Excretion is important because of the following reasons - It helps in the elimination of nitrogenous wastes formed during the metabolism of proteins (amino acids) and nucleic acids.Removes the excess salts like common salt (NaCl), vitamins, bile pigments (from the breakdown of old RBCs)Removes the excess water or its retention just in case of shortage. This also helps to take care of the specified quantity of water – osmoregulation within the body.