Question

Q- classify phylun mollusca upto orders giving diagnostic characters and suitable example of each other.

Answer 1

Hii...that's your answer....
Phylum Mollusca is a group of invertebrates which has fascinated man from the dawn of civili­zation. It is a major group in the animal kingdom as regards the number which occu­pies next to arthropods. The members of this group have adapted either on land or in water.
Bilaterally symmetrical, coelomate protostomia with spiral cleavage and soft un-segmented body, covered by a thick muscular fold, the mantle which secrets a single or many shells, and a radula in the oesophagus except Bivalvia, and ventral muscular foot for locomotion.
1. Majority of the members aquatic and a few terrestrial.

2. Bilaterally symmetrical body except some gastropods and cephalopods be­come secondarily asymmetrical.

3. Body soft and un-segmented in the adult stage.

4. Exoskeleton, in the form of calcareous shell, present in most of them except aplacophorans, nudibranchs and most octopuses. The shell is mostly located externally, although a few forms with internal shell.