDS with openings--the mouth and the anus.

The brain of a flatworm is called a GANGLIA.

Tapeworms cling to the intestinal wall of another animal using HOOKS and SUCKERS.