Mollusks - PowerPoint PPT Presentation

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Mollusks

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  1. Mollusks Emily Yau and Bridget Waas

  2. Germ Layers • Mollusks are tripoblastic: they have three germ layers • Endoderm, ectoderm, and mesoderm

  3. Symmetry Most of mollusks are bilaterally symmetrical

  4. Coelom Mollusks are coelomates, and have a true coelom Most coeloms are small and located around the heart, gonads, and metanephridia(organ similar to the kidneys)

  5. Digestive Tract • All mollusks have a complete digestive tract • Mouth, stomach, and anus • Tube-like

  6. Cephalization Evidence of cephalization increases from chitons to cephalopods

  7. Segmentation None!

  8. Skeleton and Appendages Most mollusks have a hydrostatic skeleton or an exoskeleton The number of appendages change from species to species

  9. Circulatory System • A mollusk’s circulatory system is mainly open • No true heart or capillaries

  10. Respiratory System Most mollusks have one gill or one pair of gills Some land mollusks have lungs

  11. Reproduction Assexual or sexual, depending on the species

  12. Habitat Mollusks are found everywhere, but most live in marine environments