Question

Which of the following is uricotelic
A. Reptile
B. Birds
C. Insects
D. Land snails
A) A,B,C only
B) B and C only
C) A,D only
D) A,B,C,D

Answer 1

The animals whose end product of nitrogen metabolism is uric acid are termed as uricotelic. These organisms excrete urea as it is least toxic and the most limited soluble in water.

Complete answer:
Excretion of uric acid as the main product of nitrogenous waste is called as uricotelism. Uric acid is much less toxic as compared to ammonia and urea. It is almost insoluble and can be eliminated from the body in a nearly solid state, thus saving water. However, being the most complex molecule, it needs maximum energy for its formation from ammonia.
Uric acid excretion is advantageous for the animals which have to conserve water for their survival. Since the kidney can handle the nitrogenous waste only in solution, animals pass a dilute solution of uric acid into the last part of the gut. Here, water is absorbed and nearly solid uric acid is passed out with the faees. Thus, minimum water is lost. Uric acid can be stored in the cells, tissues and organs without any toxic effects. Animals which excrete uric acid are referred to as uricotelic. They also secrete some ammonium urate.
Reptiles conserve water in the body which usually reduces water by evaporation. Water is needed to flush out sodium and potassium ions are also saved. These ions combine with uric acid to form insoluble sodium and potassium urates which are excreted with uric acid.
Birds skin is selectively permeable to water and the loss of water by evaporation is done by feathers. Nitrogenous waste matter is uric acid. It is eliminated in hypertonic urine. It gets passed out with urine through cloaca.
Insects produce metabolic wastes such as urea and amino acids that freely diffuse into the tubules, while ions are transported through an active pump mechanism. Ions are secreted with the ions into the tubules which get out of the body with urine.
Land snails are terrestrial gastropod mollusks that have a shell. They also secrete urea as a by-product so as to reduce loss of water.

So, the correct answer is “Option D”.

Note:
The uricotelic animals conserve water in their bodies and synthesize crystals of uric acids from the ammonia. These crystals can be retained in the body in solid form for a considerable amount of time before being discharged from the body. The uricotelic animals differ greatly in structure, but all have the same enzymes needed for urea formation.