Question 1
Triple only (what this means)
Triple only: only in Triple Biology. Combined Science students can skip it. What the labels meanHigher tier (what this means)
Higher tier: only on the Higher tier papers. Foundation students can skip it. What the labels meanA river contains many bloodworms and sludgeworms but no stonefly nymphs or freshwater shrimps. What does this suggest about the water?
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- it is polluted (1)
- with low oxygen levels / for example sewage (1)
Question 2
Triple only (what this means)
Triple only: only in Triple Biology. Combined Science students can skip it. What the labels meanHigher tier (what this means)
Higher tier: only on the Higher tier papers. Foundation students can skip it. What the labels meanEvaluate the use of lichens as indicator species to assess air quality, compared with measuring the concentration of sulfur dioxide with a meter.
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- lichens are cheap / easy / need no special equipment (1)
- they show the effect of pollution over a long period of time (1)
- but other factors, such as habitat or temperature, may affect lichens (1)
- they do not give an accurate or quantitative measure of pollution, whereas a meter gives a precise value for sulfur dioxide (1)
Question 3
Triple only (what this means)
Triple only: only in Triple Biology. Combined Science students can skip it. What the labels meanExplain how (a) vacuum packing and (b) adding salt each preserve food.
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- vacuum packing removes oxygen (1)
- microorganisms need oxygen for aerobic respiration, so decomposition is slower (1)
- salt removes water from the microorganisms by osmosis / reduces available water (1)
- microorganisms need water to grow and reproduce (1)
Question 4
Triple only (what this means)
Triple only: only in Triple Biology. Combined Science students can skip it. What the labels meanA gardener turns the compost heap regularly and keeps it moist but not waterlogged. Explain why this speeds up decomposition.
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- turning adds oxygen to the heap (1)
- decomposers need oxygen for aerobic respiration (1)
- decomposers need water, but waterlogging fills the air spaces so there is less oxygen (1)
Question 5
Triple only (what this means)
Triple only: only in Triple Biology. Combined Science students can skip it. What the labels meanA sample of leaves had a mass of 20.0 g. After 5 days its mass was 14.0 g. Calculate the mean rate of decay in g per day.
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- change in mass = 20.0 − 14.0 = 6.0 g (1)
- 6.0 ÷ 5 = 1.2 g per day (1) award 2 marks for a correct answer with no working