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Date May 2019 Marks available 2 Reference code 19M.3.SL.TZ2.3
Level Standard level Paper Paper 3 Time zone Time zone 2
Command term Compare and contrast Question number 3 Adapted from N/A

Question

A study was conducted on 25 healthy, non-smoking males to look at the effect of exercise and altitude on ventilation rate. Subjects were first asked to rest in a sitting position for six minutes. They then pedalled for three periods of six minutes at increasing exercise intensity: at 20 %, 30 % and 40 % of their maximal aerobic power. The entire study was conducted either in normal sea level oxygen conditions or in lower oxygen conditions simulating an altitude of 4000 m. The results are shown in the bar chart.

[Source: E Hermand, et al., (2015), Periodic breathing in healthy humans at exercise in hypoxia,
Journal of Applied Physiology, 118, pages 115–123. https://doi.org/10.1152/japplphysiol.00832.2014]

State one other variable that should have been controlled in this study.

 

[1]
a.

Compare and contrast the effect of increasing exercise intensity at sea level and at an altitude of 4000 m.

[2]
b.

Outline how ventilation rate could have been monitored in this study.

[2]
c.

Markscheme

age/height/fitness level/weight/room temperature/rest in between tests/model or type of bike ✔

Other valid factor. Only mark first factor listed.

Do not accept sex, health, smoking, oxygen level or altitude as this already listed.

a.

a. in both sea level and 4000m ventilation rate while exercising «at all intensities» is «significantly» more than at rest
OR
both sea level and 4000m show an increase in ventilation rate «dm3 min–1» as exercise intensity increased ✔

b. ventilation rate at 4000m «slightly» higher than at sea level for all conditions
OR
higher ventilation rate at 4000m not «significantly» different as error bars overlap ✔

Accept positive correlation.

b.

a. «data logging» with spirometer
OR
chest belt ✔

b. «tidal» volume recorded for a given period of time
OR
average «tidal» volume found and multiplied by number breaths per minute ✔

Do not accept confusion with respirometer (measuring oxygen consumption or CO2 release).

Must include a reference to time.

c.

Examiners report

In this question the candidates were asked to look at data on the effect of exercise and altitude on ventilation rate. Most candidates could state one other variable that should have been controlled in this study.

a.

In this question the candidates were asked to look at data on the effect of exercise and altitude on ventilation rate. Most candidates could state one other variable that should have been controlled in this study and could compare and contrast the effect of increasing exercise intensity in the two groups.

b.

Question (c) was poorly answered. Many candidates thought a respirometer would be used to measure ventilation rate while other candidates gave a description of how to measure the number of breaths per minute. This was considered inadequate as the Y axis of the graph indicated that ventilation rate was volume per minute, so reference to volume and time were required in the response.

c.

Syllabus sections

Core » Topic 6: Human physiology » 6.4 Gas exchange
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