In the lemon shark experiment, what is the role of samarium?

• A. Experimental group
• B. Control group
• C. Independent variable
• D. Dependent variable

Answer: (A)

In experiments, you compare groups to see what a treatment does. The group that receives the treatment is the experimental group, because they’re exposed to the variable you’re testing. In the lemon shark setup, samarium is the treatment you apply to the sharks in that group. So the role samarium plays is to identify which sharks are in the experimental group—the ones that get the substance and are being tested for any resulting effects. The sharks that don’t get samarium form the control group, used for comparison. If you were naming the actual factor being changed, that would be the independent variable (samarium itself), and what you measure afterward would be the dependent variable (such as a physiological response).