Mollusca

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 MOLLUSCA


General Characteristics


• They are mostly found in marine and freshwater , very few are terrestrial and found in moist soil.

•They exhibit organ level of organization.

•Their body has a cavity. Bilaterally symmetrical.

•Body is divided into head, visceral mass , muscular foot and mantle.

• Head comprises of tantacles and compound eyes.

•Body is covered by calcareous shell.

•Muscular foot help in locomotion.

•They have a well developed digestive system, the radula is respire through organ for feeding.

• They respire through the general body surface, gills or pulmonary sac.

• The blood circulates through open circulatory system.

•Nervous system consist of number of paired ganglia .

•The sexes are separate in most of the molluscs but some species are hermaphrodite.

•Fertilization may be external or internal.

•Generally oviparous with indirect development.


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