The following substances are the excretory products in animals. Choose the least toxic form among them.

1. Urea

2. Uric acid

3. Ammonia

4. Carbon dioxide

(b) Uric acid is the least toxictions. 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 there are in solid form, thus, contains the least water. In birds, uric acid mixes with undigested foodto form the bird dropping.

Urea moves to blood get filtered and eliminated with waterin urine via kidneys.
Ammonia is very toxic and needs water for diffusion.
Carbon dioxide excretion takes place through the lungs.