`star` Introduction
`star` Characteristic Features
`star` Development


● `color{Brown}"Members"`: This is the `color{Violet}"second largest phylum"` of Animalia which includes `color{Violet}"soft bodied and shelled"` animals.

● `color{Brown}"Habitat"`: Molluscs are terrestrial or aquatic (marine or fresh water).

● `color{Brown}"Basic Features"`: They have `color{Violet}"organ-system"` level of organization. They are `color{Violet}"bilaterally symmetrical"`(few are secondarily asymmetrical due to twisting or torsion during growth like snail), `color{Violet}"triploblastic"` and `color{Violet}"coelomate"` animals.

● `color{Brown}"Examples"`: 𝘗𝘪𝘭𝘢 (Apple snail), 𝘗𝘪𝘯𝘤𝘵𝘢𝘥𝘢 (Pearl oyster), 𝘚𝘦𝘱𝘪𝘢 (Cuttlefish), 𝘓𝘰𝘭𝘪𝘨𝘰 (Squid), 𝘖𝘤𝘵𝘰𝘱𝘶𝘴 (Devil fish), 𝘈𝘱𝘭𝘺𝘴𝘪𝘢 (Seahare), 𝘋𝘦𝘯𝘵𝘢𝘭𝘪𝘶𝘮 (Tusk shell) and 𝘊𝘩𝘢𝘦𝘵𝘰𝘱𝘭𝘦𝘶𝘳𝘢(Chiton).

`color{Green}♣ color{Green} "Just for Curiosity"`

● Study of molluscs is known as `color{Violet}"Malacology"` and study of shells of molluscs is known as `color{Violet}"Conchology"`.

● Molluscs are classified into `color{Violet}"six classes"` on the basis of Shell, Foot, Nervous system and Gills.


● `color{Brown}"Body"` is `color{Violet}"unsegmentated"` with various shapes and covered with `color{Violet}"calcerous shells"`. Neopilina shows exceptional segmentation.

● `color{Brown}"Body is divided into three parts"`:
`star` `color{Violet}"Head"`: with sense organs like eyes and Sensory tentacles.

`star` `color{Violet}"Dorsal Visceral mass/ Hump"`: Contains all visceral organs.

`star` `color{Violet}"Ventral muscular foot"` for locomotion

● `color{Brown}"Other structures"`:
`star` A `color{Violet}"soft and spongy layer"` of skin forms a `color{Violet}"mantle"` over the visceral hump.

`star` The space between the hump and the mantle is called the `color{Violet}"mantle cavity"`.

`star` Mantle usually secretes an external `color{Violet}"calcareous shell"` made up of `color{Violet}"calcium carbonate"` and `color{Violet}"concheolin protein"`.

● `color{Brown}"Digestive system"`: Digestive tract is `color{Violet}"Complete"`; the mouth contains a file-like rasping organ for feeding, called `color{Violet}"radula"`.

● `color{Brown}"Respiratory System"`: Usually by feather like `color{Violet}"gills"` present in the mantle cavity.

● `color{Brown}"Circulatory System"`: open

● `color{Brown}"Excretory system"`: Contains 1 or 2 pairs of kidneys called `color{Violet}"Kaber’s organs"` or `color{Violet}"Organ of Bojanus"`. Excretory mater is Ammonia or Uric acid.

● `color{Brown}"Nervous system"` consist of 3 or 4 pairs of Ganglia:
`star` Cerebral ganglia (in head)

`star` Pedal Ganglia (in foot)

`star` Visceral Ganglia (in visceral mass)

● `color{Brown}"Sense organs"`: `color{Violet}"Eye"`, `color{Violet}"Statcosyst/lithocyst"` for locomotion and `color{Violet}"Osphradia"` for testing chemical nature of water.


● `color{Brown}"Sexes"`: They are usually `color{Violet}"dioecious"` and `color{Violet}"oviparous"`.

● `color{Brown}"Fertilization"`: Maybe external or Internal

● `color{Brown}"Development"`: Mostly `color{Violet}"indirect"` development. `color{Violet}"Trochophore"` is very common larva of Molluscs.

`color{Green}♣ color{Green} "Just for Curiosity"`

● `color{Violet}"Hydrated organic gemstones"` known as `color{Violet}"Pearls"` are commonly produced by `color{Violet}"bivalve molluscs"`, especially Pearl oysters and some species of freshwater mussels.

● Found between the mantle and shell, pearls consist of a protective material called `color{Violet}"Nacre"`, or `color{Violet}"Mother of Pearl"`, which is secreted in reaction to some form or irritation to parasite or food particle or wound.

● Nacre layer is made up of `color{Violet}"calcium carbonate"` and a binding protein `color{Violet}"concheolin"` which settles on the irritant.