Amphibians use their kidneys and bladder for excretion. The bladder is used to store the urine before it is excreted outside of the body. This urine is what allows amphibians to come onto land because it provides it with the water reserves.
Amphibians have a hard time keeping balance and their body.
They are known as terrestrail animals meaning they can live on land. However, the have not adapted to life on land very well. While on land, they lose water very quickly because of evaporation. And when in fresh water they can suffer from osmosis. This is when they excrete diluted urine in a large volume.
They also excrete nitrogen in the form of urea.

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