Question

The following substances are the excretory products in animals. Choose the least toxic form among them.
(a) Urea (b) Uric acid
(c) Ammonia (d) Carbon dioxide

Answer 1

Uric Acid is the least toxic. Insects, land tortoises, lizards and birds change most of their nitrogenous waste into uric acid. It is the least toxic because it is insoluble in water as they are in solid form hence contains the least amount of water.

• In birds, uric acid mixes with undigested food to form the bird dropping.
• Urea gets dissolved into the blood to get filtered and eliminated with water in urine via the kidneys.
• Ammonia is very toxic and needs water for diffusion.
• Carbon dioxide excretion takes place through the lungs.