Phylum Platyhelminthes

Phylum Platyhelminthes

1. Structure: Flatten dorsoventrally and are ribbon - like (ensuring large surface area), highdrostatic structure

   • Gas exchange through diffusion, Tissue / organ level organization, Bilateral symmetry, Incomplete digestion, Nervous system (textial, chemo)
   • Posses a mouth connected to the gasterovascular cavity, by a muscular pharynx,

2. Parasitic, have a brain, no circulatory system, Protostomes

   • Acodomate: Flat worms, true body cavity
   • False Body cavity, (round room)
   • Coelomate: True body cavity (half and half)

3. 3 Classes

   • Class Turbellaria
     • Live in Marine Environments, size range 5mm - 60cm, Many color shades (gray - bright colors), Carnivores (food moves through diffusion),
   • Class Cestoda
     • Tapeworms (endoparasites), Live up to 25 years, Anterior region called scolex that contains hooks and suckers for attachment
   • Class Trematoda
     • Parasitic flukes, 11,000 flukes, reside in organs like lungs, liver, intestines and the blood, leaf like appearance, Lack cell membrane

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