Daphnia are small water fleas that are relatively transparent and thus their heart beat can be monitored under a microscope. In a series of experiments, 3 different Daphnia fleas were exposed to either water (control) or dilute solutions of different drugs (shown in the table below). After a brief period of equilibration after exposure to the drug, the heartbeat of the flea was counted for 1 minute and recorded in the table below: Control Adrenaline Nicotine Alcohol Caffeine Flea 1- 50 80 30 27 38 Flea 2- 28 74 35 28 24 Flea 3-- 55 64 34 27 50