IBBiologySLExam QuestionsForm & FunctionGas Exchange

Syllabus Edition

First teaching 2023

First exams 2025

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Gas Exchange (SL IB Biology)

Exam Questions

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Gas Exchange

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Gas Exchange

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1
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Which row of the table describes the best overall conditions for gas exchange in the lungs?

  Surface Area Diffusion Pathway Concentration Gradient
A. Large Long Steep
B. Large Short Steep
C. Large Short Shallow
D. Small Short Shallow

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    2
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    Which row of the table shows the events of inspiration in the correct sequence?

      1 2 3 4
    A. Diaphragm and external intercostal muscles contract Volume of thorax increases Thorax pressure drops Air is drawn into the lungs down its pressure gradient
    B. Thorax expands Thorax pressure drops Diaphragm and external intercostal muscles contract Volume of thorax increases
    C. Air is drawn into the lungs down its pressure gradient Diaphragm and external intercostal muscles contract Thorax pressure drops Volume of thorax increases
    D. Thorax pressure drops Volume of thorax increases Thorax expands Air is drawn into the lungs down its pressure gradient

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      3
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      Which of the following is a feature of forced expiration?

      • The diaphragm contracts.

      • The thorax undergoes a drop in pressure. 

      • The internal intercostal muscles contract. 

      • The external intercostal muscles contract.

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      1
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      An alveolus has several features to allow efficient gas exchange.

      7xBrVPfx_1

       

      Which row of the table below matches each feature of gas exchange to the correct label on the alveolus?

        I II II
      A High concentration of oxygen to maintain a steep concentration gradient One cell thick for short diffusion distance Allows gases to dissolve to aid diffusion
      B High concentration of carbon dioxide to maintain steep concentration gradient Allows gases to dissolve to aid diffusion One cell thick for short diffusion distance
      C One cell thick for short diffusion distance High concentration of oxygen to reduce the concentration gradient Allows gases to dissolve to aid diffusion
      D Allows gases to dissolve to aid diffusion Allows gases to dissolve to aid diffusion High concentration of oxygen to maintain a steep concentration gradient

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        2
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        What is the function of pulmonary surfactant?

        • To increase surface tension on the alveolar walli.

        • To reduce the diffusion distance across the alveolar wall.

        • To stop the alveoli sacs from sticking together.

        • To trap microorganisms and prevent infection.

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        3
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        A scientist examines a cross section of the wall of a bronchus under an electron microscope. Which of the following would be observed?

        1. Smooth muscle.
        2. Cartilage cells.
        3. Ciliated cells.

        • I and II.

        • I and III.

        • II and III.

        • I, II and III.

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        4
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        Which set of conditions is required to allow the intake of air into the lungs during ventilation?

        • Contracted diaphragm, increased volume and increased pressure inside the thorax.

        • Relaxed diaphragm, increased volume and decreased pressure inside the thorax.

        • Relaxed diaphragm, decreased volume and increased pressure inside the thorax.

        • Contracted diaphragm, increased volume and decreased pressure inside the thorax.

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        5
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        The diagram shows a trace recorded from a spirometer.

        5ktomJeq_4Which label represents the tidal volume?

         

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          6
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          Identify the set of conditions under which transpiration would occur at the slowest rate.

           

          Humidity

          Temperature

          Air movement

          Light intensity
          A

          Low

          Low

          Low

          Low
          B

          High

          Low

          Low

          Low
          C

          High

          High

          Low

          Low
          D

          High

          Low

          High

          Low

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            7
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            What does a potometer measure?

            • The rate of photosynthesis of a plant

            • The rate of water uptake of a plant

            • The rate of respiration of a plant

            • The rate of transpiration of a plant

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            8
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            Certain environmental factors can affect the rate of transpiration in plants. The effect of one environmental factor on transpiration rate is shown in the graph below.q9_9-1_transport_in_the_xylem_of_plants_ib_biology_hl_mcq

            Identify the environmental factor that is having this effect on transpiration rate.

            • Temperature

            • Humidity

            • Air movement

            • Light intensity

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            1
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            During a gas exchange investigation, measurements were recorded from four animals that were observed as they breathed normally over a period of 5 minutes. Note that the efficiency of gas exchange was the same in all four animals and that tidal volume refers to the volume of air that moves into the lungs with each normal breath.

            Which animal had the highest oxygen intake during five minutes of normal breathing?

            Animal Tidal volume / dm3 Breathing rate / breaths per minute
            A. 0.2 10
            B. 0.6 20
            C. 0.5 18
            D. 0.33 24

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              2
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              Which row of the table contains five correct statements about forced expiration?

                Ribs Diaphragm Pressure in thorax External intercostal muscles Internal intercostal muscles
              A. Move down and inwards Contracts Increases Relax Relax
              B. Move down and inwards Relaxes Increases Relax Contract
              C. Move down and inwards Relaxes Decreases Recoil Contract
              D. Move up and outwards Contracts Decreases Contract Contract 

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                3
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                The diagram shows a potometer set up to measure the rate of transpiration in a piece of cut plant. 

                potometer

                For a potometer with a cylindrical capillary of the internal diameter of d mm, the bubble was measured to travel h mm in an experimental time of s seconds. 

                Which is the correct formula to calculate the rate of transpiration (as a volume of water uptake per unit time) in this experiment?

                • fraction numerator pi italic space d to the power of italic 2 h over denominator s end fraction

                • pi italic space d to the power of italic 2 h space s

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