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Spontaneous Generation versus Biogenesis

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					Prevailing Theory questioning scientist
No theory (lots of folk tales, myths, and inferences) Jean Baptiste Van Helmont & many others try to be careful observers Redi

Spontaneous Generation versus Biogenesis Experiment findings Outcome of experiment Description ( Brief)
He and many others have recipes for how to create living things. (horse to bees , shirts to mice, mud to frogs etc…) Recipes seem to work (if you are NOT a careful observer) Sp. Gen. is maintained as the prevailing theory (Life arises from non-life)

Spontaneous generation

His controlled experiment uses a variable and control setup

Gauze covered jars – NO maggots Are they special?

Biogenesis (life arises only from other organisms)

Biogenesis (until new Discovery of “animalcules”) Biogenesis (but do animalcules arise spontaneously? )

Anton Van leeuwenhoek

Discovers tiny animalcules while looking at pond water with his microscope. Heats a flask with Hay/pond water mixture to “Kill” the contents and lets it sit to cool and then covers it with cork. Boils and seals the flask better than Needham did

Do they spontaneously arise? Spontaneous Generation starts to arise again as a possible theory to explain animalcules in water. Microorganisms seem to have spontaneously arisen.

Needham

Cloudy growth eventually shows up in the flask.

Spontaneous generation of tiny animalcules Lg organism – biogenesis Animalcules – Sp. Gen.

Spallanzani

Nothing grows

Vitalists complain – “no air” to support life

Pasteur

Uses curve-necked flask to trap the dust and allow air in/out

Vitalists are satisfied

Spont. Gen loses all acceptance. Biogenesis is currently the supported theory.

Q. If life only comes from pre-existing life by biogenesis, then where did the first life come from?
Scientists have generated many hypotheses, have been able to collect relatively little ancient evidence, and have formed few solid, well-tested theories. Today, we can try to play the biological and geological clocks backwards and surmise what most likely happened to get us to where we are today. Scientists, such as Stanley Miller and Harold Urey also simulate early Earth Atmospheric conditions to test the possibility of life arising spontaneously. The key is understanding a past with a reducing atmosphere (without oxygen) compared to our oxidizing one now.


				
Lingjuan Ma Lingjuan Ma
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