What Is Reptiles?
The word "reptile" means "to creep"; a reference to the fact that except for snakes, all reptiles have four legs and creep when walking.
All reptiles reproduce by laying eggs. Females lay their eggs in decayed wood, a nest of leaves and mud, or elsewhere on land. Reptiles do not sit on their eggs to incubate them like birds do. Instead, they abandon their eggs and rely on the heat from the sun to hatch them. Unlike newborn mammals which cared for by their parents, new-born reptiles are left to fend for themselves.
Reptiles have dry scaley or scale-like skin. The scales are made of keratin, the same material that makes hair, feathers and fingernails in other classes of animal. Some species of reptiles, like snakes, shed their scaly skin as they grow. Turtles are the only reptiles with a shell. Some turtles can pull their head, legs, and tail into the shell for protection. There are about 250 species of turtles. They live on land, in fresh water, and in the ocean.
Reptiles breathe air with their lungs just as mammals. This means that reptiles who live in water must at some time come to the surface to breathe.
Reptiles are often called "cold-blooded". This doesn't mean that their blood is cold though. It means that they can change their body temperature to match their surroundings. If the temperature of the air goes up, reptiles will raise their body temperature. If the air temperature goes down, they will lower their body temperature. In hot climates, reptiles usually seek shaded shelter during the day and are eat or search for prey mainly in the night. If air temperatures do not suit them, some reptiles can hibernate until the temperatures are right again.
Another unique characteristic of reptiles is their eyes. The shape of a reptile's pupil, the black spot in the center of the eye, indicates whether the animal is active at night or during the day. Most reptiles active at night have slit-like pupils that can close tightly in bright light. Reptiles active in daytime have round pupils just like ours. Most reptiles have good vision. Some can see in colour.
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. There are more than 7,100 species of reptiles. Most of them live on land. Some, like the sea turtle, make their home in the ocean and others, like crocodiles, live in fresh water.
