life cycle of the frog
The stages of development are the egg, the tadpole and the adult; each stage usually lasts several weeks, but can last up to two years in some species.
tadpole 
Aquatic larva of the frog having a large head and a slender body ending in a tail; it breathes through gills.
forelimb 
The forelimbs appear during the last stage of the tadpole’s metamorphosis.
hind limb 
The hind limbs appear after the gills.
operculum 
Thin bony plate of skin covering the gills and having a posterior valvular opening, the hearing organ.
external gills 
Respiratory organs that filter water and take in food particles; they are later replaced by internal gills.
eggs 
Embryonic stage of the frog resulting when the egg is fertilized by the sperm.