1. Mollusca
IB biology
Hana

2. Mollusca Mollusc and mollusc are both
derived from the French mollusque which originated from the Latin molluscus, from mollis (soft)

3. What is it
Mollusca is the second largest phylum of invertebrate animals
Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms.
They are highly diverse in
Size
Anatomical structure
Behaviour
habitat

4. class Mollusca is classified into seven classes
Gastropoda (single shelled cowries, cones, etc.)
Bivalvia (two shelled like clams, mussels, etc.)
Aplacophora (solenogasters)
Monoplacophora (segmented limpets)
Polyplacophora (or amphineura as it was earlier called – chitons)
Scaphopoda (tusk shells)
Cephalopoda (nautilus, squids, cuttlefish, octopus, etc.)

5. Features
Molluscs have developed such a varied range of body structures, It is difficult to find defining characteristics to apply to all modern groups.

6. Features
Mantle
mantle with a significant cavity used for breathing and excretion
Anus and genitals open into mantle cavity
Dorsal body wall which covers the visceral mass (usually protrudes in the form of flaps)
For gastropods, the mantle is usually fully or partially hidden inside the gastropod shell

7. FEATURES Radula A hard rasping radula is used for feeding
It is sometimes compared to a tongue.
It is like teeth, a minutely toothed, chitinous ribbon typically used for scraping or cutting food before the food enters the oesophagus.
The radula is unique to molluscs, and with the exception of the bivalves, every class of mollusc has it.

8. Features Bilateral symmetry
Most molluscs have one pair of gills/singular gills
Two pairs of nerve cords, the visceral cords serving the internal organs and the pedal serving the foot.
All produce eggs
Some rely on external fertilization, some on internal fertilization
Calcareous Shells
Mostly made of CaCO3 
Containing lime or being chalky

9. examples
“head-footed”
“stomach-footed”

10. (“bearing many plates”)
Examples
Aplacophora
(“without plates”)
Small, cylindrical, worm-like creatures
(sea cucumber)
Monoplacophopora
(“with one plate”)
Small and have a single cap like shells that make them look like limpets.
Head is reduced with no tentacles or eyes; they have a rounded foot.
(neopilina)
Scaphopoda
(“boat-footed”)
Usually remain buried in sand. Worm-like animal is found within tusk shaped shells that are open at both ends.
(Tusk shells) They do not have eyes, tentacles or gills.
Polyplacophopora
(“bearing many plates”)
Eight plates called valves that are overlapping and attached to a part of the mantle called girdle. These plates are distributed around and underneath the edges. 
(Chiton)