Week 1 Ch 1 Lab 2. The Scientific Method

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Dec 6, 2023

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Note: All your answers to questions must be in Red or other color (not including blue) for easier grading. Points will be deducted if you do not distinguish your answers. Lab 2. Scientific Method Objectives:  Identify the importance of asking questions.  Explain how the steps of the scientific method are used to answer questions.  Differentiated between observations, hypothesis, conclusions, and theories.  Develop a hypothesis based on observations.  Design an experiment that can be repeated.  Formulated a conclusion based on observation and experimentation. Vocabulary:  Scientific method  Hypothesis  Scientific theory  Experiment  Independent variable  Dependent variable  Control group  Experimental group  Scientific journal Introduction: The scientific method is central to the study of biology: it is a process of acquiring and verifying information through experimentation. The general steps of the scientific method are depicted in the figure below. The hypothesis, or suggested explanation for the observation, is the basis for setting up experiments. A good experimental design is essential to the scientific method. A few keys to good experimental design include effective use of controls, reproducibility, a large sample size, and multiple trials. In an experiment, to determine that any changes that occur are due to investigator manipulation only, there must be some basis for comparison. A control group is necessary to establish this basis of comparison. There are positive and negative controls. The positive control will give a positive result

for the test, while a negative control is shown to have no effect. Everything is kept the same as the experimental group and in the control group except for the independent variable. The experimental group is the actual group being experimented upon. For example, in a drug trial, a group receives the drug (the experimental group), and another group receives a placebo (the control group). The drug itself is considered the independent variable, and any change(s) that occurs because of the drug is considered the dependent variable. To ensure that it is the drug causing the changes to the subject, all other variables must be tightly controlled (such as diet, exercise, smoking, etc.). These are referred to as controlled variables. When designing experiments, we only want to test one variable at a time. The control and experimental group should only have one different variable. In designing experiments, it is also essential to have multiple trials. This will allow the scientist to verify that their results are accurate and not just random. Usually, three trials would be sufficient to conduct statistics such as a T-test. After preforming the statistical analysis scientist can then “accept” or “fail to reject” the null hypothesis. H 0 : The null hypothesis: It is a statement of no difference between sample means or proportions or no difference between a sample mean or proportion and a population mean or proportion. In other words, the difference equals 0. H a : The alternative hypothesis: It is a claim about the population that is contradictory to H 0 and what we conclude when we reject H 0 .

Figure 1: Illustration of the scientific method. Review the Scientific Method by watching the following video: https://youtu.be/yi0hwFDQTSQ Part 1: Animal Behavior Lab Background Information: Terrestrial isopods are land-dwelling crustaceans, commonly known as sowbugs or pillbugs (or roly-poly's). They are related to lobsters, crabs, and shrimp, and terrestrial isopods breathe with gills. While they look similar, sow bugs are different from pill bugs. Pillbugs ( Armadillidum vulgare) will curl into a ball when threatened, whereas sow bugs will attempt to flee. Land isopods (including sow bugs and pill bugs) live in dark, moist places beneath undisturbed objects lying on the ground -- rotting logs, boards, bricks, or rocks. Sometimes isopods can be found alongside buildings with moisture and food (decaying matter, fungi). In the lab, we provide them with potatoes as a food source. Living organisms, in general, avoid some chemicals and are attracted to others. This experiment will study the typical pillbug response to being exposed to sand and cornstarch. Keep in mind that since you are online, you are not ACTUALLY performing the experiment, instead you will have to watch the video associated with this lab to answer the questions. Question: Which substance will attract or repel the isopods and why? Hypothesis: (Write your own) Cornstarch may possibly attract pill bugs more than dry sand. Materials:  10 pill bugs in petri dish  1 Choice-chamber  Timer  Sand  Corn starch  4 Weight boats  Electronic balance  Scoopula  3 blank sheets of paper  Pen/pencil and paper to record results Procedure:

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 Label a blank sheet of paper “Left” and “Right”. This will be placed under the two sides of the choice chamber.  After you have placed the chamber above the labeled blank sheet of paper, you will place 10 pillbugs in the center of the choice chamber, See Figure 2. Figure 2: Illustration of the negative control chamber.  Start your timer and record your results every 20 seconds for a total of 3 min. Keep in mind that if they are in the middle, you will count them as undecided in Table 1 .  Do not stop the timer while taking records. You are encouraged to take a picture at each interval for easier counting.  Clear out the pillbugs, place them back in the petri dish.  Label a new blank sheet of paper “Left Sand” and “Right Sand”. Place the clean choice chamber above.  Using your electronic balance and weigh boats, weigh two 2g of sand, one for each side of the chamber.  Place 2g of sand on each side of the chamber.  Put the 10 pillbugs back in the center of the chamber, see Figure 3 . Figure 3: Illustration of the positive control chamber.  Start your timer and record your results every 20 seconds for a total of 3 min in Table 2 .

