Question

Identify the phylum which shows the following characteristics: 
1. Animals are exclusively marine, radially symmetrical, and diploblastic. 
2. Body bears eight external rows of ciliated comb plates which help in locomotion. 
3. Digestion is both extracellular and intracellular. 
4. Reproduction only by sexual modes.

• A. Coelenterata
• B. Mollusca
• C. Arthropoda
• D. Ctenophora

Hint:

Ctenophora is known for its bioluminescence and comb-like cilia.

Answer 1

The Correct Option is D

Phylum identification based on characteristics:

(A) Coelenterate - Incorrect: While marine and diploblastic, they lack comb plates and show both sexual/asexual reproduction.

(B) Mollusca - Incorrect: These are triploblastic and show bilateral symmetry (except cephalopods).

(C) Arthropoda - Incorrect: Triploblastic with chitinous exoskeleton and jointed appendages.

(D) Ctenophora - Correct: Comb jellies match all characteristics - eight ciliated comb rows, diploblastic, marine, exclusively sexual reproduction with bioluminescence.

The correct answer is (D) Ctenophora, commonly called comb jellies or sea walnuts.

Answer 2

These characteristics describe the phylum Ctenophora (comb jellies) :

1. Exclusively marine, radially symmetrical, and diploblastic : Ctenophores are marine animals with radial symmetry and two tissue layers (diploblastic).
2. Eight rows of ciliated comb plates : Ctenophores have eight longitudinal rows of cilia called comb rows or combs , which are used for locomotion.
3. Digestion is both extracellular and intracellular : Ctenophores have a gastrovascular cavity where digestion occurs both inside and outside cells.
4. Reproduction only by sexual modes : Ctenophores reproduce sexually, with no known asexual reproduction.

Other options:

• Coelenterate (Cnidaria) : Also radially symmetrical and diploblastic but lack comb plates.
• Mollusca : Not exclusively marine, lack radial symmetry, and have different body structures.
• Arthropoda : Not radially symmetrical and lack comb plates.

Final Answer:
(D) Ctenophora