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IB Biology HL D2.3.4 Changes in Plant Tissue Questions

Control plant-tissue osmosis experiments and use percentage-mass graphs to estimate isotonic concentration from the zero-change point in IB Biology HL D2.3.4.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Describe controls for a plant-tissue osmolarity experiment, such as equal sample size, immersion time, temperature and blotting method.
  • Explain why percentage mass change lets plant-tissue samples with different starting masses be compared fairly.
  • Plot percentage mass change against solution concentration and use the zero-change intercept to estimate plant-tissue osmolarity.
  • Use an isotonic sucrose concentration to determine how many potato cylinders lost mass across the tested solutions.

IB Biology HL D2.3.4 Changes in Plant Tissue Questions question 1

[Maximum number: 3]

Data was collected on rabbit red blood cells that were exposed to sodium chloride (NaCl) and scorpion venom. Under some osmotic conditions red blood cells swell and burst, releasing hemoglobin (hemolysis). The graph shows the response of red blood cells to different concentrations of sodium chloride, with and without scorpion venom.

Figure for Question IB Biology HL D2.3.4 Changes in Plant Tissue Questions question 1 — IB Biology HL

Describe how the variables would be controlled in an experiment to estimate the osmolarity of plant tissue.

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