WHAT IS A REPTILE?
Reptiles are vertebrates, they have scaly skin that keeps their bodies from drying out, their young do not go through a larva stage like amphibians, but instead look like small versions of the adults when they hatch. Reptiles are ectotherms, so they must bask in the sun or find a warm spot to get warm and become active, and they must find shade or a cool spot to cool off. In cold conditions they become sluggish and don't move around much, and some enter a state of torpor or hibernation if it will be cold for a long time.
There are four main groups of reptiles: turtles and tortoises; lizards and snakes; crocodiles and alligators; and the tuatara, the only species left from an ancient group of reptiles that goes back to the dinosaurs. Some reptiles spend most of their time in water, like crocodiles, alligators, turtles, some species of snakes, and some species of lizards. Many spend their time on land, and reptile species can be found in all types of habitats except polar ice and tundra.
REPTILES START LIFE READY TO GO
Most reptiles make nests or dig holes to lay their eggs in. Some then stay to guard the nest and even get the hatchlings started in life, like crocodiles and alligators and some species of snakes. But most mother reptiles leave the nest once the eggs are laid. The hatchlings are independent from the start, and must find their own food and shelter.
There are more than 6,500 known species of reptiles. The heaviest is the saltwater crocodile Crocodylidae porosus, weighing up to 2,200 pounds (1,000 kilograms). The smallest is the dwarf gecko Sphaerodactylus ariasae, measuring only 3/4 of an inch (19 millimeters). The longest snake is the reticulated python Python reticulatus, at up to 33 feet long (10 meters). The largest lizard is the Komodo dragon Varanus komodoensis, weighing up to 175 pounds (80 kilograms) and measuring up to 10 feet long (3 meters). Tortoises have the longest life span in the reptile order; some can live more than 150 years.