Uric Acid

The excretory system functions in ridding the body of nitrogenous (nitrogen-containing, discussed below) and other wastes. Nitrogenous wastes of animals are excreted in form of ammonia, urea, or uric acid. They are excreted in the urine. Because ammonia is so water-soluble, aquatic animals often can get rid of it just by diffusion into the surrounding water. That’s one reason why the water in your aquarium gets “bad” and needs to be changed, and why not changing the water could kill the fish. However, ammonia doesn’t readily go from body fluids into air, so terrestrial animals need other ways of getting rid of nitrogenous wastes.