Phylum Ctenophora (Sea walnut) NCERT Notes & MCQs for NEET Biology

Definition : Ctenophora are marine zooplankton invertebrate and called as sea gooseberries or Sea walnut.

Table of Contents:

• ​Introduction to Phylum Ctenophora (Comb Jellies)
• ​General Characteristics and Habitat
• ​The Mystery of Bioluminescence
• ​Body Structure: Comb Plates and Digestion
• ​Reproduction and Development
• ​Ctenophora vs. Cnidaria (Quick Comparison Table)
• ​Important Examples: Pleurobrachia and Ctenoplana
• ​NEET 100% Selection Challenge: MCQs

General features 

• Ctenophores are commonly known as sea walnuts or combe Jellies 
• They are exclusively marine.
• They are Diploblastic,radially symmetrical, Acoelomate organisms with tissue level of organisation. 
• The body bears eight external rows of ciliated comb plates  which help in locomotion.
•  Digestion is both extracellular and intracellular.

Watch Detailed video lecture on Ctenophora here:

• Bioluminescence  is the property of a living organism to emit light,  well-marked in ctenophores. 
• Sexes are not separate therefore they are Monoecious 
• Reproduction takes place only by sexual mode.Development is indirect.
•  Fertilisation is external with indirect development.

Examples of Ctenophora  

Pleurobrachia 

• It is commonly called as sea gooseberries.
• It is a pelagic animal caught in coastal area but some time it is present in intertidal zone. It is widely distributed in all over the world.

• It has two tentacles which are long it's length of body.
• This ctenophora does not show Bioluminescence but has some shining effect.
• It uses Eight  row of comb plate for the movement.
• It is hermaphrodite and has both male and female reproductive organ
• It does not has nematocyst has special cell colloblast for the attachment.

Ctenoplana 

• It is commonly called as sea walnut.
• It has reduced nervous system including non polar neurons without synapsis.
• It has two tentacles which are long it's length of body.
• Ctenoplana  show Bioluminescence and it glow in dark.
• It uses Eight  row of comb plate for the movement.
• It is hermaphrodite and has both male and female reproductive organ
• It does  has special cell colloblast  which release stick material to catch the prey.

Feature	Phylum Cnidaria (Coelenterata)	Phylum Ctenophora (Comb Jellies)
Habitat	Mostly marine, some freshwater (Hydra)	Exclusively marine (Sirf Samundar mein)
Special Cells	Cnidoblasts (Stinging cells) present	Cnidoblasts are Absent (Lasso cells present)
Bioluminescence	Usually absent	Strikingly Present (Chamkilay jeev)
Locomotion	Through tentacles or body wall	8 Ciliated Comb Plates (8 kangi jaisi plates)
Body Forms	Polyp and Medusa both present	No Polyp or Medusa forms
Reproduction	Both Sexual and Asexual	Only Sexual reproduction

1. Comb Plate in Ctenophora are involved in

A. Asexual reproduction 

B. Digestion

C. Locomotion

D. Transportation

Answer : C  

2. Which of the following feature is not present in both Cnidarian and Ctenophora.

A.Extracellular and Intracellular digestion

B. External fertilisation with indirect development

C. Radial symmetrical and Diploblastic condition 

D.Bioluminescence - Property of emit light

Answer : D  

3. Ctenophora are also known as  

A. Coral

B. Sea walnut 

C. Comb jellies 

D. Sea walnut and Comb jellies

Answer : D  

4. Which of the following feature is present in both Cnidarian and Ctenophora.

A. Eight row of Comp plate

B. Skeleton of calcium carbonate

C. Radial symmetrical and Diploblastic condition 

D. Bioluminescence - - Property of emit light

Answer : C  

5. Which of the following feature is not present in  Ctenophora.
A.  Animals are Monoecious.
B. They reproduce only by sexual means.
C. They have eight row of comb plate for locomotion.
D. Aurelia is a Ctenophora and commonly called as Jelly fish.

Answer : D 

6. Which of the following feature is not present in  Ctenophora.

A. Non cilliated comb plate 

B. Tentacles 

C. External fertilisation 

D. Bioluminisence 

Answer : A  

7. Consider the following feature with respect to Ctenophora and select the correct code:

1. Indirect development

2. Saxes are Separate 

3. Asexual reproduction by budding 

4. Sexual reproduction 

A. 1, 2 and 4

B. 2, 3 and 4

C. 1, 3 and 4

D. 1, 2 and 3 

Answer : A  

8. Which of the following statement is correct for   Ctenophora.

A. They have 6 to 15 row of  non ciliated comb plate.

B. Digestion is intracellular. 

C. They reproduce only sexual means.

D.  They are also called as sea hare.

Answer : C  

9. Which of the following are example of Ctenophora.
A. Balanoglossus and Saccoglossus
B. Obelia and Aurelia
C. Pleurobrachia  and              Ctenoplana
D. Neophron and Pteropus
Answer : C  

10. Identify the following diagram 

A. Ctenoplana

B. Saccoglossus 

C. Balanoglossus

D. Pleurobrachia

Answer : D

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