Experiment #1 Question : Does penicillin prevent infection? Hypothesis : If the

Question

Experiment #1

Question: Does penicillin prevent infection?

Hypothesis: If the medicine prevents infection, than the medicine will prevent the growth of bacteria that cause infection.

Experiment: Leo placed two circles of paper in a 500 Petri dish (something used for growing bacteria).In 250 dishes, the paper was soaked with Peniccilin solution and then inoculated with bacteria. The other 250 dishes were soaked in water only and inoculated with same bacteria .All other conditions including light and temperature remained the same. After 48 hours, Leo observed all dishes and noticed there was no bacteria growth in the penicillin dishes a circle. All dishes with water only had large colonies of bacteria growing in them.

At the end of the experiment, a circle with a radius of 2cm formed around the circle of paper soaked in penicillin. There were no bacteria growing in the 2cm circle. No change had occurred around the other circle of paper. The bacteria were growing well.

A. What was the independent variable? ______________________________________________________

B. What was the dependent variable? ________________________________________________________

C. What was the control? _____________

D. What was the constant

E. What type of study is this? Explain

Explanation / Answer

A. Independent variable is the variable that has following characteristics:

In this experiment, the manipulated variable is the treatment given to the paper discs. Hence that is the independent variable.

B. Dependent variable is the variable which changes due to the change in the other variable.

In this experiment, the growth of bacteria is changing because of the manipulation in the paper disc. Hence, it is the dependent variable.

C. The control in this experiment is the petri dish which has the untreated paper disc because the growth of bacteria will be used for the comparison with other petri dishes to explain what effect penicillin has on the growth of bacteria.

D. The conditions like the temperature, light, amount of nutrients and humidity were the constant in this experiment.

E. This study is the experiment to test the antibiotic sensitivity of a bacteria and it is known as the Kirby Bauer antibiotic testing. In this experiment, as explained in the question as well, there are two petri dishes, one contains paper disc which are treated with penicillin and other with the untreated paper disc. Both petri dishes are inoculated with the bacteria.

The petri with untreated disc have normal growth of the bacteria while other petri has zone of inhibition around the penicillin soaked disc. This shows that the penicillin inhibits the growth of the bacteria and hence proving that this bacteria is sensitive to the penicillin.

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.