Ask a Teacher

For frog,ammonia is a eliminated as a waste.but for its tadpole urea is eliminated instead of ammonia.Why?

Dear Student,

There is a small mistake in your question, that is frogs eliminate urea and tadpole eliminates ammonia. Further explanation is given below:

Animals are categorised on the basis of their nitrogenous waste products. They are:

1. Ammonotelic animals are animals which excrete nitrogenous wastes as ammonia.
2. Ureotelic animals are animals which excrete nitrogenous wastes as urea.
3. Uricotelic animals are animals which excrete nitrogenous wastes as uric acid.

Hence, Tadpole is ammonotelic because it lives in water and has a large volume of water that is needed for the elimination of ammonia. It can eliminate ammonia was rapidly as it is formed, into the surrounding water.

Adult frog is ureotelic because urea is far less toxic than ammonia and can be concentrated in the urine and excreted at slower rate.

Note: Birds excrete their nitrogenous wastes in the form of uric acid, because they do not have access to have large amount of water that is needed for the elimination of ammonia.