MOLLUSCA PHYLUM

*habitat-mostly marine, some are fresh water living and some live in damp area.
*body form-unsegmented, but Neopilina is segmented.
*symmetry-usually bilateral,but some mollusca,due to torsion during growth, the adults become asymmetrical.
*germ layer-triploblastic
*level of organisation-organ system level.
*shell-it is secreted by mantle. it is made up of calcium carbonate.
*mantle-it is thin fleshy fold of dorsal wall more or less covering the body.
*body wall-ciliated
*body cavity-coelom is greatly reduced.
*digestive tract-complete.
*blood vascular system-it is open type.blood is generally blue due to presence of haemocyanin.
*respiratory organs-exchange of gases usually takes place through gills called ctenidia.
*excretory organ-one or two pairs of sac like kidney.
*nervous system- it consists of cerebral, pleural, pedal and visceral ganglia.
*sense organ-in many moluscs eyes and tentacles are present on head. osphradium is present in some molluscs for testing chemicalsexes-generally separate, some are hermaphrodite.
*development-either direct or indirect.
*e.g.- Pila, Chiton, Dentalium, Unio

PILA

CHITON

DENTALIUM

UNIO