Newly hatched alligator Reptiles are cold-blooded animals with scaly skins. They include snakes, lizards, turtles and crocodiles. Most reptiles lay eggs, either soft and leathery or hard-shelled, but some give birth to live young. A few reptiles guard their eggs until they hatch. Apart from the crocodilians, most reptiles abandon their young after hatching or birth. Land-living reptiles must bask in the sun to warm up before going in search of food.
A snake shedding its skinReptiles have dry, scaly skins—not slimy. The scales form one continuous sheet, not individual scales like fish. Water cannot pass out through their skins, unlike those of amphibians. This means that reptiles do not need to keep their skins moist. Some reptiles moult regularly, shedding their skins when new ones have grown underneath.
Because they are cold-blooded animals, reptiles need to bask in the sun to raise their body temperature before they are able to move about in search of food. However, they do not need to eat as much food as the warm-blooded birds and mammals, so are able to survive more easily in harsh desert environments.
Rise of the reptiles
Reptiles are descended from the early amphibians. The first reptiles were probably small, lizard-like creatures that inhabited the Carboniferous swamps about 320 million years ago. Unlike the amphibians, they did not have to stay close to water to keep moist and lay their eggs. They were able to live more easily on land. The lizards, turtles and tortoises and the crocodilians (crocodiles and alligators) appeared during the Triassic Period, about 250 million years ago. Snakes evolved later, about 135 million years ago. Some modern-day reptiles have hardly changed since the time of the dinosaurs.
Some reptiles of the Amazon rainforest
Consultant: Chris Jarvis
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