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Practical skills assessed in a written examination

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Question 45

An investigation was carried out using a simple respirometer to determine the rate of cellular respiration in woodlice, and their net gas exchange under different light levels.

  • Twelve woodlice were placed in a respirometer containing potassium hydroxide (KOH) solution and kept in the dark for five hours to measure cellular respiration.
  • The distance moved by the fluid in the capillary tube during this period was 7.5 mm7.5\text{ mm}7.5 mm.
  • In a separate setup without KOH, the woodlice were exposed to different light intensities for five hours at a time, and the distance moved by the fluid was recorded:
    • At 500 lux: 2.4 mm2.4\text{ mm}2.4 mm
    • At 1500 lux: 6.6 mm6.6\text{ mm}6.6 mm
a.

The diameter of the capillary tubing was 0.4 mm0.4\text{ mm}0.4 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 woodlice 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 woodlice between 500 lux and 1500 lux. Show your working.

[3]

Practical skills assessed in a written examination Questions

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