Flatworm Characteristics--Flat bodies (gases move by diffusion)--bilateral symmetry--gastrovascular cavity--some flatworms are parasitic, some are freeliving--they have anterior and posterior heads and exhibit cephalization

Types of Flatworms (planarian, tapeworm, fluke) Planarian (also known as Dugesia)--lives in freshwater--mostly a scavenger, also feeds on protists--hermaphrodites--has a simple brain (ganglia) and nervous system, plus 2 eyespots--they can regenerate (regrow parts)

Anatomy of the PlanarianBrain (ganglia) - planarian can process information about their environmentPharynx - used for suckling food in (the mouth is at the end of the pharynx)Eyespot - simple eye, can detect lightIntestine - digestion (does not have an anus)

                                                                           

                      Tapeworms

--parasitic worms that live in the digestive system.Diffuse nutrients into body--they have segmented bodies (each segment is called a proglottid)--each proglottid is a reproductive organ--tapeworms can grow very long (40 feet!)--attach to the intestine with hooks and suckers on the head 

Flukes--most have complex life cycles involving more than one host--Schistosoma (blood fluke) spends part of its life in a snail, humans get infected when they wade in the water containing the snails, the larva then invade the human's blood vessels--eggs are passed thru human feces into water where the snail is infected

Roundworms--have a complete digestive tractAscaris -common roundworm infection in humans and dogsTrichinella -roundworms that invade muscle tissue, get by eating undercooked porkVinegar eel - free living roundworm

Roundworms- Ascaris

Trichinella worm

Hookworm