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Cambridge IGCSE Biology practice

Paper 6 structured question: Transpiration

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6

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6

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Topic

Transpiration

Exam-style question

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Paper 6Alternative to PracticalPractical6 marks

Investigating the effect of temperature and wind speed on transpiration rate using a simple experiment.

Method

Method to Investigate Transpiration Rate

1. Cut a leafy shoot and immediately place it in water. 2. Set up a potometer to measure water uptake by the shoot. 3. Place the potometer in a controlled environment. 4. Measure the volume of water taken up over 10 minutes at different temperatures (15°C, 25°C, 35°C). 5. Repeat the measurements with a fan blowing at different wind speeds (0 m/s, 2 m/s, 4 m/s) at a constant temperature. 6. Record all data carefully and repeat each measurement three times for accuracy.

Temperature (°C)Wind Speed (m/s)Water Uptake (cm³/10 min)
1502.0
2503.5
3505.0
2503.5
2524.5
2546.0
  1. a

    Identify the independent variable in this investigation.

    Aim for approximately 1 distinct marking point.

    [1]
  2. b

    Describe how the rate of transpiration changes with temperature based on the data.

    Aim for approximately 2 distinct marking points.

    [2]
  3. c

    Explain why increasing wind speed increases the rate of transpiration.

    Aim for approximately 3 distinct marking points.

    [3]

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Paper 6 structured question: Transpiration

Paper 6Alternative to PracticalPractical6 marks

Results Table

Transpiration Rate Data

The table shows water uptake by a plant shoot under different conditions of temperature and wind speed.

ConditionTemperature (°C)Wind Speed (m/s)Water Uptake (cm³/10 min)
A2002.5
B2034.0
C3004.5
D3036.5
  1. a

    Calculate the increase in water uptake when wind speed increases from 0 m/s to 3 m/s at 20°C (Condition A to B).

    Aim for approximately 1 distinct marking point.

    [1]
  2. b

    Suggest why water uptake is higher at 30°C compared to 20°C at the same wind speed.

    Aim for approximately 2 distinct marking points.

    [2]
  3. c

    Explain how both temperature and wind speed together affect transpiration rate based on the data.

    Aim for approximately 3 distinct marking points.

    [3]