1.2: Scientific Method

Purpose:

This lab provides hands-on experience with the scientific method by studying animal behavior. Students will explore how pill bugs respond to environmental stimuli, practice experimental design, and apply data analysis to understand their behavior.

In this laboratory students will:

1. Observe pill bug behavior in a neutral environment.
2. Develop a hypothesis and design an experiment to test pill bug preference for moist vs. dry environments.
3. Collect, record, and graph data from multiple trials.
4. Analyze results and draw conclusions about pill bug behavior.

Student Learning Objectives

• Develop a clear and logical hypothesis based on observations.
• Conduct a controlled experiment with reliable data collection methods.
• Create accurate, well-labeled graphs of your result.
• Explain the findings clearly and relate them to your hypothesis.

Lab Safety

Safety Guidelines for Handling Pill Bugs and Lab Equipment:

1. Handle pill bugs gently using a soft brush or plastic spoon to prevent injury to the animals.
2. Ensure behavior chambers are stable and securely assembled.
3. Avoid over-moistening the environment to prevent accidental spills.
4. Wash hands thoroughly after handling pill bugs or environmental materials.
5. Dispose of any biological waste in designated containers.

What is Science and how do we do science?

Science is how we gain knowledge about the natural world. Typically, it pertains only to what we can investigate or observe using our senses – or instruments that extend the ability of our senses. As a science, biology concerns itself with understanding the unity and diversity of living things – the 2,300,000, or so, described (and millions of undescribed) species with which we share the planet.

Ideally, the Scientific Method is a process that describes how scientists perform investigations to provide a systematic and rational approach to answering questions about the natural world. One goal is to be as objective as possible in what we study. Ideas that can’t be tested, directly observed, or measured in some way should not be subjected to the scientific method. There are other ways to obtain knowledge (cultural, emotional, etc.), but they usually do not qualify as science because they do not follow the axioms of science. An axiom, in a general sense, is a truth that is accepted without proof. It might seem that science does not assume anything, but many assumptions are often ignored such as the relationship between cause and effect, and that our senses and measurements accurately represent reality.

The goal of today’s lab is to familiarize you with the idealized steps of the scientific method but it's important to recognize that science rarely proceeds so linearly.

You will use these steps to determine the effects of different environmental conditions on the behavioral patterns of pill bugs (Armadillidum vulgare).

Figure 1: Armadillidum vulgare

Model organisms are non-human species used in research to investigate biological processes. Information learned in studies of model organisms can often be applied to other species, including humans. We use model organisms to learn about many different processes, including genetics, cellular mechanisms, and growth and development. Certain characteristics make a species an ideal model organism. For example, it must be easy to manipulate for study, inexpensive and easy to cultivate, and produce many offspring. The best model organism to use for a study depends upon the question being investigated. In this study, Armadillidium is a good model organism because of its simple behavioral patterns, which allows measurement of responses to a stimulus and gathering data on how this organism is affected by different environmental conditions.

Steps of the Scientific Method

The scientific method consists of the following steps:

1. Making an observation
2. Asking a question based on that observation
3. Forming a logical AND testable answer to that question, the Hypothesis
4. Designing a controlled experiment to see if the hypothesis is supported or rejected
5. Collecting, analyzing, and interpreting the data generated by the experiment
6. Making a Conclusion: Do the results support the hypothesis?

If the conclusion of an experiment does not support a hypothesis, another hypothesis must be developed and another experiment designed to test it. Many times, designing an experiment to test the hypothesis is one of the most difficult aspects of science. Ultimately, the results of experimentation are often published in peer-reviewed journals so that other researchers can replicate the experiment and build on that work.

An idealized version of the scientific method is demonstrated in Figure 2. It is considered “idealized” because chance sometimes play an important role. Sometimes, observations that result in important discoveries are stumbled upon by accident.

Figure 2: Idealized Steps of the Scientific Method (This image is an SVG adaptation of the original JPEG image by Whatiguana CC-BY)

Purpose

The purpose of this experiment is to provide hands-on experience with the scientific method by studying animal behavior. You will investigate how environmental factors affect pill bug habitat preference. This experiment will help you practice key scientific skills: observation, hypothesis formulation, experimental design, data collection, and data analysis. Moreover, you will develop your ability to reason scientifically about biological phenomena and connect experimental results to real-world behaviors in organisms.

