For example, a frog's heart has three chambers instead of four. And although adult frogs breathe by means of lungs, they also breathe through their skin. A few burrowing species have short hind legs and cannot hop. But all other frogs have long, powerful hind legs, which they use for jumping. Many frogs can leap 20 times their body length on a level surface.
Frogs also use their large hind legs for swimming.
Most water-dwelling species have webbed toes on their hind feet. The smaller front legs, or arms, prop a frog up when it sits. The front legs also help break the animal's fall when it jumps. Frogs that live in trees have tiny, sticky pads on the ends of their fingers and toes. The pads help the animal cling to the tree trunk as it climbs.