Question

question 7
you expose the bacteria staphylococcus aureus to low levels of the antibiotic methicillin. the surviving bacteria are then exposed to higher concentrations of methicillin and the process repeated until a strain of methicillin - resistant s. aureus (mrsa) was generated. to test your hypothesis, you perform an experiment by spreading the original strain of s. aureus and the mrsa strain onto agar plates containing doses of methicillin used in the hospital, and only the mrsa survives. which of the following is the dependent variable in this experiment?
a the strain of s. aureus
b the dose of methicillin
c survival in the presence of methicillin
d the agar plates
e the time of bacterial growth

Explanation:

In an experiment, the dependent variable is what is being measured or observed, which depends on the independent variable. Here, the experiment tests how different strains (original vs. MRSA) respond to methicillin. The survival of bacteria in the presence of methicillin is what's being observed (it depends on the strain and methicillin dose). Option A: The strain is an independent variable (being tested). Option B: The dose is an independent variable (controlled). Option D: Agar plates are the medium, not a variable. Option E: Time of growth isn't the focus here. So the dependent variable is survival in methicillin's presence.

Answer:

C. Survival in the presence of methicillin