State the contribution of Louis Pasteur in understanding the origin of life on earth. Explain the procedure that he followed to arrive at his conclusion.

First, he demonstrated that air is alive with microorganisms and that was the foundation for the law of biogenesis: life only comes from life. The genesis of germs in patients was the result of microbes having origins, not a result of automatic generation. This was achieved by filtering air through a cotton filling, trapping microorganisms and examining them under a microscope. He noticed, Bacillus anthracis cultures sometimes lose their pathogenicity when heated, and then preserve this attenuated feature through many generations. His concept to vaccinate sheep from death and his understanding of this natural variation was applied in developing vaccines for chicken cholera and rabies.