Stages of Frogs to Tadpoles & In Between

Frogs are small amphibians that have existed for more than 200 million years. They are found all over the world in moist environments such as marshes, ponds and streams. Frogs must live near water to obtain the moisture necessary for their survival and also to lay eggs that hatch into tadpoles. The small tadpoles develop into adult frogs through the process of metamorphosis, which can take weeks or months, depending on the species.

  1. Egg

    • Female frogs lay a sac of eggs that are then fertilized by the male frog. The eggs are contained in a jelly-like substance that provides nutrients to the developing embryos. The eggs absorb water, swell and then hatch into tadpoles.

    Tadpole

    • When tadpoles first hatch, they float around the water until they learn how to swim. Tadpoles in this stage are considered frog larvae and they resemble fish. Unlike frogs, tadpoles cannot survive out of the water. Tadpoles have no lungs; instead, they have gills, which they use to obtain oxygen. Tadpoles are primarily herbivores, feeding on vegetation such as pond algae, which they consume in large quantities to obtain the energy necessary for metamorphosis.

    Tadpole With Legs

    • Metamorphosis begins when a tadpole starts to develop legs. Once this process begins, tadpoles can no longer consume food and must rely on stored energy. Throughout metamorphosis, hormones regulate a number of changes in the tadpole. The gills disappear and are replaced by lungs; during this process tadpoles develop the ability to breathe through their skin. Simultaneously, the tadpole's arms start to develop. The tadpole's digestive system also changes, which will allow it to consume a carnivorous diet once it becomes an adult frog; as part of this change, a tadpole's mouth elongates, its tongue lengthens and it grows a jawbone. The final part of metamorphosis occurs when the tadpole's tail grows into its body.

    Froglet

    • Once metamorphosis is complete, a tadpole is considered a froglet. Froglets look like miniature versions of adult frogs with small, stubby tails. Once tadpoles have become froglets, they can start eating insects along with plants. Froglets must remain in the water until they become full-grown frogs.

    Frog

    • Once frogs are fully grown, they leave the water and are able to survive on land. Full-grown frogs have powerful legs for jumping. They are also able to camouflage themselves by changing color to blend in with their surroundings. Despite the large prevalence of frogs in certain regions, many species have become endangered; 32 species of frogs have now become extinct.