PLATYHELMINTHES

Characteristics Flatworms Class Trematoda: Tapeworms Class Cestoda: Flukes Class Turbellaria: Planarians Bilateral symmetry Many are parasites Size 1mm to 1 M

Anatomy Long narrow body No legs Acoelomates Epidermis cells make up “skin” No circulatory system

Anatomy Takes in oxygen but no formal respiratory system First phylum with muscles No skeleton Simplest organisms with a brain Two simple nerve cords and two brains are small bundles of nerves

Feeding Planarians are scavengers Tapeworms and flukes are all parasites Flatworms feed through tube-like mouth. Digestive juices flow out to start digestion, worm sucks up partially digested food

Reproduction Asexual reproduction: Regeneration (like in planarians) Sexual Reproduction: Flatworms are hermaphrodites Produce both eggs and sperm. Exchange sperm with other worms

Habitat Free-living: Ocean Freshwater Moist soil Parasites: On or in host organism What are some biotic and abiotic factors?

Adaptations Parasites live off host organism, but rarely kill the host – Why? Adults produce a lot of eggs and sperm Liver flukes have multiple hosts. Why do you think this is advantageous? Do you eat sushi?