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Platyhelminthes : The Flatworms. Platyhelminthes : The Flatworms . What makes something a planarian (member of phylum platyhelminthes )? Bilateral symmetry cephalization Single digestive opening (pharynx) Respire via diffusion Triploblastic body plan. Bilateral Symetry.
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Platyhelminthes: The Flatworms • What makes something a planarian (member of phylum platyhelminthes)? • Bilateral symmetry • cephalization • Single digestive opening (pharynx) • Respire via diffusion • Triploblastic body plan
Pharynx: Mouth on a tube Cephalization Pharynx Mouth
Respiration: No Lungs… just diffusion • That’s why they’re flat! More surface area for diffusion
Human Germ Layers • Ectoderm : skin + nerve system • Endoderm : digestive & respiratory organs • Mesoderm : everything else (heart, kidneys, muscles, etc.)
Types of Platyhelminthes • There are 3 groups of platyhelminthes • Planarians • Flukes • Tapeworms
Planarians: Free living nice guys • Predators. Usually aquatic
Flukes: Parasites with Multiple Hosts • Fluke are obligate pathogens. • They have complex life cycles which require infection of multiple hosts.
Tapeworms • Parasites.