Question

Assertion (A): Physiological uremia is seen in cartilaginous fishes. Reason (R): Urea is formed in liver via ornithine cycle.

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

Hint:

Cartilaginous fishes keep their internal osmolarity close to seawater by hoarding urea!

Answer 1

The Correct Option is B

Step 1: Read both parts carefully.
Assertion (A) says cartilaginous fishes show physiological uremia. Reason (R) says urea is made in the liver through the ornithine cycle. We must judge if each is true, and if R explains A.

Step 2: Check the Assertion.
Sharks and other cartilaginous fishes live in salty sea water. To stop losing water to the sea, they keep a lot of urea in their blood on purpose. This high blood urea is called physiological uremia. So (A) is true.

Step 3: Check the Reason.
Urea in vertebrates is built in the liver using a set of steps called the ornithine cycle, also known as the urea cycle. This is a correct fact, so (R) is true.

Step 4: Test the link between them.
Reason (R) only tells us where and how urea is made. It does not tell us why the fish keeps urea in its blood for osmotic balance.

Step 5: Decide the relationship.
Since the fish stores urea for osmoregulation, that is a different idea from simply making urea. So (R) does not explain (A), even though both are true.

Step 6: Pick the matching option.
Both statements are correct, but the reason is not the correct explanation of the assertion.
\[ \boxed{\text{Both (A) and (R) are true. (R) is not the correct explanation for (A)}} \]