Question

Assertion : Sharks are said to be ammonotelic animals
Reason : Sharks can retain considerable amounts of ammonia in their blood

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (D)

Sharks are not ammonotelic, but they are ureotelic animals. Ureotelic animals excrete urea instead of ammonia as the major nitrogenous waste product. Sharks need to avoid water loss from body, thus they cannot excrete ammonia, as it requires enough water to be eliminated. Sharks can retain so much urea in their blood that their blood osmotic pressure approaches that of sea water. This minimises water loss from their body to adjust to the concentrated saline water of the sea.