The Scientific Method

1. The Scientific Method

2. What is the Scientific Method? • The principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to demonstrate the truth or falseness of the hypothesis, and a conclusion that validates or modifies the hypothesis. • A method which may be used to logically solve problems.

3. The father of modern microbiology Showed that airborne microbes were the cause of disease. Developed the first vaccines. Debunked the myth of spontaneous generation. Described the scientific basis for fermentation, wine-making, and the brewing of beer. The pasteurization process is named after him. Louis Pasteur (1822-1895)

4. The fermentation of Beer and Wine is done with small microorganisms called yeast. In 1865, a French beer maker had a problem with vats of beer going sour. Louis Pasteur began investigating the cause of the “bad beer”. Pasteur’s Problem

5. When alcohol was produced normally, the yeast cells were plump and budding. Bad beer contained lactic acid (vinegar) instead of alcohol. “Bad beer” contained small rod like microbes mixed in with the yeast cells. Pasteur’s Observation

6. The fermentation of Beer is soured by the production of vinegar. Vinegar might be produced by the rod like microorganisms found in the “bad beer.” Eliminating the rod like microorganisms will stop the production of vinegar and consequently stop the souring of the beer. Pasteur’s Hypothesis and Prediction

7. Over the next several years Pasteur identified and isolated the microorganisms responsible for “bad beer”. He showed that if he heated beer to moderately high temperatures for a few minutes, he could kill living microorganisms and thereby sterilize (pasteurize). Sterilizing the batches before fermentation ensured the production of “good beer”. Pasteur’s Experiments

8. Microorganisms were responsible for the formation of “bad beer” His discovery led to… The process of pasteurization. The germ theory of disease Disproving the concept of spontaneous generation. Pasteur’s Conclusions

9. The Scientific Method

10. Good scientists are observant and notice things in the world around them. They see, hear, or in some other way notice what’s going on in the world and becomes curious about what’s happening. Observation: Flies and rotting meat are often found together. Observation

11. Scientists then raise a question about what they see. The question raised must have a “simple,” concrete answer that can be obtained by performing an experiment. Question: Where do the flies at the butcher shop really come from? Does rotting meat turn into or produce the flies? Questions

12. A tentative scientific explanation (educated guess) that attempts to answer questions asked about natural phenomena. A hypothesis must be testable! Hypothesis: Rotten meat does not turn into flies. Only flies can make more flies. Hypothesis

13. Prediction • Next, the experimenter uses deductive reasoning to test the hypothesis. • Prediction: If meat cannot turn into flies, rotting meat in a sealed (fly-proof) container should not produce flies or maggots. • Inductive reasoning goes from a set of specific observations to general conclusions: I observed cells in x, y, and z organisms, therefore all animals have cells. • Deductive reasoning flows from general to specific. From general premises, a scientist would extrapolate to specific results: if all organisms have cells and humans are organisms, then humans should have cells.

14. The scientist performs the experiment to see if the predicted results are obtained. Controls are supplementary experiments set up to allow comparisons Testing: Wide-mouth jars each containing a piece of meat were subjected to several variations of “openness” while all other variables were kept the same. Control group: These jars of meat were set out without lids so the meat would be exposed to whatever it might be in the butcher shop. Experimental group(s): One group of jars were sealed with lids, and another group of jars had gauze placed over them. Experiment

15. Data • Accurate recordings of what happened during the experiment is recorded. • All data must be recorded even if it doesn’t support your hypothesis (including errors). • Data: Presence or absence of flies and maggots seen in each jar was recorded. • In the control group of jars, flies were seen entering the jars. Later, maggots, then more flies were seen on the meat. • In the gauze-covered jars, no flies were seen in the jars, but were observed around and on the gauze, and later a few maggots were seen on the meat. • In the sealed jars, no maggots or flies were ever seen on the meat.

16. Analyzing Data and Conclusions • Rigorous analysis of your data is essential to reaching valid conclusions. If the expected results are obtained, they support (but do not prove) the hypothesis. • Conclusion(s): Only flies can make more flies. In the uncovered jars, flies entered and laid eggs on the meat. Maggots hatched from these eggs and grew into more adult flies. Adult flies laid eggs on the gauze on the gauze-covered jars. These eggs or the maggots from them dropped through the gauze onto the meat. In the sealed jars, no flies, maggots, nor eggs could enter, thus none were seen in those jars. Maggots arose only where flies were able to lay eggs. This experiment disproved the idea of spontaneous generation for larger organisms.

17. Characteristics of Scientific Explanations • Based upon observations • Rational • Consistent with known natural laws • Consistent with well-established theories • Utilize natural cause and effect • Testable • Conclusions tentative

18. Operational Rule The simplest interpretation that is consistent with all of the pertinent data is most likely to be correct.

19. Limitations of Natural Science • Can only study natural phenomena • Can neither confirm nor refute supernatural explanations • Does not make moral decisions • Does not produce absolute final truths

20. Scientific Method Activity • Working in groups, write a problem or observation for an experiment. • Exchange cards with another group. • Generate a hypothesis for the problem or observation you have been given. • Exchange cards with another group. • Devise an experiment to test the hypothesis you have been given.