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Invertebrates Lesson for Kids: Characteristics & Facts

Instructor: April Gwen Ellsworth

April has a master's degree in psychology and has experience teaching special populations from preschoolers to adults.

What has eight legs and a body divided into two segments? What kind of animal stays in just one place all the time because it can't walk, run, swim, or fly? Find the answers and many interesting facts in this lesson about invertebrates.

What Makes an Animal an Invertebrate?

Invertebrates are almost everywhere. In fact, at least 95% of all the animals in the world are invertebrates! Do you know the one thing that all of them have in common? Invertebrates do not have a backbone.

You have a backbone, which lets your body stand up straight, protects your organs, and connects your other bones together. This makes you a vertebrate. But invertebrates do not have the support of bones, so their bodies are often more simple, soft, and small. They are also cold-blooded, which means their body temperature changes when the air or water around them changes.

Invertebrates can be found flying, swimming, crawling, or floating, and provide important things to the environment and to people. No one knows just how many different kinds of invertebrates exist, but there are millions! Let's find out about some of the most common ones.

Arthropods are Segmented

Scientists have divided invertebrates into many different groups, depending on what the animals have in common. Arthropods are the largest group of invertebrates. They can live on land, like spiders and insects, or in water, like crayfish and crabs. Insects are the largest group of arthropods, so of course many even fly, like mosquitoes, bees, locusts, and ladybugs.

Something that makes all arthropods special is that their bodies are segmented, or divided into parts (think of an ant). They also have jointed legs or limbs to make it easier to walk, just as you have knees for your legs and elbows for your arms. Most arthropods also have an exoskeleton, which is a tough outer skin or shell that protects their body. Have you ever wondered why a bug makes that crunching sound when you squish it? It's the exoskeleton!

Many invertebrates are arthropods. Spiders have eight legs and two body segments. Centipedes have many body segments and many legs. Crabs live in the ocean and have a hard exoskeleton. All insects, like the ladybug and ant, have three body segments.
Picture of arthropods - spider, centipede, crab, ladybug, and ant

Mollusks are Soft

Mollusks are the second largest groups of invertebrates. They have soft bodies and live on the land or in the water. Lots of mollusks, like snails, oysters, clams and scallops, have shells to protect their soft bodies. However, not all have a shell, like octopus, squid, and cuttlefish.

Invertebrates like the snail and octopus are in the mollusk group.
Picture of mollusks - snail and octopus

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