The term "amphibian" derives from the Ancient Greek term amphibios, which translates to "both kinds of life," since amphi means "of both kinds" and bio means "life." While the term originally was used for all animals that could live on land or in water, it later was restricted to what we now call amphibians. These cold-blooded animals have four limbs, and they can only maintain their body temperatures at the level of their surroundings. There are three types (or orders) of amphibians: Anura, Caudata, and Gymnophiona.
The Anura order contains frogs and toads. Frogs and toads are classified in this order, since Anura means "absence of tail." While baby frogs have tails, the adult frogs are what the classification is based on. There are approximately 4500 species of frogs and toads spread across the globe. These amphibians can be found in all different sizes, from a few millimeters to a couple of feet. Frogs and toads have four limbs, with hind legs that are longer than the frong legs. This allows frogs and toads to climb and leap.
Frogs and toads make great pets if people research their needs. They come in many different colors and need different habitats, based on their origins. Frogs typically need water, and toads prefer to live on dry land.
The Caudata order contains salamanders, newts, sirens, waterdogs, mudpuppies, and amphiuma. These amphibians are classified in this order, since Caudata means "tail." There are approximately 500 species, but the number keeps growing as new discoveries are made. The tails on amphibians in the Caudata species tend to by as long, or longer, than the bodies of the animals. These animals have four limbs of equal size and prefer to walk on land, even though their tails make them great swimmers.
The least studied order, Gymnophiona contains caecilians. These amphibians are characterized by long, worm-like bodies. Found in South America, Africa, and Southern Asia, there are approximately 50 known species of caecilians. These amphibians resemble eels or earthworms more than other amphibians, since they have reduced tails and lack legs.