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Phylum Mollusca!!. Created by: Mariah Ghant , Saori Ishizuka, and Monica Lin. Germ Layers. 3 germ layers Ectoderm Mesoderm Endoderm. Symmetry. Bilateral. Coelom. Mollusca are true c oelom Fluid filled cavity within the mesoderm. Digestive Tract. Extracellular digestion
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Phylum Mollusca!! Created by: Mariah Ghant, Saori Ishizuka, and Monica Lin
Germ Layers • 3 germ layers • Ectoderm • Mesoderm • Endoderm
Symmetry • Bilateral
Coelom • Mollusca are true coelom • Fluid filled cavity within the mesoderm
Digestive Tract • Extracellular digestion • Complete digestive tract • Mouth • Anus
Cephalization • Evident in mollusca • Cephalopods have eyes with image formation • Neurons concentrate in a ganglial pattern
Segmentation • No segmentation • Instead, body divided into head, foot and visceral mass
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
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
Respiratory System • Gills in aquatic forms • Discrete respiratory system • Improved capacity for oxygen uptake and distribution • Increases body mass
Reproduction • Single or double set of gonads and ducts in each sex • Bivalves and some snails of mollusca are hermaphrodites
Habitat • Occur in almost every habitat found on Earth • Most are found in marine environments, extending from the intertidal to the deepest oceans