Hint: Ammonotelic organisms include organisms living in water bodies such as bony fishes, aquatic amphibians, and aquatic insects as ammonia requires a large amount of water. Ureotelic animals include mammals, terrestrial amphibians, and marine fishes.
A living organism carries out metabolic reactions constantly in order to stay alive. The products of these metabolic reactions are mostly non-useful and toxic for the living tissues and thus have to be excreted to keep the body in optimum conditions. Most of the excretory products are nitrogenous wastes such as ammonia, urea, and uric acid.
Ammonia is the most toxic form of nitrogenous waste and thus requires large amounts of water so that the living tissue is least harmed. Animals like bony fishes that excrete ammonia are known as ammonotelic animals. As ammonia is readily soluble, it diffuses out of the body surface or gill surface through diffusion as ammonium ions. Thus, ammonotelic organisms do not require any specialized excretory structures like kidneys.
As animals started to adapt to become terrestrial, large amounts of water were not available to them for the excretion of ammonia. Thus, such animals developed metabolic reactions in their body which converts ammonia into less toxic forms like urea or uric acid. These nitrogenous wastes could be excreted from the body with less water resulting in the conservation of water. Such animals that excrete urea are known as ureotelic animals. Examples include mammals, terrestrial organisms like amphibians, etc. Ammonia is converted into urea inside the liver of the body, and kidneys filter out the urea from the blood.
Note: -Animals that excretes uric acid require a minimum amount of water as it is the least toxic nitrogenous waste.
-Such animals are known as uricotelic animals and examples include reptiles, birds, land snails, insects, etc.
-The excretory structures that are seen in insects are Malpighian tubules which help in osmoregulation and excretion.