Question

Which of the following is not an excretory substance in humans?

• A. Carbon dioxide
• B. Excess water
• C. Bile pigments
• D. Ammonia

Answer 1

The correct option is D

Ammonia

Excess water, carbon dioxide, nitrogenous wastes (urea, uric acid, and creatinine) and bile pigments are the excretory substances in animals. However, the chief excretory products - urea, uric acid and ammonia, differ in different organisms. Most aquatic animals are ammonotelic, meaning, they excrete ammonia. However, ammonia is not an excretory substance in humans. Ammonia is converted into urea and then is excreted.