Pasteur's experiments proved that . Pasteur's experiments proved that . spontaneous generation can only occur if nutrient broth is left open to the environment cells cannot survive in swan-necked flasks preexisting cells present in the air can grow in sterilized nutrient broth sterilizing nutrient broth prevents spontaneous generation in order to grow, cells need to be supplied with oxygen

Spontaneous generation, which is the theory that life can arise from nonliving matter, has long been believed to be the way living organisms develop. However, in 1858, a French scientist called Louis Pasteur disproved the theory of spontaneous generation.

Louis Pasteur conducted an experiment to show that it is the existing microorganisms in air that causes life to grow and not the air itself. Pasteur made use of a swan-necked flask, which contained a sterilized (by boiling) broth. The swan-necked flask was designed in such a way that it would allow air to enter but trap any airborne microorganism, preventing them from reaching the broth.

Hence, if it were truly air and not existing life organisms that caused life growth, organisms should begin to grow from the broth. He conducted another experiment where be broke the neck of the flask to allow the entry of microorganisms into the sterilized broth and found out that growth of microorganisms occured on the broth.

Therefore, Pasteur, via his experiment was able to prove that preexisting cells present in the air can grow in sterilized nutrient broth if allowed entry but when there is no entry, there would be no life growth. This experiment disproved the theory of spontaneous generation.