The Scientific Method. What is the Scientific Method? The principles and empirical processes of discovery and demonstration considered characteristic.

The Scientific MethodThe Scientific Method

What is the Scientific Method?What is the Scientific Method?

• The principles and empirical processes of discovery and The principles and empirical processes of discovery and demonstration considered characteristic of or necessary demonstration considered characteristic of or necessary for scientific investigation, generally involving the for scientific investigation, generally involving the observation of phenomena, the formulation of a observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation hypothesis concerning the phenomena, experimentation to demonstrate the truth or falseness of the hypothesis, to demonstrate the truth or falseness of the hypothesis, and a conclusion that validates or modifies the and a conclusion that validates or modifies the hypothesis. hypothesis.

• A method which may be used to logically solve A method which may be used to logically solve problems.problems.

Louis Pasteur (1822-1895)Louis Pasteur (1822-1895)

• The father of modern The father of modern microbiologymicrobiology

• Showed that airborne Showed that airborne microbes were the cause of microbes were the cause of disease. disease.

• Developed the first Developed the first vaccines. vaccines.

• Debunked the myth of Debunked the myth of spontaneous generation.spontaneous generation.

• Described the scientific Described the scientific basis for fermentation, basis for fermentation, wine-making, and the wine-making, and the brewing of beer. brewing of beer.

• The pasteurization process The pasteurization process is named after him.is named after him.

Pasteur’s ProblemPasteur’s Problem• The fermentation of The fermentation of

Beer and Wine is done Beer and Wine is done with small with small microorganisms called microorganisms called yeast.yeast.

• In 1865, a French beer In 1865, a French beer maker had a problem maker had a problem with vats of beer going with vats of beer going sour.sour.

• Louis Pasteur began Louis Pasteur began investigating the cause investigating the cause of the “bad beer”. of the “bad beer”.

Pasteur’s ObservationPasteur’s Observation

• When alcohol was When alcohol was produced normally, the produced normally, the yeast cells were plump yeast cells were plump and budding. and budding.

• Bad beer contained acetic Bad beer contained acetic acid (vinegar) instead of acid (vinegar) instead of alcohol.alcohol.

• ““Bad beer” contained Bad beer” contained small rod like microbes small rod like microbes mixed in with the yeast mixed in with the yeast cells. cells.

Pasteur’s Hypothesis and PredictionPasteur’s Hypothesis and Prediction

• The fermentation of Beer is The fermentation of Beer is soured by the production of soured by the production of vinegar.vinegar.

• Vinegar might be produced Vinegar might be produced by the rod like by the rod like microorganisms found in microorganisms found in the “bad beer.”the “bad beer.”

• Eliminating the rod like Eliminating the rod like microorganisms will stop microorganisms will stop the production of vinegar the production of vinegar and consequently stop the and consequently stop the souring of the beer.souring of the beer.

Pasteur’s ExperimentsPasteur’s Experiments

• Pasteur identified and Pasteur identified and isolated the microorganisms isolated the microorganisms responsible for “bad beer”.responsible for “bad beer”.

• He showed that if he heated He showed that if he heated beer to moderately high beer to moderately high temperatures for a few temperatures for a few minutes, he could kill living minutes, he could kill living microorganisms and thereby microorganisms and thereby sterilize (pasteurize).sterilize (pasteurize).

• Sterilizing the batches before Sterilizing the batches before fermentation ensured the fermentation ensured the production of “good beer”. production of “good beer”.

Pasteur’s ConclusionsPasteur’s Conclusions

• Microorganisms were Microorganisms were responsible for the responsible for the formation of “bad beer”formation of “bad beer”

• His discovery led to…His discovery led to…• The process of The process of

pasteurization.pasteurization.• The germ theory of The germ theory of

diseasedisease• Disproving the concept Disproving the concept

of spontaneous of spontaneous generation. generation.

The The Scientific Scientific MethodMethod

ObservationObservation

• Good scientists are Good scientists are observant and notice things observant and notice things in the world around them.in the world around them.

• They see, hear, or in some They see, hear, or in some other way notice what’s other way notice what’s going on in the world and going on in the world and becomes curious about becomes curious about what’s happening. what’s happening.

• Observation:Observation: Flies and Flies and rotting meat are often found rotting meat are often found together.together.

QuestionsQuestions

• Scientists then raise a Scientists then raise a question about what they see.question about what they see.

• The question raised must The question raised must have a “simple,” concrete have a “simple,” concrete answer that can be obtained answer that can be obtained by performing an experiment. by performing an experiment.

• Question:Question: Where do the flies Where do the flies at the butcher shop really at the butcher shop really come from? Does rotting come from? Does rotting meat turn into or produce the meat turn into or produce the flies? flies?

HypothesisHypothesis

• 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.

PredictionPrediction

• A prediction is a broad A prediction is a broad statement of what will statement of what will happen in a based on the happen in a based on the hypothesis.hypothesis.

