Phylum Mollusca: Characteristics, Examples & NEET MCQs

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05 February

Phylum Mollusca: Characteristics, Examples & NEET MCQs | Animal Kingdom Class 11

Definition

Molluscs are soft body animals with unsegmented bodies bodies with calcareous shell.

Hum isse pehle Jointed appendages animals jo ki Phylum Arthropoda main hai study kar chuke hai.

This is the second largest phylum of Animals after the arthropods.

Sirf Notes hi nahi, is chapter ke Full Video Lectures aur MCQs ke liye hamara [NEET Biology Master Hub] visit karein — Jahan milega NEET 2026 ka complete study material ek hi jagah!

📍 Table of Contents

📍 Is Post Mein Aap Padhenge:

Introduction: Phylum Mollusca kya hai?

General Features: Organization, Symmetry aur Coelom.

Body Structure: Head, Muscular Foot aur Visceral Hump ka raaz.

The Mantle: Mantle Cavity aur Gills (Ctenidia) ke functions.

Radula: NEET ka sabse important "Rasping Organ".

Examples & Tricks: Pila, Octopus aur Pinctada ko yaad karne ki trick.

NEET MCQ Challenge: 100% Questions yahi se aayenge!

General characters

They are terrestrial and also found in fresh and marine water.
They have an organ-system level of organisation.
They are bilaterally symmetrical, triploblastic and coelomate animals.
Body is covered by a calcareous shell. with unsegmented body.
Body is divided into with a distinct head, muscular foot and visceral hump.
A soft and spongy layer of skin forms a mantle over the visceral hump.

Comparison table between Head Muscular foot and Visceral hump.

Body Part Description Main Function
Head Front part with sensory tentacles. Sensing the environment.
Muscular Foot Ventral muscular structure. Locomotion (Movement).
Visceral Hump Soft hump containing internal organs. Digestion, Excretion, Reproduction.

Body Part	Description	Main Function
Head	Front part with sensory tentacles.	Sensing the environment.
Muscular Foot	Ventral muscular structure.	Locomotion (Movement).
Visceral Hump	Soft hump containing internal organs.	Digestion, Excretion, Reproduction.

The space between the hump and the mantle is called the mantle cavity in which feather like gills are present.
Gills are respiratory and excretory functions.
The anterior head region has sensory tentacles.
The mouth contains a file-like rasping organ for feeding, called radula.
Saxes are separate and development is indirect.
Mostly they are oviparous, they lay eggs.

🎥 Video Highlights & Timestamps

Click the time to jump to that part in the video:

00:00 — Introduction to Phylum Mollusca
01:02 — General Features (Coelom & Symmetry)
03:07 — Body Parts: Head, Foot & Visceral Hump
06:02 — What is Mantle?
07:17 — Mantle Cavity & Gills (Respiration)
08:25 — Radula: The Rasping Organ
09:44 — Important Examples (Pila, Octopus, etc.)

💡 Tip: Watching the video while reading notes helps in 100% retention!

Examples of Mollusca

Octopus

It is commonly called as Devil fish.
Body of octopus is divided into head and Visceral hump.
Octopus is Di branchiate having two gill , two auricle and two kidney.
Nervous system is well developed.
Head contain eyes, siphon and eight long arms and two arms posses suckers for the attachment.
One of the arms is male is modified into Hectocotylized arm.

Octopus ( Devil fish )

Animal can crawl by its arms and swim backwards.
Visceral mass and mantle cavity are enclosed by mantle.
Shell and nidamental glands are absent.

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Sepia

It is commonly called as cuttle fish.
Body of sepia is divided into head collar and trunk or Visceral hump.
Sepia is Dibranchiate having two gill , two auricle and two kidney with luminescent property.
Nervous system is well developed.
Head contain ten oral arms. Eight are long arms with several pedicellate suckers around the Mouth. And two arms posses pedicellate suckers at the called Hectocotylized arms.


Sepia ( cuttle fish )

Head bear a pair of eye without olfactory crest.
Calcareous shell is well developed and maintain buoyancy.
Ink gland secrete ink during irritation and get protection from predator.
Loligo

It is commonly called as cuttle fish.
Body of sepia is divided into head collar and trunk or Visceral hump.
Head bear a pair of eye without olfactory crest.
Head contain ten oral arms.out of ten, eight oral arms has four row of pedicellate suckers.  
Remaining two arms has six pairs of pedicellate suckers, used in capturing of prey. These are Hectocotylised arms.

Loligo ( Squids)
In male oral arms are modified into copulatory organ .
Loligo has two ctenidia , two auricle and two kidney.
Calcareous shell is well developed and maintain buoyancy.
Ventral siphon is modification of foot.
Pinctada
It is commonly called as Pearl Oyster .
Shell valves are unequal. Hinge line is straight and bear ear and wing like process.
Left shell is large ,convex and permanently attached with the rock by byssal thread.
Pinctada ( Pearl oyster)

Right shell is small and thin covers the visceral organ.
A single adductor muscle is present.
Right and left mantle lobe are free.
Shell of animal secrete pearl when any insect create irritation.

Pila
It is commonly called as Apple snail .
Body is covered by thick univalved shell and comprises body whorl , penultimate whorl and apex.
Surface of shell is marked by line of growth.
🎯 NEET Must-Know Points:
1. Radula (The File-like Organ):"The mouth contains a file-like rasping organ for feeding called Radula."
(Hinglish: Ye molluscs ka 'Grinder' hai jo khane ko peesta hai.)
2. Mantle & Mantle Cavity:A soft/spongy layer of skin forms the Mantle over the visceral hump. The space between the hump and mantle is the Mantle Cavity.
Gills (Ctenidia): Located in the cavity; used for both Respiration and Excretion.
Shell is spirally coiled round the axis called as columella.
Soft parts are differentiated into head, muscular foot and visceral mass.
Pila ( Apple snail)

Head is located at the upper side with one pair of eyes.
Visceral mass contain internal organs and covered by mantle or pallium.
It has great medicinal and experimental value.

