Every adaptation is a trade-off. A thick fur coat (good for cold) is bad for heat. A powerful diving reflex (good for seals) causes brain damage in humans. A camel’s water economy limits its sprinting speed.
At 5,000 meters, a human suffers hypoxia (low oxygen). A bar-headed goose flies over Everest (8,800m). Schmidt-Nielsen’s analysis showed that these birds have a modified hemoglobin that binds oxygen with extreme affinity. Llamas, native to the Andes, have red blood cells shaped like tiny ovals (not discs) that flow more easily through viscous, cold, high-altitude blood. Every adaptation is a trade-off
Schmidt-Nielsen devoted significant chapters to the physics of gases. He explained that oxygen doesn’t know percentages; it knows . native to the Andes