To Begin

On Earth, there is more than 80 million species of all kinds. Learning every single one would take maybe more than a lifetime. If you are just starting out and want to learn about wildlife, then lets make this the most basic structure to learn possible.
 Animals are classified in six groups. Amphibians, birds, fishes, invertebrates, mammals and reptiles.Every single group mentioned here evolved from each other. For example, amphibians evolved from fish and so on. Each containing hundreds of species with in their class. This is a very vague classification, but it is a start."Once you have a understanding of these six groups, you'll be on your way to grasping the basic characteristics of virtually every animal on the planet." (Classification)

Reptiles  animals, comprising today's turtles, crocodilians, snakes, lizards, and tuatara, as well as many extinct groups. A reptile is any amniote (a tetrapod whose egg has an additional membrane, originally to allow them to lay eggs on land) that is neither a mammal nor a bird.^[1] Unlike mammals, birds, and certain extinct reptiles, living .The earliest known reptiles originated around 340-335 million years ago.