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Q231.
Assertion (A): The most distinctive feature of echinoderms is the water vascular system.
Reason (R): The water vascular system helps in locomotion, food capture, and respiration.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: The water vascular system is unique to echinoderms and is crucial for several key life functions, including locomotion, feeding, and respiration.
Q232.
Assertion (A): Adult echinoderms are radially symmetrical, but their larvae are bilaterally symmetrical.
Reason (R): All echinoderms are exclusively marine.
[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 correct facts about echinoderms. However, their marine habitat does not explain their change in symmetry during development.
Q233.
Assertion (A): An excretory system is absent in echinoderms.
Reason (R): In echinoderms, the digestive system is incomplete.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Assertion is correct; echinoderms lack a specialized excretory system. The reason is false; their digestive system is complete, with a mouth and an anus.
Q234.
Assertion (A): Hemichordata is now placed as a separate phylum under non-chordata.
Reason (R): Hemichordates have a rudimentary structure called a stomochord, which is similar to a notochord.
[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. Hemichordata was moved out of Chordata, and it possesses a stomochord. However, the presence of a stomochord was the reason it was previously included in Chordata; its reclassification is due to understanding that the stomochord is not homologous to the notochord.
Q235.
Assertion (A): Chordates are characterized by a dorsal, hollow nerve cord.
Reason (R): Non-chordates have a ventral, solid, and double central nervous system.
[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 correctly describe the nervous systems of chordates and non-chordates, respectively. However, the state of the non-chordate nervous system is a point of contrast, not an explanation for the chordate condition.
Q236.
Assertion (A): All vertebrates are chordates, but all chordates are not vertebrates.
Reason (R): In vertebrates, the notochord is replaced by a vertebral column in the adult, which is not true for protochordates.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: This statement is justified because all vertebrates possess a notochord at some stage (making them chordates), but protochordates are chordates that never develop a vertebral column (so not all chordates are vertebrates).
Q237.
Assertion (A): Urochordata and Cephalochordata are referred to as protochordates.
Reason (R): In Urochordata, the notochord is present only in the larval tail.
[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 reason describes a key feature of Urochordata, but it doesn't explain why both subphyla are grouped as protochordates.
Q238.
Assertion (A): In Cephalochordata, the notochord is persistent throughout life.
Reason (R): It extends from the head to the tail region.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: The persistence of the notochord throughout life and its extension from head to tail are the defining characteristics of the subphylum Cephalochordata.
Q239.
Assertion (A): Cyclostomes are ectoparasites on some fishes.
Reason (R): They have a sucking and circular mouth without jaws.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: The sucking, circular, jawless mouth of cyclostomes is an adaptation for their ectoparasitic lifestyle on other fish.
Q240.
Assertion (A): Cyclostomes die after spawning.
Reason (R): They are marine but migrate to fresh water for spawning.
[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 facts about the life cycle of cyclostomes. However, their migration to freshwater for spawning doesn't explain why they die afterward.