Question

One of the following excrete urea
A. Snakes
B. Birds
C. Insects
D. None of the above

Answer 1

Hint: Excretion helps in the removal of carbon dioxide, water, and other harmful substances from the human body. All vertebrate animals excrete nitrogenous waste in form or another. Ammonia, urea, and uric acid are the most common forms of nitrogen excreted. The availability of water for the organism is a major determining factor for the type of waste excreted.

Complete step by step answer:
-Nitrogen has various physiological functions such as acid-base regulation, osmoregulation, and buoyancy.
-The proteins are hydrolyzed in the body to generate a pool of amino acids. But the amino acids cannot be stored for long.
-The unused amino acids are then catabolized to form ammonia which is then excreted as urea or uric acid.
-Nitrogen constitutes a major part of the excreta.
-A wide number of factors determine the form in which the nitrogen is excreted.
-Aquatic animals are highly tolerant to elevated levels of ammonia in their blood.
-Therefore they along with invertebrates and amphibians excrete ammonia as ammonia is highly water-soluble.
-Terrestrial animals mostly excrete nitrogen only in the form of urea or uric acid in order to conserve water.
-Urea requires 10 times less water than ammonia.
-Uric acid is insoluble and therefore requires 50 times less water than ammonia.
Therefore, None of the above excrete urea. So, the correct answer is option (D).

Note: Animals that excrete nitrogen in the form of uric acid are referred to as uricotelic organisms. The animals that excrete it in the form of ammonia are known as ammonotelic organisms and the ones that excrete in the form of urea are called ureotelic organisms.