Abstract
This report aims to provide an excellent example of the scientific method through a detailed study of pill bugs. It details the set up and execution of a study that reveals the pill bugs’ preference toward corn starch as opposed to fine sand using an accurate test that is pitted against a control. The study deals with problems one might face in seeking proper adjustment of timing for measurements of the bugs as well as controlling against alternate factors that could influence the pill bugs, and provides solutions that work to mitigate and eliminate these issues. The experiment concludes that pill bugs have a preference toward the starch and that the experiment was not only accurate, but scientific.
Introduction
Pill bugs, also known as armadillidiidae or Roly-polys, are small isopods known for their ability to roll into a ball in order to protect their soft underbelly when they feel threatened. These creatures are relatively simple, making them an ideal candidate to demonstrate how the scientific method can be used to learn the truth about what we observe. This is the heart of science itself.
To conduct this demonstration on the scientific method, we will be learning about the preferences of pill bugs regarding corn starch. By applying the known fact that animals will move towards what they prefer and away from that which they don’t, we use deductive reasoning to apply this to pill bugs. With this information we will design an experiment that will effectively measure whether or not pill bugs generally move towards, away from, or independently of corn starch and thus prove any preference or lack thereof that the bugs have for corn starch. I hypothesize that the pill bugs will show that they prefer the corn starch by moving toward it.
This process should thoroughly demonstrate the usefulness of the scientific method. An important factor to the success of the experiment is how long we allow it to run. Obviously, the bugs do not immediately streak toward any substance they prefer, and their preferences can be shown much more subtly. This raises the question of how much time the bugs should be allotted to find their way toward or away from the corn starch. Stopping the clock whenever most of the bugs seem to have moved in one direction or another is not a good solution, as it is not statistically unlikely that most bugs could move one direction based merely on chance. We will explore the answer to this question when discussing our data.
Methods
Two pill bug housings were set up side by side. Each of the enclosures were identical in size and shape and consisted of two round sections connected closely by a passage for the pill bugs to travel to and from either section. The enclosures were made from a clear material allowing the observers a plain view of the pill bugs. Each section was small enough for the pill bug to easily find their way out through the passage, but not so small as to become crowded if too many pill bugs favored one room.
One housing was used a control group while the other served to house the pill bugs during the trial. The two housing were placed side by side and one spoon of fine sand was deposited around the edges of each section of the control housing. As for the trial housing, a spoonful of fine sand was placed around the edges of one section while the same amount of corn starch was placed in the opposite section.
A timer was started and a total of 10 pill bugs were placed into each of the housings in an evenly distributed manner. Then the pill bug locations were recorded into a table, and this location recording was repeated every two minutes up to and including the 10 minute mark for a total of 6 readings if you include the initial minute 0 reading. After 10 minutes, our data collection process was complete and we moved on to analyzing our results.
As displayed in the table above, the two control housing sections were fairly balanced throughout the experiment. They reached a maximum imbalance of 7 pill bugs on one side compared to only 3 on the other, but over the next two minutes the pill bugs rebalanced themselves as we would expect with identical sections in the control. They then even skewed slightly toward the opposite sections as they had before, leading to an overall nearly balanced result; on average, control sand section 1 had roughly 94% of the pill bugs that section 2 had.
The test housing tells us an entirely different story. It starts out balanced between the sand and corn starch sections of course because they were placed into the housing in a balanced manner, but the data quickly shows the bias of the pill bugs. Within two minutes, the corn starch section gained two net pill bugs making a 7 to 3 ratio – the highest discrepancy achieved by the control during the course of the entire experiment. The test housing quickly surpassed that discrepancy within the next measurement interval when another pill bug chose to stay in the corn starch section bringing the ratio to 8 to 2. The numbers did not move for the next interval but subsequently shifted when 100% of the pill bugs were found to be in the starch area, where they stayed for the remainder of the experiment. The average ratio of pill bugs in the test housing was far different than the control, with the sand section containing, on average, only 25% of the bugs contained by the corn starch section. These average ratios are shown in the chart labeled “Average Bugs Per Section” for easy comparison. The results from the test housing are extremely different from the control housing which leads me to believe that the corn starch was indeed the only factor that influenced the change.
Discussion
These findings do not take a great deal of consideration to determine our result that pill bugs have a preference for corn starch. The numbers show that the number of pill bugs in the corn starch area strictly increased until all of the bugs inhabited that space, and they all stayed there for the length of the study. Our aim for this experiment was not only to prove the existence or lack thereof a preference for or against the starch from pill bugs, but it was also to provide an simple and easy to follow example of the scientific method being used to discover something previously unknown to us. The research we conducted is indeed an excellent instance of using the scientific method; we gathered information about our topic, formed a hypothesis, tested it against a control, recorded our data, and drew a conclusion from said data in a way that can is well documented and can be easily replicated.
While there is no doubt that our numbers indicate that our hypothesis was correct, some may doubt our methods. Recording the data in six instances spaced two minutes a part can seem abstract at first glance and can cause one to wonder if the times could be affecting the results. After all, who is to say that pill bugs do not simply like to group up and merely happened to group near the corn starch? This is a valid question, and it was considered during the design of the experiment.
Firstly, the two minute intervals are not as arbitrary as they may seem, as they were formed by examination of the speed at which pill bugs move around. Longer intervals would allow too much to happen before it was measured and shorter intervals would provide too much repetitive data. Furthermore, the choice of six data recordings was also not arbitrary; through a small amount of testing with the pill bugs, it was found the 10 minutes that this number of recordings caused was an ideal time to allow the pill bugs to settle into their places and show that they had stopped shifting positions.
Secondly, the theory of grouping pill bugs can be disproved because of our control. The control group clearly shows an extremely even dispersal of the pill bugs, contradicting that theory and supporting the idea that the only causal factor of the grouping in the corn starch section was the corn starch itself.
Conclusion
This experiment has shown us through a scientifically sound and replicable manner that pill bugs have a preference toward corn starch. This was found using the scientific method and is a prime example of simple scientific research. It demonstrates the benefits of some previous research and the development of a hypothesis. It exemplifies proper techniques for collecting, analyzing, and displaying data. It shows how one can draw conclusions from the data and come an overall conclusion in a way that allows readers not only to understand the underlying reasoning, but also and reproduce the experiments and reach the conclusion by themselves.
