Q.23

Match the animals in Group I with the major form of excreted nitrogen metabolite in

Group II

(A) P – 3, Q – 1, R – 2

(B) P – 1, Q – 2, R – 3

(C) P – 2, Q – 3, R – 1

(D) P – 3, Q – 2, R – 1

The correct matching is: P – 3, Q – 1, R – 2, so the right option is (A).

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Correct matching and concept

• Bony fishes (P) – Ammonia (3):
  Most bony fishes are ammonotelic, directly excreting highly soluble ammonia into the surrounding water through gills and skin.

• Lions (Q) – Urea (1):
  Lions are mammals and predominantly ureotelic, excreting nitrogenous waste chiefly as urea in urine, which is less toxic and conserves water compared with ammonia.

• Birds (R) – Uric acid (2):
  Birds are uricotelic, converting nitrogenous waste to poorly soluble uric acid, which is excreted as a semi-solid paste with minimal water loss—an adaptation to terrestrial and often arid habitats.

Thus, P – 3, Q – 1, R – 2 ⇒ Option (A) is the only fully correct pairing.

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Explanation of all options

Option (A): P – 3, Q – 1, R – 2

• P – 3: Bony fishes → Ammonia; correct because most bony fishes excrete ammonia and are classified as ammonotelic animals.

• Q – 1: Lions → Urea; correct as lions, like other mammals, excrete urea as the chief nitrogenous waste.

• R – 2: Birds → Uric acid; correct since birds mainly excrete uric acid and are uricotelic.

Therefore, Option (A) is the correct answer.

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Option (B): P – 1, Q – 2, R – 3

• P – 1: Bony fishes → Urea; incorrect because their chief excretory product is ammonia, not urea, though some may produce minor urea.

• Q – 2: Lions → Uric acid; incorrect, as mammals primarily excrete urea, not uric acid.

• R – 3: Birds → Ammonia; incorrect, birds excrete uric acid, not ammonia.

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Option (C): P – 2, Q – 3, R – 1

• P – 2: Bony fishes → Uric acid; incorrect because uric acid is not the major nitrogenous waste in fishes.

• Q – 3: Lions → Ammonia; incorrect as direct ammonia excretion is characteristic of many aquatic animals, not terrestrial mammals.

• R – 1: Birds → Urea; incorrect since the main excretory product of birds is uric acid, not urea.

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Option (D): P – 3, Q – 2, R – 1

• P – 3: Bony fishes → Ammonia; this individual pair is correct.

• Q – 2: Lions → Uric acid; incorrect because lions excrete urea as the chief nitrogenous waste.

• R – 1: Birds → Urea; incorrect since birds are uricotelic and excrete uric acid.

Since only Option (A) correctly matches all three organisms with their major excreted nitrogenous metabolites, it is the correct choice.