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Q99 (CDS-I/2004) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Animal diversity behaviour Answer Verified

Assertion (A) : Birds can considerably use water loss in the urine. Reason (R) : Birds store urine along with faeces in cloaca.

Result
Your answer: —  Â·  Correct: A
Explanation

Assertion (A) is true as birds are uricotelic, converting nitrogenous waste into uric acid, which is nearly insoluble and requires very little water for excretion [t3, t8, t9]. This adaptation allows birds to conserve water and reduce weight for flight [t8, t10]. Reason (R) is also true and provides the correct explanation. Birds lack a urinary bladder; instead, ureters transport urine to the cloaca [t3, t10]. In the cloaca, urine is stored and mixed with fecal matter [t1, t7]. Crucially, the cloacal chambers (coprodeum and urodeum) and the lower intestine facilitate the reabsorption of water from the urine-feces mixture before expulsion [t2, t5, t10]. This post-renal modification significantly reduces total water loss, making the storage and processing of urine within the cloaca the physiological mechanism that enables the water conservation mentioned in the assertion.

Sources

  1. [1] https://pubmed.ncbi.nlm.nih.gov/3970190/
  2. [2] https://www.nhm.ac.uk/discover/do-birds-pee.html
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