1. Redi’s Famous Experiment Hypothesis, Theory and Inference

2. Designing an Experiment 1.Observation 2.Ask a Question 3.Form a Hypothesis 4.Set up an Experiment 5.Record Data 6.Draw a Conclusion 7.Repeat…..Repeat…..Repeat 8.Theory…. maybe

3. ObservationQuestionHypothesisExperiment Record Data ConclusionRepeatTheory Steps of the Scientific Method

4. Redi’s Experiment - 1668 1.Observation: Something you “see” People noticed maggots on meat, mice on grains, and beetles on cow dungPeople noticed maggots on meat, mice on grains, and beetles on cow dung What could be the Inference ???? 2.Question How do new living things, organisms, suddenly come into being?How do new living things, organisms, suddenly come into being? 3.Hypothesis: Proposed explanation for observation…testable!! Redi noticed that maggots appeared a few days after flies were presentRedi noticed that maggots appeared a few days after flies were present Hypothesis = Flies produce maggotsHypothesis = Flies produce maggots

5. Redi’s Experiment 4.Set up an Experiment Control: stays constant (jars, meat, location, temperature, time) Independent Variable: something scientist changes or manipulates (gauze covering keeping flies away from meat) Dependent Variable: changes due to other variables (what you measure) (whether maggots appear)

6. Redi’s Experiment 5.Record Data Maggots appeared in jars which were not covered by gauzeMaggots appeared in jars which were not covered by gauze Usually done in tables and graphsUsually done in tables and graphs Numbers and observations are recordedNumbers and observations are recorded 6.Draw Conclusions : Was the hypothesis correct or incorrect??? Must be based on data from experimentMust be based on data from experiment Maggots form only when flies come in contact with meat.Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did NOT occur.Spontaneous generation of maggots did NOT occur.

7. Redi’s Experiment 7.Repeat….Repeat….Repeat Other scientists must be able to duplicate results in order for other to believe it! NeedhamNeedham Grew “bacteria” in heated gravy containersGrew “bacteria” in heated gravy containers Found “bacteria” in heated, sealed containers of gravyFound “bacteria” in heated, sealed containers of gravy Disagreed with RediDisagreed with Redi SpallanzaniSpallanzani Thought gravy was not heated enoughThought gravy was not heated enough Repeated & boiled gravyRepeated & boiled gravy The sealed jar remained free of bacteriaThe sealed jar remained free of bacteria Agreed with RediAgreed with Redi

8. Spallanzani’s Test

9. Louis Pasteur  About 200 years later (late 1800’s)  People argued  air was the “life force” needed to produce life  Spallanzani didn’t account for this  Pasteur repeated the experiment using a different container  Protected from microorganisms  Allowed air “life force” to flow freely

10. Louis Pasteur Curved NeckBroken Neck Air Enters

11. Pasteur’s Impact  Saved the French wine industry  Unexplained souring of wine  Saved the silk industry  Silkworm disease  Began to uncover the nature of infectious disease  Showed how microorganisms enter the body  “Pasteurization”

12. Hypothesis vs. Theory  Theory – A well-tested explanation that unifies a broad range of observations  Plate Tectonics  Evolution  Hypothesis – A proposed scientific explanation for a set of observations How does a hypothesis become a theory??