How Spontaneous Generation was disproven Biogenesis How Spontaneous Generation was disproven

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

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!

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

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

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

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???

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!

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

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

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

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

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

Louis Pasteur’s experiment:

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.

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