Metamorphosis of a Frog

During the rainy season frogs are often seen near ponds. Frogs lay thousands of eggs at one time. The eggs are laid in ponds. These single-celled eggs, collectively known as frogspawn, are protected by a jelly-like covering.

Slowly, the eggs develop into embryos, over a period of 21 days. Each embryo divides and re-divides, to form gills, a tail and other organs.

In this early developmental stage of the frog, the embryo leaves its jelly shell, and attaches itself to a weed in the water, with the help of its sucker. The embryo soon turns into a tadpole, detaches itself from the weed, and starts swimming in the water.

Its long, vertically-flattened tail helps it to swim, and because it has gills, it is able to respire in the water. Tadpoles are herbivorous and feed on algae. In a few weeks’ time, a tadpole begins to grow. Its gills disappear and lungs begin to develop. At this stage, the hind limbs grow, followed by the fore limbs. In about nine weeks, the mouth widens, the limbs grow, the tail becomes smaller, and the tadpole becomes a froglet, and is more like a frog.

By this time, the lungs start functioning, and, in order to breathe, the froglet needs to be on land. At the end of the tadpole stage, the body undergoes a sudden transition and the tadpole develops into an adult frog with lungs, limbs, and no tail. The frog then spends its life mostly on land, and swims occasionally. An adult frog finds a mate. The female lays eggs, which are then fertilised by the male, and the whole process repeats itself again.