Question

Assertion (A): A person goes to high altitude and experiences 'altitude sickness' with symptoms like breathing difficulty and heart palpitations.

Reason (R): Due to low atmospheric pressure at high altitude, the body does not get sufficent oxygen.

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

Answer 1

The correct option is B Both (A) and (R) are true and (R) is the correct explanation of (A)

Adaptation refers to the morphological, physiological or behavioural adjustments that allow organisms to survive in new environments or in changing conditions in their current environment.

As we move to higher altitudes, the atmospheric pressure decreases or becomes low. Due to this the availability of oxygen at higher altitudes is less. This causes people, moving to places at higher elevations, to initially experience difficulty in breathing, dizziness, heart palpitations, nausea, vomiting, fatigue, etc. This is called altitude sickness. It usually occurs when a person who is accustomed to low elevations travels to higher elevation.

The feeling however passes with time and an individual gets adapted to the atmospheric conditions of places at higher altitudes. This is due to some physiological adaptations that the body undergoes to adjust to the less availability of oxygen in the air.

For short term relief, the rate of breathing is increased so that more oxygen can be inhaled per minute. The affinity of haemoglobin towards oxygen is also reduced to allow faster dissociation of the oxyhaemoglobin complex near the tissues so that oxygen is free to diffuse into the cells.

A long-term adaptation is the increase in the number of red blood cells to increase the transport of available oxygen to the tissues.