| About 4,000 species of frogs and toads are known to scientists, and  another ten to twenty species are discovered each year. They are very sensitive  to changes in the environment. Because of this they are disappearing faster  than most other wildlife. |  | 
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Frogs lay their eggs in the water. The eggs hatch out into tiny tadpoles which cling to the pond weed.
The tadpoles grow larger and breathe through feather -like external gills on the side of the head. At this stage the frog grows legs.
At the metamorph stage, the almost mature frog bresathes with lungs and still has some of its tail
The adult frog breathes with lungs and has no tail (it has been absorbed by the body).