Ap Biology Paper

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August 20, 2012

AP
Biology
Paper
thing

Daniel Gildenbrand

Many scientists have contributed to the subjects of nature, evolution, medicine, and to the development of how experiments are executed. In this essay I will go over four scientists, their experiments, and how those experiments benefited the scientific community and the way we currently live our lives. These four scientists greatly contributed to science and were arguably the greatest contributors to their field of study. First, we have Francesco Redi and his famous experiments challenging the previous assumption that maggots underwent "spontaneous generation”, a theory about the formation of living organisms without descent from similar organisms, and naturally spawned from rotting meat. Redi disproved this theory with his experiments. In one of those experiments, Redi took three groups of jars: in the first jar of each group he put an unknown object; in the second, a dead fish; and in the third, a rotting piece of meat. The first group of jars was left open with no lid, the second group was covered in a woven piece of gauze, so that only air could get into the jar, and the third group was firmly sealed with a lid. After a few days of wait, Francesco noted that maggots appeared in the open jars where he saw flies had landed. The group of jars covered with the gauze had maggots on top of the gauze because the flies could smell the rotting meat so they laid their eggs there. Finally, he observed jars sealed with a lid had no maggots. With this experiment he disproved the theory of abiogenesis. His contribution to the scientific community did not end with just the results of his experiments as he was credited with the development of the “controlled experiment.” Controlled experiments changed the way we conduct experiments and greatly increased the accuracy of our results. The famous quote "Omne vivum ex ovo" ("All life comes from an egg") is commonly associated with Redi’s experiments.

A great contributor to the field of medicine and microbiology was Louis Pasteur. He was famous for his experiments with micro-organisms and for inventing the S-flask, which is now of great use in scientific experiments. Louis’ experiments saved the silk industry, and solved problems with the manufacture of alcoholic drinks. Most importantly, Pasteur invented the process now known as pasteurization. While working with the germ theory, which he bettered with his research, Pasteur proved that micro-organisms such as bacteria were responsible in the souring of alcoholic drinks such as beer and wine. He also discovered that microbes where infecting silk worm eggs and advocated that only disease-free eggs should be selected, which saved the industry.

Another one of Pasteur’s accomplishments was when he confirmed the disproval of abiogenesis through his experiments. In the experiment, he put exposed boiled broth into two groups of S-flasks, which he invented to slow the growth of bacteria in test tubes. Then, he covered one of the groups of flasks with a filter designed to prevent any particles from entering the tube. The other group was group of S-flasks was left alone (the S-flasks also only allowed a minimal amount of particles to enter the tube). He concluded that bacteria only grew in the flasks after they were broken open; therefore, the microbes had to come from the outside, in the form of spores on dust particles. To counter the growth of these bacteria, he developed “pasteurization” which is a process that kills bacteria within a liquid by heating then cooling the liquid. Pasteurization is now used just about anywhere beverages are manufactured to prevent any bacteria from entering the products.

Finally, Louis Pasteur’s arguably greatest contribution to science was bettering the concept of vaccination. When Pastuer was working on a problem causing chickens to die from a virus called “chicken cholera” on a farm, he exposed some of the healthy chickens to a weaker form...
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