Vertebrates vs invertebrates · Mammals, birds, reptiles & more · Grades 3–7
Scientists classify animals into groups based on shared characteristics. This system of classification, called taxonomy, helps us organize the millions of animal species on Earth and understand how they are related to each other. The main categories that students learn are vertebrates (animals with backbones) and invertebrates (animals without backbones).
Vertebrates are divided into five main classes. Mammals are warm-blooded, have fur or hair, and feed their young with milk. Birds are warm-blooded, have feathers, and lay eggs. Reptiles are cold-blooded, have scales, and most lay eggs on land. Amphibians are cold-blooded, have moist skin, and begin life in water. Fish are cold-blooded, have scales and gills, and live in water.
Invertebrates make up about 97 percent of all animal species. They include insects, arachnids, crustaceans, mollusks, and worms. Insects are the largest group with over one million known species. They have six legs, three body segments, and most have wings. Understanding animal classification helps students see patterns in nature and is a key part of life science education.
In this interactive tool, students sort animals into their correct classification groups, learn the characteristics of each class, and take a quiz. The drag-and-drop sorting activity makes learning hands-on and fun. Aligned with Next Generation Science Standards for grades 3 through 5.
Last reviewed: April 2026