Breathing as Tadpoles
Frogs are small animals classified as amphibians. They begin their lives as tadpoles, which are tiny fish-like creatures. They have no neck and resemble a round form with a tail. Tadpoles are found swimming in mud puddles, ponds or other bodies of water. During this period of their life, they breathe using internal gills hidden under their skin.
Tadpoles evolve into adult frogs, developing legs and eventually loosing their tails. This process might take anywhere from a few weeks (for tadpoles in temporary ponds) or up to three years for a bullfrog. During this process they begin developing lungs.
Just before its metamorphosis, when it changes into a frog, the tadpole will loose its gills. When it emerges from the water, the frog, still with a tail, will use its lungs for breathing. Its breathing is controlled by its pulsing throat during both the tadpole and frog stage of their life.
Breathing as Frogs
When breathing, the frog will keep its mouth closed. Air is then drawn through the nostrils to the lungs. This action is caused by the movement of their pulsing throat. Body contractions enable them to release carbon dioxide. When a frog fills its lungs with air, it enhances its buoyancy when back in the pond. Tiny blood vessels beneath the outer skin layers also assist in the frog's breathing.
A concise summary of tadpoles as pets, touching on where to find them, how to feed them and metamorphosis.