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Edexcel IGCSE Biology 2 44b Light Intensity and Net Gas Exchange Questions

Practise respiration practicals using indicator colour, CO2 release, light intensity and the balance between respiration and photosynthesis.

Syllabus
First assessment 2019
Course
Biology 4BI1

Exam points

  • explain unchanged indicator colour when CO2 released equals CO2 absorbed
  • predict net CO2 or O2 exchange in bright light, low light or darkness

Edexcel IGCSE Biology 2 44b Light Intensity and Net Gas Exchange Questions question 1

[Maximum number: 2]

The diagram shows a single-celled organism called Chlorella that lives in fresh water. Chlorella has a chloroplast and can photosynthesise.

Figure for Question Edexcel IGCSE Biology 2 44b Light Intensity and Net Gas Exchange Questions question 1 — Edexcel IGCSE Biology

The graph shows the effect of light intensity on gas exchange by Chlorella.
oxygen released by Chlorella
oxygen taken in by Chlorella

Figure for Question Edexcel IGCSE Biology 2 44b Light Intensity and Net Gas Exchange Questions question 1 — Edexcel IGCSE Biology

Explain why Chlorella takes in oxygen at light intensities below 10 arbitrary units.

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