• Prediction:Prediction: If meat cannot If meat cannot turn into flies, rotting meat turn into flies, rotting meat in a sealed (fly-proof) in a sealed (fly-proof) container should not container should not produce flies or maggots. produce flies or maggots.

ExperimentExperiment• The scientist performs the experiment to The scientist performs the experiment to

see if the predicted results are obtained.see if the predicted results are obtained.• Controls are supplementary experiments Controls are supplementary experiments

set up to allow comparisons set up to allow comparisons • Testing:Testing: Wide-mouth jars each containing Wide-mouth jars each containing

a piece of meat were subjected to several a piece of meat were subjected to several variations of “openness” while all other variations of “openness” while all other variables were kept the same.variables were kept the same.

• Control groupControl group: These jars of meat were : These jars of meat were set out without lids so the meat would be set out without lids so the meat would be exposed to whatever it might be in the exposed to whatever it might be in the butcher shop.butcher shop.

• Experimental group(s):Experimental group(s): One group of jars One group of jars were sealed with lids, and another group were sealed with lids, and another group of jars had gauze placed over them.of jars had gauze placed over them.

DataData

• Accurate recordings of what happened during the experiment is Accurate recordings of what happened during the experiment is recorded. recorded.

• All data must be recorded even if it doesn’t support your All data must be recorded even if it doesn’t support your hypothesis (including errors).hypothesis (including errors).

• Data:Data: Presence or absence of flies and maggots seen in each jar Presence or absence of flies and maggots seen in each jar was recorded. was recorded.

• In the control group of jars, flies were seen entering the jars. In the control group of jars, flies were seen entering the jars. Later, maggots, then more flies were seen on the meat. Later, maggots, then more flies were seen on the meat.

• In the gauze-covered jars, no flies were seen in the jars, but were 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 observed around and on the gauze, and later a few maggots were seen on the meat. seen on the meat.

• In the sealed jars, no maggots or flies were ever seen on the In the sealed jars, no maggots or flies were ever seen on the meat. meat.

Analyzing Data and ConclusionsAnalyzing Data and Conclusions

• Rigorous analysis of your data is essential to reaching valid Rigorous analysis of your data is essential to reaching valid conclusions. If the expected results are obtained, they support conclusions. If the expected results are obtained, they support (but do not (but do not proveprove) the hypothesis. ) the hypothesis.

• Conclusion(s):Conclusion(s): Only flies can make more flies. In the Only flies can make more flies. In the uncovered jars, flies entered and laid eggs on the meat. Maggots uncovered jars, flies entered and laid eggs on the meat. Maggots hatched from these eggs and grew into more adult flies. Adult hatched from these eggs and grew into more adult flies. Adult flies laid eggs on the gauze on the gauze-covered jars. These flies laid eggs on the gauze on the gauze-covered jars. These eggs or the maggots from them dropped through the gauze onto eggs or the maggots from them dropped through the gauze onto the meat. In the sealed jars, no flies, maggots, nor eggs could the meat. In the sealed jars, no flies, maggots, nor eggs could enter, thus none were seen in those jars. Maggots arose only enter, thus none were seen in those jars. Maggots arose only where flies were able to lay eggs. This experiment disproved the where flies were able to lay eggs. This experiment disproved the idea of spontaneous generation for larger organisms. idea of spontaneous generation for larger organisms.

Operational RuleOperational RuleOperational RuleOperational Rule

The simplest interpretation The simplest interpretation that is consistent with all of that is consistent with all of the pertinent data is most the pertinent data is most

likely to be correct.likely to be correct.

The simplest interpretation The simplest interpretation that is consistent with all of that is consistent with all of the pertinent data is most the pertinent data is most

likely to be correct.likely to be correct.

Limitations of Natural ScienceLimitations of Natural ScienceLimitations of Natural ScienceLimitations of Natural Science

• Can only study natural phenomenaCan only study natural phenomena

• Can neither confirm nor refute Can neither confirm nor refute supernatural explanationssupernatural explanations

• Does not make moral decisionsDoes not make moral decisions

• Does not produce absolute final truthsDoes not produce absolute final truths

• Can only study natural phenomenaCan only study natural phenomena

• Can neither confirm nor refute Can neither confirm nor refute supernatural explanationssupernatural explanations

• Does not make moral decisionsDoes not make moral decisions

• Does not produce absolute final truthsDoes not produce absolute final truths

ScientificScientific Method Activity Method Activity

1.1. Working in groups, write a problem or Working in groups, write a problem or observation for an experiment.observation for an experiment.

2.2. Exchange cards with another group.Exchange cards with another group.3.3. Generate a hypothesis for the problem or Generate a hypothesis for the problem or

observation you have been given.observation you have been given.4.4. Exchange cards with another group.Exchange cards with another group.5.5. Devise an experiment to test the hypothesis Devise an experiment to test the hypothesis

you have been given.you have been given.