http://www.youtube.com/watch?v=jPaGOHwv7mQ

1

The Scientific MethodDiane Caporale

Department of Biology, College of Letters and ScienceUWSP

2

3

4

5

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.

Premise: In experiments A, B, C, when the independent variable changed according to X, the dependent variable changed according to Y.

Subconclusion: What happened in experiments A, B, C will happen generally.

Premise: The laws of nature are uniform.

+

6

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.

Premise: In experiments A, B, C, when the independent variable changed according to X, the dependent variable did not change according to Y.

Subconclusion: What happened in experiments A, B, C will happen generally.

Premise: The laws of nature are uniform.

+

7

8

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 DaphniasVariable: expose different % of caffeine, with increasing concentrations

At low concs, HR increasedBut 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?