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2.7.9Structure & Functions in Living Organisms

Practical: The Effect of Age on Breathing — Edexcel International GCSE Biology 4BI1 Revision Notes & Topical Questions

5 min read 5 parts Lesson 16 of 21 Unit quiz

📚 Edexcel International GCSE Biology 4BI1 Hub / Topical Revision
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Section 1 of 5Method

2.7.9 Practical: The Effect of Age on Breathing

Breathing rate is the number of breaths taken per minute, where one breath is one inhalation plus one exhalation.

1
Choose participants from clearly defined age groups, such as children, teenagers and adults, with several people in each group.
2
Each participant sits quietly for one minute while a partner counts their resting breaths.
3
Every participant then does the same exercise for the same time, such as running on the spot for one minute.
4
Immediately after exercise, count the breaths again, either for one minute or for 15 seconds and multiply by four.
5
Calculate the change in breathing rate for each person and then the mean change for each age group.

Section 2 of 5Interpreting the Results

Interpreting the Results
Effect of exercise
  • Exercise increases both the rate and the depth of breathing, bringing in more oxygen and removing carbon dioxide faster.
Why
  • Muscles respire faster, so they need more oxygen and produce more carbon dioxide, which is detected and triggers faster breathing.
Age comparison
  • Mean values show whether the rise differs between age groups, but fitness and health also affect each person's response.
Recovery
  • Breathing rate falls back to the resting value over time once the exercise stops and the demand for oxygen drops.

Section 3 of 5Variables and Evaluation

Use CORMS to structure a plan and evaluate it.

Change
  • The independent variable is the age group of the participants, or the activity done, if exercise is the factor studied.
Measure
  • The dependent variable is the number of breaths per minute before and after the activity, giving the change in rate.
Same
  • Exercise type, duration, room temperature, rest time before measuring and the method of counting breaths are all kept constant.
Repeat
  • Using several participants per group and finding a mean reduces the effect of individual differences and anomalies.
Limitations
  • Fitness differs between people, effort varies, and counting errors occur;
    • a fixed-pace step exercise and a standard counting period help.

Section 4 of 5Worked Example

Question

  • A student counts 7 breaths in 15 seconds immediately after exercise and 4 breaths in 15 seconds at rest.
  • Calculate the change in breathing rate in breaths per minute.

  1. Rate after exercise = 7 × 4 = 28 breaths per minute.
  2. Resting rate = 4 × 4 = 16 breaths per minute.
  3. Change in rate = 28 - 16 = 12 breaths per minute.

Answer The breathing rate increased by 12 breaths per minute.

Section 5 of 5Exam Checklist & Tips

2.7.9 – Key Points for the Exam

  • Breathing rate The number of breaths taken in one minute.
  • Ventilation The movement of air into and out of the lungs.
  • Mean The sum of the values divided by the number of values.
  • Variable A factor that can change in an investigation.
  • Anomalous result A result that does not fit the pattern of the others.

Common Mistakes

  • Counting an inhalation and an exhalation as two breaths when they make one breath.
  • Starting to count a long time after exercise stops, by which time the rate has already fallen.
  • Allowing different participants to do different amounts of exercise, which is not a fair test.
  • Drawing a firm conclusion about age from only one participant per group.

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