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Invertebrates
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Animals that lack a backbone
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Vertebrates
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Animals that possess a backbone
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Spherical symmetry
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An organism possesses spherical symmetry if it can be cut into two identical halves by any cut that runs through the organism's center
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Radial symmetry
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An organism possesses radial symmetry if it can be cut into two identical halves by any longitudinal cut through its center
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Epidermis
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An outer layer of cells designed to provide protection
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Polyp
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The sessile, tubular form of a cnidarian with a mouth and tentacles at one end and a basal disk at the other
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Mesenchyme
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The jellylike substance that separates the epidermis from the inner cells in a sponge
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Collar cells
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Flagellated cells that push water through a sponge
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Amoebocytes
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Cells that move using pseudopods and perform a variety of functions in animals
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Gemmule
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A cluster of cells encased in a hard, spicule-reinforced shell
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Medusa
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A free-swimming cnidarian with a bell-shaped body and tentacles
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Ovaries
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Organs that produce eggs
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Mesoglea
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The jelly-like substance that separates the epithelial cells in a cnidarian
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Nematocysts
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Small capsules that contain a toxin which is injected into prey or predators
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Testes
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Organs that produce sperm
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