Frogs belong to chordates, amphibians, Anura and Ranidae. Frog's head is flat, slightly triangular and its snout is slightly sharp. The mouth is wide and horizontal, and consists of upper and lower jaws. There are 1 external nostril at the front end of the dorsal maxilla, and there are alars at the outer edge of the external nostril. Adults are tailless, eggs are laid in water, fertilized in vitro, hatched into tadpoles, and breathed through gills. After the mutation, adults mainly breathe through the lungs and skin.
Frogs breathe with their lungs, but they can also draw oxygen from the air through wet skin. Various pigment cells in its skin will also expand or contract with the change of humidity and temperature, thus changing the depth of skin color. Frogs usually inhabit rice fields, ponds, ditches or grass by the river, sometimes they lurk in the water and usually hunt at night.