What's the difference between an amphibian and a reptile? Presented by Julia Gregory, Senior educator, Tennessee Aquarium, Chattanooga, Tennessee.
Reptile is an animal that has dry, scaly skin and breathes by means of lungs. There are thousands of species (kinds) of reptiles, and they make up one of the classes of vertebrates (animals that have a backbone). Reptiles include alligators, amphisbaenians, crocodiles, lizards, snakes, tuataras, and turtles.
Reptiles are cold-blooded—that is, their body temperature stays about the same as the temperature of their surroundings. To stay alive, these animals must avoid extremely high or low temperatures. Most reptiles that are active during the day keep moving from sunny places to shady spots. Many species of reptiles that live in hot climates are active mainly at night. Reptiles in regions that have harsh winters hibernate during the winter.
The various species of reptiles vary greatly in size. For example, pythons grow more than 30 feet (9 meters) long, and leatherback turtles may weigh up to 2,000 pounds (900 kilograms). On the other hand, some species of lizards measure no more than 2 inches (5 centimeters) long.
Many reptiles live a long time, and some turtles have lived in captivity for more than 100 years.
Reptiles live on every continent except Antarctica and in all the oceans except those of the polar regions. They are most abundant in the tropics. Many kinds of lizards and snakes thrive in deserts. Other reptiles, such as rat snakes and box turtles live in forests. Still others, including marine iguanas and sea turtles, spend much of their life in the ocean. Some sea snakes spend their entire life in the water.
Many people fear reptiles, but most species are harmless and avoid human beings if possible. The Nile crocodile and the saltwater crocodile may attack and kill people. The Gila monster, the Mexican beaded lizard, and numerous snakes, including the rattlesnake, have venomous (poisonous) bites.
In many parts of the world, people eat reptiles and reptile eggs. Some reptiles, including alligators, crocodiles, lizards, and snakes, are hunted for their skin. Manufacturers use the skin as leather for belts, shoes, and other products. The United States government prohibits the import of the hides of those reptiles classified as endangered species.
Amphibian, «am FIHB ee uhn», is an animal with scaleless skin that usually lives part of its life in water and part on land. There are thousands of kinds of amphibians. They make up one of the classes of vertebrates (animals with backbones) and include frogs, toads, salamanders, and the wormlike caecilians.
Most amphibians hatch from eggs laid in water or moist ground, and they begin life as water-dwelling larvae (young). Through a gradual process called metamorphosis, the larvae change into adults. The adults of most amphibians look much different from larvae. Some adults continue to live in water, but most spend their lives on land. Almost all return to water to find mates and produce young, often returning to the same pond or stream each year.
Amphibians generally grow smaller than such other vertebrates as fish, birds, and mammals. Most amphibians measure no more than 6 inches (15 centimeters) long and weigh less than 2 ounces (60 grams). The smallest amphibians are frogs that can sit on a person's thumbnail. The largest, the Chinese giant salamander, may grow up to about 6 feet (1.8 meters) long.
Amphibians are cold-blooded—that is, their body temperature stays about the same as the temperature of their surroundings. Those that live in regions with harsh winters hibernate during the cold weather. Some amphibians, including the gray tree frog of North America, have evolved substances similar to antifreeze in their blood and tissues. These substances enable the animals to freeze solid and then thaw without suffering harm. Many amphibians that live in warm, dry climates estivate (become inactive during summer). Several kinds, including the Australian water-holding frog, produce a cocoon and may remain in estivation for months at a time.
Amphibians live on every continent except Antarctica. They generally live in moist habitats near ponds, lakes, or streams. Certain tropical tree frogs never leave the trees. They lay their eggs in rainwater that collects at the base of leaves. Some amphibians live in dry regions. They survive for weeks or months in moist places underground, waiting for rain to create puddles. After a rainfall, they gather at the puddles to mate and lay eggs. The eggs hatch and the larvae develop quickly, before the puddles dry up.
Most amphibians eat insects. In some regions, amphibians are quite numerous, and they help maintain the balance of nature. Amphibians aid people by eating insects and insect larvae that destroy crops and carry disease. In some places, people use amphibians as food.
This information is from The World Book Encyclopedia. For a more complete summary of reptiles and amphibians, consider World Book's animal books for kids.