In this article we are going to learn about the life cycle of frog. Frog is an amphibian. It lives both on land and in water. The life history of frog starts in water. It has three stages in its life history. They are the egg, the larva and the adult.

Egg: The eggs of frog float on water. The eggs are surrounded by a jelly like substance. They are incubated by the warmth of sunlight. In about ten to fifteen days a larva comes out of the egg.

Larva: The newly hatched larva has a large head, a small trunk and a short tail. It has no mouth. There is a sucker at the anterior end on the ventral side. The larva attaches itself to the weeds by means of this sucker. It has two pairs of external gills for respiration. After about a week the larva develops into a tadpole larva.

Tadpole larva: The tadpole larva resembles a small fish. It develops a mouth, a third pair of external gills and a tail. The jaws have teeth. It feeds on plants. The intestine is coiled like a watch spring. The tail increases in size. It helps in swimming.

Metamorphosis: A series of changes take place in tadpole internally and externally to transform in into an adult frog. The tadpole larva of frog is fish like. It lives in water and breathes through gills. It grows in size and slowly transforms into a frog. During this transformation, the forelimbs appear. At the same time gills disappear and lungs will develop. At this stage, the small frog leaves water as it cannot breath, with lungs in water. Tail persists for some more time b ut finally it also disappears. The marked cahnge in the form of an animal during development is called metamorphosis. The metamorphosis in frog is initiated by a hormone called thryoxine. This is secreted by a gland know as thyroid.