HSEB zoology notes | General characteristics of mollusa

1. Habitat : Mollusca are widely distributed all over the world. They are mostly freshwater or marine and few are terrestial found in damp places.

2. Body form : They are triploblastic animals. They have organ system of body organization. Their body is soft, unsegmented without appendeges and body divided into head, mantle, foot and vesciral mass.

3. Coelom : They are haemocoelomate animals. Their true coelom is reduced.

4.Symmetry : They are billaterally symmetrical but except gastropods which are asymmetrical due to coiling or torion during growth.

5. Respiration in mollusca take place with the help of feathers like fins or ctenidia in aquatic form and lungs or pulmunary sac in terrestrial form.

6. Excretion takes place with the help of paired metanephridia or kidney.

7. Sensory organs are eyes , tentacles, osphradium , statocysts.

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