Question

Nate placed two circles of paper in a Petri dish (something used for growing bacteria). One circle of paper was soaked in penicillin. The other had nothing on it. He poured a liquid filled with bacteria into the Petri dish. Both circles of paper were placed in the Petri dish about 3 cm apart. At the end of the experiment, a circle with a radius of 2 cm formed around the circle of paper soaked in penicillin. There were no bacteria growing in the other circle. No change had occurred around the other circle of paper. The bacteria were growing well. What is the Independent variable?

Answer 1

The independent variable in Nate's experiment is the presence of penicillin on the circle of paper in the Petri dish, which is used to observe its effect on bacterial growth.

Step-by-step explanation:

The independent variable in Nate's experiment is the variable that is changed or controlled by the researcher. In this case, it is the presence of penicillin on one of the paper circles placed in the Petri dish. The purpose of Nate's experiment is to observe the effect of penicillin on bacterial growth. When one circle of paper is soaked in penicillin and the other is not, it creates two conditions for the bacteria: one with the antibiotic (penicillin) and one without. The growth of bacteria around each paper circle can then be compared to see the impact of penicillin.

The dependent variable, which is the outcome the researcher measures, is the bacteria's growth around the paper circles in response to the presence or absence of penicillin. The independent variable 'penicillin' causes the zone of inhibition—a clear area surrounding the paper soaked in penicillin where bacteria do not grow—while the circle without penicillin shows no such change, indicating that bacteria are growing well.