1. How Spontaneous Generation was disproven
Biogenesis
How Spontaneous Generation was disproven

2. Spontaneous Generation is the thought that living things come from non-living things

3. Spontaneous Generation is the thought that living things come from non-living things
Example: earthworms after
a rain; People used to think
they had fallen from the sky!

4. Example: Recipe for making
mice by placing grain and dirty
clothes in a jar for 3 weeks

5. First controlled experiment:
1668 by an Italian doctor, Redi
Meat in 2 jars-one covered and one open

6. First controlled experiment:
1668 by an Italian doctor, Redi
Meat in 2 jars-one covered and one open
Maggots formed on meat of opened jar

7. Refuted Redi’s experiment and ideas Experiment:
John Needham- 1668
Refuted Redi’s experiment and ideas
Experiment:
Briefly heated broth (gravy) to kill all organisms inside
Sealed container
Organisms grew in sealed container
Thought this supported spontaneous generation
What did he do wrong???

8. Thought that he PROVED spontaneous generation Did NOT heat
John Needham- 1668
Thought that he
PROVED
spontaneous
generation
Did NOT heat
broth long enough
to kill everything!

9. Spallanzani’s Experiment
Scientist (late 1700’s) thought Needham’s expt. was flawed
proved that tiny organisms come from other tiny organisms in the air

10. Spallazani’s Experiment:
Broth (gravy) in 2 flasks; one corked and one opened; opened flask turned cloudy with bacteria

11. Spallazani’s Experiment:
Disproved spontaneous generation
Critics thought that you needed air to spontaneously generate and he excluded air- still not convinced!

12. Officially Disproved Spontaneous Generation!
Mid-1800’s Louis Pasteur (French chemist)
Officially Disproved Spontaneous Generation!
Boiled broth and created a vacuum by trapping microbes in a curved neck of flask

13. One year later broth remained clear
Louis Pasteur
One year later broth remained clear
Took curved neck off and microbes developed in broth

14. Louis Pasteur’s experiment:

15. Louis Pasteur
Conclusion: As long as dust and other airborne particles were trapped in the S- shaped neck of the bottle, no life was created until this obstacle was removed.
He reasoned that the contamination came from life-forms in the air.

16. Biogenesis
The theory of Spontaneous Generation was replaced with the theory of Biogenesis: living things come only from other living things