The effect of coffee on the heart rate of daphnia

Investigating the effect of coffee on the heart rate of daphnia Aim:
To find out the effect of different caffeine concentrations on heart rate in daphnia Independent variable:
•Caffeine concentration
Dependent variable:
•Daphnia heart rate
Controlled variables:
•Size of daphnia
•Habitat from which the daphnia is obtained
•Temperature of the surrounding
How the variables can be controlled:
•Equally sized daphnia should be used in the experiment
•All daphnia should be collected at a same place, in uncontaminated waters •Experiment should be carried out in a lab at room temperature Apparatus/materials:
•Petri dish
•Filter paper
•Silicon grease
•0.1%, 0.2%,0.3%,0.4%,0.5% of caffeine solutions
•Daphnia culture
•Select a large specimen and, with a pipette, transfer it to the centre of a small, dry petri dish. with filter paper remove excess water from around the specimen so that it is completely stranded •With a seeker place a small blob of silicone grease onto the floor of the petri dish. Then wipe the needle clean and use it to gently push the posterior end of the animal into the grease so that it is firmly anchored. Now fill the petri dish with a caffeine solution. •Place the petri dish on the stage of a microscope and observe the animal under low power and watch the heart beating •Repeat the experiment with the rest of the caffeine solutions Results:

Caffeine concentration/%Heart rate/Beats per 2 minutes
Trial 1Trial 2Trial 3Trial 4Trial 5AverageAverage beats/min

In conclusion the data collected supports that an increase in the caffeine concentration leads to an increase in the heart rate of the daphnia