The Scientific Method
Diane Caporale
Department of Biology, College of Letters and Science
UWSP
http://www.youtube.com/watch?v=jPaGOHwv7mQ
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Premise: The laws of nature are
uniform.
Premise: In experiments A, B, C, when the
independent variable changed according to X,
the dependent variable changed according to Y.
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Subconclusion: What
happened in experiments A, B,
C will happen generally.
Ultimate Conclusion: In general, if the independent variable changes
according to X the dependent variable will change according to Y, provided
that other variables are held constant.
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Premise: The laws of nature are
uniform.
Premise: In experiments A, B, C, when the
independent variable changed according to X,
the dependent variable did not change
according to Y.
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Subconclusion: What
happened in experiments A,
B, C will happen generally.
Ultimate Conclusion: In general, if the independent variable changes
according to X, the dependent variable will not change according to Y,
provided that other variables are held constant.
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How does caffeine affect heart rate of Daphnia?
•Caffeine increases activity of vert CNS
•Caffeine makes pacemaker cells fire more rapidly
If levels of caffeine exposure is increased,
Daphnia’s heart rate will increase, relative to
its resting heart ate
Control: determine average resting heart rate
using 5 Daphnias
Variable: expose different % of caffeine, with
increasing concentrations
At low concs, HR increased
But at higher concs, HR decreased
Is there a threshold as to when caffeine levels
start to have a negative effect on Daphnia’s
heart rate?
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