question_answer 9)

Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic, why? 

Answer:

Terrestrial adaptation requires the production of lesser toxic nitrogenous wastes like urea and uric acid for the conservation of water. Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals. Ammonia produced by metabolism is converted into urea in the liver of these animals and released into the blood which is filtrated and excreted out by the kidneys. Some amount of urea may be retained in the kidney matrix of some of these animals to maintain a desired osmolarity. Reptiles, birds, land snails and insects excrete nitrogenous wastes as uric acid in the form of pellet or paste with a minimum loss of water and are called uricotelic animals.