A-LevelBiologyGas exchangeMay/June 2025Paper 1 Q321 Mark
The graph shows oxygen dissociation curves for three animals. The shape of each curve is influenced by respiration rate and the affinity of haemoglobin for oxygen. [Figure 32.1 (graph of percentage saturation of haemoglobin with oxygen vs partial pressure of oxygen for animal 1, 2, 3)] What can be concluded from the graph?
AAnimal 1 has haemoglobin adapted to have a higher affinity for oxygen than animal 2.
BAnimal 3 has haemoglobin adapted to have a higher affinity for oxygen than animal 2.
CAnimal 3 has haemoglobin adapted to maintain a lower respiration rate than animal 2.
DAnimal 1 has haemoglobin adapted to maintain a higher respiration rate than animal 2.
✓ Correct Answer
The correct answer is A. This question tests the candidate's understanding of gas exchange within the Biologysyllabus. The examiner's mark scheme requires...
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Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
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