Ch 19'3 Invertebrates

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Ch 19.3 Invertebrates
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• Animal that does not have a backbone
• Make up 97 of animal species

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Sponges

• Simplest animals, two layers of cells
• Live in water, food from particles strained
  through pores in body wall

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Cnidarians

• All live in water
• Body parts arranged like spokes on a wheel
  radial symmetry
• Armlike tentacles used to capture prey by
  stinging them and push into body

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Flatworms

• Flat and thin, right and left side of body are
  the same bilateral symmetry
• most are parasites, live on or inside other
  animals

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Roundworms

• Long, round bodies come to a point at end
• Bilateral symmetry
• Live in soil or water, most are not parasitic
• Some can be parasitic (hookworm)

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Segmented Worms

• Body divided into segments
• Live in soil, freshwater or ocean
• Earthworms food from soil, help plants
• Leeches feed from host

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Mollusks

• Divided into 3 parts head, body, foot
• Snails/slugs
• Hinged shells (clams)
• Hunt other fish or animals

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Arthropods (4 types)

• Largest group
• Segmented animals with jointed legs, most have
  antennae
• External skeleton to protect them
• Molting shed external skin

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Arthropods (cont.)

• A. Crustaceans (crabs, crayfish)
• 5 pairs of legs
• Claws
• B. Arachnids (spiders, ticks)
• Four pairs of legs
• Inject poison

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Arthropods (cont.)

• C. Centipedes/Millipedes
• 1 pair of legs/segment
• Fast
• Kill insects
• D. Insects (mosquitoes, flies)
• 3 pairs of legs
• Most have wings
• Go through metamorphosis
• 2 pair of legs/segment
• Slow
• Eat dead plant matter

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Echinoderms (seastars,urchins)

• Radial symmetry
• Tube feet used for movement