Final answer:
John Needham's 1745 experiment briefly boiled broth before sealing it in flasks, which soon showed microbial growth he attributed to spontaneous generation. However, his results were due to insufficient boiling, not spontaneous generation. This led to further research, ultimately disproving the theory.
Step-by-step explanation:
John Needham conducted an experiment in 1745 to support the theory of spontaneous generation, which posits that life can arise from nonliving matter. Needham briefly boiled broth infused with plant or animal matter and then sealed the flasks.
After a few days, he observed that the broth had become cloudy with microscopic creatures, which he attributed to the spontaneous generation of life. In reality, Needham's boiling was likely insufficient to kill all preexisting microbes, leading to his mistaken conclusion that new life had arisen spontaneously.
Needham's findings initially contributed to the support of spontaneous generation. However, they were later challenged by Lazzaro Spallanzani's experiments which suggested that life comes from preexisting life, as Spallanzani's sealed and sufficiently boiled flasks remained clear.
Needham's experiment, therefore, had a significant effect on the development of the theory of spontaneous generation, as it sparked further experimentation and research that ultimately led to its disproof by Louis Pasteur.