Frogs breathe through their skin when underwater. Oxygen in the water can pass through their porous skin and go directly to the blood. They also have a pair of lungs that allow them to breathe when on land. They have a highly specalised sense of hearing detecting high-pitched sounds with their ears and low-pitched sounds through their skin.
They also have a highly developed sense of sight and smell enabling them to detect predators. Their sense of smell detects chemical signals that also help them identify a food source.