Final answer:
The independent variable in Lisa’s experiment is the concentration of carbon dioxide. This variable is manipulated to determine its effect on the growth of oak tree seedlings, with the goal of testing the hypothesis that higher CO2 leads to taller trees.
Step-by-step explanation:
The independent variable for Lisa’s experiment is the concentration of carbon dioxide in the laboratory environment where the oak tree seedlings are grown. The independent variable is the factor that is manipulated by the researcher to observe its effects on the dependent variable, which in this case would be the growth or height of the oak trees. By comparing the growth of the seedlings in normal levels of CO2 with those in an environment with twice the normal level, Lisa is able to test her hypothesis that higher levels of carbon dioxide lead to taller oak trees.
The process of photosynthesis, whereby plants use carbon dioxide to synthesize organic compounds, is influenced by the amount of available CO2. As such, an increase in atmospheric carbon dioxide could lead to changes in plant physiology, including growth patterns. Additionally, the rise in atmospheric carbon dioxide levels, largely due to the burning of fossil fuels, is a driving force behind climate change and has multiple ecological effects, including possible impacts on stomatal density and ocean acidification.