Mollusca is the second largest phylum in the animal kingdom. In Latin Mollis means soft. The animals of this phylum have a soft body. Hence they are called molluscans.

 Aplacophora (including Caudofoveata and Solenogastres)  Monoplacophera  Polyplacophora  Scaphopoda  Gastropoda  Bivalvia  Cephalopoda

 The animals are mostly aquatic & some are found in moist soil.  They are triploblastic animals. The body of these animals are unsegmented. The body has three divisions namely head, ventral muscular foot, mantle.  The inner body wall is thick & covered by muscles. A part of this is modified for locomotion.

 Digestive system is complete with mouth, oesophagus,& anus. Mouth has a muscular organ called RADULA, bearing row of teeth, which help in grasping food. The radula serves both to scrape off algae and other food materials and also to convey them backward to the digestive tract..  Mollusca has an excretory system with an anus. It has an organ called the nephridium that gets rid of wastes.

Respiratory system  Respiration takes place through special structure called Ctenidia found in the mantle cavity & through epidermis of the mantle cavity itself which are typically flattened, lamellar structures with a central axis from which numerous smaller gill filaments project.  A Mollusca has tubes called siphons that bring water in and out of their bodies so that they can get oxygen and give off carbon dioxide. They have gills that help with this.

 The blood vascular system contains the heart & the associated blood vessels. The heart has auricles & ventricles.  A Mollusca has a heart, blood and blood vessels.  Blood may be colorless fluid or bluish green in color or red in color containing HAEMOGLOBIN. CIRCULATORY SYSTEM

NERVOUS SYSTEM  A Mollusca has no formal nervous system, but has a series of ganglia that conduct impulses.  Different types of sense organs like eyes, tentacles, balancing organs & to perceive smell, organs of equilibrium, are present.  A pair of nephridia serve as an excretory organ, open on the body through the pores.

REPRODUCTION 1.In the molluscs reproduction is sexual. 2.Sexes are separate. 3.In some animals male & female reproductive organs are found in the same individual 4.A Mollusca is either male or female and reproduces sexually with a large organ called a gonad.

CHITON SNAIL OCTOPUS NEOPOLINA

SCALOP TWO SHELLS SHELLS

BIVALVIA CLAM A SHELL A CLAM

 The GIANT SQUID is the largest among invertebrates. It is about 2000k.gms. in weight.  Lamellidens lives in sand. Its shells are composed of right & left halves.  Octopus is also known as devil fish which lives in bottom in the shallow water along the coast.

 Octopus is one of the largest invertebrates It gets the name because of the presence of 8 long arms in its head region.  Octopus has an ink gland in their body. To confuse the enemy they squirt ink out of the siphon & can not be seen behind the dark watery screen.

 Beautiful shell are used in making decorative materials.  Pearly layer is used for making buttons.  Shells are used in preparing lime, which serves as food for poultry birds to improve their egg production.  Certain bivalves are used as food.

 Cowries are used for playing are also the shells of mollusc. They are beautiful & shining.  The shell of cuttle fish is found inside the body. It is rich in calcium & is used for cleaning glasses.  Pearl oyster gives pearl which is used as pearl.

FORMATION OF PEARL OYSTER PEARL OYSTER IS A MOLLUSCA WHICH IS KNOWN FOR PRODUCING PEARLS OF COMMERCIAL IMPORTANCE. THE FORMATION OF A PEARL OCCURS WHEN AN UNWANTED SUBSTANCE SUCH AS STONE OR A SAND PARTICLE ENTERS THE BODY. THE PARTICLES BECOME SURROUNDED BY A SECRETION PRODUCED BY GLANDS IN THE SHELL. THE SECRETION GRADUALLY HARDENS TO FORM A PEARL. THIS NATURAL PROCESS HAS BEEN USED BY MAN FOR ARTIFICIAL PRODUCTION OF PEARLS.

PROJECT DONE BY, K.S.SINDHU RAO DEEPIKA R.R.