Common characteristics of reptiles include having scales, cold-bloodedness, breathing through lungs, and laying soft-shelled eggs. Reptiles differ from mammals in that they do not have hair or fur, they lay eggs rather than giving birth to live young, and they have a three-chambered heart.
Reptiles are also ectothermic, meaning they rely on external sources of heat to regulate their body temperature. They have a dry and scaly skin, with most species shedding their skin periodically. Reptiles also have a unique skeletal structure, with most species having a backbone and ribs that support their body. They typically have four legs, although some species, such as snakes, have lost their limbs through evolution.
Reptiles are found in a wide variety of habitats, from deserts to forests to aquatic environments. They come in a wide range of sizes, from tiny geckos to massive snakes and crocodiles. Reptiles play important roles in their ecosystems as predators, prey, and ecosystem engineers.
Overall, reptiles are a diverse group of animals with unique adaptations that have allowed them to thrive in a variety of environments throughout the world.