The correct option is A is true but R is false
Explanation
Animals excrete nitrogenous wastes primarily in three forms: ammonia, urea, and uric acid. The specific mode of excretion adopted by an organism depends largely on the toxicity of the waste product and the availability of water in its environment.
Statement-wise Analysis
- Assertion (A) is Correct: Reptiles, birds, land snails, and insects are uricotelic animals. They excrete nitrogenous wastes in the form of uric acid. This is excreted as a pellet or thick paste, allowing for significant water conservation, which is an essential adaptation for terrestrial life.
- Reason (R) is Incorrect: Uric acid is the least toxic among the major nitrogenous wastes and requires the least amount of water for elimination. Conversely, ammonia is the most toxic form and requires large volumes of water to be excreted safely. Therefore, the claim that uric acid is the most toxic and water-intensive is factually wrong.
Key Takeaway: The hierarchy of nitrogenous wastes based on toxicity and water requirement for elimination is Ammonia > Urea > Uric Acid.