Those described above are not the same as modern reptiles: They have evolved even more since that time. Then and now, these creatures are vertebrates, which is a word that means joint of the spine. In other words, they have spinal columns and backbones. They are cold-blooded, meaning they cannot control their body temperature internally and mostly depend on the environment to maintain it. Some, though, flex their muscles to generate warmth, and most all of them bask in the sun to stay warm.
Reptiles are typically covered in scales and may have bony external plates such as the skin of an alligator or the shell of a tortoise. Don’t let the appearance fool you, though. Compared to many other animals that are used for producing leather goods, the skin is actually quite thin. Fortunately, the armor, scales and spines protect them against many predators, but not all of them. For example, the jaws of a crocodile are strong enough to crush the shell of a large tortoise.
If you think about it, you can probably envision a crocodile or a snake lying low and being very still. One reason for this is so they can possibly capture passing food, but there is another good reason: They are conserving energy so they can get by with less food. Additionally, they have a low resting metabolism, and that, and a cold internal temperature, requires less energy from food. Some of them, like a very large snake, can open its jaws so wide that it can swallow a pig. That buys a lot of time before the snake has to eat again. Incidentally, most reptiles are carnivores, but some, such as turtles, some dragons and some iguanas, are mostly herbivorous.
Most reptiles reproduce just like people and other animals; however, some are capable of asexual reproduction and need no partner. Some geckos are like that. It may not seem like much fun, but it is functional for them. Another interesting thing is that for some reptiles, the temperature during the incubation of an egg can determine the sex of the hatchling.
Many reptiles have become popular as exotic pets, and some are great as pets. Good examples would be chameleons, dragons, geckos, many lizards, some snakes and tortoises. If this interests you, try starting with a gecko. They do not require as much care as some of the others, and they are very attractive and interesting. You may even find that yours takes to you and looks forward to your visits – especially if you are bringing a treat.