Explain the general characters of phylum Mollusca. Give one exarnple of following classes of Mollusca; (i) Gastropoda; (ii) Pelecpoda; (iii) Cephalopoda.

Characters of phylum Mollusca: This is the second largest animal phylum

● Molluscs are terrestrial or aquatic (marine or fresh water) having an organ-system level of organisation.

● They are bilaterally symmetrical, triploblastic and coelomate animals

● They have an open circulatory system and kidney-like organs for excretion.

● Body is covered by a calcareous shell.

● Body divisible into head, muscular foot and visceral hump.

● The mouth contains a file-like rasping organ for feeding, called radula.

● Respiration by gills.

● They are usually dioecious and oviparous with indirect development.

(i) Gastropoda - Pila (Apple snail);

(ii) Pelecpoda- Unio (Mussel);

(iii) Cephalopoda – Sepia (Cuttle fish).