1. Phylum Mollusca!! Created by: Mariah Ghant, Saori Ishizuka, and Monica Lin

2. Germ Layers • 3 germ layers • Ectoderm • Mesoderm • Endoderm

3. Symmetry • Bilateral

4. Coelom • Mollusca are true coelom • Fluid filled cavity within the mesoderm

5. Digestive Tract • Extracellular digestion • Complete digestive tract • Mouth • Anus

6. Cephalization • Evident in mollusca • Cephalopods have eyes with image formation • Neurons concentrate in a ganglial pattern

7. Segmentation • No segmentation • Instead, body divided into head, foot and visceral mass

8. Skeleton & Appendages • Mollusca have soft bodies • Often protected by a shell • Some have lost their shells because of evolution • Muscular tube feet • Skeleton • Shell with three layers: periostracum, prismatic layer, nacreous layer

9. Circulatory System • Open circulatory system • Except for Cephalopods, blood does not circulate within the vessels • Collected from the gills • pumped through the heart • released directly into spaces in the tissues from which it returns to the gills and then to the heart • Closed circulatory system for cephalopods

10. Respiratory System • Gills in aquatic forms • Discrete respiratory system • Improved capacity for oxygen uptake and distribution • Increases body mass

11. Reproduction • Single or double set of gonads and ducts in each sex • Bivalves and some snails of mollusca are hermaphrodites

12. Habitat • Occur in almost every habitat found on Earth • Most are found in marine environments, extending from the intertidal to the deepest oceans