Aplysia
It is commonly called as Sea hare.
Anterior end has head and neck.
Animal is slug like and anterior head are extended into two tentacular folds.
Aplysia (Sea hare)

Head bear a pair of eye at anterior tentacular folds. Behind the eyes, rhinophores are present as tentacular folds.
Mantle cavity is opened at right side and backward pointing into ctenidium.
Anus is posterior located.
There are a pair large fleshy outgrowth called parapodia help in swimming.
Shell is internal and rudimentary.
Dentalium
Animal is commonly called as Tusk shell.
Body is covered by arched shell secreted by mantle.
Body of animal has vestigial head which represents by proboscis without eyes.
Mouth is surrounded by leaf tentacles called captacules which are sensory , prehensile and regenerative.
Ctenidia are absent.
Conical foot is emerged from shell to make burrow in sand.
Dentalium ( Tusk Shell)

Liver , muscle and kidney are seen after removing the shell.
Radula is well developed. Anus is located behind the foot.
Respiration takes place by lining of mantle because gills are absent.

Chiton
Animal is commonly called as sea mouse.
Body is divided into district head large foot and mantle which form leaf like roof of body.
Head contain ventral mouth and labial palps.
Mouth and anus are located at opposite end of the body.
Eyes and tentacles are absent.
Dorsal side of mantle contains series of eight calcareous overlapping plates.
Chiton ( sea mouse)

Several pairs of bipectinate ctenidia are present on either side of body.
Side of mantle form mantle girdle which contain small calcified Spicules .
Mollusca Examples Yaad Karne ki "Bhole Nath" Trick:
Trick: "Pila Apple lekar Pinctada (Pearl) dhundhne Gaya, tabhi Octopus (Devil) ne use Dentalium (Shell) aur Chaetopleura pakda diya."
Pila – Apple Snail
Pinctada – Pearl Oyster
Sepia – Cuttlefish
Loligo – Squid
Octopus – Devil fish
Aplysia – Sea hare
Dentalium – Tusk shell
Chaetopleura – Chiton
Next Topic main Hum baat karenge ek aise phylum ki. Jisme animals exclusively marine hote hai Phylum Echinodermata ki.

🎯 NEET MULTIPLE CHOICE QUESTIONS
🔥 100% CHALLENGE
"Questions yahi se aayega... taiyari jeet ki!"
1. Consider the following sentences and select the number of correct statements.
1. Mollusca is the second largest phylum of Animals after the arthropods.
2. Molluscan are found in fresh and marine water but some are terrestrial.
3. Body of Molluscan is covered by a Chitin.
4. Molluscan are Coelomate.
5. Molluscan are triploblastic with organ system level of organisation.
A. Two B. Three
C. Four D. Five
Answer : C

2. Body of Molluscan animal is covered by the
A. Glucosamine
B. Chitin
C. Calcareous ossicles
D. Calcareous Shell
Answer : D

3. Body of Molluscan is divided into
A. Proboscis, Collar and trunk
B. Head , neck and Trunk
C. Head, Muscular foot and visceral hump.
D. Head. Thorax and abdomen.
Answer : C
4. Visceral hump is covered by the mantle which is
A. Soft and spiny skin
B. Hard and spiny skin
C. Soft and spongy skin
D. Hard and spongy skin
Answer: C

5. Which of the following statement is not correct.
A. The space between the hump and the mantle is called the mantle cavity.
B. A soft and spongy layer of skin forms a mantle over the visceral hump.
C. Gills are only respiratory in function in Mollusc.
D. Feather like gills are present inside the mantle cavity.
Answer: C

6. In Mollusc, Gills are involved in
A. Respiration only
B. Excretion only
C. Respiration and Excretion
D. Respiration , Excretion and Reproduction
Answer : C

7. Gills are enclosed in mantle cavity which is space between
A. Muscular foot and mantle
B. Visceral hump and mantle
C.Muscular foot and Visceral hump.
D. Calcareous shell and mantle
Answer : B

8.The mouth of mollusc contains a file-like rasping organ for feeding called A.Radula
B.Muscular pharynx
C.Ctenidia
D.labrum
Answer : A

9. Consider the following sentences and select the number of correct statements.
1. Mostly Molluscan are oviparous, they lay eggs.
2. Molluscan have tentacles on anterior head.
3. Saxes are separated in Molluscan.
4. Development is indirect in Mollusca.
A. Two B. Three
C. Four D. One
Answer : C

10. Which of the following Mollusca is called as Pearl oyster.
A. Pinctada B. Aplysia
C. Dentalium D. Chiton
Answer : A

11. Which of the following pair is not correctly matched.
A. Aplysia : Sea mouse
B. Dentalium: Tusk shell
C. Pila : Apple Snail
D. Loligo : Squid
Answer : A

12. Match the list
A. Aplysia 1. Sea hare
B. Octopus 2.Cuttle fish
C. Sepia 3. Devil fish
D. Chiton 4. Sea mouse

A B C D
A. 1 2 3 4
B. 1 3 2 4
C. 4 3 2 1
D. 4 2 3 1
Answer: B Explanation

13. Identify the animal of Mollusca in given Diagram

A. Unio B. Pila
C. Pinctada D. Chiton
Answer : B