1.Use a
toothpick to smear vaseline onto
a glass slide. Use a plastic pipette to place one Daphnia onto
smudge.
2.Focus
slide under a microscope under dim lighting to see through transparency of skin
and view the fast-beating heart.
3.Measure
the initial heart rate for baseline by tapping a pen on paper for each beat. Do
this for 10 seconds, count the number of dots on the paper, and multiply by 6
to get beats per minute.
4.With
the assigned concentration of caffeine, apply 2 drops of solution to Daphnia,
wait for 60 seconds, and measure the heart rate again.
5.Calculate
percent change of heart rate: ((Final-Initial)/Initial) x 100
6.Graph
these results and compare.
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