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Lecture 15 – Parazoa, Eumetazoa Radiata

Lecture 15 – Parazoa, Eumetazoa Radiata -...

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Lecture 15 – Parazoa, Eumetazoa: Radiata A. Porifera - The sponges - The only phylum name under parazoa 1. Mostly marine (fig. 29.9) - Found in salt water 2. 3 Classes – they have 3 classes because in sponges they have things that looks like pick- up-sticks (that’s their skeleton; they are made of different materials) a. Calcispongiae - Have support systems made of calcium carbonate b. Hexactinellida - Known as the “glass sponges” - Skeletons made of silica c. Demosporangia - Made of a protein called spongin, that keeps them soft - These are the bath sponges 3. Body plan (fig. 29-9) - This organism is multicellular, meaning there is a division of labor It is felt however, that it is not unified enough to be a tissue, if there is no tissue level there is no organ level, if there is no organ level there is no system level a. Sac – pores, spongocoel, osculum - A sac with pores in it, a nd two important parts are the spongocoel and osculum The central cavity is called the spongocoel The opening at the top is called the osculum b. Epiderm al cells – on the outside of the spong e Collar cells (choanocytes): this is the inner-m ost layer of cells; cells ar e flagellated c. Mesohyl – a thin jellylike m at erial that keeps the e pider m al cell and choanocytes s ep arat ed d. Skelet al spicules – a loose n etwork of skeletal spicules that supports the spong e
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e. Amoebocytes – amoeba-like cells; they move around inside; one of the functions is th   will secrete the skeletal spicules and can create gametes
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Lecture 15 – Parazoa, Eumetazoa Radiata -...

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