brief history of scientific methods
TRANSCRIPT
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Introduction to Biology
Chapter 1, Section 2
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History of Scientific Method
Aristotle: Greek philosopher (2300 yag)Explanations based on logic
2 broad classesLiving (biotic)Non-living (abiotic)
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History of Scientific Method
Common knowledge:Living things possess a “vital force” that
allows living things to spawn from non-living sources
Theory of “Spontaneous generation”
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History of Scientific Method
Common knowledge:Living things possess a “vital force” that
allows living things to spawn from non-living sources
Theory of “Spontaneous generation”
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History of Scientific Method
• Francesco Redi (1668) Italian physician– Challenged spontaneous generation
• Observation: meat left in open air produced maggots• Common Knowledge: maggots come from dead meat• Redi’s hypothesis: Flies lay eggs on raw meat, these
eggs turn into maggots.
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History of Scientific Method
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History of Scientific method
• Redi’s experiment:• 2 glass containers– One covered– One uncovered
• Same type of meat• Same location• Same temperature• Same amount of time
• VARIABLES
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History of Scientific Mehtod
• Redi’s Experiment– Findings– The container with a cover (gauze to allow equal
air flow) did not generate any maggots.– Conclusion:• Maggots only appear on meat that has been exposed to
flies.
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History of Scientific Mehtod
• Needham (mid 1700s)• Combined Redi’s findings with the research of
Leeuwenhoek.– Leeuwenhoek made the first microscope
• Needham’s experiment– 2 identical containers– Both heated, then allowed to sit at same temperature– Same gravy
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History of Scientific Mehtod
• Needham’s Experiment– Findings: gravy was teeming with microbes – Conclusion: Microbes come from gravy– spontaneous
generation
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History Of Scientific Method
• Spallanzani (Italian Scholar)– Spallanzani’s Experiment:• 2 identical containers• Same gravy• Heated–One container sealed immediately–Other left open to air
• Left to sit for same amount of time
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History of Scientific Mehtod
• Spallanzani’s Experiment:– Findings: Gravy open to air teeming with microbes, while
sealed container had none.– Conclusion: Microbes too small to see had entered the jar
from the air and reproduced in the gravy.
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History of Scientific Method
• Pasteur (1881)• Pasteur’s Experiment– Special flask–Boiled broth
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History of scientific Method
• Pasture’s Experiment• Findings: Broth was free of microorganisms• Conclusion: So long as broth is protected from
microorganisms broth remains free of life.
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History of Scientific Method
• Pasteur’s work lead to other revolutions in science–Nature of food spoilage–Nature of disease
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Did I mention History’s Not my thing…. Brain Break!