When was a control used in the investigation of the amphipods and sea butterflies Why was a control necessary?

A control was used in the investigation of amphipods and sea butterflies to provide a baseline for comparison. By having a control group of organisms that were not exposed to the same conditions as the experimental group, researchers were able to measure the effects of the specific variables being tested. This helps to determine if changes observed in the experimental group were due to the variables being studied or other factors.