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An ammonotelic organism excretes nitrogenous waste as soluble ammonia. Most of the aquatic animals including protozoans, crustaceans, platyhelminths, cnidarians, poriferans, echinoderms, fishes, larvae / tadpoles of amphibians are ammonotelic. A ureotelic organism excretes excess nitrogen as urea. Urea is less toxic and needs less water in comparison to Ammonia. Ureotelic organisms include cartilaginous fish, few bony fishes, adult amphibians and mammals including humans. The uricotelic organism excretes uric acid or its salts. In comparison to Ammonia and Urea, Uric acid is the least toxic and the least soluble in water. It can be stored in cells and body tissues without toxic effects and thus needs least water and is highly efficient mode of excretion in comparison to two other methods. Uricotelic organisms include terrestrial arthropods (including insects), lizards, snakes, and birds. The excreta of uricotelic organisms is typically white paste.