Question

An aquarium fish and a pigeon were fed on protein diet. In what different forms would they excrete their nitrogenous wastes? Why do they excrete so differently?

Answer 1

An aquarium fish excrete ammonia whereas a pigeon excretes uric acid. Ammonia is highly toxic and needs to be eliminated as rapidly as it is formed. A fish living in water have immediate access to water and can eliminate ammonia easily and directly. Ammonia being soluble in water requires a large volume of water for its elimination which a fish can afford. A bird has very less access to water and can conserve water in its body by eliminating insoluble uric acid crystals.