Which nitrogenous waste is least toxic and requires the least amount of water for excretion?
Uric acid is the least toxic nitrogenous waste and is excreted as a paste with minimal water loss in birds and reptiles.
Ref: NCERT Class 11 Biology Chapter 16: Excretory Products and their Elimination Modes of Excretion - Ammonotelism Ureotelism Uricotelism