AP BIOLOGY

Detailed explanation-1: -In 1859, Louis Pasteur set up his demonstrative experiments to prove biogenesis right down to a bacterial level. By 1861, he succeeded in establishing biogenesis as a solid theory rather than a controversial hypothesis.

Detailed explanation-2: -Pasteur prepared a broth. Pasteur added the prepared broth to the first set of S-shaped flasks, boiled it, and sealed the flasks with lids. Pasteur added the prepared broth to the second S-shaped flasks, boiled it, and uncovered it. Later, he placed both flasks (first and second) sets at different locations.

Detailed explanation-3: -Pasteur’s experiment showed that microbes cannot arise from nonliving materials under the conditions that existed on Earth during his lifetime.

Detailed explanation-4: -But in 1857, Pasteur proved that a microscopic plant caused the souring of milk (lactic acid fermentation). Pasteur was able to prove that living cells, the yeast, were responsible for forming alcohol from sugar, and that contaminating microorganisms found in ordinary air could turn the fermentations sour.

Detailed explanation-5: -Louis Pasteur is credited with conclusively disproving the theory of spontaneous generation with his famous swan-neck flask experiment. He subsequently proposed that “life only comes from life.”