Origin of Life

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Anton van Leeuwenhoek 1632-1723

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Leeuwenhoek’s Microscope

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John Needham (1745)

Showed that microorganisms flourished in various soups that had been exposed to the air

Claimed that there was a “life force” present in the molecules of all inorganic matter, including air and the oxygen in it, that could cause spontaneous generation to occur

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Needham’s Results

Needham’s experiments seemed to support the idea of spontaneous generation

People didn’t realize bacteria were already present in Needham’s soups

Needham didn’t boil long enough to kill the microbes

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Needham’s Experiment

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Lazzaro Spallanzani’s (1765)

Boiled soups for almost an hour and sealed containers by melting the slender necks closed.

The soups remained clear.

Later, he broke the seals & the soups became cloudy with microbes.

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Spallanzani’s Results

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Conclusion

Critics said sealed vials did not allow enough air for organisms to survive and that prolonged heating destroyed “life force”

Therefore, spontaneous generation remained the theory of the time

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The Theory Finally Changes

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How Do Microbes Arise?

By 1860, the debate had become so heated that the Paris Academy of Sciences offered a prize for any experiments that would help resolve this conflict

The prize was claimed in 1864 by Louis Pasteur, as he published the results of an experiment he did to disproved spontaneous generation in microscopic organisms

Slide 42

Louis Pasteur (1822-1895)

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Pasteur's Problem

Hypothesis: Microbes come from cells of organisms on dust particles in the air; not the air itself.

Pasteur put broth into several special S-shaped flasks

Each flask was boiled and placed at various locations

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