Redi: Scientific Method and Heather Ramirez Page

1. State a possible hypothesis for Redi’s experiment. -Hypothesis for Redi’s experiment is that maggots come from larva of flies and that the meats only serve as food for the developing insects. 2. Which of the three jars in Redi’s experiment would be considered the control and why? -The jar that was left uncovered in the experiment would be considered the control because this jar represented the meat as it would normally be found with the maggots attached. 3. Give a brief explanation of Redi’s experimental procedure. Redi preformed an experiment to prove where maggots came from. He took three jars and put a piece of meat in each jar. Jar 1 was left uncovered, jar 2 was covered with netting (gauze), and jar 3 was sealed from the outside. In jar 1, maggots were found on the meat and there were flies flying around that had laid eggs on the meat. Jar 2 was found to have maggots on the netting of the jar, because the flies had begun to lay their eggs. Jar 3 ha d not developed any maggots on the meat, which proved that living things are not spontaneously generated. Heather Ramirez Page 2 4. Why would the experiments run by Redi, Spallanzani, and Pasteur be considered as a possible basis for a theory? -Redi, Spallanzani, and Pasteur all used similar experiments to prove that living things are not spontaneously generated and through their experiments they were able to support their hypothesis with scientific reasoning. The experiments preformed were considered valid because of the reproducible outcome in each study. 5-6. What were the possible conclusions reached from Spallanzani’s experiment? Why were his conclusions not accepted? -After boiling the broths no bacteria was present. Although his experiment was successful, his conclusions were not accepted because he had deprived the sealed flasks of air by melting their glass necks and it was thought that air was necessary for spontaneous generation to occur. The experiment was also contradicting because, if the flasks neck became cracked the broth would then obtain a rapid growth of microorganisms. 7. Why would Aristotle’s thoughts on spontaneous generation be considered nonscientific reasoning? -Aristotle believed that living things arose and always had arisen from lifeless matter. This would be considered nonscientific reasoning because these were just his thoughts and beliefs, not something that was scientifically tested. For something to be classified as scientific reasoning it would require an actual scientific research method, such as an Heather Ramirez Page 3 xperiment to first predict and then test the hypothesis to ultimately come to a conclusion based on the results from the experiment. 8. How did Pasteur modify Spallanzani’s experiment in order to provide further experimentation on spontaneous generation? -Pasteur used swan-necked flasks which allowed air into the flasks but the route was so convoluted that any particles drifting in from the air would settle out in the folds of the glass before reaching the broth. His flasks were open to the air but did no t support bacterial growth like Spallanzani’s flasks did. This method had rejected the possibility of spontaneous generation because the broth in the swan-necked flasks remained clear which concluded the previous tests done by Spallazani and Needham were not accurate. The normal flasks allowed bacteria to drift into the broth causing cloudy bacterial soups and had thickened the rich nutrients due to the bacteria multiplying. 9-10. In Order for experimental results to be accepted, the results must be reproducible. Why did Tyndall have problems reproducing Pasteur’s work and how did he solve the problem? Pasteur and others scientist were using different types of broths. (Pasteur only used broths made with sugar or yeast extract, and the other scientist were using broths made from hay) As a result, Tyndall found that these different types of broths required different boiling times to be sterilized. He found that certain microorganisms can exist in heat- Heather Ramirez Page 4 resistant forms, which are called endospores. Once this confl icting data was brought to light Tyndall was able to reproduce Pasteur’s experiment and prove him to be correct.