Aquatic animals generally are ammonotelic

Organisms which generally excrete ammonia as nitrogenous wastes are said to be ammonotelic in nature.

Excretion of urea requires a large amount of water which can only be provided by aquatic animals while on the other hand, terrestrial animals cannot afford to lose so

much water. The terrestrial mammals or even amphibians mainly excrete nitrogenous wastes in form of urea and hence are known as ureotelic organisms