Question

The characteristic that is shared by urea, uric acid and ammonia is/are
(A) They are nitrogenous wastes.
(B) They all need very large amount amount of water for excretion.
(C) They are all equally toxic.
(D) They are produced in the kidneys.

• A. A and C
• B. A and D
• C. A, C and D
• D. A only

Answer 1

The correct option is D A only

Animals excrete a variety of nitrogen waste products, but ammonia, urea and uric acid predominate. A major factor in determining the mode of nitrogen excretion is the availability of water in the environment. Generally, aquatic animals excrete mostly ammonia, whereas terrestrial animals excrete either urea or uric acid. Ammonia, urea and uric acid are transported across cell membranes by different mechanisms corresponding to their different chemical properties in solution. Mammals such as humans excrete urea, while birds, reptiles, and some terrestrial invertebrates produce uric acid as wastes. Uricothelic organisms tend to excrete uric acid waste in the form of a white paste or powder. Producing uric acid instead of urea is advantageous because it is less toxic and reduces water loss and the subsequent need for water.