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Section 1.2: How Scientists Work

Exercise 1

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Solution 2

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Only one variable is changed at a time. All other variables should be kept unchanged, or controlled. This type of experiment is called a controlled experiment.

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Redi’s experiment is controlled because he only changed one variable. He wanted to test whether or not maggots spontaneously generated on raw meat. He kept the jars and the type of meat the same. He placed all the jars in the same location with the same temperature at the same time. He placed them in that location for three days. The only thing that was different is that some jars had a gauze covering the jars so that flies could not get to the meat in those jars. He only changed one variable: the gauze.

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Exercise 2

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A scientific hypothesis is a testable idea which can support an explanation or a theory. On the other hand, a scientific theory is a well-tested explanation about the ideas and the events that occur in the natural world.

Exercise 3

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Scientists communicate mainly through the methods of writing and speaking. In addition, they also employ other ways to communicate which include giving talks or seminars during scientific meetings, exchanging information using the internet, or publishing scientific journals and articles.

Exercise 4

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Louis Pasteur placed broth in a sterile flask that had a thin and winding neck so that dust and microorganisms could not get into the flask, but air could. A year later and nothing had grown in the broth, which somewhat disproves the hypothesis of spontaneous generation. At the end of that year, he broke the neck of the flask so that the broth was exposed to dust and other airborne particles. Within a day, the broth showed growth of microorganisms. This finally convinced other scientists that spontaneous generation was an incorrect hypothesis.

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Exercise 5

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Louis Pasteur’s flask experiment had a large impact on scientific research and society in general. He disproved the hypothesis of spontaneous generation, and in doing so helped the French wine industry by explaining why the wine would mysteriously sour. This was also a step in the right direction to discovering infectious diseases by showing that people get sick because of microorganisms that enter the body.

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Section 1.2: How Scientists Work

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