The gradual development of an organism with a visible change in the external appearance is called Metamorphosis. The best example is that of a life cycle of a butterfly. The butterfly lays a number of eggs. Each egg hatches out to become a worm like creature called LARVA. The larva slowly feeds on leaves and grows into a Caterpillar. The caterpillar slowly moves and finds a safer place. It surrounds itself with a cocoon shaped covering and grows inside.It is called a PUPA. After some time a butterfly emerges out of the cocoon.

The life cycle can be given this way,

Butterfly - Egg - Larva - Caterpillar - Pupa - Butterfly

Similar is the life cycle of a Frog. The Frog being an amphibian lives both in water and land. A frog lays eggs in water.The tadpoles hatch out from them,just like fishes. They swim in water and reach the land. Slowly grow up as frogs.

Frog - Egg - Tadpole - Frog