Question

Which of the following are excretory products in animals?
A. Urea
B. Uric acid
C. Ammonia
D. All of the above

Answer 1

Hint:- The removal of waste products and excess substances from the internal environment and the external environment of the body is called excretion. A number of metabolic wastes are produced inside our cells which have toxic effects if they are retained in the body itself. The timely removal of these metabolic wastes is very essential. Different animals have different excretory organs.

Complete Answer:-
Animals are classified according to the type of nitrogenous compounds they excrete. Animals excreting ammonia are called an ammonotelic. Ammonia is the most toxic nitrogenous waste and should be eliminated as soon as it is formed. This form of excretion is exhibited by freshwater and marine invertebrates, larval and permanently aquatic amphibians etc. Ammonia formed diffuses out through their cell membrane and dissolves in water.
Uric acid is the least toxic nitrogenous waste material. Less amount of water is required for its elimination. Therefore it can be eliminated as paste or crystals. This form of excretion is exhibited by terrestrial insects, reptiles and birds.
Urea is less toxic than ammonia. Animals that excrete urea as the main metabolic waste are called ureotelism. Urea can be accumulated in body fluids or blood to a certain extent without significant toxic effects. Ammonia formed during the deamination of amino acids reacts with carbon dioxide forming urea.
Therefore ammonia, urea and uric acid are the excretory products in animals.

Thus the correct answer is option (D). All of the above

Note:- Besides ammonia urea and uric acid other nitrogen is waste formed in animals are creatinine, trimethylamine oxide,ornithuric acid, allantoin etc. Different types of excretory organs are seen in animals. In lower animals, protonephridia, metanephridia, green glands, coxal gland Malpighian tubules, proboscis gland etc. are present. The human excretory system consists of a pair of kidneys, a pair of ureters, urinary bladder and urethra.