Platyhelminthes – flatworms

Platyhelminthes – flatworms -...

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Unformatted text preview: Platyhelminthes – flatworms They’re kind of a big deal…..i guess • • • • • • • • • • • • Primitively evolved Hermaphrodite – sperm and eggs at different times Bilaterally symmetrical Tripoblastic (composed of three cell layers No body cavity other than gut - acoelomates o No anus (same opening takes in food and expels waste No circulatory and respiratory organs o Respire by diffusion to the outside – requires flattened shape Have a central nervous system No organs for circulation Protonephridia – network of tubules with ciliated structures that lead to the outside Most have a gastrovascular cavity with one opening Parasitic: o Cestoda – tape worms o Trematoda - flukes o Monogenea Attach to the surface or internal organs of their hosts o Have multi hosts Non-parasitic: o E.g. planarians o Most are marine and some are freshwater o Turbellaria – planarians Move by cilia on their surface Feed on dead stuff Primitive nervous system with light sensitive eyespots o ...
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