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Francesco Redi
Redi challenged the idea of spontaneous generation by testing whether maggots could arise from rotting meat. He placed meat in jars, some open to the air and others sealed. He found that maggots only appeared in the open jars, proving that flies (not spontaneous generation) were the source of the maggots. -
John Needham
Needham performed an experiment where he boiled broth to kill microorganisms and then sealed it in flasks. After some time, he observed microorganisms in the sealed flasks and concluded that spontaneous generation occurred, especially for microbes. However, his experiment was flawed because the boiling process was insufficient to kill all microorganisms, and contamination may have occurred during cooling or improper sealing. -
Lazzaro Spallanzani
Spallanzani improved on Needham’s experiment by boiling the broth in sealed flasks for a longer time. He found no microbial growth in the sealed flasks, suggesting that life did not arise spontaneously, but came from the air. However, some critics argued that his boiling process removed a "life force" that they believed was needed for life to form. -
Louis Pasteur
Pasteur performed a definitive experiment using swan-neck flasks. He boiled broth in these flasks, which allowed air to enter but trapped dust particles. The broth remained free of life unless the flask was tilted and exposed to the air. Pasteur’s experiment showed that life comes from other life, disproving spontaneous generation once and for all and proving that microorganisms in the air were responsible for contamination.