The Effect of Caffeine on heart rate. I think that the amount of caffeine in the blood will determine the heart rate of the daphnia.
Jerry George
The Effect of Caffeine on heart rate.
Hypothesis
I think that the amount of caffeine in the blood will determine the
heart rate of the daphnia. It will be directly proportional to each
other i.e. the increase of the % of caffeine will also increase the
heart rate of the daphnia.
Equipment List
• Culture of Daphnia (water fleas)
• Cavity slides and cover slips
• Dropping pipettes
• Distilled water
• Cotton wool
• Standard glassware (beakers, measuring cylinders etc)
• Stop watch
• Paper towels or filter paper
• Microscope.
Plan
1. The beating heart of a water flea can be seen through its
translucent body,
by placing the flea in a few drops of water in a cavity slide. A cover
slip
helps stop the water evaporating.
2. Place a few strands of cotton wool on a cavity slide; this will
help restrict
the movement of the water flea.
3. Using a pipette, transfer one large water flea to a cavity slide.
Remove the water from around the water flea using filter paper, then
add one or two drops of distilled water.
4. Use as much water as you can and do not use a cover slip.
5. Together these precautions will help maintain sufficient oxygen
supply to the flea. A cavity slide filled with iced water and placed
under the slide will act as a heat sink.
6. View the water flea under low power. Focus on its heart which can
be seen
through it translucent body.
7. Use a stop watch to record the number of heart beats per minute.
8. Tap a pencil on a piece of paper and count up the pencil marks at
the end of the time period.
9. Record the heart rate at intervals of two minutes over a 10 minute
period. It is a good idea to do a ‘blind’ study to avoid bias in the
results.
10. In order to make the best assumptions of the results the reader of
the amount of heart beats there are and the concentration of the
solution should be uninformed.
11. Repeat the procedure using other water fleas from the culture
solution and fresh, clean slides and cover slips. Replace the water
with caffeine solution. Repeat the procedure using several different
concentrations of caffeine.
