IntroductionPorifera (pōrĭfˈərə) [key] [Lat., = pore bearer], animal phylum consisting of the organisms commonly called sponges. It is the only phylum of the animal subkingdom Parazoa and represents the least evolutionarily advanced group of the animal kingdom. All adult sponges are sessile (nonmotile), and nearly all are marine; there are four families of freshwater sponges. Sponges are subdivided into three classes.
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