Final answer:
At oxygen concentrations of 15-19, the body compensates by producing more red blood cells which increases the amount of hemoglobin available for oxygen transport. Additionally, dissolved oxygen in the blood is transported at a higher rate.
Step-by-step explanation:
At oxygen concentrations of 15-19, the body undergoes changes to compensate for the lower oxygen levels. One response is the stimulation of the production of erythrocytes (red blood cells) by the kidneys, leading to an increased number of circulating erythrocytes.
This results in more hemoglobin available to transport the limited oxygen, allowing the person to partake in physical exertion without developing AMS (Acute Mountain Sickness). Additionally, dissolved oxygen in the blood is transported at a higher rate by dissolving in blood, and oxygen has more affinity for hemoglobin than carbon dioxide.