Question

Assertion (A): Most marine bony fishes drink sea water continuously.
Reason (R): They lose water from their body to the surrounding sea water by osmosis.

• A. Both (A) and (R) are true. (R) is correct explanation for (A)
• B. Both (A) and (R) are true. (R) is not correct explanation for (A)
• C. (A) is true. But (R) is false
• D. (A) is false. But (R) is true

Hint:

Hypotonic organisms in a hypertonic medium always lose water by osmosis.
Therefore, marine bony fishes must drink water to survive, whereas freshwater fishes do not drink water because they absorb it continuously.

Answer 1

The Correct Option is A

Step 1: Think about the salinity gradient marine fish face.
Seawater is more concentrated than the fish's own body fluids, so water naturally tends to move out of the fish and into the sea.
Step 2: Confirm the assertion.
To make up for this constant water loss, marine bony fish drink seawater almost continuously and then actively pump out the excess salt through their gills and kidneys.
Step 3: Confirm the reason explains the assertion.
The reason describes exactly why the fish needs to drink so much, because it is steadily losing water to the hypertonic sea by osmosis, so the reason is both true and the direct cause of the behaviour in the assertion.
Final answer: Option 1, both true, reason correctly explains assertion.