diploblasts - A. Phylum Cnidaria 10,000 species, mostly...

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A. Phylum Cnidaria 10,000 species, mostly marine Radial symmetry Diploblastic Two tissue layers o o Tissue layers separated by mesoglea (“middle jelly”) Have a mouth surrounded by tentacles o Tentacles have nematocysts (stinging cells) Two morphologies: o Polyp Stage Sessile (stationary) Asexual o Medusa Stage Mobile Sexual o Both stages have a sac-like gut Only one opening into the digestive tract Nematocyst a structure that makes up the outer covering of tentacles o Unique to cnidaria o Cnidocil/”trigger” causes operculum to open o Operculum o Coiled thread inverted out as trigger releases it; attaches itself to prey o Functions in food acquisition and predator defense
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Have muscle-like cells that allow them to swim (not very effective) o Actin filaments used to contract cells No centralized nervous system—have a “nerve net” o Connected with ghanglia
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This note was uploaded on 04/29/2008 for the course BS 104 taught by Professor Wolbach during the Spring '08 term at University of the Sciences in Philadelphia.

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diploblasts - A. Phylum Cnidaria 10,000 species, mostly...

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