Different frog varieties have different reproductive methods. Most species, however, start life as tadpoles and grow into adult frogs. Many people find this process fascinating to watch and raise tadpoles in captivity so they can watch the tadpole grow and change. It can take from 11 to 16 weeks for a tadpole to fully mature into a frog, depending on the frog species.
Before they are tadpoles, baby frogs are eggs. When most frog species reproduce, they do so with the male sitting on top of the female. The female release her eggs into the water and the male fertilises them as they are laid. Many eggs are laid at once because the adult frogs do not stay and take care of the eggs. As a result, not all of the eggs will hatch because they will be eaten by ducks, fish and insects.
Tadpoles emerge from the fertilised eggs anywhere from three to 25 days after fertilisation. To stay safely hidden from predators, a newborn tadpole immediately attaches itself to a plant in the water. At this stage, the tadpole is very small and looks like a head with a long tail attached to it. The newborn feeds on tiny algae plants that are drifting through the water. The tadpole breathes using gills and cannot leave the water at this stage of development.
It does not take long before tadpoles need to eat more food than what floats by the plant they are attached to. At about six weeks old, tadpole's tails become longer so that they can more easily swim trough the water to find food. At this point, the tadpole will begin to grow back legs, which are quickly followed by front legs. Eyelids and thicker skin also form. The tadpole's body starts to slowly absorb the gills. After the legs are fully developed, the tadpole's longer tail will shrink and eventually be absorbed into the body.
At birth, a tadpole is essentially a head with eyes and a tail. Many internal changes must occur before a tadpole is ready to be a land dwelling frog. As a tadpole grows, she will develop bones. Teeth and the long tongue frogs are known for form while a tadpole is transforming into a frog. The tadpole must also grow some new internal organs, the most important of which are the lungs. Unlike tadpoles, adult frogs live on land rather than in the water, making it necessary to trade gills for lungs.
When all of the necessary changes and adaptations have been made, what was once a tadpole hops onto land as a fully formed adult frog. The mature frog will occasionally swim through water but will spend most of her time on land, feeding on insects. When mating season comes around again, the frog will find a mate and lay or fertilise another batch of tadpole producing eggs.