Edexcel IGCSE Biology 复习笔记 2.6.3 Practical: Investigating Respiration

Edexcel IGCSE Biology 复习笔记 2.6.3 Practical: Investigating Respiration

Practical: Investigating Respiration

 

  • 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 COlevels
  • In high CO2 levels the indicator absorbs the COand becomes yellow
  • In low CO2 levels it loses CO2 and becomes purple

 

 

 

Hydrogencarbonate-indicator

 

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-1Evolution-of-carbon-dioxide-in-respiration-2

 

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

 

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

 

 

 

Applying CORMS evaluation to practical work

  • When working with practical investigations, remember to consider your CORMS evaluation

 

CORMS-evaluation

 

CORMS evaluation

 

 

 

  • In the first investigation, your evaluation should look something like this:
    • Change - We will change the content of the boiling tube (germinating seeds, dead seeds or glass beads)
    • Organisms - The seeds used should all be of the same age, size and species
    • Repeat - We will repeat the investigation several times to ensure our results are reliable
    • Measurement 1 - We will observe the change in the hydrogen carbonate indicator
    • Measurement 2 - ...after 3 hours
    • Same - We will control the volume of hydrogen carbonate indicator, the number of seeds/beads, the temperature of the environment

     

  • For the second investigation, your evaluation should look something like this:
    • Change - We will change the content of the flasks (germinating seeds or dead seeds)
    • Organisms - The seeds used should all be of the same age, size and species
    • Repeat - We will repeat the investigation several times to ensure our results are reliable
    • Measurement 1 - We will observe the change in the temperature on the thermometer
    • Measurement 2 - ...after 4 days
    • Same - We will control the number of seeds, the starting temperature of the flasks, the material and size of the flasks

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