Question

Marine teleost fishes excrete:
A. Uric acid
B. Ammonia
C. Urea
D. None of these

Answer 1

Hint: Excretion is the process of removing undigested food and metabolic waste from the body of an organism. Any metabolic waste product that contains nitrogen is called nitrogenous waste. There are three major types of nitrogenous waste present namely ammonia, urea and uric acid.
The waste in the body needs to be excreted out for normal functioning of the body.
Ammonia being the most toxic form requires a large amount of water to be removed from the kidney and uric acid is the least toxic form and requires a small amount of water to be excreted out.
Kidneys remove urea by the help of the structure and functional unit of the kidney called nephrons. These are tubular structures.

Complete answer:
URIC ACID:- This is the least toxic nitrogenous waste and requires very less amount of water to be removed. Terrestrial invertebrates, reptiles and birds produce uric acid to be excreted out. So this option is incorrect.
AMMONIA:- This is the most toxic form and requires a large amount of water to be removed.
Protozoans, crustaceans, platyhelminthes, cnidarians, poriferans, echinoderms, and other aquatic invertebrates excrete ammonia. Thus, this option is also incorrect.
UREA:- Urea is chiefly produced in the liver and excreted through the urine. Humans and marine teleost fishes excrete urea. So, this option is correct.
NONE OF THESE:- As marine teleost excrete urea. Thus, this option is incorrect.

Our correct option is c that is urea.

Note:
Urea is formed when protein rich in dairy products makes amino acids after digestion. The liver then converts the amino acid in excess amounts into ammonia, and finally converts into urea. Urea is not as toxic as ammonia and requires less amount of water.
The nephrons of the kidney are tubular structures and consist of glomerulus, bowman’s capsule and tubular parts like PCT, DCT and collecting duct.