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Q21.
The name Cnidaria is derived from the presence of:
[Animal-Kingdom] [class-xi]
Correct option: C [ Cnidoblasts or cnidocytes ]
Remark: Explanation: The name Cnidaria is derived from the presence of specialized stinging cells called cnidoblasts or cnidocytes.
Q22.
Which of the following is NOT a function of cnidoblasts?
[Animal-Kingdom] [class-xi]
Correct option: D [ Digestion ]
Remark: Explanation: Cnidoblasts are used for anchorage, defense, and the capture of prey. Digestion in cnidarians is extracellular and intracellular.
Q23.
The two basic body forms in cnidarians, such as the sessile, cylindrical form and the umbrella-shaped, free-swimming form, are called:
[Animal-Kingdom] [class-xi]
Correct option: B [ Polyp and medusa ]
Remark: Explanation: Cnidarians exhibit two basic body forms: the polyp, which is sessile and cylindrical, and the medusa, which is umbrella-shaped and free-swimming.
Q24.
The alternation of generations seen in cnidarians like Obelia is called:
[Animal-Kingdom] [class-xi]
Correct option: C [ Metagenesis ]
Remark: Explanation: Cnidarians that exist in both polyp and medusa forms exhibit an alternation of generations called Metagenesis.
Q25.
Ctenophores are commonly known as:
[Animal-Kingdom] [class-xi]
Correct option: B [ Sea walnuts or comb jellies ]
Remark: Explanation: Ctenophores are commonly known as sea walnuts or comb jellies.
Q26.
Locomotion in ctenophores is carried out by:
[Animal-Kingdom] [class-xi]
Correct option: C [ Eight external rows of ciliated comb plates ]
Remark: Explanation: The body of a ctenophore bears eight external rows of ciliated comb plates, which help in locomotion.
Q27.
The property of a living organism to emit light, which is well-marked in ctenophores, is known as:
[Animal-Kingdom] [class-xi]
Correct option: C [ Bioluminescence ]
Remark: Explanation: Bioluminescence, the property of a living organism to emit light, is a well-marked characteristic of ctenophores.
Q28.
The specialized cells that help in osmoregulation and excretion in Platyhelminthes are called:
[Animal-Kingdom] [class-xi]
Correct option: A [ Flame cells ]
Remark: Explanation: In Platyhelminthes (flatworms), specialized cells called flame cells help in osmoregulation and excretion.
Q29.
Platyhelminthes are described as:
[Animal-Kingdom] [class-xi]
Correct option: B [ Bilaterally symmetrical and acoelomate ]
Remark: Explanation: Flatworms (Platyhelminthes) are bilaterally symmetrical, triploblastic, and acoelomate animals.
Q30.
The body of Aschelminthes is circular in cross-section, hence they are called:
[Animal-Kingdom] [class-xi]
Correct option: C [ Roundworms ]
Remark: Explanation: Aschelminthes have a body that is circular in cross-section, which is why they are called roundworms.