In an experiment testing temperature effects on daphnia population size, what is the independent variable?

In an experiment, the independent variable is the factor that is deliberately manipulated to observe its effect on another variable, known as the dependent variable. In this case, the independent variable is the temperature of the water. By changing the temperature and observing how it affects the daphnia population size, researchers can draw conclusions about the relationship between water temperature and daphnia growth or survival. This manipulation allows the experiment to yield results that indicate how temperature influences daphnia populations.

The number of daphnia reflects the outcome of the experiment and is therefore considered the dependent variable, while the control group’s temperature is not relevant to the manipulation of the experiment. The type of daphnia used can also be controlled, but it isn’t the focus of the experiment concerning temperature's effects. Therefore, the temperature of the water is indeed the independent variable, as it is being tested for its influence on the daphnia population.