You will design and carry out an experiment to study how pill bugs respond to different two different environments, one moist and the other dry.

Formulating a Question and Stating a Hypothesis

In science, observations often lead to the formulation of questions that generate hypotheses and predictions that are testable. In today’s lab, we are considering the following question: “Do pill bugs show a preference for a dry environment or a moist environment”?

A hypothesis is a testable explanation of a set of observations based on available data. It is a tentative answer to the question you are asking based on knowledge about what you're observing and asking. This knowledge can be pre-existing or information from a published resource.

In this lab, you need to formulate a hypothesis about how you believe these two different environment conditions will affect the behavior of pill bugs based on your knowledge of pill bugs. After you formulate the hypothesis, you will test predictions based on these hypotheses. Hypotheses can be rephrased as predictions and can be written as “If…., then….” statements.

Formulate a hypothesis to describe what you predict will happen in your experiment (dry versus moist environments). Read through the procedure section of the lab before you define the variables.

Hypothesis: Pill bugs are more likely to spend time in a _________ environment because _____________________________________.

Prediction: If pill bugs can choose between a dry and a moist area, then more pill bugs will be found in the __________ area after 10 minutes.

An independent variable is the condition or event under study. It is the condition the investigator sets. Only one independent variable is tested at a time so that an observed response is a response to just that variable.

A dependent variable is what happens in response to the independent variable. The dependent variable provides your data. This is what you measure in your experiment.

Controlled variables are conditions kept the same during an experiment because they could affect the results. For example, both sides of the pill bug dish should be kept at the same temperature. In the spaces below, define the variables that will be considered in your experiment today:

What is the independent variable? ____________________________________

What is the dependent variable? Be specific with your answers. ___________________

What other variables should be controlled? List at least 2 controlled variables.

1. ___________________
2. ___________________

Importance of a Control Group:

Most well-planned experiments contain a control group in addition to an experimental group. The control group is not manipulated and is used for a comparison to the experimental group; it serves as a baseline against which the experimental group is compared. Not all experiments have a traditional control group.

MATERIALS AND METHODS

Materials and Supplies:

Materials

Equipment	Materials
Behavior chambers: Divided containers that allow separation of different environmental conditions (moist and dry sides)	Pill bugs (Armadillidium vulgare): 5-10 pill bugs (per group).
Soft brush or plastic spoon: To safely handle and transfer pill bugs between environments.	Moist substrate: Damp paper towels or moistened soil, used to create a humid environment on one side of the chamber.
Stopwatch or timer: To keep track of when to count the pill bugs on each side of the chamber (every 2 minutes).	Dry substrate: Dry paper towels or dry soil, used to create a dry environment on the other side of the chamber.
Data sheets: For recording observations, including the number of pill bugs on each side of the chamber at each time interval.	Transfer pipette: To add moisture to the substrate as needed throughout the experiment.

PROCEDURE

Part 1: Initial Observations and Drawing

Observation Period:

Place 5 pill bugs in a neutral environment (such as an empty Petri dish) and observe their behavior for 5-10 minutes. Record observations about their movements, responses to stimuli, and any distinctive behaviors below.

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

Part 2: The Pill bug Enclosure

Each group will receive one Petri Dish Enclosure:

• The enclosure consists of two large petri dishes connected by a small opening in the side of the dish. This connection allows the pill bugs to travel from one dish to the other.
• The enclosure allows you to create two different environments, designed on the variables you plan to test, in this case a moist versus a dry environment.
• Prepare each dish by setting up your chosen environment in each. For example, one Petri dish might be lined with damp paper towels while the other is kept dry.

Figure 3: Environmental Chamber (By MG)

Part 3: Conducting the Experiment

Introduce Pill bugs to the Attached Dishes:

• Using a soft brush or plastic spoon, gently place 5 pill bugs into the dry dish of the connected Petri dishes, allowing them to explore both environments freely.
• Make sure that the pill bugs can easily move between the two dishes.

