Ch. 13

•Phylum 3 – Platyhelminthes, Flatworms

•Planarians, Tapeworms

•Soft, wormlike animals with flattened, elongated bodies

•3 tissue layers – endoderm, mesoderm, ectoderm

•Bilateral Symmetry – left/right, anterior/posterior, dorsal/ventral

•Cephalization – have a head with sensory structures on it, able to detect and respond to environment they are going into

•Shows organs and organ systems – Digestive, Respiratory, Excretory, Nervous, Muscle

•Most are parasite, live in a host animal

•Some are free living, not in a host

Some fresh water, some salt water

•Class – Turbellaria – Planarian

•Free living, not a parasite

•Ciliated epidermis, helps in moving

•Mouth is on ventral surface, end of pharynx, leads to gastrovascular cavity

•No anus, incomplete digestive system

•Freshwater or marine

•Planaria – cross eyed worm

•Found on underside of rocks, leaves sticks, submerged in lakes, ponds, streams

•Movement – gliding through water, made possible by cilia on bottom, and coordinated and rhythmic contractions of muscle

•Anatomy –

•1cm. - .4 in.

•Head

•Eyespots – light sensitive, Photosensitive

•Auricles – touch, chemical, smell

•Mouth ad Pharynx (feeding tube) located on ventral side middle of body

•Scavengers – eat dead organic matter

•Digestive system – 3  branched intestines, gastrovascular cavity

•2 to posterior, 1 to anterior

•Food is digested in intestine by cells and nutrients are diffused into body tissues

•No circulatory system – nutrients are taken directly to tissues by digestive system

Food not digested leaves through pharynx