Which type of organism would likely use urea for waste elimination?

The use of urea for waste elimination is characteristic of organisms that live in environments where water conservation is critical, especially those that have adaptations to terrestrial or semi-aquatic lifestyles. Marine mammals, such as dolphins and whales, are known to excrete urea rather than ammonia. This is an adaptation to their environment, as it allows them to conserve water while effectively excreting nitrogenous waste. Urea is less toxic and requires less water for excretion compared to ammonia, making it advantageous for organisms that may not have access to large amounts of fresh water.

In contrast, birds primarily excrete uric acid, which is even less toxic and conserves water even more efficiently. Fish, on the other hand, typically excrete ammonia directly into the water, which is possible due to the abundant water available to dilute the ammonia. Land snails, while they may become desiccated, do not primarily utilize urea; instead, they have adaptations to retain moisture and eliminate waste in a way that suits their terrestrial living conditions.

Thus, marine mammals' reliance on urea as their primary waste product is a key adaptation that aligns with their need to conserve water in a saline environment, ultimately affirming the appropriateness of this choice.