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As altitude increases, the partial pressure of oxygen (pO₂) in air decreases - HSC - SSCE Biology - Question 31 - 2016 - Paper 1
Question 31
As altitude increases, the partial pressure of oxygen (pO₂) in air decreases. Species A and B are closely related endotherms that live in different habitats in Asia... show full transcript
Worked Solution & Example Answer:As altitude increases, the partial pressure of oxygen (pO₂) in air decreases - HSC - SSCE Biology - Question 31 - 2016 - Paper 1
Step 1
Explain how the differences in these species could have arisen, using the Darwin/ Wallace theory of evolution and your understanding of the adaptive advantage of haemoglobin.
Answer
The differences in species A and B can be attributed to natural selection, as proposed by Darwin and Wallace.
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Adaptation to Altitude: Species A inhabits high altitudes where the pO₂ is lower, requiring adaptations in its haemoglobin to ensure sufficient oxygen saturation. The minimum pO₂ of 54 for 100% Hb saturation indicates a higher affinity for oxygen, allowing species A to thrive despite the reduced air pressure.
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Evolutionary Pressure: In contrast, species B, which lives at lower altitudes with higher pO₂ levels (80), might not face the same evolutionary pressure to enhance its oxygen-carrying capacity, resulting in a haemoglobin structure less specialized than that of species A.
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Genetic Variation: Genetic variations that provided a survival advantage in low-oxygen environments would be selected for in species A over generations, reinforcing traits that lead to more efficient oxygen uptake.
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Adaptive Advantage: The ability to saturate haemoglobin at lower pO₂ levels gives species A a distinct advantage in high-altitude environments, where oxygen is scarce. This evolutionary adaptation is crucial for survival and reproductive success in harsher conditions.
In summary, the differences in haemoglobin structure between these two species are a result of adaptive evolution driven by the specific environmental pressures they face.