Correct Option
The correct option is Birds.
Explanation
Animals excrete nitrogenous wastes in three primary forms: ammonia, urea, and uric acid. The mode of excretion depends largely on the availability of water in the animal's environment. The toxicity of these waste products varies, with ammonia being the most toxic and uric acid being the least toxic.
Detailed Analysis
- Birds (Correct): Birds are uricotelic animals. They convert nitrogenous waste into uric acid, which is insoluble in water and is excreted as a semi-solid paste or pellet. This process requires a minimal amount of water, serving as a crucial adaptation for water conservation in terrestrial environments.
- Mammals (Incorrect): Mammals are primarily ureotelic. They excrete nitrogenous waste in the form of urea. While urea is less toxic than ammonia and requires less water for excretion than ammonia, it requires significantly more water than uric acid.
- Amphibians (Incorrect): Amphibians exhibit different modes of excretion depending on their habitat and life stage. Aquatic forms (like tadpoles) are generally ammonotelic (excreting ammonia), while terrestrial adults are typically ureotelic (excreting urea). They do not primarily excrete uric acid.
- Prawns (Incorrect): Prawns are aquatic crustaceans and are primarily ammonotelic. They excrete ammonia directly into the surrounding water, as ammonia is highly soluble and requires a large volume of water for safe elimination.
Key Takeaway
Uricotelism (excretion of uric acid) is an adaptation found in birds, reptiles, land snails, and insects to minimize water loss. Uric acid is the least toxic nitrogenous waste and can be eliminated with the least amount of water.