Question

A scientist studying algae growth in a coral reef observed that the presence of a certain type of zooplankton inhibited the algae growth. The scientist hypothesized that the zooplanton was eating the algae. Which experimental design would best test this hypothesis?

A. Measure the amounts of algae and zooplankton in a sample of water, and record the change in algae over several days. Keep other variables constant.
B. Measure out amounts of three different algae, then release the zooplanton into the sample. Observe which algae the zooplankton eat. Adjust the temperature of the water daily.
C. Choose two different types of zooplankton and place them in a sample of water with the algae. Observe which zooplankton consume the most algae.
D. Increase algae growth by increasing the temperature of the water daily. Observe if the amount of zooplankton increases or decreases.

Answer 1

A. Measure the amounts of algae and zooplankton in a sample of water, and record the change in algae over several days. Keep other variables constant.

Step-by-step explanation:

Answer 2

Answer A is better because
1. You only have 1 independant variable, the zooplankton
2. You take periodic and relevant observations of the Dependant Variable (amount of algae)
3. Other variables (that could otherwise mess with your results on the dependant variable) are kept constant, thus enforcing the effect the independant variable has on the dependant variable (which is what youre trying to observe).