Carbon Dioxide Enrichment Experiments (HL IB Biology)

• Future rates of photosynthesis and plant growth can be predicted using experiments such as
  • enclosed greenhouse experiments
  • free air carbon dioxide enrichment experiments (FACE)
• Due to the impact of global warming already documented and rising levels of greenhouse gases, including carbon dioxide, it is fundamental that studies are carried out to establish the effect of carbon dioxide on plant growth and photosynthesis to develop a clearer idea of the potential future risks that we may encounter

Enclosed greenhouse experiments

• Monitoring photosynthesis and growth can be done using an enclosed greenhouse or polytunnel set up
• This allows variables to be manipulated or controlled in order to establish the impact of different factors
• Only small species that can be contained in a greenhouse can be studied using this method
• Variables that would be manipulated might include
  • light
  • carbon dioxide
  • temperature
  • wavelengths of light
• Other variables should be controlled so as to ensure that the effect of only one variable is being considered at any one time

Free air carbon dioxide enrichment experiments (FACE)

• These experiments are carried out in natural ecosystems where carbon dioxide is pumped into the area to increase the localised carbon dioxide concentrations
• This set up allows larger plants and trees to be studied
• Other variables cannot be controlled in these scenarios but they can be monitored to establish any relationships that may become apparent in the data

NOS: Finding methods for careful control of variables is part of experimental design

• In an experiment, a variable is any factor that could change or be changed
  • The independent variable: the only variable that should be changed throughout an experiment
  • The controlled/confounding variables: any other variables that may affect the results of the experiment that need to be controlled or monitored
  • The dependent variable: the variable that is measured to determine the outcome of an experiment (the results)
• It is essential that any variable that may affect the outcome of an experiment is controlled in order for the results to be valid
• Preliminary research and preliminary studies can be used to identify variables within an experiment and to determine ways of controlling these variables effectively
• The science surrounding the issue/problem being investigated is likely to contain information about different factors or variables that may exist