Describe the experiments by early scientists to Approve Abiogenesis

(i) John Needham – Experimented to support spontaneous generation theory
? Boiled mutton broth and closed it tightly in a glass and stored.
? After a few days it became cloudy – indicating growth
? Concluded that micro-organisms arose spontaneously.

(ii) Lazaro Spallanzani (experimented to disapprove the theory)
? Boiled the mutton broth longer and stored in a sealed flasks instead of glass
? Some of the flasks has cracks on the mouth and growth was observed.
? For those without cracks no growth was observed.

(iii) Theodor Schwann
Previously sterilized broth / infusion remains sterile.
? He passed air through a hot glass tube into heat treated broth in flasks
? The broth remained devoid of living things / no growth
? Concluded that microbes originate from the air and heating the air to destroy / kill them.

(iv) Schrodder and Dusch
Modified Schwann experiment by blocking the mouth of the glass tube with a cotton wool.

(v) Louis Pasteur – Researched on role of microbes in fermentation of beer and wine
• Filled flasks with broth and fashioned their openings into elongate, swan-neck shaped tubes
• The flasks openings were freely open to the air but were curved so that gravity would make any airborne dust particles to deposit in lower parts of the neck.
• He heated the flasks to sterilize the broth and incubated them.
• As long as the flask remained intact, the broth remained sterile, but if the neck was broken off so that the dust fell directly into the container, microbial growth was observed.
• Concluded that microbes were carried in air

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Kavungya answered the question on March 12, 2019 at 13:04