Question

The chief nitrogenous waste in urine of rabbit or terrestrial mammals is
A) Urea
B) Uric acid
C) Ammonia
D) None of the above

Answer 1

Hint: This nitrogenous waste is formed from the ammonia in the liver of rabbit or terrestrial mammals. It is then released into the blood for elimination. The filtration of blood is done by the kidney. These animals are called ureotelic animals.

Complete answer:
Nitrogenous wastes are toxic and hence harmful for the body. So, it is important to eliminate these products from the body as soon as possible. Almost all animals eliminate the nitrogenous waste from their body in the form of ammonia, urea or uric acid.

The animals in which the nitrogenous wastes are eliminated from the body in the form of ammonia are called ammonotelic animals. As ammonia is very toxic, a large amount of water is required for its removal. Examples of ammonotelic animals include aquatic amphibians, aquatic insects and bony fishes.

To prevent the loss of water for excretion of ammonia, most of the animals are adapted to eliminate the nitrogenous waste in the form of urea and uric acid. The animals in which nitrogenous wastes are eliminated from the body as urea are called ureotelic animals. Examples include terrestrial mammals such as rabbits and some fishes.

Uricotelic animals are those in which nitrogenous wastes are removed as uric acid. Examples include snails, insects, birds and reptiles. The removal of uric acid involves minimum loss of water as it is least toxic.

Thus the answer of the above question is Urea as it is present in the urine of mammals and terrestrial animals. As ammonia is very toxic and involves maximum loss of water, it is converted into urea in the liver and excreted out of the body with the help of kidneys.

Hence the final answer is option ‘A’ i.e, ‘Urea’.

Note: Kidney is the main excretory organ in ureotelic animals. It filters the blood and helps in the excretion of urea out of the body. Apart from this, it also perform other functions such as osmoregulation, pH regulation, production of hormones etc.