Question

Why do human beings have difficulty breathing at high elevations?
A) O₂ makes up lower percentage there
B) The temperature is higher there
C) The barometric pressure is higher there
D) Pressure of O₂ is lower there.

Answer 1

Hint: At high altitudes, the air has less density and as the altitude increases, the air pressure also decreases.

Complete step by step answer:
Step I:
Air is a mixture of many gases like nitrogen, oxygen etc. in particular amounts. The composition of air almost remains the same at sea level and at altitudes.
Step II:
But as the altitude increases, the air pressure decreases. Due to the lower air pressure, the molecules of oxygen tend to move far apart from each other. There is no force to push the oxygen molecules together. Therefore, the amount of oxygen is less available at heights.
Step III:
That is why at higher altitude, the human body requires more breathing in order to get the same amount of oxygen. But even after an increased breathing, the amount of oxygen that reaches the circulatory system is very less. This means that the muscles of the body will not get the amount of oxygen they need to function properly.
Step IV:
Therefore, the higher the altitude, the more difficult it will become to breathe due to insufficient supply of oxygen. It can be said that the amount of oxygen is insufficient to sustain human life at an extended life span.
Hence, Option A is the right answer.

Note: Higher altitudes can put strain on the breathing of human beings. The less volume of oxygen molecules in human beings is termed as ‘Hypoxia’. The people living at heights have developed a greater tendency to transport oxygen to the tissues of the body, in order to survive.