Animals excrete waste in different forms:

• Ammonia (Ammonotelic animals) – Highly toxic, requires large amounts of water (e.g., fish, amphibians).

• Urea (Ureotelic animals) – Less toxic, requires moderate water (e.g., mammals, amphibians).

• Uric Acid (Uricotelic animals) – Least toxic, excreted as a paste to conserve water (e.g., birds, reptiles).