Gaseous exchange in plants — KCSE Biology

KCSE Biology · 75 practice questions · 3 syllabus objectives

24 easy30 medium21 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

Describe gaseous exchange through stomata and lenticels

Draw and label a cross-section of a leaf to show gaseous exchange

Gaseous exchange in plants

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easySHORT ANSWER2 marks

Explain why the presence of stomata is crucial for gaseous exchange in leaves. (2 marks)

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Part (a) — 2 marks

Stomata allow CO₂ to enter the leaf for photosynthesis (1 mk)

Stomata enable O₂, a by-product of photosynthesis, to exit the leaf (1 mk)

easySHORT ANSWER2 marks

Describe two ways the structure of a leaf facilitates gaseous exchange. (2 marks)

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Part (a) — 2 marks

The leaf has a large surface area to enhance exposure to air for gas exchange (1 mk)

The leaf is thin, which shortens the diffusion distance for gases (1 mk)

easySHORT ANSWER2 marks

State two environmental conditions that can affect the rate of gaseous exchange in plants. (2 marks)

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Part (a) — 2 marks

Temperature (1 mk)

Humidity (1 mk)

State the main gas released by plants during photosynthesis. (1 mark)

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