PHYLUM MOLLUSCA: MOLLUSCUS-SOFT
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This group is comprised of soft bodied animals.
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Habit and Habitat: they are free-living, aquatic animals that live in mostly sea water and some occur in fresh water.
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Symmetry: they are bilaterally symmetric with little segmentation and without appendages.
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Body cavity: True coelomic cavity is reduced, general body cavity is filled with blood. So it is known as hemocoel.
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Body differentiation: They are multicellular, real developed organs are present.
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Germ layer: They are triploploblastic animals.
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Body organization: Body is divided into anterior head, ventral foot and hard dorsal visceral mass. Foot is mainly used for locomotion.
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Skeleton: Their body is supported with hard shell made up of calcium carbonate.
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Life processes:
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Alimentary canal/ digestive tract is simple.
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Open blood circulatory system is present.
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Respiration occurs through body gills, mantle or lung type structures.
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Excretion takes place through kidney like structures.
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Sense organs are developed in some of them.
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They are unisexual. Reproduction is sexual with internal fertilisation.
Examples:
Chiton, octopus, unio, pila etc.