The Story of
Spontaneous
Generation
Spontaneous generation
 Spontaneous generation is the idea
that living things can be produced from
non-living things.
 From the time of the ancient Romans, through the
Middle Ages, and until the late nineteenth century, it
was generally accepted that some life forms arose
spontaneously from non-living matter.
The Question
 Where did life forms such as mice,
maggots, and microorganisms come
from?
Different Theories of
Spontaneous Generation
 Theory 1 = the spontaneous
production of mice required placing
sweaty underwear and husks of wheat
in an open-mouthed jar, then waiting for
about 21 days, during which time it was
alleged that the sweat from the
underwear would penetrate the husks of
wheat, changing them into mice.
The Theories
 T2 = maggots arise spontaneously in
rotting meat
 T3 = microorganisms arise spontaneously
in broth.
 Different scientist tested theses theories
over the years
 Francesco Redi
 An Italian doctor
 Louis Pasteur
 A French Scientist
 Lazzaro Spallanzani
 An Italian Scientist
Redi’s Experiment
 Question: where did
maggots come from
 Hypothesis:
maggots came from
the eggs of flies
Redi’s Experiment
 Procedure: Redi put rotting meat into
three jars.
 Jar 1 – open to the air
 Jar 2 – covered with netting
 Jar 3 – sealed off completely from
outside
Redi’s Experiment
 Results:
 Jar 1 = maggots developed on rotting
meat
 Flies were observed on meat
Redi’s Experiment
 Results
 Jar 2 = maggots appeared on netting
 Flies were observed on netting
Redi’s Experiment
 Results
 Jar 3 = maggots did not appear at all in or
around the sealed jar
 No flies were observed near jar 3
Redi’s Experiment
 Conclusion:
 The hypothesis was supported by the data
and therefore accepted
 Because there were no maggots in or
around the jar it was concluded the maggots
came from the fly eggs.
Spallanzani’s Experiment
 Question: What causes microbes to
form from decaying broth?
 Hypothesis: Microbes come from the air.
Boiling will kill microbes.
Spallanzani’s Experiment
 Procedure:
 Spallanzani put broth into four flasks
 Flask 1 – left open to the air
 Flask 2 – was sealed
 Flask 3 – was boiled and left open
 Flask 4 – was boiled then sealed
Spallanzani’s Experiment
 Results
 Flask 1 – left open to the air
 Turned cloudy (microbes found)
 Flask 2 – was sealed
 Turned cloudy (microbes found)
 Flask 3 – was boiled and left open
 Turned cloudy (microbes found)
 Flask 4 – was boiled then sealed
 Did not turn cloudy (NO MICROBES)
Spallanzani’s Experiment
 Conclusions:
 The hypothesis was accepted
 Because the combination of boiling the
broth (killing bacteria that were in the jar to
start) and sealing the jar (keeping bacteria
in the air out) it was concluded that boiling
does kill bacteria and that Microbes come
from the air.
Pasteur’s Experiment
 Question: Where do microbes come
from to cause chicken broth to decay?
 Hypothesis: Microbes come from cells
of organisms on dust particles in the air;
not from the air itself.
Pasteur’s Experiment
 Procedures:
 Control Group
 One flask of broth open to the air
 Experimental group
 One S-shaped flask that prevents dust from
entering the flask.
Pasteur’s Experiment
 Procedure:
 Pasteur put broth in both the open flask and into
special S-Shaped flasks and boiled it.
 S-shaped flask was used to trap any dust
particles
 Boiling was done to kill all the microbes already
in the flask.
Pasteur’s Experiment
 Procedure (cont.)
 Pasteur then watched to see if any changes
took place with the appearance of the broth
in the flasks.
 If the broth became cloudy that meant microbes
were present
Pasteur’s Experiment
 Results:
 Open flask – the
broth became
cloudy
 Closed flask – the
broth remain clear
 Dust was
observed in the
neck of the Sshaped neck of
the flask.
Pasteur’s Experiment
 Conclusion:
 The hypothesis was supported by the data
therefore it was accepted.
 Because the broth did not turn cloudy and
dust was observed trapped in the neck of
the S-Shaped flask, it was concluded that
the microbes came from cells of organisms
riding on dust particles.
The Scientific Method
 Each of these scientist used the scientific
method of investigation to successfully
disprove spontaneous generation.
 Remember Science is not just a body of
facts but a method of investigation.