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[7] Platyhelminthes.docx

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York University
BIOL 2030
Scott Kelly

Platyhelminthesflatworms flukes tw Bilateral Symmetry Having two sides symmetrical about one median axis only so that one side is a mirror image of the other Planarian Any member of the order Tricladida freeliving flatworms platyhelminths living in streams ponds lakes and the sea They have abroad flattened body welldeveloped sense organs at the anterior end and an intestine with three main branches Rhabdite Short rodlike body in epidermal cell of turbellarians which is discharged if the worm is injured and swells up to form a gelatinous covering Viscid Cells Sticky cellsAnchor Cells Attachment cells Releasing Cell Gland Secreting cell Pedal Wave foot wavemeans of freeliving flatworm movement Protonephridum Branching excretory duct of the protonephridial systemexcretory system in some simple invertebrates such as flatworms nematodes annelids and rotifers It consists of a system of branching ducts protonephridia each enclosed at its internal end by a flame cell and opening into a central duct or to the surface through pores Flame cells beat a large bundle of flagella which project into the duct and whose motion gives a flickering appearance under the light microscope similar to a flame NephridioporesCerebral Ganglion The supraoesophagal gangla or brain of invertebrates Strobila Chain of proglottids of tapeworms Scolex Region at anterior end of tapeworm containing minute hooks and a sucker by which it attaches itself to the gut wall ThigmotacticProglottid Individual segment of an adult tapeworm containing a set of reproductive organs Eggs are formed in the posterior proglottids and are shed in the feces and then enter the alternative host where they hatch Oncospheres Spherical hooked larva that hatches from tapeworm egg and develops into a cysticercoid Intermediate host Organism in which a parasite lives for part of its lifecycle but in which it does not become sexually mature Definitive Host Host of an adult parasite Miracidium Ciliated larval stage of gut liver and blood flukes which hatches out of the egg and infects the snail host Sporocyst One of the larval stages in the lifecycle of endoparasitic flukes which develops from the miracidium in the snail host I thas no mouth or gut and reproduces asexually to produce rediae or cercariae Rediae A larval stage of some endoparasitic flukes in the snail host I tis produced asexually from the sporocyst has a mouth and gut and reproduces asexually to produce a further generation of rediae or cercariae Cercariae Heartshaped tailed larval stage of a trematode fluke produced in the snail host It is released from the snail sometimes then encysting and subsequentily infects a vertebrate host
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