The Nature of Science

1. The Nature of Science How Scientists Work

2. Designing an Experiment • Based on Observations You Make, You Develop Logical Reasons To Explain What You Are Experiencing e.g. • Your Car Won’t Start • Then You Start Testing Each Reason To See If It Is True

3. Designing an Experiment • Science Does The Same Thing • Science Develops Explanations That May Define What Causes Something To Happen AND THEN TESTS IT! • YOU HAVE TO BE ABLE TO TEST IT!!!!! Here Is The Process:

4. Designing an Experiment Step 1:Observe & Ask Questions • For Years You Observe That Maggots Appear In Dead Meat • Where Do They Come From? • For Centuries People Thought They Came From Spontaneous Generation • But Nobody Tested It

5. Designing an Experiment Step 2: Form a Hypothesis • Spontaneous Generation Was A Hypothesis • A Possible Explanation For A Set Of Observations, or Possible Answer To A Scientific Question • But a Hypothesis Must Be Tested and That is What Francesco Redi Finally Did In 1668

6. Designing an Experiment Step 3: Set Up A Controlled Experiment • Variables= Factors That Can Change • Light, Temperature, Time, Materials, etc. • Only One (1) Variable Tested At A Time • Constants= • Are the Variables that are NOT Changed

7. Designing an Experiment Step 3: Set Up A Controlled Experiment(cont.) • Independent Variable = • The Variable That Is Changed • Dependent Variable = • The Variable That Responds/Changes To Changes To The Independent Variable • Observed Results = DATA

8. Designing an Experiment Key Concept: • Whenever Possible, A Hypothesis Should Be Tested By an Experiment In Which Only One Variable Is Changed At A Time (the Independent Variable) • All Other Variables Should Be Kept Unchanged, or Controlled (the Dependent Variable)

9. Designing On Experiment • So What Did Redi Do? • 1st He Observed • Dead Meat Attracted Flies. Did They Have Anything To Do With Maggots? • 2nd He Formed A Hypothesis • Maggots Were Caused By Flies.

10. Designing An Experiment • So What Did Redi Do? (cont.) • 3rd He Designed A Controlled Experiment • He Controlled All The Variables Except One • The Flies Access To The Meat

11. Designing An Experiment

12. Designing An Experiment Step 4:Recording & Analyzing Results • Scientific Experiments Have Standards of Documentation • All Aspects Of The Experiment Must Be Clearly Recorded So Other Scientists Can Repeat The Experiment

13. Designing An Experiment • So What Did Redi See? • Maggots Only Appeared In The Experimental (Uncovered) Jars!

14. Designing An Experiment Step 5:Drawing a Conclusion • Based On The Results Of The Experiment, Scientist Conclude That The Experiment Supports: • The Hypothesis or • The Null Hypothesis • Data Does NOT Support Your Hypothesis

15. Designing An Experiment Redi’s Experiment Is One of The Earliest Examples of Proper Scientific Inquiry • Documented • Reproducible • Overturns Accepted Dogma • Disrupts Established Beliefs

16. Designing An Experiment So What Did Redi Conclude? Maggots Are Produced By Flies. So what is the big deal? Everyone knows that!

17. Publishing & Repeating Investigations Properly Designed Experiment Are Reproducible! • Single Experiments Do Not Prove A Hypothesis • Other Scientists Must Reproduce The Same Experiment! • With The Same Results!

18. Needham’s Test of Redi’s Findings • Discovered “animalcules” (bacteria & Protozoa) • Some Scientists Assumed They Must Be Spontaneously Generated • Oops……Back As Excepted Dogma Leeuwenhoek – 1673Invented The First Working Microscopes

19. Needham’s Test of Redi’s Findings Needham– 1750’s Designs Experiment To Prove Spontaneous Generation • Boiled Beef Broth In A Sealed Container • Still Developed Bacteria • Obviously Spontaneous Generation Occurred What Was Wrong With Needham’s Experiment?

20. Spallanzani’s Test of Redi’s Experiment • Repeated Needham’s Procedure With One Improvement • He Sealed One Set Of Flasks IMMEDIATELY • Controls Grew Bacteria • Sealed Flasks Did Not LazarroSpallanzani, Late 1700’s

21. Spallanzani’s Test of Redi’s Experiment

22. Spallanzani’s Test of Redi’s Experiment Spallanzani’s Procedure Criticized Critics Complained: “You Cut Off Life Giving Air” Any Idiot Knows All Life Needs Air (They Didn’t Know About Anaerobes Yet)

23. Pasteur’s Test of Spontaneous Generation Louis Pasteur(1822-1895) He & Robert Koch Were The Fathers of Microbiology Developed • The Germ Theory of Disease • Immunization • Pasteurization • Canning

24. Pasteur’s Test of Spontaneous Generation Created Flasks That Were Open To The Air Through Long, Undulating Glass Tubes • Boiled Beef Broth In The Flasks • Bacteria Did NOT Develop • Over 1 Year Later, Broke The Glass Tubing • Bacteria Immediately Developed

25. Pasteur’s Test of Spontaneous Generation

26. When Experiments Are Not Possible • Sometimes Experiments Are Not Possible • Impossible To Isolate Single Variable • Unethical Human Experimentation • Use Chemicals To Cause Cancer • Human Tissue/Organ Transplants • Etc.

27. How A Theory Develops Scientific Definition Theory= Well TestedExplanation That UnifiesA Broad Range of Observations or Proven Hypothesis

28. How A Theory Develops Non Scientific Definition Theory = Abstract reasoning; speculation An assumption based on limited information or knowledge; a conjecture