Students in a high school biology class are observing the effects of different environments on the heart rate of the organism Daphnia. Daphnia is a small, planktonic freshwater crustacean whose body is transparent. Daphnia are good test subjects due to the fact that their heartbeat is visible under low power on a basic microscope. The students conducted their experiment in two parts.
For Part A of the experiment, the students predicted that the daphnia heart rate would decrease as concentrations of ethanol in the environment increased. The students placed the daphnia into different concentrations of alcohol, and observed their heart rates after being in the environments for two minutes. Their results are as follows:
For Part B of the experiment, the students placed daphnia into different concentrations of caffeine and observed their heart rates after two minutes. The students predicted that the heart rates would increase with the concentrations of caffeine in the environment.
Which of the following would best describe the hypothesis for Part A of the experiment?