2017-08-03 ZEN161 Prac 2.pdf - PRACTICAL 2 Platyhelminthes...

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1 PRACTICAL 2: Platyhelminthes, Nemathelminthes, Annelida, Mollusca and Echinodermata Phylum Platyhelminthes Flatworms are dorsoventrally flattened They are triploblastic Acoelomates means that they lack a body cavity Bilateral symmetry Unsegmented worms (except member from the class Cestoda/Cestoidea) Protonephridia are used for excretion and osmoregulation Most forms are monoecious by having both the male and female reproductive organs in the same individual Class Rhabditophora Also called the Planarians Dugesia Aquatic They have two simple eyespots that orientate the animal to the direction of the light Auricles are sensory lobes on their heads that contain sensory cells (chemoreceptors) that help them detect food from a distance Pharynx serves as the ingestive organ that can be extended when feeding They have an incomplete digestive tract They are monoecious
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