 Clear out the pillbugs, place them back in the petri dish.  Label a new blank sheet of paper “Cornstarch” and “Sand”. Place the clean choice chamber above.  Using your electronic balance and weigh boats, weigh two 2g of sand and 2g of cornstarch, one for each side of the chamber.  Place the 2g of sand and cornstarch under their labeled side of the chamber.  Put the 10 pillbugs back in the center of the chamber, see Figure 4 . Figure 4: Illustration of the positive control chamber.  Start your timer and record your results every 20 seconds for a total of 3 min in Table 3.  Clean up according to instructor's directions. Results: (Watch the Lab 2. Scientific Method video) Table 1: Results of Negative Control Group Left Right Middle: Undecided 0 seconds 0 4 6 20 3 4 3 40 3 3 4 1 minute 5 4 1 20 4 3 3 40 5 4 1 2 minutes 4 3 2 20 4 3 3 40 5 2 3 3 minutes 2 8 1

Table 2: Results of Positive Control Group Left: Sand Right: Sand Middle: Undecided 0 seconds 1 8 1 20 5 3 2 40 3 5 1 1 minute 5 5 0 20 6 3 1 40 8 1 1 2 minutes 7 2 1 20 5 2 2 40 4 2 4 3 minutes 4 6 0 Table 3: Results of Experimental Group Sand Cornstarch Middle: Undecided 0 seconds 1 8 1 20 1 3 6 40 1 3 6 1 minute 0 5 5 20 1 6 3 40 3 7 0 2 minutes 2 1 7 20 3 7 0 40 3 7 0 3 minutes 2 7 1 Conclusion: 1. In this experiment why do we need a chamber with sand on both sides? What is the purpose of sand? The experiment is set in a dry environment with sand on both sides, the purpose of the sand is to show the behavior of organisms to different stimuli; the sand is the control variable. 2. What are the variables? Sand, pill bugs, cornstarch. 3. Was your hypothesis supported? Use the data to explain your answer. Although the pill bugs crawled into both chambers (sand/cornstarch),

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they favored the cornstarch probably because it was damp, and the sand was dry. My hypothesis was supported. 4. Use what you know about organisms, cells, and homeostasis to explain your results. Living things are made of cells and organisms are either made up of a single cell or made up of more than one cell. Pill bugs are organisms because they fit into one of these categories: animal, plant, fungus, protist, bacterium, or archaeon. An organism must have cells to be considered living. Organisms also adapt to their environment. Living organisms regulate their internal environment to maintain the relatively narrow range of conditions needed for cell function through steady state/homeostasis. 5. How could this experiment be improved? (Hint: How can we prove that the results are accurate.) By adding moist sand or rotted items is one way to improve this experiment in the experimental chamber. 6. Hypothetically speaking, if we had more pill bugs go to the right side in both the control and experimental groups, how would this affect your conclusion? Explain your answer. The pill bugs illustrated their behavior does not change in a control environment in this case sand but if the sand in the control group on the right side was damp then that would explain why the pill bugs would be drawn to the ride side in the control group. In the experimental group they went towards the cornstarch because they liked it but also because it was damp. Part 2: Identify the Controls and Variables: Read the following scenario and answer the questions below. Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they are supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks; Group B made 2,113 stacks.

7. Which is the control group, how do you know this? The control group is the assignment of stapling a set of papers. 8. What is the independent variable? Group A is the independent variable. 9. What is the dependent variable? Group B is the dependent variable. 10. What should the conclusion be? An individual’s ability to be productive does not depend on drinking a special juice while they work. In this scenario, it decreased their productivity. 11. How could this experiment be improved? A way to improve this experiment would be to make an adjustment dose of the special juice given to the independent variables. LICENSES AND ATTRIBUTIONS  " The Scientific Method" by Susan Burran and David DesRochers , LibreTexts is licensed under CC BY-SA .  "Investigation: Habitat Selection in Flour Beetles" by Shannan Muskopf , LibreTexts is licensed under CC BY-NC-SA .  Introductory Statistics by OpenStaxCollege is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

Week 1 Ch 1 Lab 2. The Scientific Method

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