Observation and Data Collection:

• Start the timer and observe the pill bugs for 10 minutes. Every two minutes, record how many pill bugs are present in each environment.
• Use a data table like the one below to track your observations:

Table \(\PageIndex{1}\)

Time (Minutes)	# of Pill bugs in Dry Environment	# of Pill bugs in Moist Environment	Notes on Behavior
0
2
4
6
8
10

Repeat the Experiment:

• After completing the first trial, return the pill bugs to their holding container.
• Repeat the experiment for two additional trials. This makes your data more reliable.

Time (Minutes) Trial Two	# of Pill bugs in Dry Environment	# of Pill bugs in Moist Environment	Notes on Behavior
0
2
4
6
8
10

Time (Minutes) Trial Three	# of Pill bugs in Dry Environment	# of Pill bugs in Moist Environment	Notes on Behavior
0
2
4
6
8
10

Part 4: Analyzing and Graphing the Results

Average the Data:

• After completing all trials, calculate the average number of pill bugs in each environment at each time point. To calculate the average, add the number of pill bugs in each environment at each time point and divide by the number of trials (3) to find the average.
• Summarize the results in a table, showing the averages for both environments across time intervals.

Summary Table of Results

Time (Minutes)	# of Pill bugs in Environment A	# of Pill bugs in Environment B
0
2
4
6
8
10

Discuss any experimental limitations and any improvements for future experiments.

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

Summarize your data in a graph.

1. Tables and graphs help you organize data and see patterns in your results. A graph can show how one variable changes in relation to another. Usually, the independent variable goes on the horizontal (X) axis, and the dependent variable goes on the vertical (Y) axis. Each axis should be labeled properly with the name of the variable and the units of measurement.

2. Use an even scale on each axis. For example, if one mark represents 2 minutes, each following mark should represent another 2 minutes. Start at zero when it makes sense for the data.
3. All graphs should have a title to describe the information presented. There are no set rules for making the title, but I recommend capitalizing the important words in the title.
4. Choose a graph that best represents the type of data you collected:
   1. Line graphs show how a measured value changes over time. Points are plotted and connected with lines so you can see whether the value increases, decreases, or stays about the same. Since the pill bug counts are recorded every two minutes, this fits this exercise well.
   2. Bar graphs compare amounts in different groups or categories. Each bar represents one group, making it easy to see which groups have more or less. For example, a bar graph could compare the number of pill bugs on the moist and dry sides at one selected time.

Graphing Your Results

• Create a line graph to visualize the data. Plot time (minutes) on the X-axis and the average number of pill bugs on the Y-axis.
• Use separate symbols to represent the number of pill bugs in each environment, such as dots or triangles. Connect the symbols with lines, as shown in the sample graph below.

Use the grid below to graph your group’s results:

Interpret Your Results:

Once you have collected your data and summarized it as a graph, the last step is to analyze and interpret your results. What do they tell you about your hypothesis? Was it supported or not supported by your results? ______________. What evidence from your data supports your answer? _____________________________________________________________________

_____________________________________________________________________

Sample Data Table and Graph

Time (Minutes)	Average # of Pill bugs in Dry Environment	Average # of Pill bugs in Moist Environment
0	5	0
2	3	2
4	2	3
6	1	4
8	1	4
10	0	5

Sample Graph

Questions for Review

1. What is the difference between a control group and a controlled variable?
2. What are some types of questions science cannot answer?
3. Where would you find an independent variable on a graph?
4. List four features of a well-formatted graph. Use the graphing guidelines above to help you.

• _______________________________________________________________

• _______________________________________________________________

• _______________________________________________________________

• _______________________________________________________________

Licensing and Attributions

This page titled Scientific Method is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Brad Basehore, Michelle A. Bucks, & Christine M. Mummert via source content that was edited to the style and standards of the Libre Texts platform.

1.1: Scientific Investigation by Brad Basehore, Michelle A. Bucks, & Christine M. Mummert is licensed CC BY 4.0. Original source: https://oer.galileo.usg.edu/biology-textbooks/18

This lab is adapted from 2: Scientific Method which is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Brad Basehore, Michelle A. Bucks, & Christine M. Mummert via source content that was edited to the style and standards of the Libre Texts platform.