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Q201.
Assertion (A): Sponges exhibit a cellular level of organisation.
Reason (R): In sponges, the cells are arranged as loose cell aggregates.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: The cellular level of organisation is defined by cells being arranged as loose aggregates, which is the pattern seen in sponges.
Q202.
Assertion (A): Coelenterates show a tissue level of organisation.
Reason (R): In coelenterates, tissues are grouped together to form organs.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Coelenterates indeed have tissue level of organisation. However, grouping of tissues to form organs is characteristic of organ level of organisation, not tissue level.
Q203.
Assertion (A): The digestive system in Platyhelminthes is called incomplete.
Reason (R): It has only a single opening to the outside that serves as both mouth and anus.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: An incomplete digestive system has a single opening for both ingestion and egestion, as in Platyhelminthes.
Q204.
Assertion (A): Arthropods have an open type of circulatory system.
Reason (R): In an open circulatory system, blood is circulated through a series of vessels of varying diameters.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Arthropods do have an open circulatory system. The reason given actually defines a closed circulatory system (blood confined to vessels). In open systems blood bathes tissues directly.
Q205.
Assertion (A): Most sponges are asymmetrical.
Reason (R): In sponges, any plane passing through the central axis of the body divides the organism into two identical halves.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Most sponges are indeed asymmetrical. The reason describes radial symmetry (where planes through an axis give equal halves), which is not applicable to asymmetry.
Reason (R): The body of an adult echinoderm can be divided into identical left and right halves in only one plane.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Adult echinoderms have radial symmetry (multiple planes through central axis produce similar halves); the reason describes bilateral symmetry (single plane produces identical left and right halves).
Q207.
Assertion (A): Coelenterates are diploblastic animals.
Reason (R): Their cells are arranged in two embryonic layers: an external ectoderm and an internal endoderm.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: Diploblastic animals have two germ layers—ectoderm and endoderm—as seen in coelenterates.
Q208.
Assertion (A): Platyhelminthes are triploblastic animals.
Reason (R): The developing embryo in Platyhelminthes has a third germinal layer, mesoderm, between the ectoderm and endoderm.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: Triploblastic animals possess mesoderm as the third germ layer; Platyhelminthes are triploblastic.
Q209.
Assertion (A): Annelids are considered true coelomates.
Reason (R): In annelids, the body cavity is lined by mesoderm.
[Animal-Kingdom] [class-xi]
Correct option: A [ ]
Remark: Both A and R are true and R is the correct explanation of A. Explanation: Coelomates have a body cavity (coelom) lined by mesoderm; annelids are true coelomates.
Q210.
Assertion (A): Aschelminthes are pseudocoelomates.
Reason (R): In aschelminthes, the body cavity is absent.
[Animal-Kingdom] [class-xi]
Correct option: C [ ]
Remark: A is true but R is false. Explanation: Aschelminthes are pseudocoelomates (they have a body cavity—the pseudocoel), but the reason incorrectly states that the body cavity is absent; absence of body cavity is acoelomate condition.