BIO 2129 Final: Final_Exam_-_Platyhelmintes.doc
1 Dec 2014
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Document Summary
Platyhelmintes: visible as paired anterior eye spots that detect light levels rather than images, chemosensory auricles on each side of the head, and an anterior brain that coordinates sensory input from the eye spots and auricles. It"s a process referred to as cephalization, a first with the flatworms, but with a difference. In other cephalized animals, the mouth is located at the anterior end but that"s not the case in flatworms, and their mouth is located on the ventral surface. The mouth connects with an incomplete gut that branches to varying degrees throughout the body or disappears completely in some of the parasitic species. Triplobast acoelomates: the platyhelminthes are the first triploblastic animals and have a third tissue layer, the mesoderm, added between the ectoderm and endoderm that cnidarians had. Can now have muscles, formed from mesoderm: flatworm"s mesoderm is solid without a cavity, a coelom, inside.
