AP BIOLOGY

Detailed explanation-1: -Louis Pasteur first demonstrated that life comes only from pre-existing life. He showed that in pre-sterilized flasks, life did not come from killed yeast while in another flask open to air, new living organisms arose from ‘killed yeast’.

Detailed explanation-2: -Pasteur attacked the problem by using a simple experimental procedure. He showed that beef broth could be sterilized by boiling it in a “swan-neck” flask, which has a long bending neck that traps dust particles and other contaminants before they reach the body of the flask.

Detailed explanation-3: -What did Louis Pasteur discover? Among Louis Pasteur’s discoveries were molecular asymmetry, the fact that molecules can have the same chemical composition with different structures; that fermentation is caused by microorganisms; and that virulence can be increased as well as decreased.

Detailed explanation-4: -Louis Pasteur designed a procedure to test whether sterile nutrient broth could spontaneously generate microbial life. To do this, he set up two experiments. In both, Pasteur added nutrient broth to flasks, bent the necks of the flasks into S shapes, and then boiled the broth to kill any existing microbes.

Detailed explanation-5: -Louis Pasteur’s 1859 experiment is widely seen as having settled the question of spontaneous generation. He boiled a meat broth in a swan neck flask; the bend in the neck of the flask prevented falling particles from reaching the broth, while still allowing the free flow of air.