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IB Biology HL 3.1.10 Stomatal Density and Water Loss Question Bank

Practise IB Biology HL 3.1.10 through exact HL questions on epidermal stomatal distribution, cobalt-chloride evidence and transpiration control.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Analyse stomatal-density differences between upper and lower epidermis using leaf adaptation evidence.
  • Use cobalt-chloride indicators to identify the leaf surface with greater water loss.
  • Evaluate how stomatal distribution balances gas exchange with prevention of excessive transpiration.

B3.1.10—Stomatal density question 1

[Maximum number: 1]

The stomatal density is the number of stomata per area of leaf epidermis. A study was done on the stomatal density of the lower epidermis of leaves from Protium decandrum, a tree found in the Amazon forest.

The image shows the epidermis stripped from the lower surface of a leaf.

Figure for Question B3.1.10—Stomatal density question 1 — IB Biology HL

The mean stomatal density for the lower epidermis of P. decandrum was around 600 per mm2\mathrm{mm}^{2}. Predict how the stomatal density for the upper epidermis would compare.

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