The word amphibian means two lives. This is very fitting for most amphibians, as they spend part of their lives in water and part of their lives on land. Frogs, for instance, lay their eggs in water which then hatch into tadpoles. The tadpole looks more like a fish than a frog. It has only a tail -- no arms or legs -- and swims through the water. As the tadpole ages, it develops arms and legs while the size of its tail shrinks. When the tadpole, now a frog, is old enough, it leaves the water and spends the rest of its life on land. This process of change is called metamorphosis.
Amphibians are divided into three main categories: caecilians, salamanders, and frogs or toads. Amphibians are similar to reptiles, except amphibians have scaleless, moist skin. Most amphibians are very small, less than 2 inches long. There are exceptions, however. For instance, the world's largest amphibian, the Japanese giant salamander, is 5 feet long!
Amphibians are found on all corners of the globe. They live everywhere except Antarctica. Amphibians usually live near sources of water or other moist areas. This is because an amphibian has to stay moist or else it may dry out. Some amphibians, however, are able to live in dry places and accomplish this feat by living in underground collections of water, staying there for weeks or even months.
Frogs and toads are creatures you are probably familiar with. They have short front arms and long back legs that help them move around by hopping. Frogs tend to be slippier than the rougher toads and also have longer legs. You may have heard that toads give you warts but this is not true. There are about 2,700 types of frogs and toads.
Salamanders look similar to lizards, but they have no scales. Their skin is slick and moist like most other amphibians. Salamanders typically live in areas where there are seasons and are most common in Central and South America. There are about 330 types of salamanders.
Caecilians have no arms or legs. They look like big worms or small snakes. They live in tropical regions such as Southeast Asia, India, and some parts of Africa. They are most commonly found in South America. There are about 150 species of caecilians.
Amphibians usually eat insects and are important in maintaining the balance of nature. Without amphibians, there would be way too many insects. Some larger amphibians, such as bullfrogs, may also eat snakes, birds or other small animals. Amphibians are eaten by snakes, mammals, birds, other amphibians, and even people. Amphibian larvae such as tadpoles live off a diet of algae and may be eaten by water creatures such as fish or turtles.
Amphibians have been around for over 350 million years. Scientists suppose that amphibians may have been some of the first land creatures. Scientists further believe that the amphibian evolved from the lobe-finned fish. These fish had lungs that allowed them to move on land for short periods of time and fins that worked much like legs. It is very likely that these fins became legs through many generations of natural selection.
Amphibians are amazing creatures that play a very important part in our ecosystem. They come in many shapes, sizes and colors. Most importantly, they need moist, humid areas to survive. Unfortunately, humans are destroying many of these environments and putting these creatures at risk. Because amphibians are so delicate, they need our protection and respect. You can help protect amphibians by donating to the World Wildlife Fund or by working to help protect the rainforest.