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Q211.
Assertion (A): Platyhelminthes are acoelomates.
Reason (R): The body cavity is absent in flatworms.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: Acoelomates lack a body cavity; Platyhelminthes (flatworms) are acoelomate.
Q212.
Assertion (A): The body of an earthworm shows metamerism.
Reason (R): The earthworm's body is externally and internally divided into segments with a serial repetition of some organs.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: Metamerism refers to segmentation with serial repetition of organs; earthworms exhibit this.
Q213.
Assertion (A): Animals with a notochord are called chordates.
Reason (R): The notochord is an ectodermally derived rod-like structure.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Animals with a notochord are chordates (true). The notochord is mesodermally derived, not ectodermal, so the reason is false.
Q214.
Assertion (A): The water canal system in sponges is helpful in food gathering and respiratory exchange.
Reason (R): Water enters through the osculum and exits through minute pores called ostia.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Sponges' water canal system aids feeding and respiration (true). Water actually enters via ostia (pores) and exits through the osculum — the reason had the flow reversed.
Q215.
Assertion (A): The name Cnidaria is derived from the presence of cnidoblasts.
Reason (R): Cnidoblasts are used for anchorage, defense, and capture of prey.
[Animal-Kingdom] [class-xi]
Correct option: B [ ]
Remark: Both A and R are true but R is not the correct explanation of A. Explanation: Both statements are true: the phylum name refers to cnidoblasts, and cnidoblasts function in anchorage/defense/prey capture; but the function is not the reason for the etymology.
Q216.
Assertion (A): Some cnidarians like Obelia exhibit metagenesis.
Reason (R): In Obelia, polyps produce medusae sexually and medusae produce polyps asexually.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Obelia shows metagenesis (true), but the reproduction modes are reversed in the reason: polyps produce medusae asexually and medusae produce polyps sexually.
Q217.
Assertion (A): Ctenophores are commonly known as comb jellies.
Reason (R): Their body bears eight external rows of ciliated comb plates which help in locomotion.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: Ctenophores are called comb jellies due to their eight rows of ciliated comb plates used for locomotion.
Q218.
Assertion (A): Bioluminescence is well-marked in ctenophores.
Reason (R): Bioluminescence is the property of a living organism to emit light.
[Animal-Kingdom] [class-xi]
Correct option: B [ ]
Remark: Both A and R are true but R is not the correct explanation of A. Explanation: Bioluminescence is indeed common in ctenophores and the reason correctly defines bioluminescence, but that definition does not explain why it occurs in ctenophores specifically.
Q219.
Assertion (A): Platyhelminthes are called flatworms.
Reason (R): They have a dorso-ventrally flattened body.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: The term "flatworms" refers to their dorso-ventrally flattened body.
Q220.
Assertion (A): Parasitic flatworms possess hooks and suckers.
Reason (R): Flame cells in flatworms help in osmoregulation and excretion.
[Animal-Kingdom] [class-xi]
Correct option: B [ ]
Remark: Both A and R are true but R is not the correct explanation of A. Explanation: Both statements are true features of parasitic flatworms. However, the presence of flame cells for excretion is a separate physiological feature and does not explain the presence of hooks and suckers for attachment.