Animals life cycles

Chapter five

Amphibians

Like fish, amphibians are cold-blooded vertebrates. Most amphibians live for some of their life in water and for some of their life on land. Salamanders, toads, and frogs are all amphibians.

Metamorphosis

All amphibians have two different parts of life. At first they are larvae that breathe in water through special gills. Then they change into adults with lungs. This change is called metamorphosis. Usually, amphibians live in water for the first part of their life and on land for the second part. Some salamanders live in water all the time.

Eggs and Larvae

Amphibians often lay thousands of eggs. The eggs have a sticky cover, and they float in water. Most amphibians do not care for their eggs, but the male midwife toad carries them on his back until they are ready to hatch.
The young that hatch from eggs are called larvae, but young frogs and toads are also called tadpoles. At first, tadpoles don't have legs or feet and they breathe through gills. It's easy for predators to catch and eat eggs and tadpoles. Frogs can lay about 2,000 eggs, but probably only 5% live to become adults.

The male Darwin's frog keeps his tadpoles safe and wet in his throat, until they are big enough to swim away.

Becoming Adults

When amphibians begin to change into adults, they grow lungs inside their body and their gills close. At the same time, most amphibians grow legs and feet.

An adult frog looks completely different from a tadpole!

Most adult amphibians can breathe through their skin and their lungs! They can only breathe through their skin if it's wet, so most amphibians live near water.
Amphibians are cold-blooded, so when it gets very cold they have no energy. Some amphibians in colder countries hibernate for the winter. They hide in a safe, wet place and go into a special, long sleep.

Breeding

Most amphibians go to wet places like ponds, lakes, or rivers to breed, because their eggs and larvae live in water. Many go back to the same place every year, and some go back to the pond or stream where they were born. Male frogs croak and shout to tell the females that they are ready to breed. They push their throats out so that their calls are louder. When the female has chosen a mate, she lays her eggs in the water, and the male covers them with sperm.