​Invertebrates

​Invertebrates do not have a backbone.

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​Invertebrates have some differences with each other:

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​One difference is their symmetry. Symmetry means that parts of the animals body match up with other parts around a midpoint line. Some animals have no symmetry.

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​Sponges

A sponge is ​the simplest kind of invertebrate.

Sponges do not have symmetry.

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​Sponges live underwater.

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​Sponges filter the water for food.

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​The adults stay in one place. Their offsprings float or swim.

​Cnidarians

​A cnidarian is an animal with armlike parts called tentacles.

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​At the top of their tentacle are poisonous stinging cells.

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​Jellyfish and corals are cnidarians.

​Mollusks

​Most mollusks have shells and live in water.

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​Snails and slugs are the only mollusks that live on land.

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​Oysters, clams , squid and octopuses are mollusks.

​Echinoderms

​Sea urchins are echinoderms.

​An echinoderm has spiny skin.

​It also has an internal support structure. This structure is called an endoskeleton.

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​Arthropods

​Arthropods have jointed legs and a body that is divided in to sections.

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Arthropods have an exoskeleton, this is a hard covering that protects the body.

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Shrimp, Crabs, Insects, Spiders are arthropods.