Practical - Investigating Respiration (OCR Gateway GCSE Biology)

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The Effect of Exercise on Heart Rate

  • There are a wide range of factors that influence the heart rate of an organism
  • Experiments can be designed to investigate the effect of a named variable on an organism's heart rate
  • These experiments are commonly done using humans
    • Serious care needs to be taken during these experiments to ensure that no test subjects are harmed
  • Some of the factors that can influence heart rate include:
    • Exercise
    • Drugs
    • Caffeine
    • Alcohol
    • Sex
    • Weight
    • Height
    • Temperature
    • Diet
    • Dehydration
  • When designing experiments investigating a single factor, it is essential to try and control the other variables

Investigating the effect of exercise on the heart rate of humans

Apparatus

  • Heart rate monitor
  • Stationary exercise bike (at a set resistance level)
  • One group of healthy humans

Method

  • Use the heart rate monitor to record the heart rates of each individual while at rest
    • These results can be used to calculate the mean heart rate of the group as well as the range of resting heart rates for the group prior to exercise
  • Ask each individual to cycle at a vigorous pace on the stationary exercise bike for a set period of time
    • It may be that the individuals are asked to maintain a particular RPM (revolutions per minute) while on the bike for 5 minutes
  • After the five minutes of exercise is over, use the heart rate monitor to record the heart rates of each individual
    • These results can be used to calculate the mean heart rate of the group as well as the range of resting heart rates for the after exercise
  • Present the results in a graph or table form

Limitations

  • Care needs to be taken when selecting the exercise intensity
    • If the intensity is too low, it may not have an effect on the heart rate
    • If the intensity is too high, it could but the safety of individuals at risk
  • It is very difficult to ensure that individuals within a sample group are sufficiently similar
    • By using the same group for the before and after measurements this is not as much of an issue
    • If multiple groups were used care would need to be taken to find individuals with a similar life history (same sex, age, weight and height etc.)

Examiner Tip

Exams may ask about the safety and ethical considerations when studying the heart rates of humans. An experiment should be designed so that the safety of any of the subjects is never at risk, for example they should not be pushed to exercise at such an intensity that could cause a heart attack.

Germinating Beans & Seeds

  • We can investigate the production of carbon dioxide and heat from respiration through experiments using germinating seeds or other living organisms such as woodlice

Practical investigation: demonstrating the production of carbon dioxide

Apparatus

  • Boiling tubes
  • Rubber bungs
  • Hydrogen carbonate indicator solution
  • Cotton wool
  • Glass beads
  • Germinating seeds
  • Boiled/dead seeds

Method

  • Measure out 10 cm3 of hydrogencarbonate indicator into 3 boiling tubes
  • Put in a layer of cotton wool
  • Place 10 germinating seeds in tube A
  • Place 10 boiled/dead seeds in tube B
  • Place 10 glass beads in tube C
  • Seal each tube with a rubber bung
  • After 3 hours, observe the colour of the indicator

Hydrogencarbonate indicator

  • Hydrogencarbonate indicator is orange in atmospheric CO2 levels
  • In high CO2 levels the indicator absorbs the CO2 and becomes yellow
  • In low CO2 levels it loses CO2 and becomes purple

Hydrogencarbonate indicator, downloadable IGCSE & GCSE Biology revision notes

Colour results for hydrogen carbonate indicator

Results

  • In this investigation, we would expect to note the following
    • Tube A should turn yellow as the seeds are respiring and producing carbon dioxide
    • Tube B should remain orange as the dead seeds produce no carbon dioxide
    • Tube C should remain orange as there is no living material in there

Evolution of carbon dioxide in respiration 1, downloadable IGCSE & GCSE Biology revision notes Evolution of carbon dioxide in respiration 2, downloadable IGCSE & GCSE Biology revision notes

Experiment to demonstrate the production of carbon dioxide by living material during respiration

Practical investigation: demonstrating the production of heat

Apparatus

  • Vacuum Flasks
  • Thermometer
  • Cotton wool
  • Germinating seeds
  • Dead/boiled seeds

Method

  • Set up the flasks as shown in the diagram
    • Flask A with the germinating seeds
    • Flask B with the dead seeds
  • Make sure the cotton wool is plugging the top of each flask
  • Hold the thermometer in place with the cotton wool
  • Invert the flask
  • Record the initial temperature
  • After 4 days, record the final temperature

Production of heat in respiration, downloadable IGCSE & GCSE Biology revision notes

Experiment to demonstrate the production of heat by living material during respiration

Results

  • The thermometer in the flask with the germinating seeds (Flask B) should show an increase in temperature
  • Flask A should remain at room temperature
  • This is because the seeds in flask B are respiring and producing heat energy in the process
  • This shows that respiration is an exothermic reaction
  • The seeds in flask A are not respiring because they are dead, so the temperature remains the same

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Lára

Author: Lára

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.