Flatworms Phlylum Platyhelminthese Flatworms Bilateral symmetry Flatworm FIRSTs

Flatworms

Phlylum Platyhelminthese = Flatworms

• Bilateral symmetry Flatworm FIRSTs!! • Directional motion = 1 st mobile predator • Cephalization – development of a head • Ganglia: bundle of nerve cells make up a pre-brain • Nerves concentrated at ‘head end’ since sensory cells were concentrated at that end • Sensory nerves formed bundles = ganglion • • • Eyespots detect light Auricles detect chemicals ‘smell’ 2 nerve cords transmit info to rest of body

New Innovations in Excretory System • cellular waste still removed by diffusion • Protonephridia (NEW) • flame cells help regulate solute concentration • Evolve in to the nephrons of mammal kidneys • First Kidney

Flatworm Reproduction • 1 st internal fertilization • Evolutionary advantage – Make fewer gametes – Save energy • Hermaphrodites = make both eggs & sperm • Evolutionary advantage = can mate with any other member of your species that you can

• Asexual reproduction by fission

Ancestral Traits • Gastrovascular cavity for digestion & circulation • Mouth in center of body • Respiration (gas exchange) by diffusion

Free-living Flatworms = Class • Marine • Fresh-water

Classes of Flatworm • 1) Free living • example = Planaria • 2) Flukes • parasites in blood & liver • swimmers itch • 3) Tapeworms

Flukes = Class • Parasites of blood and liver

Swimmer’s Itch =Schistosoma

Tape Worms = Class

Human Tape Worm • Sources =Under cooked – Beef (N. America) – Pork(S. America) – Fish (Asia) • Prevention – Cook your meat!!! – Wash your hands after using the restroom – Don’t drink contaminated water