BIOL 2030 Lecture Notes - Lecture 7: Turbellaria, Gastrointestinal Tract, Cestoda
17 Sep 2015
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Phylum platyhelminthes flatworms, flukes and tapeworms lecture 7. Phylum platyhlminthes ( 20000 species 80% are parasitic; either directly or indirectly affect humans) Incomplete digestive system animal feeds by wrapping around its prey, then insert the pharynx into the prey to begin extracellular digestion: partially digested pieces of food are then sucked in through the pharynx. Internal parasitic mode in final adult stage living in a definitive host: digestive tract = present because actively feeds in host, gut is absent. Monogenea flatworms: on the skin of aquatic vertebrates ex. fish (marine external skin organisms, external parasitic mode (fishes) Cestoda tapeworms: don"t have digestive tract absorb nutrients that are broken down by the gut of the host (because they live in the host"s gut, use pinocytosis or phagocytosis. Body plans: external architecture symmetry, bilateral symmetry. Body parts oriented about single anterior to posterior axis. Division along the midsaggital plane results in two equal halves. Controlled mobility, anterior of animal confronts environment first.
