Lab 1 - The Scientific Method

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1 Lab 1 - The Scientific Method As Biologists we are interested in learning more about life. Through observations of the living world we often develop questions about various phenomena occurring around us. The scientific method is a systematic process used to answer these questions using logical processes involving observation and experimentation. The scientific method often starts with a question. Why do plants bend as they grow? Why do we get sick? Why is my computer not connecting to the Internet? A scientist next develops a hypothesis, which is an answer to that question or an explanation for the observed phenomena. Hypotheses are written as statements and they should always be testable. It is not necessary for a hypothesis to be based on years of research or for it to be correct; as long as it is testable we can use the scientific method to test it. For example, my hypothesis might be that I cannot connect to the Internet because I happen to be outside of a wireless zone. Once a scientist has developed their hypothesis, they will want to test it. The first step in testing a hypothesis is developing a prediction based on that hypothesis. A good prediction is something you expect to happen, or you expect to be true if your hypothesis is correct. For example, I might predict that if I go to another part of campus (e.g. the library) then I will be able to get on the Internet with my computer. Now it is time to perform your experiment. If you have developed a good prediction, your experiment will just be a matter of following that prediction. In the example problem, I would go to the library and try to get on the Internet. The results of your experiment will either support or refute your hypothesis (though they may also be inconclusive). If your results do not support your hypothesis, you can revise your hypothesis (in light of your new data) and develop another prediction. If your results support your hypothesis, you can make a different prediction based on the same hypothesis to further test the validity of your hypothesis. For example, if I was able to get on the Internet at the library, I might predict that if I return to the original classroom I would lose the connection. Below, you will be presented with three observations. For each observation, formulate a scientific question related to that observation. The best scientific questions will lead you to 5

2 developing a testable hypothesis; therefore try to avoid questions with a yes or no answer. Most questions will start with How, What or Why? Once you have thought of a question, formulate a hypothesis related to that question (typically, it is your answer to the question). Finally, develop a prediction based on your hypothesis. Your prediction should be what you expect to be true as long as your hypothesis is correct. Table 1: Formulating questions, hypotheses and predictions Observation Question Hypothesis Prediction I feel sick after eating pizzza There is a traffic jam on Daniel s Parkway It has been 2 minutes and my friend still hasn t replied to my text. 6

3 Data graphing Data that you collect through experimentation is often easiest to display through the use of a graph. In order to clearly depict your data a graph must be constructed carefully and include certain components. An improperly constructed graph can lead to the acceptance of an incorrect hypothesis or detract from the acceptance of a correct hypothesis. Take a look at the graph in Figure 1 and compare it to the graph in Figure 2. In figure 1 the results of an experiment on breathing rate was conducted. However, several things are wrong in this figure. On the X-axis, the distance between 15 and 18 minutes is the same as the distance between 60 and 90 minutes. This gives a false impression of the rate at which the respirations change. As you can see from Figure 2, the rate respirations increase rapidly from 15 to 25 minutes and gradually declines after 45 minutes, in figure 1 the increase appears as gradual as the decrease. Additionally the scale on the Y-axis is too vague, it is difficult to tell how many respirations per minute there were at any given time given there is only an indication of 0 and 100. The axis labels are also lacking units in Figure 1. Time is in minutes and Respirations are in breaths/minute as indicated in Figure 2. 7

4 Figure 1: How not to make a graph Figure 2: How to make a graph Using the following table of data, construct a line graph on your lab worksheet. In order to graph two independent variables (Month and Location) you will have to use multiple lines and a key to differentiate between them. Be sure to include a title, and properly label your axes (including units where appropriate). Table 1: Rainfall over five-month period at three locations Rainfall (mm) Month Location 1 Location 2 Location

5 The Black Box experiment You will now use the scientific method to determine the contents of a black box. Each lab group will be given a sealed box containing various items. Your instructor will provide a list of items that may be present in your box. Each group will also be provided with an empty box of the same type as the sealed box, access to each of the items that may be present in the sealed box as well as a balance. After making some observations of your sealed box and the potential contents develop a hypothesis (or guess) as to what you think is in the box. Write down your guess under hypothesis on your lab sheet. Do not worry at this point is your hypothesis is correct. As long as your hypothesis is consistent with the observed behavior of the object in the box, your hypothesis is valid. The only way to invalidate your hypothesis is to discover some property of the object for which your hypothesis does not account. Next, you will use the available tools to test and revise your hypothesis about the contents of the box. The best way to test your hypothesis is to generate a prediction that is consistent with your hypothesis. For example, if my hypothesis were that the box contained a round ball then I might predict that if I rocked the box from side to side I would hear it roll. Keep in mind that each of your experiments should ideally only test one variable at a time (your independent variable), so you will need to conduct several experiments to come up with a complete list of the box s contents. Using the provided worksheet, record your hypothesis, prediction, experimental design, results, and conclusions for each experiment. Once you think you know what is in your box, record your conclusions as well as an explanation of how you arrived at that conclusion. Check with your instructor to see if you were correct in your conclusions and finish the worksheet. 9

6 Lab Worksheet 10

7 Hypothesis Prediction Experiment Result Conclusion 11

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