BIOL 202 Chapter Notes - Chapter 11: Zygote, Osculum, Mesohyl
18 Jun 2015
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Supported by skeleton that may consist of microscopic needlelike spikes called spicules: formed by amoeboid cells, made of calcium carbonate or silica. Alternatively skeleton may be made of sponging: fibrous protein made of collagen. Do not have nerve cells to coordinate body functions. Most reactions result from individual cells responding to stimulus: e. g. water circulation minimum at sunrise, maximum at sunset because light inhibits the constriction of porocytes and other cells surrounding ostia, keeping incurrent canals open. Other reactions do suggest some communication among cells: amoeboid cells transmitting chemical messages and ion movement over cell surfaces are possible control mechanisms. Have precursor genes for the post-synaptic proteins used in other invertebrates: first evidence of neurological system. Diffusion: large volumes of water filtered so nitrogenous waste (principally ammonia) and gas exchange occurs by diffusion) Suspension feeder (a few sponges are carnivorous deep-water, can capture small crustaceans)
