Final answer:
Microorganisms are the common component in our atmosphere that prevents spontaneous generation from occurring today. Through experiments, scientists like Louis Pasteur have shown that life only arises from existing life.
Step-by-step explanation:
The common component in our atmosphere that stops spontaneous generation from happening today is microorganisms. Through experiments conducted by scientists such as Francesco Redi, John Needham, Lazzaro Spallanzani, and Louis Pasteur, it was demonstrated that life only comes from existing life. Pasteur's swan-neck flask experiment conclusively disproved the theory of spontaneous generation, showing that airborne microorganisms were responsible for contaminating and reproducing in broths.