O LevelBiologyCambridgeExam Questions9. Human Gas Exchange9.1 Human Gas Exchange

Human Gas Exchange (Cambridge O Level Biology)

Exam Questions

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9.1 Human Gas Exchange

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9.1 Human Gas Exchange

1a
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Fig. 1 shows a photomicrograph of part of the lung of a mammal.

screenshot-2022-10-18-10-53-29

Fig. 1

i)

The two lines drawn on the capillary labelled A represents the diameter of the capillary measured at different points. The two lines on the image have the following measurements:

Diameter 1 = 6 mm

Diameter 2 = 9 mm

Calculate the average diameter of the image of capillary A.

[1]

ii)

Calculate the actual average diameter of capillary A using your answer to a) i) and the formula:

magnification space equals space fraction numerator average space diameter space of space capillary space bold A space on space Fig.1 over denominator actual space average space diameter space of space capillary space bold A end fraction

1mm = 1000 μm

Give your answer to the nearest whole μm.

[3]

iii)

Make a large drawing of three alveoli and one capillary, that are next to each other in Fig.1. Do not draw individual cells.

[4]

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1b
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Some students measured the average increase in chest circumference, during breathing, and when at rest. Each student wrapped a tape measure around their body just below the armpits, as shown in Fig. 2.

screenshot-2022-10-18-11-09-13

Fig. 2

Each student then breathed out and took a measurement of their chest circumference. They then breathed in and took a second measurement. The difference between the two measurements is the increase in chest circumference.

Table 1 shows the results of their measurements.

Table 1

  Increase in chest circumference / mm
  male  female
  40 32
  31 37
  48 25
  28 38
  46 27
  33 30
  39 22
  41 38
  25 27
  39 34
average 37  

 

i)

Calculate the average increase in chest circumference for females.

Write your answer in Table 1.

[1]

ii)

Describe how the students could find out the effect of exercise intensity on chest circumference during breathing.

[5]

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2a
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A student investigated the effect of exercise on breathing rate.

The breathing rates of five people were measured at rest and after running for different periods of time. The people rested between each period of running.

The results are shown in Table 1.

Table 1

Running
time
/minutes		 Breathing rate/breaths per minute
Person Average
One Two Three Four Five
0 20 24 22 26 28 24
2 32 31 28 32 32 31
4 39 41 38 42 40  
6 46 52 52 46 44 48
8 48 50 52 46 44 48
10 49 51 51 46 43 48

(i)

Complete Table 1 by calculating the average breathing rate for four minutes of running.

[1]

(ii)

The student thought that the result for person two at six minutes was an anomaly.

Suggest what the student should do to determine if the result is anomalous.

[1]

(iii)
Plot a graph to show the relationship between running time and the average breathing rate. Draw a line of best fit.

graph-paper-6x6

[4]

(iv)

Use your graph to estimate the average breathing rate for one minute of the running.

Show on the graph how you obtained your answer.

[2]

(v)

Use your graph to describe the relationship between running time and the average breathing rate.

[3]

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2b
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(i)

Suggest one safety precaution for this investigation.

[1]

(iii)

State two variables that should be kept constant during this investigation.

[2]

(iii)

State the variable that has been changed (the independent variable) in this investigation.

[1]

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3a
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Fig. 1 shows a micrograph of a section of the trachea wall.

vhW4Y~oQ_picture1

magnfication: x40

Image courtesy of Magscope. Licenced under CC BY-SA 4.0 under conditions found at: https://creativecommons.org/licenses/by-sa/4.0/deed.en.

Fig. 1

(i)

Line XY measures 6 cm and the magnification of the micrograph is x40.

Calculate the actual width of the trachea wall in mm.

Use the following formula:

magnification space equals space fraction numerator measured space width space of space XY over denominator actual space width space of space trachea space wall end fraction

[3]

(ii)

Make a large drawing of the wall of the trachea to indicate the different tissue layers.

Do not draw individual cells or include line XY.

[4]

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3b
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An investigation was conducted on the effect of different types of exercise on the breathing rate.

Table 1 shows the results of this investigation.

Table 1

type of exercise breathing rate / breaths min-1
trial 1 trial 2 trial 3 mean
walking 12 10 12 11
running 18 16 8  
swimming 15 17 14 15
jumping 16 16 14 15
push-ups 17 18 16 17

(i)

The investigator thought that the running measurement taken during trial 3 was anomalous.

Explain why they thought this and suggest how they could test whether this measurement is an anomaly.

[2]

(ii)

Use the data in Table 1 to calculate the mean breathing rate for running.

[2]

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3c
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.

(i)

Use the data in Table 1 to plot a bar chart on the grid below.

lfI8Tujj_picture4

[3]

(ii)

Describe the data from Table 1 and the bar chart.

[3]

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3d
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A student stated that:

'Breathing rate decreases with age'

Plan an investigation to test this statement.

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