Reptiles are a class of vertebrate animals that have been on Earth for around 300 million years. They are ectothermic (“cold-blooded”), meaning they cannot regulate their own body temperature and must rely on external sources to warm or cool themselves. Reptiles are found all over the world, from deserts to rainforests, and come in a variety of shapes and sizes. The majority of reptiles are terrestrial (land-dwelling), but some, such as sea snakes, live in aquatic habitats.
There are approximately 10,000 species of reptiles, which can be divided into four main groups: lizards, snakes, turtles and crocodilians. Lizards make up the largest group of reptiles, with more than 6,000 species. They come in a wide range of sizes and shapes, from the tiny gecko to the massive Komodo dragon. Snakes are elongated reptiles with no legs; there are more than 3,000 species of snake worldwide. Turtles and tortoises are reptiles that have a hard shell that protects them from predators; there are around 350 species of turtle. Crocodilians include alligators, caimans and crocodiles; these large reptiles can grow up to 20 feet long and weigh over 2,000 pounds!
Reptiles play an important role in many ecosystems; they help to control populations of other animals by preying on them or competing with them for food and resources. Some reptile species also play key roles in seed dispersal; for example, iguanas eat fruits and distribute the seeds through their droppings. Unfortunately, many reptile populations are declining due to habitat loss (due to human activity) and exploitation by humans (for their meat, skin or shells).