InvertebrateInvertebratess

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Invertebrate Phyla• Sponges• Cnidarians• Platyhelminthes• Nematodes• Mollusks• Annelids• Echinoderms• Arthropods

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Sponges (Porifera)• Most primitive• Cells relatively

independent• Mostly marine• No Symmetry

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Cnidarians• Mostly marine• Radial Symmetry

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Cnidarians• Jellyfish• Hydra• Coral

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•Sea anemone

•Portuguese Man-O-War

Platyhelminthes• Flatworms• Bilateral

symmetry• Cephalization

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Planarian – freshwater flatworm

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Nematodes• Tube-like

digestive tract• Roundworms!• Mouth and anus• No segmentation

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Mollusks• Clams, snails,

squids• Varied habitats

– Marine– Freshwater– Terrestrial

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Annelids• Segmented

worms• Common

earthworm• Leech

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Arthropods• Joint-legged

animals• External skeleton• Huge variation –

mostly insects

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Echinoderms• Always marine• Starfishes, sea

urchins, sea lilies• Spiny skin

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Brittle Star – An Echinoderm

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