Biology: Amphibians

Gills to Lungs

Source: National Geographic Kids

An amphibian is an ectothermic vertebrate that spends its early life in water.

Amphibian (double life)

After beginning their life in water, most amphibians spend their adulthood on land, returning to water to reproduce.

Most amphibians lay their eggs in water. Amphibian eggs hatch into larvae that swim and have gills for obtaining oxygen. As they undergo metamorphosis and become adults, most amphibians lose their gills and acquire lungs. Adult amphibians also obtain oxygen and get rid of carbon dioxide through their thin, moist skin.

Amphibian Circulation

Source: Natural History on the Net

The hearts of most amphibians have three inner spaces, or chambers. The two upper chambers of the heart, called atria, receive blood.

From the atria, blood moves into the lower chamber, the ventricle, which pumps blood out to the lungs and body.

Reproduction and Development

Source: Education.com

Most amphibians undergo metamorphosis. Hind legs appear first, accompanied by changes in the skeleton, circulatory system, and digestive system. Later the front legs appear. At about the same time, tadpole loses its gills and starts to breathe with its lungs.

Getting Around on Land

Most adult amphibians have strong skeletons and muscular limbs adapted for movement on land. Amphibians were the first vertebrates to have legs.

Although most tadpoles are herbivores, most adult frogs and toads are predators that feed on insects or other small animals.