RAH_20Lec_203_20__20Porifera_2C_20Cnida - Hough Lecture...

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Hough Lecture Outline – Porifera, Cnidaria, Ctenophora 1 Subkingdom Parazoa (no true tissue differentiation) PHYLUM PORIFERA Sponges (“Pore Bearers”) mostly marine (10,000 sp); some freshwater (150 sp) larvae motile; adult bodies sessile (attached to substrate) mostly irregular cell masses with no symmetry some with loosely organized vase shape structure body has many pores leading to internal water channels for environmental exchange (food, gases, wastes) no organs or organ systems (respiration and excretion are by simple diffusion) Specialized cell groups (not true tissues) epithelial – flat cells on outer surfaces choanocytes – collared flagellated cells on inner surface of water channels; create water current, and capture plankton food amoebocytes – motile cells in mesohyl zone between epithelium and choanocyte layers porocytes – lining of water pores, which allow outer seawater into water channels (exiting at top through osculum opening) support structures in mesohyl layer: crystals (lime) – Calcarea class spicules (silica) – six spined : Hexactinella class
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RAH_20Lec_203_20__20Porifera_2C_20Cnida - Hough Lecture...

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