This document provides an overview of the classifications of animals in the Animal Kingdom, dividing them into two main groups - vertebrates and invertebrates. Vertebrates are defined as animals with a backbone or spinal column, and are further classified as fishes, mammals, birds, reptiles, amphibians, and marsupials. Invertebrates lack a backbone, and include mollusks, echinoderms, arachnids, insects, and annelids.