Why do many amphibians go through metamorphosis?

Metamorphosis allows amphibians such as frogs and many salamanders to exploit two different environments during their lives. The larval stage is usually adapted for growth in water, while the adult stage often develops lungs, limbs, and body structures better suited to land. Thyroid hormones, especially thyroxine, drive much of this transformation. This life-cycle change helps reduce competition between young and adults and makes use of different habitats and food sources. It is one of the defining traits of amphibian biology.