Mario performed an experiment to determine if photosynthesis was affected by the amount of light that a plant received. the data from his experiment are shown in the table below. amount of light (hours) number of plants average volume of oxygen produced (ml) 1 4 0.50 6 4 2.0 10 4 5.0 what could he have done to increase the validity of his data?

The answer is to add a 0 hours control.

In every experiment, the control group is necessary. That way, effects of all variables except the independent one will be minimized. The independent variable is variable that is not affected in the experiment. In this example, the amount of light. The dependent variable is called dependent because it depends on the independent variables. In this example, the dependent variable is the average volume of oxygen (photosynthesis).
But to minimize effects on variables, it is necessary to include the 0 hours group, so it can be compared to the other groups. 

Because the carnivores keep the herbivore population in check