A-LevelBiologyHomeostasisMay/June 2022Paper 4 Q19 Marks
(a) The water potential of mammalian blood needs to be maintained within narrow limits so that cells function efficiently. This process is called osmoregulation. The relative medullary thickness (RMT) indicates the proportion of a kidney that is composed of medullary tissue. RMT = thickness of medulla / kidney size X 10 Table 1.1 shows the relationship between the RMT and the concentration of urine produced by four mammals from different habitats. Table 1.1 mammal | habitat | RMT | urine concentration/arbitrary units -------|-------------------|-----|------------------------------------ beaver | rivers and lakes | 1.4 | 0.90 warthog| savannah | 2.8 | 2.35 human | variable | 3.2 | 2.50 kangaroo rat| desert | 8.6 | 10.50
📋 Examiner Report & Trap Analysis
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...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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