21.Which nutrient, when metabolized for energy, produces nitrogenous wastes? A. Amino acids B. Carbohydrates C. Lipids D. Vitamins E. Minerals 22.What is the waste product of fish? A. Urea B. Ammonia C. Uric acid D. Urine 23.Reptiles, birds, and insects excrete nitrogenous wastes in the form of: A. urea B. ammonia C. uric acid D. urine 24.Most mammals have uricase, which converts uric acid into ________. A. urea B. water C. ammonia D. allantoin 25.All of the following animals lack the enzyme uricase except: A. tigers B. dalmatian dogs C. apes D. humans  Â