Only the male frog has vocal sacs that fill with air and act as a resonator to amplify their mating calls, much like the box on a guitar.
The largest living species of frog in the world is the Goliath frog, which can grow to lengths of 13 inches and weighs about 8 lbs.
Insects and amphibians are the only creatures that go through the process of metamorphosis, and amphibians are the only animals with a backbone that can metamorphose.
Cold-blooded and incapable of regulating their body temperatures, amphibians are the most primitive class of land-living vertebrates, and the first to emerge from an aquatic environment to live on land for much of their adult lives.