In which form the mammals excrete out nitrogen ?

The correct answer is (d), all of these. Mammals excrete nitrogen in the form of ammonia, urea, and uric acid. The form of nitrogen excreted depends on the animal’s diet and environment.

• Ammonia is the most toxic form of nitrogen and is the primary form of nitrogen excreted by aquatic animals. It is also the primary form of nitrogen excreted by young mammals, as their kidneys are not yet developed enough to excrete urea or uric acid.
• Urea is a less toxic form of nitrogen and is the primary form of nitrogen excreted by adult mammals. It is produced in the liver from ammonia and carbon dioxide.
• Uric acid is the least toxic form of nitrogen and is the primary form of nitrogen excreted by birds, reptiles, and insects. It is produced in the liver from ammonia and glutamine.

The form of nitrogen excreted also affects the animal’s water requirements. Ammonia is highly soluble in water, so animals that excrete ammonia must drink a lot of water to maintain their body fluids. Urea is less soluble in water than ammonia, so animals that excrete urea do not need to drink as much water. Uric acid is the least soluble form of nitrogen, so animals that excrete uric acid can survive on very little water.