OpenSciEd 7.5 Ecosystem Dynamics Practice Test

In an experiment, you want to see how a specific factor affects an outcome while keeping everything else the same. The factor you deliberately change is the independent variable, and the baseline you compare to is the control kept in a constant, unmanipulated state. In ecosystem dynamics, this means setting up a control where the environment stays the same and nothing is altered, so you have a true baseline. The independent variable should be the factor you test—such as the presence or absence of a predator or the amount of light—so you can observe how those changes influence the ecosystem. The other options mix up these roles: a control should not be the manipulated factor, random environmental changes aren’t a stable baseline, and varying environments or measurement methods aren’t appropriate as the primary independent variable for isolating the effect of a single factor.