This document classifies and describes the key characteristics of vertebrates and invertebrates. Vertebrates include mammals, fish, reptiles, birds and amphibians, and can be found around the world. They are divided into groups based on traits like whether they lay eggs, have feathers or fur, breathe through lungs or gills, and how they regulate their body temperature. Invertebrates make up 97% of animal species and lack backbones, including insects, worms, sponges, jellyfish, starfish, mollusks and arthropods. They are grouped by their exoskeleton, body structure and environment.