Question

Juvenile amphibians (i.e., amphibians that still live exclusively in water) excrete nitrogenous waste in the form of ammonia instead of urea. Why Ammonia is less toxic than urea Juvenile amphibians want to maximize energy expenditure Ammonia is not soluble in water and can be excreted as a paste Ammonia cannot be lost across the body surface via diffusion Synthesis of ammonia requires less ATP than synthesis of urea

Answer 1

Juvenile amphibians excrete nitrogenous waste in form of ammonia instead of urea because synthesis of ammonia requires less ATP than synthesis of urea.

Tadpole is ammonotelic and requires large volume of water which needed for the elimination of ammonia. It can eliminate ammonia rapidly as it is formed, into the surrounding water. But Adult frog is ureotelic because urea is less toxic than ammonia and can be concentrated in the urine and excreted at slower rate.