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Bio 205: Two Discussion Questions

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1. How did the theory of biogenesis lead the way for the germ theory of disease?

Answer below:

Where organisms originate from is something that we take for granted today because of our advanced knowledge of cells, but in ancient times without a microscope the leading theory was vastly different. In this time the leading theory was that organisms spontaneously came to being. Even though in this day and age the thought of something spontaneously coming to life is ridiculous it wasn’t until the 17th century that this idea was challenged. An Italian physician named Francesco Redi sought to disprove the common idea. Despite his efforts he could not provide the evidence to persuade other scientists of the time. It wasn’t until Louis Pasteur came out with his scientific findings that biogenesis gained traction.

In the 1860’s Louis Pasteur set out to disprove the theory of spontaneous generation and devised an experiment to test his ideas. Louis took several flasks and filled them with beef broth, a growth medium, and boiled them to sterilize the broth. He then sealed some of the flask and left some of them open to the air. He checked on them several days later and saw microorganism growth in the ones that were open to the air, and a lack of any growth in the sealed flasks. This finally showed that life has to come from pre-existing life, and that the air was full of microorganisms and that they cause the generation of life, not it just popping into existence.

After discovering biogenesis the natural progression was to study these microorganisms found everywhere and what they can do to larger organisms. These questions about what was in the air lead to the germ theory of disease. The experiments began when sailors approached Louis Pasteur in his home country of France. They were perplexed by their wine and beer that was stored on the ships turning into vinegar over time. Studying the beer and wine Pasteur found that there was a bacterium in the air and when the bottles or barrels were opened it could get into the liquid. Then it would convert the alcohol into vinegar, but without the presence of air. This discovery paved the way for scientists to look at microorganisms as the cause for diseases. Pasteur’s idea set the stage for another scientist Robert Koch who armed with biogenesis thought to identify where disease comes from.

Robert Koch was a 19th century scientist that wanted to find out what was responsible for causing disease in the domesticated animals in Europe. He devised an experiment to isolate the cause of the disease. Koch found an animal that was infected with the disease and cultured their blood. He was able to then isolate the bacterium found in the blood. He then took the isolate and injected it into a healthy specimen. The animal quickly fell ill and died, and Koch repeated the first step and isolated the bacterium from the animal’s blood. The two different bacterium samples were examined and found to be the same. This was the proof that Koch needed to show that microorganisms were the cause of disease. He then went on to write his 4 postulates, which are still used today.



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