The correct option is 1 and 3 only.
Explanation
Animals excrete nitrogenous wastes generated during metabolic activities. The three major forms of nitrogenous wastes are ammonia, urea, and uric acid. The form of waste produced depends primarily on the toxicity of the substance and the availability of water for its elimination.
Statement-wise Analysis:
- Statement 1 is Correct: Ammonia is the most toxic form of nitrogenous waste. Because of its high toxicity, it cannot be stored in the body and must be eliminated immediately or converted into less toxic forms.
- Statement 2 is Incorrect: Uric acid is the least toxic among the three major nitrogenous wastes. Consequently, it can be removed with a minimum loss of water. It is typically excreted in the form of a pellet or paste, which is an adaptation for water conservation in animals such as reptiles, birds, land snails, and insects (uricotelic animals).
- Statement 3 is Correct: Due to its high toxicity, ammonia requires a very large volume of water for dilution and elimination. Urea is significantly less toxic than ammonia and therefore requires less water for excretion. Uric acid requires the least amount of water.
Key Takeaway:
The order of toxicity for nitrogenous wastes is Ammonia > Urea > Uric Acid. The requirement of water for elimination follows the same order: Ammonia > Urea > Uric Acid.