There is less oxygen in air at higher altitudes than at sea level. Scientists have shown that people living at sea level have 5 million red blood cells per mm3 of blood whereas people living at high altitude have 7 million red blood cells per mm3 of blood. Suggest a reason for this difference

Answer with Explanation:

"Red Blood Cells" (RBCs) contain Hemoglobin that is responsible for carrying oxygen into the body. When people are exposed to higher altitudes, the number RBCs in the body increases. This is because the body has a hard time taking in oxygen due to low atmospheric pressure. It makes it hard for oxygen to pass through the lung membranes. This is called "hypoxia." Such condition deprives the body from oxygen, thus, it creates more red blood cells in order to compensate the condition.

When it comes to people living at sea level, the oxygen can easily pass through the lung membranes due to higher atmospheric pressure. This doesn't require the body to build new RBCs. Therefore, the numbers of RBCs needed by people to thrive is lower than living at higher altitudes.