Question

Read the following statements (I - III) and identify by which of the following mechanisms, the human body acclimatizes to the less availability of oxygen at higher altitudes?

I. Increasing the number of red blood cells.
II. Increasing the affinity of haemoglobin towards oxygen.
III. Decreasing breathing rate.

• A. I and III
• B. II and III
• C. I and II
• D. Only I

Answer 1

The correct option is D Only I

Adaptation or acclimatisation refers to the morphological, physiological or behavioural attributes that allow organisms to survive in their habitats (the natural environment of the organism).

As we move to higher altitudes, the density of gases in air decreases gradually. Due to this the availability of oxygen at higher altitude is less. This causes people, moving to places at higher elevations, to initially experience (altitude sickness) difficulty in breathing, dizziness, etc.

This feeling however passes with time and an individual gets adapted to the atmospheric conditions of higher altitudes. This is due to some short term and long term physiological adaptations in the body. They are as follows :

• For short term relief, the breathing rate 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. Hence statement II and III are incorrect.
  
• Long term adaptation include the increase in the number of red blood cells to increase the transport of available oxygen to the tissues. Thus statement I is correct.