The Story of Spontaneous Generation. Spontaneous generation Spontaneous generation is the idea that...

The Story of The Story of Spontaneous Spontaneous GenerationGeneration

Spontaneous generationSpontaneous generation

Spontaneous generationSpontaneous generation is the idea is the idea that living things can be produced from that living things can be produced from non-living things.non-living things.

From the time of the ancient Romans, through the From the time of the ancient Romans, through the Middle Ages, and until the late nineteenth century, it Middle Ages, and until the late nineteenth century, it was generally accepted that some life forms arose was generally accepted that some life forms arose spontaneously from non-living matterspontaneously from non-living matter..

The Question The Question

Where did life forms such as mice, Where did life forms such as mice, maggots, and microorganisms come maggots, and microorganisms come from?from?

Different Theories of Different Theories of Spontaneous Generation Spontaneous Generation

Theory 1Theory 1 = = the spontaneous the spontaneous production of mice required placing production of mice required placing sweaty underwear and husks of wheatsweaty underwear and husks of wheat in an open-mouthed jar, then waiting for in an open-mouthed jar, then waiting for about 21 days, during which time it was about 21 days, during which time it was alleged that the sweat from the alleged that the sweat from the underwear would penetrate the husks of underwear would penetrate the husks of wheat, changing them into mice.wheat, changing them into mice.

The TheoriesThe Theories

TT22 = maggots arise spontaneously in = maggots arise spontaneously in

rotting meatrotting meat

TT33 = microorganisms arise spontaneously = microorganisms arise spontaneously

in broth. in broth.

Different scientist tested theses theories Different scientist tested theses theories over the years over the years Francesco RediFrancesco Redi

An Italian doctorAn Italian doctor

Louis PasteurLouis Pasteur A French ScientistA French Scientist

Lazzaro Spallanzani Lazzaro Spallanzani An Italian ScientistAn Italian Scientist

Redi’s ExperimentRedi’s Experiment

Question:Question: where did where did maggots come frommaggots come from

Hypothesis:Hypothesis: maggots came from maggots came from the eggs of fliesthe eggs of flies


ProcedureProcedure: Redi put rotting meat into : Redi put rotting meat into three jars.three jars.

Jar 1 – open to the airJar 1 – open to the air Jar 2 – covered with nettingJar 2 – covered with netting Jar 3 – sealed off completely from Jar 3 – sealed off completely from

outsideoutside


Results:Results: Jar 1 = maggots developed on rotting Jar 1 = maggots developed on rotting

meatmeat Flies were observed on meatFlies were observed on meat


ResultsResults Jar 2 = maggots appeared on nettingJar 2 = maggots appeared on netting

Flies were observed on nettingFlies were observed on netting


ResultsResults Jar 3 = maggots did not appear at all in or Jar 3 = maggots did not appear at all in or

around the sealed jararound the sealed jar No flies were observed near jar 3No flies were observed near jar 3


Conclusion:Conclusion: The hypothesis was supported by the data The hypothesis was supported by the data

and therefore acceptedand therefore accepted Because there were no maggots in or Because there were no maggots in or

around the jar it was concluded the maggots around the jar it was concluded the maggots came from the fly eggs.came from the fly eggs.

Spallanzani’s ExperimentSpallanzani’s Experiment

Question:Question: What causes microbes to What causes microbes to form from decaying broth?form from decaying broth?

Hypothesis:Hypothesis: Microbes come from the air. Microbes come from the air. Boiling will kill microbes. Boiling will kill microbes.


Procedure:Procedure: Spallanzani put broth into four flasksSpallanzani put broth into four flasks

Flask 1 – left open to the airFlask 1 – left open to the air Flask 2 – was sealedFlask 2 – was sealed Flask 3 – was boiled and left openFlask 3 – was boiled and left open Flask 4 – was boiled then sealedFlask 4 – was boiled then sealed


ResultsResults Flask 1 – left open to the airFlask 1 – left open to the air

Turned cloudy (microbes found)Turned cloudy (microbes found)

Flask 2 – was sealedFlask 2 – was sealed Turned cloudy (microbes found)Turned cloudy (microbes found)

Flask 3 – was boiled and left openFlask 3 – was boiled and left open Turned cloudy (microbes found)Turned cloudy (microbes found)

Flask 4 – was boiled then sealedFlask 4 – was boiled then sealed Did not turn cloudy (NO MICROBES)Did not turn cloudy (NO MICROBES)


Conclusions:Conclusions: The hypothesis was acceptedThe hypothesis was accepted Because the combination of boiling the Because the combination of boiling the

brothbroth (killing bacteria that were in the jar to (killing bacteria that were in the jar to start) start) and sealing the jarand sealing the jar (keeping bacteria (keeping bacteria in the air out) in the air out) it was concluded that boiling it was concluded that boiling does kill bacteria and that Microbes come does kill bacteria and that Microbes come from the air.from the air.

Pasteur’s ExperimentPasteur’s Experiment

Question:Question: Where do microbes come Where do microbes come from to cause chicken broth to decay?from to cause chicken broth to decay?

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


Procedures:Procedures: Control GroupControl Group

One flask of broth open to the air One flask of broth open to the air

Experimental groupExperimental group One S-shaped flask that prevents dust from One S-shaped flask that prevents dust from

entering the flask.entering the flask.

Pasteur’s ExperimentPasteur’s Experiment ProcedureProcedure::

Pasteur put broth in both the open flask and into Pasteur put broth in both the open flask and into special S-Shaped flasks and boiled it.special S-Shaped flasks and boiled it. S-shaped flask was used to trap any dust particlesS-shaped flask was used to trap any dust particles Boiling was done to kill all the microbes already in Boiling was done to kill all the microbes already in

the flask.the flask.


Procedure (cont.)Procedure (cont.) Pasteur then watched to see if any changes Pasteur then watched to see if any changes

took place with the appearance of the broth took place with the appearance of the broth in the flasks.in the flasks. If the broth became cloudy that meant microbes If the broth became cloudy that meant microbes

were presentwere present


Results:Results: Open flaskOpen flask – the – the

broth became broth became cloudycloudy

Closed flaskClosed flask – the – the broth remain clearbroth remain clear Dust was Dust was

observed in the observed in the neck of the S-neck of the S-shaped neck of shaped neck of the flask.the flask.


Conclusion:Conclusion: The hypothesis was supported by the data The hypothesis was supported by the data

therefore it was accepted.therefore it was accepted. Because the broth did not turn cloudy and Because the broth did not turn cloudy and

dust was observed trapped in the neck of dust was observed trapped in the neck of the S-Shaped flask, it was concluded that the S-Shaped flask, it was concluded that the microbes came from cells of organisms the microbes came from cells of organisms riding on dust particles.riding on dust particles.

The Scientific MethodThe Scientific Method

Each of these scientist used the scientific Each of these scientist used the scientific method of investigation to method of investigation to successfully successfully disprove spontaneous generation.disprove spontaneous generation.

Remember Science is not just a body of Remember Science is not just a body of facts but a method of investigation.facts but a method of investigation.

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