Brief explanations of early scientists and their contributions to scientific methods. Appropriate for high school biology.

1. Introduction to Biology
Chapter 1, Section 2

2. History of Scientific Method
Aristotle: Greek philosopher (2300 yag)
Explanations based on logic
2 broad classes
Living (biotic)
Non-living (abiotic)

3. 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”

4. 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”

5. 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.

6. History of Scientific Method

7. 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

8. 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.

9. 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

10. History of Scientific Mehtod
• Needham’s Experiment
– Findings: gravy was teeming with microbes
– Conclusion: Microbes come from gravy– spontaneous
generation

11. 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

12. 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.

13. History of Scientific Method
• Pasteur (1881)
• Pasteur’s Experiment
–Special flask
–Boiled broth

14. 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.

15. History of Scientific Method
• Pasteur’s work lead to other revolutions
in science
–Nature of food spoilage
–Nature of disease

16. Did I mention History’s Not my thing….
Brain Break!