lecture 3 - Hydrostatic skeleton fluid filled cavity that...

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Hydrostatic skeleton – fluid filled cavity that works like a water balloon Most efficient when body cavity is completely enclosed Contractile cells can act against it to allow the organism to move incertain ways Can move around independently of the rest of body True ceolom Body cavity that is completely lined with mesoderm Pseudoceolom Body cavity that is partily lined with mesoderm but also partly lined with endoderm Does not represent primitive condition but descended from true coelom but developmental pattern change Aceolom Descended from true ceolomates but have become simplified Gastrovascular cavity Radially symmetrical animals Only one opening One-way digestive system One way of movement of materials through the system Two openings Archenteron – forerunner of the digestive system (primitive gut) Opening to outside is called the blastopore Blastopore can become mouth or anus Protostomes blastopore develops into the mouth and the anus difevelops later at a different location Deuterostomes blastopore becomes the anus and mouth develops later Open vs. closed circulatory system Closed – what we have, all of the circulation is in blood vessels o Most efficient Open – some in blood vessels
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lecture 3 - Hydrostatic skeleton fluid filled cavity that...

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