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Symmetry


Animals can be categorised on the basis of theirsymmetry. Sponges are mostly asymmetrical,i.e., any plane that passes through the centredoes not divide them into equal halves. Whenany plane passing through the central axis ofthe body divides the organism into two identicalhalves, it is  called radial symmetry.Coelenterates, ctenophores and echinoderms have this kind of body plan Animals like annelids, arthropods, etc., where the body can be divided into identical left and right halves in only one plane, exhibit bilateral symmetry
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