Home / IB DP Biology B3.1 Gas exchange -FA 2025-IB Style Questions- SL Paper 1

IB DP Biology B3.1 Gas exchange -FA 2025-IB Style Questions- SL Paper 1

Question 

The diagram shows an alveolus from a healthy human lung with type I and II pneumocytes and phagocytes.

What are the main functions of these cells?

▶️Answer/Explanation

Ans. D

Question

The graph shows the concentration of the lipid lecithin in the amniotic fluid surrounding the fetus during normal gestation. This lipid is produced in the lungs of the fetus and acts as a surfactant.

What problem may occur in a baby born before 34 weeks gestation?

A. Type I pneumocytes do not produce sufficient surfactant for lungs to inflate.

B. There are no type II pneumocytes.

C. The alveolar walls stick together.

D. The alveoli are too large.

Answer/Explanation

Ans:C

Question

Pressure changes inside the thorax cause the movement of air in and out of the lung alveoli
during ventilation. Alveolar pressure correlates to thoracic pressure. The diagram shows pressure
changes in lung alveoli during ventilation in relation to normal atmospheric pressure. What causes
forced movement of air out of the lungs at T?

Answer/Explanation

Ans: B

Question

Where in the body are type I pneumocytes found?

    1. Alveoli

    2. Nephrons

    3. Capillaries

    4. Trachea

Answer/Explanation

Ans: A

Question

Which is an adaptation to increase rates of gas exchange in the lung?

    1. Small surface area

    2. Dry surface

    3. High vascularization

    4. Muscular alveoli

Answer/Explanation

Ans: C

Question

For what reason do large organisms need specialized gas exchange structures?

A.  They have a large surface area to volume ratio.

B.  There is a short distance to the centre of their body

C.  They have a relatively small surface in contact with the outside

D.  Their skin is impermeable to respiratory gases.

▶️Answer/Explanation

C

Question

What can be seen in a plan diagram of a leaf?

A.  Spongy cells and surface of the upper epidermis

B.  Chloroplasts in palisade cells and position of waxy cuticle

C.  Vascular bundles and thickness of palisade mesophyll

D.  Guard cells and distribution of air spaces

▶️Answer/Explanation

C

Question

What occurs at gas exchange surfaces in the lungs of mammals?

I.  Gases diffuse across a moist surface.
II.  Concentration gradients are maintained by ventilation.
III.  Water is lost.

A.  I and II only

B.  I and III only

C.  II and III only

D.  I, II and III

▶️Answer/Explanation

D

Question

What is always a consequence of the evaporation of water from mesophyll cells in leaves of a healthy plant?

A.  Plasmolysis occurs in mesophyll cells.

B.  Photosynthesis stops.

C.  Stomata close to reduce transpiration.

D.  Water moves up the stem in the xylem.

▶️Answer/Explanation

D

Question

A plant is allowed to photosynthesize in an atmosphere containing radioactive 14C. Where in the plant stem would radioactive sugars be found?

▶️Answer/Explanation

B

Question

The apparatus in the diagram was used to assess the effects of factors on transpiration rates.

Which factor would be a controlled variable in an experiment designed to assess the effects of temperature on transpiration rate?

A. The opening and closing of stomata

B. The intensity of light striking the plant

C. The height of the water in the reservoir

D. The evaporation of water from the leaves

▶️Answer/Explanation

B

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