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Practical skills assessed in a written examination

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Question 16

An investigation was carried out to measure the rate of respiration and photosynthesis of pea seedlings at different light intensities using a respirometer.

  • Fifteen seedlings were placed in a respirometer containing soda-lime and kept in the dark for four hours to measure respiration.
  • The distance moved by the fluid in the capillary tube during this time was 4.5 mm4.5\text{ mm}4.5 mm.
  • In a separate setup without soda-lime, the seedlings were exposed to different light intensities for four hours at a time, and the distance moved by the fluid was recorded:
    • At 1200 lux: 1.5 mm1.5\text{ mm}1.5 mm
    • At 1800 lux: 3.6 mm3.6\text{ mm}3.6 mm
a.

The diameter of the capillary tubing was 0.2 mm0.2\text{ mm}0.2 mm. The volume of a cylinder can be calculated using the formula:

volume of cylinder=πr2l \text{volume of cylinder} = \pi r^2 l volume of cylinder=πr2l

Calculate the rate of oxygen uptake by the seedlings in the dark in mm3 h−1\text{mm}^3\text{ h}^{-1}mm3 h−1. Give your answer to two significant figures. Show your working.

[4]
b.

Calculate the percentage increase in net gas production by the seedlings between 1200 lux and 1800 lux. Show your working.

[2]

Practical skills assessed in a written examination Questions

  1. A Level
  2. /Biology
  3. /Practical skills assessed in a written examination