IB Biology HL 3.1.7 Leaf Gas Exchange and Stomata Question Bank

Practise IB Biology HL 3.1.7 through exact HL questions on stomatal opening, guard-cell control, mesophyll diffusion and water-loss adaptation.

Exam points

Analyse how stomatal opening, guard-cell control and mesophyll structure regulate gas exchange.
Use daily stomatal patterns to infer plant adaptation to water loss and desert conditions.
Evaluate leaf structures by linking pores, air spaces and moist mesophyll to diffusion.

[Maximum number: 2]

The micrograph shows part of a lilac (Syringa vulgaris) leaf in vertical section.

Figure for Question B3.1.7—Leaf gas exchange adaptations question 1 — IB Biology HL

Explain the roles of two leaf structures that help with the process of gas exchange in the leaf.

a. spongy mesophyll provides a large/moist/permeable surface area (for gas exchange);

b. guard cells form pores/stomata (through the epidermis) / open and close stomata OR stomata are pores (through the epidermis that) allow $\mathrm{CO}_{2} / \mathrm{O}_{2} /$ gases to enter/exit the leaf/to pass through the epidermis;

c. (air) spaces for diffusion/movement/transfer of gases (to/from spongy mesophyll cells and stomata);

2 max

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B3.1.7—Leaf gas exchange adaptations question 1