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Essentials of the Living World 5th Edition by George Johnson
Edition 5ISBN: 978-0078096945Essentials of the Living World 5th Edition by George Johnson
Edition 5ISBN: 978-0078096945 Exercise 1
How Do Llamas Live so High Up?
Because of mixing, the air animals breathe is 21% oxygen everywhere, even way up into the sky 100 kilometers above earth's surface. However, the amount of air (the number of molecules in a unit volume) decreases sharply with altitude, as shown in the upper graph. Air pressure at 5,000 meters is half of that at sea level. This lack of air presents a serious problem to humans, as mountain climbers know. The amount of oxygen in the air (measured as oxygen partial pressure) is lower, so there is simply too little oxygen to fuel a climber's muscles. To combat this problem, high-altitude climbers typically spend months acclimating to high altitudes, a period in which their bodies greatly increase the amount of hemoglobin in their red blood cells and so increase the amount of oxygen the red blood cells can capture. Many mammals live their entire lives at high altitudes. The llama and the vicuna (pictured here) both live in the high Andes of South America, often above 5,000 meters. Do they deal with the problem of low oxygen in the same way, with elevated hemoglobin levels, or is there another answer?
The graph on the lower right displays three "oxygen loading curves" that reveal the effectiveness with which hemoglobin binds oxygen. The more effective the binding, the less oxygen required before hemoglobin becomes fully loaded. In the graph, the percent hemoglobin saturation (that is, how much of the hemoglobin is bound to oxygen) is presented on the y axis, and the oxygen partial pressure (a measure of the amount of oxygen available to the hemoglobin molecules) is presented on the x axis. Oxygen-loading curves are presented for three mammalian species: humans living at sea level, and llamas and vicunas, each living in the Andes above 5,000 meters.
Applying Concepts
Comparing Curves. Extrapolating on the lower graph, which ofthe three species possesses hemoglobin able to load oxygen wellat sea-level partial pressures (160 mm Hg)? Which of the threepossesses hemoglobin better able to load oxygen on Mount Everest(get oxygen partial pressure value from the upper graph)?
Because of mixing, the air animals breathe is 21% oxygen everywhere, even way up into the sky 100 kilometers above earth's surface. However, the amount of air (the number of molecules in a unit volume) decreases sharply with altitude, as shown in the upper graph. Air pressure at 5,000 meters is half of that at sea level. This lack of air presents a serious problem to humans, as mountain climbers know. The amount of oxygen in the air (measured as oxygen partial pressure) is lower, so there is simply too little oxygen to fuel a climber's muscles. To combat this problem, high-altitude climbers typically spend months acclimating to high altitudes, a period in which their bodies greatly increase the amount of hemoglobin in their red blood cells and so increase the amount of oxygen the red blood cells can capture. Many mammals live their entire lives at high altitudes. The llama and the vicuna (pictured here) both live in the high Andes of South America, often above 5,000 meters. Do they deal with the problem of low oxygen in the same way, with elevated hemoglobin levels, or is there another answer?
The graph on the lower right displays three "oxygen loading curves" that reveal the effectiveness with which hemoglobin binds oxygen. The more effective the binding, the less oxygen required before hemoglobin becomes fully loaded. In the graph, the percent hemoglobin saturation (that is, how much of the hemoglobin is bound to oxygen) is presented on the y axis, and the oxygen partial pressure (a measure of the amount of oxygen available to the hemoglobin molecules) is presented on the x axis. Oxygen-loading curves are presented for three mammalian species: humans living at sea level, and llamas and vicunas, each living in the Andes above 5,000 meters.
Applying Concepts
Comparing Curves. Extrapolating on the lower graph, which ofthe three species possesses hemoglobin able to load oxygen wellat sea-level partial pressures (160 mm Hg)? Which of the threepossesses hemoglobin better able to load oxygen on Mount Everest(get oxygen partial pressure value from the upper graph)?
Explanation
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Human beings are the ones that are capab...
Essentials of the Living World 5th Edition by George Johnson
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