Question

Assertion:
The birds can maintain a constant body temperature.
Reason:
Birds possess feathers covering their body.
(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: Thermoregulation is an ability that not only humans but nearly all animals and plants, possess. It is the phenomena by which an organism keeps its body within a certain temperature range, even when the temperature outside its body is very different.

Complete answer:
Birds have a constant body temperature which commonly remains in between 40°C to 45°C, even in sub-zero weather. The feathers play a very important function of retention of heat. The feathers create an efficient, non-conduction covering with its countless dead air spaces, useful as insulation. In winters, the heat loss is reduced to a minimum by fluffing out the feathers, which increases the depth of insulating material by adding to the air spaces within the feathery layers. In summers, the feathers are often held close to the body to allow some of the body heat to escape.

The right answer is 'Both Assertion and Reason are correct and Reason is the correct explanation for Assertion'
Hence, the correct answer is option (A).

Additional information:
Birds have many physical and behavioural adaptations to keep warm.
Physical Adaptations:
a) Feathers provide them with insulation.
b) Legs and feet are covered with specialized scales that minimise loss of heat.
c) Fat reserves serve as insulation.

Behavioural Adaptations:
a) Fluffing out their feathers
b) Tucking their bills into their shoulder feathers
c) Sunning
d) Shivering
e) Roosting

Note: Birds are warm-blooded animals that have a much higher metabolism, and thus higher body temperature, than humans. The feathers help the birds in keeping them warm in cold weather due to air trapped in them. Air being a bad conductor of heat prevents the body heat of birds from escaping to the cold surroundings and hence keeps the bird warm.