This document provides an overview of the animal kingdom, describing their key characteristics and how they are classified. It discusses that animals are divided into invertebrates and vertebrates. Invertebrates make up 98% of animal species and lack backbones, while vertebrates make up the remaining 2% and include fish, amphibians, reptiles, birds and mammals which all have backbones. It then examines several animal phyla in more detail, describing their defining features, organs and organ systems.