Final answer:
When someone is developmentally acclimatized to high altitudes, they experience physiological changes that help them adapt to the low oxygen levels. These changes include an increase in red blood cells and hemoglobin levels, which improves oxygen transport. This adaptation allows them to engage in physical activity without developing altitude sickness.
Step-by-step explanation:
When someone is developmentally acclimatized to high altitudes, their body undergoes physiological changes to adapt to the low oxygen levels. One of the main features is an increase in the number of red blood cells, which helps transport more oxygen. This adaptation is triggered by the kidneys producing a hormone called erythropoietin (EPO), which stimulates the production of more erythrocytes. As a result, individuals acclimatized to high altitude may have a higher level of hemoglobin in their blood. These changes allow them to participate in physical exertion without developing acute mountain sickness (AMS), which is characterized by symptoms like headaches, disorientation, fatigue, and nausea.