UPSC MAINS 2018 DAF
DAF for mains 2018 has been out
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CANAL SYSTEM IN Porifera
Canal system in Porifera (sponges) Body of all sponges is the perforated by large number of apertures through which water enters Inside body and flows through a system of criss-crossing canals collectively forming the canal system which is a characteristic feature of poriferans. Following types of canal systems are found in sponges: Ascon type, with flagellated spongocoel Sycon type, with flagellated radial canals Leucon type, with flagellated chambers Rhagon type, with conical shape and broad base ASCON TYPE This is the simplest type of canal system and is found in Leucosolenia and other homocoela. Ostia are present on the surface of body and lead directly into the spongocoel, which is lined by flagellated choanocyte cells. Spongocoel opens to the outside through a narrow circular opening, the osculum located at the distal free end of the sponge body. Water enters through ostia into spongocoel and goes out of body through the osculum . SYCO...
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