Echinoderms Lesson for Kids

Instructor: Heather Pier

Heather has taught high school and college science courses, and has a master's degree in geography-climatology.

Come learn about the echinoderms! Echinoderms are a group of animals that have several features in common. All echinoderms have spiny skin, five-sized symmetry, and live in the ocean.

What Is an Echinoderm?

You have probably seen an echinoderm before. Starfish, sand dollars and sea urchins are all echinoderms. Echinoderms (pronounced e-kine-o-derms) are a group of animals that can only live in the ocean. They are grouped together because they have many things in common.

The name echinoderm comes from a word in the Latin language that means spiny skin. All echinoderms have spiny or bumpy skin. Their bumps aren't always easy to see like the bumps on a toad's skin, but they are there if you look closely.

All echinoderms are also invertebrates. This means they do not have a back bone. You have a back bone that helps hold your body up straight. Echinoderms crawl on the ocean floor. They do not need to be able to stand up straight like we do.

All echinoderms have something called radial symmetry on their bodies. This means that you could divide their bodies into five identical pieces. If you can picture how you would divide a pizza into five equal slices then you can picture radial symmetry.

The yellow lines show what radial symmetry looks like. Each section of the starfish looks the same when divided into five pieces.

Humans don't have radial symmetry. We could be divided into two identical halves but not into five identical pieces.

Types of Echinoderms

The following animals are all examples of echinoderms.

  • Starfish are the most famous echinoderm. Their five arms make the radial symmetry easy to see. Their arms are very thick and fleshy looking. They also have very bumpy skin. Some types even have extremely large bumps.

The most famous echinoderm is the starfish.

  • Brittle stars look like starfish but are actually a different animal. They have much skinnier arms than starfish but usually still have five arms. Their arms also don't look fleshy like regular starfish. Their bumps look more spiny than bumpy.

Brittle stars have more bumps and spines than starfish do.

  • Echinoid (pronounced e-kin-oyd) is just a fancy name for sand dollars and sea urchins. Echinoids have very easy to see spines. Most of them look like pincushions that can move. They have no arms but their bodies can still be divided into five parts.

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