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IB Biology SL B3.1 Gas Exchange Questions

Practise IB Biology SL B3.1 by linking diffusion and ventilation to gas-exchange surfaces, spirometry, leaf adaptations and transpiration questions.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Distinguish ventilation, gas exchange and cell respiration; trace oxygen and carbon dioxide diffusion.
  • Relate alveolar area, thin moist walls, capillary contact and surfactant to rapid diffusion.
  • Explain how ventilation and blood flow maintain oxygen and carbon dioxide gradients.
  • Trace inspiration and expiration from muscle action through thoracic pressure to airflow.
  • Interpret spirometry to calculate lung volumes and compare ventilation as exercise intensity rises.
  • Explain stomatal control and trace gas exchange through leaf stomata and air spaces.
  • Identify leaf tissues on diagrams and relate their positions to light capture and gas exchange.
  • Predict how environmental changes affect transpiration and plant water loss.
  • Estimate stomatal density from counts and a known field of view.

Covered syllabus points

B3.1.1—Gas exchange as vital functionB3.1.2—Properties of gas-exchange surfacesB3.1.3—Maintaining concentration gradientsB3.1.4—Mammalian lung adaptationsB3.1.5—Lung ventilationB3.1.6—Lung volume measurementsB3.1.7—Leaf gas exchange adaptationsB3.1.8—Leaf tissue distributionB3.1.9—TranspirationB3.1.10—Stomatal density

Question 1

[Maximum number: 3]

Outline the process of gas exchange necessary for aerobic respiration in a unicellular eukaryotic organism.

Question 2

[Maximum number: 1]

Emphysema is a condition where the alveoli of the lungs are destroyed, resulting in patients feeling out of breath. The micrograph shows air pockets resulting from emphysema.

Figure for Question 2 — IB Biology SL

What is a direct consequence of the destruction of alveoli?

A

Decrease in surface area for gas exchange

B

Increased blood flow to the lungs

C

Increase in pulmonary surfactant production

D

Decrease in ventilation rate

Question 3

[Maximum number: 4]

Compounds of carbon, hydrogen and oxygen are used to supply and store energy.

Describe how a concentration gradient of oxygen is maintained between the lungs and blood capillaries.

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