Question

ASSERTION: In birds, the skin is moist.
REASON: Moist skin of birds reduces effects of friction due to flying in air.
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' internal features 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 and some commendable 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.

Now let us first discuss the assertion given in the question that is In birds, the skin is moist.
- The skin of birds is not moist but dry. The bird skin does not possess any kind of glands so as secretion is not poured in the skin it is dry.
- Only one gland namely oil gland is present at the base of the tail. This gland is used for lubrication of feathers and not to make skin moist. The skin of birds is covered with feathers which provides them insulation. Thus the given assertion is exactly incorrect.

Now let us discuss about given reason that is:
- Moist skin of birds reduces effects of friction due to flying in air.
- The skin of birds is not moist as discussed above. The friction is reduced because in birds the endoskeleton is fully ossified and the long bones present in them are hollow.
- They possess air cavities. These kinds of bones are called pneumatic bones and they lack bone marrow which helps them to fly.
Thus, the reason given in the question is not correct.

Our required answer is D that is Both Assertion and Reason are incorrect.

Note: T.H. Huxley said "birds are glorified reptiles". The feathers are highly modified reptilian scales. Birds have scales on their legs. Their eggs resemble reptilian eggs in general but have a calcareous shell. Oil glands, keel, pygostyle and syrinx are absent in flightless birds.