9 Invertebrates-Low

Invertebrates Written by Brooke Bessesen

Introduction Invertebrates are "spineless" animals. That means they have no backbone. Feel the bumps in the middle of your back. The bones of your backbone, or spine are called vertebrae (VER-tuh-bray). Animals with a spine are called vertebrates. You are a vertebrate. But most animals are invertebrates.

What Do Invertebrates Have in Common? Invertebrates have many things in common. You already know they have no spine. But they have other things in common, too: Like all animals, invertebrates have more than one cell. All invertebrates move their body in some way. Invertebrates need oxygen, but they do not breathe as we do.

Most invertebrates have symmetry. That means the sides of their body look alike. Invertebrates can't make their own heat. They are cold-blooded. Most invertebrates make young with sperm from males and eggs from females. Invertebrates eat to stay alive. In this book, you will learn about some groups of invertebrates. You will find out how they move and eat.

Classifying Invertebrates Invertebrates have things in common, but they are very different, too. A fruit fly is smaller than a grain of rice. A giant squid can be as long as a bus. Centipedes eat worms. Butterflies drink from flowers. Bees fly, and crabs crawl. Earth has many, many kinds of invertebrates!

Scientists classify, or group, animals by the things they have in common. Animals are either vertebrates or invertebrates. Each kind is made up of smaller groups. Read on to learn about some groups of invertebrates. VERTEBRATES Mammals Birds Reptiles Amphibians Fish Invertebrates Poriferans sponges Cnidarians sea jellies corals sea anemones Echinoderms sea stars sea urchins sand dollars Mollusks octopuses squids snails clams Annelids earthworms Arthropods insects spiders lobsters millipedes These are the invertebrate groups covered in this book