The chief nitrogenous waste product of humans is

Explanation

Surplus amino acids are deaminated in the liver and the toxic ammonia produced is converted at once into far less toxic urea by the ornithine cycle, which the blood then carries to the kidney. Ammonia is too poisonous to accumulate and is excreted directly only by animals surrounded by water, such as bony fish. Uric acid is the main waste of birds, reptiles and insects.