Scientific Method and Animal Behavior: Pill Bug Experiments

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Introduction to the Scientific Method

Overview of the Scientific Method

The scientific method is a systematic process used by scientists to investigate natural phenomena and answer questions about the world. It consists of several key steps that ensure observations and conclusions are reliable and reproducible.

Observation: Gathering information about phenomena through the senses or instruments.
Question: Generating questions based on observations.
Hypothesis: Proposing a tentative explanation or answer to the question. This is often stated as an "if...then" statement.
Prediction: Making a statement about what will happen if the hypothesis is correct.
Experiment: Designing and running tests to collect data and test the hypothesis.
Conclusion: Analyzing results to determine if the hypothesis is supported or refuted. Hypotheses may be accepted, rejected, or modified.

The process is often represented as a flowchart:

Observations & Questions	Hypothesis (Tentative Explanation)	Prediction (If/Then Statement)	Experiment	Analyze & Conclude

Animal Behavior

Introduction to Ethology

Ethology is the scientific study of animal behavior, focusing on how animals orient themselves and respond to environmental stimuli. Animal behavior can be classified based on the type of response:

Kinesis: A random movement in response to a stimulus, such as scattering in all directions when disturbed.
Taxis: A directed movement toward or away from a stimulus. For example, movement toward light is called phototaxis, and movement toward moisture is called hydrotaxis.

These behaviors help animals survive and adapt to their environments.

Pill Bug Behavior Experiments

Background on Pill Bugs

Pill bugs (commonly known as "roly-polies") are land-dwelling crustaceans. They are often used in behavioral studies due to their observable responses to environmental changes. Pill bugs exhibit behaviors such as phototaxis and hydrotaxis, making them ideal subjects for experiments on animal orientation.

Initial Observations of Pill Bugs

Before conducting experiments, students are asked to observe pill bugs and answer questions about their physical characteristics and behavior:

Are all pill bugs the same size?
How many eyes and antennae do pill bugs have?
Are the legs all the same size or do they vary?
Can you tell the difference between male and female pill bugs?
How do pill bugs sense their environment?
Describe their movement and interactions.

Experiment 1: The Effect of Light on Pill Bug Movement

Phototaxis in Pill Bugs

Phototaxis is the movement of an organism in response to light. Movement toward light is called positive phototaxis, while movement away from light is called negative phototaxis. Some organisms may not respond to light at all (non-phototactic).

Hypothesis Example: Pill bugs are positively phototactic.
Prediction Example: If pill bugs are positively phototactic, then they will move toward the light source.

Materials

10 pill bugs
Behavior chamber
Plastic spoon
Square of foil (to cover one side of chamber)
Stop watch

Procedure

Transfer 5 pill bugs to each side of the chamber.
Cover one side with foil to create a dark region.
Expose the other side to light.
Allow pill bugs to acclimate for 5 minutes.
Count the number of pill bugs in each region after 15 minutes.
Record data in Table 1.

Total number of pill bugs	Light region	Connector	Dark region
Group totals
Class totals

Discussion and Questions

Can you determine if your hypothesis is correct based on the data?
Identify the independent variable (the factor being manipulated: presence of light).
Identify the dependent variable (the outcome measured: pill bug movement).
List controlled variables (constants: chamber size, number of pill bugs, time).
Describe a control group (pill bugs not exposed to light).

Experiment 2: The Effect of Moisture on Pill Bug Movement

Hydrotaxis in Pill Bugs

Hydrotaxis is the movement of an organism in response to moisture. Movement toward moisture is called positive hydrotaxis, while movement away from moisture is called negative hydrotaxis.

Hypothesis Example: Pill bugs are positively hydrotactic.
Prediction Example: If pill bugs are positively hydrotactic, then they will move toward the moist region.

Materials

10 pill bugs
Behavior chamber
Plastic spoon
2 circles of white filter paper
Dropper bottle of spring water

Procedure

Moisten one side of the chamber with water.
Place 5 pill bugs on each side.
Allow pill bugs to acclimate for 5 minutes.
Count the number of pill bugs in each region after 15 minutes.
Record data in Table 2.

Total number of pill bugs	Dry region	Connector	Moist region
Group totals
Class totals

Discussion and Questions

What is the independent variable? (Moisture)
What is the dependent variable? (Pill bug movement)
Does your data support your hypothesis?
Are pill bugs positively, negatively, or not hydrotactic?

Experiment 3: Inquiry Experiment

Designing Your Own Experiment

Students are encouraged to design an experiment to test the effect of another environmental factor on pill bug movement. Possible factors include pH, temperature, color, substrate, or odor.

State your hypothesis and prediction.
Identify the independent and dependent variables.
Describe your procedure and how it differs from previous experiments.
Record and analyze your data in Table 3.

Number of pill bugs in regions of behavior chamber after exposure to	Region 1	Connector	Region 2
Group totals

Key Terms and Concepts

Hypothesis: A tentative explanation for an observation, often stated as an "if...then" statement.
Prediction: A statement about what will happen if the hypothesis is correct.
Independent Variable: The factor that is manipulated in an experiment.
Dependent Variable: The factor that is measured in response to changes in the independent variable.
Controlled Variable: Factors kept constant to ensure a fair test.
Control Group: A group not exposed to the independent variable, used for comparison.
Phototaxis: Movement in response to light.
Hydrotaxis: Movement in response to moisture.
Kinesis: Random movement in response to a stimulus.
Taxis: Directed movement toward or away from a stimulus.

Formulas and Equations

General format for hypothesis: $\text{If [independent variable], then [dependent variable]}$
Example: $\text{If pill bugs are positively phototactic, then they will move toward the light region.}$

Summary Table: Types of Animal Movement

Type	Definition	Example
Kinesis	Random movement in response to a stimulus	Pill bugs scatter when disturbed
Taxis	Directed movement toward or away from a stimulus	Phototaxis (movement toward light), Hydrotaxis (movement toward moisture)

Example Application: These experiments help students understand how to apply the scientific method to real biological questions, analyze data, and draw conclusions about animal behavior.