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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
Answer
The differences between species A and B can be understood through the principles of natural selection posited by Darwin and Wallace. Adaptation to different environmental conditions, particularly altitude, is a key aspect of evolution.
As species A is adapted to high altitudes where the partial pressure of oxygen is lower (minimum pO2 = 54), it has likely developed a form of haemoglobin that has a higher affinity for oxygen. This adaptation enables it to effectively utilize the limited oxygen available in its high-altitude habitat, maximizing oxygen uptake despite the lower pO2 levels.
Conversely, species B, which occupies a low-altitude habitat (minimum pO2 = 80), may have evolved a haemoglobin variant that works efficiently at higher pO2 levels. The higher oxygen saturation needed for species B means its haemoglobin likely has a different structure or properties that optimize oxygen binding under higher pO2 conditions.
This evolutionary divergence is a classic example of adaptive radiation, where closely related species develop different traits to survive in varying environments. Additionally, the ability to effectively transport oxygen, through these differences in haemoglobin structure, directly relates to the species' fitness in their respective habitats, showcasing the role of natural selection in shaping these physiological traits.