Cnidarian Movement POLYP is sessile – does not move MEDUSA is motile – squeezes bell (umbrella) to move uses simple ring of contractile tissue (not muscle tissue yet)
Feeding Use tentacles to capture food. Tentacles have NEMATOCYSTS – stinging cells that grab and immobilize prey using toxins. Waste products and undigested materials are expelled through the mouth.
Organization Nerve net – conducts impulses from all parts of the body. No brain. Two layers of tissues derived from endoderm and ectoderm
Cnidarian Reproduction Asexually – budding (polyp form) Sexually –have separate male and female medusae that produce gametes that join through external fertilization to produce polyps.
Flatworms - Platyhelminthes Bilateral Symmetry Free-living in freshwater or parasitic in a host Has all three layers (endoderm, mesoderm, ectoderm) Acoelomate – no body cavity.
An Important Group Many nasty parasitic infections. Dugesia Tapeworms Flukes
Flatworm Feeding Free living flatworms are scavengers. Parasitic flatworms use specialized structures (usually with hooks) to attach to a host.
Respiration & Excretion Excretion - Flame cells remove excess water Respiration - Oxygen diffuses into body cells directly.
Flatworm Nervous Systems First appearance of cephalization. Primitive brain. Eyespots
Flatworm Reproduction Sexually - Hermaphrodites – internal fertilzation. Asexually – fission – when damaged, regenerates new body parts. Proglottids – found in tapeworms – each is shed off individually.
Roundworms - Nematoda Bilateral Symmetry Free-living in soil or parasitic in a host Pseudoomate – false body cavity. Movement - Longitutdinal muscles produce a thrashing movement
Respiration & Excretion Respiration - Oxygen diffuses into body cells. Digestive wastes are excreted through the anus. Flame cells remove excess water through pores in body surface.
Roundworm Feeding Have a simple digestive system. Have a mouth and an anus Parasitic roundworms use specialized structures (usually with hooks) to attach to a host.
An Important Group Many nasty parasitic infections in humans, livestock Importanceand IMPORTANT AGRICULTURAL PEST Pinworms, Ascaris, hookworms, Trichinella