IB Biology HL B3.1.7 Leaf Gas Exchange Adaptations Questions

Practise interpreting daily stomatal-opening graphs, explaining guard-cell control of water loss, and describing how spongy mesophyll and air spaces support leaf gas exchange.

Exam points

Compare daily stomatal-opening graphs to identify when different plants can take up carbon dioxide.
Explain how guard cells alter stomatal opening to regulate gas exchange and limit water loss.
Explain how spongy mesophyll and air spaces support diffusion of gases through a leaf.

[Maximum number: 2]

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

Figure for Question IB Biology HL B3.1.7 Leaf Gas Exchange Adaptations Questions 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);

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IB Biology HL B3.1.7 Leaf Gas Exchange Adaptations Questions question 1