External features of the frog

The skin is smooth and slippery because of mucus, and it is always kept moist. The frog never drinks water; it absorbs water through its skin.

The dorsal side is generally olive green with dark irregular spots; the ventral side is uniformly pale yellow.

The body is divided into head and trunk only. A neck and a tail are absent.

A pair of nostrils lies above the mouth. The eyes are bulging and covered by a nictitating membrane that protects them in water.

On either side of the eyes lies a membranous tympanum (ear) that receives sound signals.

Fore limbs and hind limbs are used for swimming, walking, leaping and burrowing. Fore limbs end in four digits; hind limbs end in five digits and are larger and more muscular. The digits of the feet are webbed for swimming.

Frogs show sexual dimorphism. A male has sound-producing vocal sacs and a copulatory pad on the first digit of each fore limb; both are absent in the female.