Here's why:
* Tadpole Stage: Frog larvae (tadpoles) live entirely in water. They breathe through external gills located behind their heads.
* Metamorphosis: As tadpoles grow, they undergo metamorphosis, a dramatic transformation into their adult form. During this process, they develop lungs and lose their gills.
* Adult Stage: Adult frogs have lungs and can breathe air. They also have moist skin that aids in gas exchange, allowing them to absorb oxygen directly from the water for short periods.