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Phylum Mollusca

Phylum Mollusca. Means “soft”…refers to their bodies Are coelemates …three body layers with true body cavity Two body parts: Head-foot…travels on and has sensory organs Visceral mass…organs Body covered by mantle (and often a shell) Bilateral symmetry. Phylum Mollusca. Systems:

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Phylum Mollusca

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  1. Phylum Mollusca • Means “soft”…refers to their bodies • Are coelemates…three body layers with true body cavity • Two body parts: • Head-foot…travels on and has sensory organs • Visceral mass…organs • Body covered by mantle (and often a shell) • Bilateral symmetry

  2. Phylum Mollusca • Systems: • Complete digestive system • Separate sexes, external fertilization (some hermaphrodites) • Breathe through gills • Open circulation (hemolymph)

  3. Phylum Mollusca

  4. Phylum Mollusca • Radula: “tongue” structure covered with “teeth” (made of chitin) scrape food.

  5. Phylum Mollusca • 3 Classes • Gastropoda • Bivalvia • Cephalopoda

  6. Class Gastropoda • “stomach-foot”… crawls on “stomach” • Snails, slugs, conch • Visceral mass turns 180o so organs exit out front (torsion) • All are motile

  7. Class Gastropoda

  8. Nudibrach

  9. Class Bivalvia • 2 halves (valves) to the shell • Clams, mussels, oysters, scallops • Most are sessile and filter feed • No head or brain, 3 pairs of ganglia • Separate sexes, external fertilization (most)

  10. Class Bivalvia

  11. Class Cephalopoda • “head foot” travel around head first, tentacles • Octopi, squid, cuttlefish, nautilus • Most advanced nervous system of any mollusk…lobes, complex eyes • Closed circulatory system (more advanced…move faster) • Separate sexes, internal fertilization • Chromatophores (change color), ink

  12. http://www.youtube.com/watch?v=zjycOCyUZ1c

  13. Phylum Echinodermata • “spiny skin” • Sea stars, sand dollars, sea urchins, sea cucumbers • Radial symmetry (bilateral larva) • No cephalization • Ossicles (endoskelton) • Water-vascular system (not blood or hemolymph) • Tube feet (water filled … suction)

  14. Tube feet

  15. Class Crinoidea e.g. crinoids, sea lillies, feather stars

  16. Class Ophiuroidea e.g. brittle stars and basket stars

  17. Class Echinoidea e.g. sea urchins, sand dollars

  18. Class Holothuroidea e.g. sea cucumber

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