Free Powerpoint Presentations

Origin of Life
Page
4

DOWNLOAD

PREVIEW

WATCH ALL SLIDES

Slide 32

Anton van Leeuwenhoek 1632-1723

Anton van Leeuwenhoek 1632-1723

Slide 33

Leeuwenhoek’s Microscope

Leeuwenhoek’s Microscope

Slide 34

John Needham (1745)

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

Slide 35

Needham’s Results

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

Slide 36

Needham’s Experiment

Needham’s Experiment

Slide 37

Lazzaro Spallanzani’s (1765)

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.

Slide 38

Spallanzani’s Results

Spallanzani’s Results

Slide 39

Conclusion

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

Slide 40

The Theory Finally Changes

The Theory Finally Changes

Slide 41

How Do Microbes Arise?

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)

Louis Pasteur (1822-1895)

Slide 43

Pasteur's Problem

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

Slide 44

Go to page:
 1  2  3  4  5 

Contents

Last added presentations

© 2010-2024 powerpoint presentations