Question

Assertion: Air sacs are connected to lungs in Class Aves.
Reason: Air sacs supplement respiration in birds.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect

Answer 1

Hint: The anatomy of the birds is somewhat different compared to all other animals, this is mainly because of the unique nature of birds that are flying, because of this all the organs and tissues are arranged in such a way to adapt to the flight mode.

Complete answer:
Birds have unique features, and this is due to the flying nature of birds, and the skeleton system is very lightweight but the musculature is powerful, and at the same time it has a powerful circulatory and respiratory system.
As birds have to fly, it has a strong metabolism and needs more oxygen, to meet the oxygen demand the respiratory system has little changes.
Birds have lungs for respiration, but it is not similar to lungs present in humans, because in humans and other animals like amphibians, and reptiles, where lungs undergo both expansion and contraction but here, the lungs are rigid, and it consists of air sacs.
The air sacs that present in the lungs of the birds acts like the bellows that ventilate the lungs are the air sacs.
Air sacs in birds are distributed throughout much of the birds' bodies.
In the air sacs, air moves in a unidirectional way, through the parabronchi of the rigid lungs.
Even though bird lungs are smaller than those of mammals of comparable size, those air sacs account for 15% of the total body volume of birds.
whereas in mammals, the alveoli are present instead of air sacs and they act as the bellows where they constitute only 7% of the total body volume.
As the walls of the air sacs do not have a good blood supply and so do not play a direct role in gas exchange. Instead, they help in the direct entry of air.

So the correct option is A.

Note: To say simply birds anatomy made it in very light weight but other systemic structures are made strong in order to meet the demands of oxygen say they have high metabolic activity, in a same way air sacs are present in lungs, but those air sacs are absent in some flightless birds.