Eggs → Tadpoles with small tails → Tadpoles with tails on two hind legs → Tadpoles with tails on two front legs → Little frogs without tails → Growing frogs.

After about 40 days, a series of changes have taken place in tadpoles.

2. Grow hind limbs first, and then grow forelimbs.

3. The tail gradually becomes shorter and finally disappears.

4. The internal gills gradually atrophy and disappear, and at the same time, lungs are formed in the body for breathing.

5. The heart becomes two atria and one ventricle, and the blood circulation path changes from one to two.

6. At this time, tadpoles have developed into young frogs, and they can go ashore without water, live by water and continue to develop into frogs.

7. Summary: The development process of frog from larva to adult is similar to insect metamorphosis, and its morphological structure and living habits have changed significantly. So the development of frogs is also metamorphosis.