Question:
Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Freshwater fishes produce a large amount of diluted urine
Reason (R): Skin has low permeability to the water and salt ions
In light of the above statements, choose the correct answer from the options given below.
Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Freshwater fishes produce a large amount of diluted urine
Reason (R): Skin has low permeability to the water and salt ions
In light of the above statements, choose the correct answer from the options given below.
Assertion (A): Freshwater fishes produce a large amount of diluted urine
Reason (R): Skin has low permeability to the water and salt ions
In light of the above statements, choose the correct answer from the options given below.
Show Hint
The primary osmotic water entry occurs through the highly permeable gill epithelium, not the skin. The skin's relative impermeability is a protective adaptation but does not drive urine dilution.
Updated On: Jul 9, 2026
- Both (A) and (R) are true and (R) is the correct explanation of (A).
- Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
- (A) is true but (R) is false.
- (A) is false but (R) is true.
Show Solution
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept:
Freshwater fishes are hyperosmotic to their environment. This osmotic gradient causes water to enter their bodies passively and salts to diffuse out.
Step 2: Detailed Explanation:
- Assertion (A): Because freshwater fish experience a constant influx of water, they must continuously remove excess water to prevent tissue swelling. Their kidneys filter water rapidly, and their renal tubules reabsorb essential ions while allowing water to pass. This results in the production of a large volume of highly dilute urine. Thus, Assertion (A) is true.
- Reason (R): To minimize osmotic stress, a fish's skin and scales have low permeability to water and dissolved ions. This barrier helps limit water influx and salt loss. Thus, Reason (R) is true.
- Relationship: The primary site of water entry is the gills, which must remain highly permeable for respiration. The low permeability of the skin helps reduce the overall water load, but it does not cause the large volume of dilute urine. The urine is produced to remove the water that enters through the gills. Therefore, both statements are true, but the Reason does not explain the Assertion.
Step 3: Final Answer:
Both statements are true, but the Reason is not the correct explanation of the Assertion.
Freshwater fishes are hyperosmotic to their environment. This osmotic gradient causes water to enter their bodies passively and salts to diffuse out.
Step 2: Detailed Explanation:
- Assertion (A): Because freshwater fish experience a constant influx of water, they must continuously remove excess water to prevent tissue swelling. Their kidneys filter water rapidly, and their renal tubules reabsorb essential ions while allowing water to pass. This results in the production of a large volume of highly dilute urine. Thus, Assertion (A) is true.
- Reason (R): To minimize osmotic stress, a fish's skin and scales have low permeability to water and dissolved ions. This barrier helps limit water influx and salt loss. Thus, Reason (R) is true.
- Relationship: The primary site of water entry is the gills, which must remain highly permeable for respiration. The low permeability of the skin helps reduce the overall water load, but it does not cause the large volume of dilute urine. The urine is produced to remove the water that enters through the gills. Therefore, both statements are true, but the Reason does not explain the Assertion.
Step 3: Final Answer:
Both statements are true, but the Reason is not the correct explanation of the Assertion.
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