IB Diploma · Biology B3.1
IB Biology B3.1: Gas Exchange — Practice Questions & Answers
IB Biology B3.1 study notes: properties of gas exchange surfaces, ventilation, alveoli, leaves and gills, and exchange by diffusion.
Here are 10 practice questions with full answers and explanations.
Start an interactive IB Biology quiz →
Practice questions with answers
1
Multiple choice
Why does gas exchange become more challenging as organisms increase in size?
- Surface area-to-volume ratio decreases.
- Metabolic rate decreases.
- Cell size increases.
- Organelle number decreases.
Tap an answer to check it.
WhyLarger organisms have a lower surface area-to-volume ratio, so their surface alone cannot supply enough gas exchange.
2
Multiple choice
Which of the following is a property of gas-exchange surfaces?
- Permeability.
- Thick tissue layer.
- Dryness.
- Small surface area.
Tap an answer to check it.
WhyGas-exchange surfaces must be permeable so gases can diffuse across them freely.
3
Multiple choice
What is required to maintain concentration gradients at exchange surfaces in animals?
- a) Dense networks of blood vessels
- b) Static blood flow
- c) Limited ventilation
- d) Thick tissue layers
- e) Constant blood flow
- a) Dense networks of blood vessels & e) Constant blood flow
Tap an answer to check it.
WhyDense blood vessels and constant blood flow continually remove and supply gases, keeping concentration gradients steep.
4
Multiple choice
What is a key adaptation of mammalian lungs for gas exchange?
- Presence of surfactant.
- Thick alveolar walls.
- Reduced capillary beds.
- Limited bronchioles.
Tap an answer to check it.
WhySurfactant in mammalian lungs lowers surface tension, keeping alveoli open for efficient gas exchange.
5
Multiple choice
Which muscle plays a primary role in lung ventilation?
- Diaphragm
- Alveoli
- Bronchi
- Trachea
Tap an answer to check it.
WhyThe diaphragm contracts and relaxes to change thoracic volume, driving lung ventilation.
6
Multiple choice
What lung volume is measured during normal breathing?
- Tidal volume.
- Vital capacity.
- Inspiratory reserve.
- Expiratory reserve.
Tap an answer to check it.
WhyTidal volume is the amount of air moved in or out of the lungs during a normal, quiet breath.
7
Multiple choice
What is the purpose of the waxy cuticle on a leaf?
- Prevent water loss.
- Facilitate gas exchange.
- Store nutrients.
- Support leaf structure.
Tap an answer to check it.
WhyThe waxy cuticle is a waterproof layer that reduces water loss from the leaf surface.
8
Multiple choice
Where does most gas exchange occur in a leaf?
- Spongy mesophyll.
- Epidermis.
- Veins.
- Cuticle.
Tap an answer to check it.
WhyThe spongy mesophyll has air spaces and moist cell surfaces where most leaf gas exchange occurs.
9
Multiple choice
What is the function of stomatal guard cells?
- Regulate stomatal opening and closing.
- Transport water.
- Store sugars.
- Provide structural support.
Tap an answer to check it.
WhyGuard cells change shape to open or close the stoma, controlling gas exchange and water loss.
10
Multiple choice
What is transpiration?
- Water loss from a leaf due to gas exchange.
- Sugar transport in phloem.
- Mineral uptake by roots.
- Photosynthesis in chloroplasts.
Tap an answer to check it.
WhyTranspiration is the loss of water vapour from leaves, largely through open stomata during gas exchange.
Key terms in Gas Exchange
Gas exchange surface: A specialised interface, large and thin, where gases diffuse between an organism and its environment.
Diffusion: Net passive movement of particles from a higher to a lower concentration; the means by which gases cross exchange surfaces.
Alveolus: A tiny air sac in the lung with a one-cell-thick wall and capillary network, the site of gas exchange.
Surfactant: A substance lining the alveoli that lowers surface tension and prevents them from collapsing.
Ventilation: The movement of air (or water) over a gas exchange surface to maintain concentration gradients.
Stoma: A pore in a leaf, controlled by guard cells, through which gases enter and leave.
Spongy mesophyll: Loosely packed leaf tissue with large air spaces providing surface area for gas exchange.
Countercurrent flow: An arrangement where water and blood flow in opposite directions in a gill, maintaining a gradient along the surface.
See the full study notes for this topic.
Practise other IB Biology topics