Isopod Activity

By Carl Benson

Type of Entry:

• Project:  modified by Carl Benson from Dr. Kenneth Bandelier, Western Montana College

Type of Activity:

• Hands-on Activity
• Inquiry lab
• Group/cooperative learning

Target Audience:

• Life Science
• Biology

Background Information:

This activity helps students to understand the methods used for scientific analysis. It uses simple quantitative testing to learn more about a living organism. Ultimately, it gives students an appreciation of quantitative analysis in biology.

Notes for teacher:

Using a spreadsheet with graphing capabilities allows the students to enter information and compare relationships that they are measuring. Examples of characteristics that can be measured are: movement, strength, food preference and response times to chemical effects. The isopod is a relatively harmless animal and is easy to take care of in the classroom.The isopods need a small container with a substrate composed of humus, dirt, and moisture. A slice of potato works well for food. A piece of chalk can be added and students enjoy trying to determine what the isopods use it for. Preparation time is determined by how this activity is used. A study of methodology, research and ecosystem interaction could be used as a precursor to the activity. I find that a brief introduction to the characteristics of the organism plus methods of measurement suffice in getting the project started. The project runs approximately nine weeks and several days per week are used for development of tests, building apparatus for testing, accumulation of data and graphing, and reporting the results in a scientific paper. I run this project concurrently with regular classroom lectures and activities.

Lesson/Activity:

One of the most innovative activities that I use in my classroom involves the study of isopods. This activity is designed to get students actively involved in biology.It uses a small creature commonly known as a 3Pill Bug2 to get students familiar with the creature, its body characteristics, its behavior, its means of growth, and other features.

This activity lasts nine weeks with reports due on certain dates. The reports follow the format that a scientific paper would have. Students work together as scientific teams. Laboratory instructions are held to a minimum so the teams are expected to develop and carry out their own ideas as to how some activity is to be done. In many of the activities the team has to decide what needs to be done to meet the requirements of the activity and secondly, carry out whatever procedure they decide upon. I do make suggestions on how to proceed, but it is left up to the teams to request such assistance.

This activity is very successful because it involves teamwork and everyone participates. Every student is an integral part of the team and each team has several responsibilities:

1. to set a suitable home for the isopod colony.
2. to observe characteristics of their isopods.
3. to run tests on their isopods to determine strength, speed, etc..
4. to use data and graphs to draw conclusions about their isopods.
5. to write a scientific paper reporting their results.

When the teams are developed, paying close attention to team dynamics is essential. I try to put students together who have different strengths and weaknesses. This allows for more creative interaction when they are deciding on procedures for testing, building the apparatus to test the organisms, developing methods used to accumulate data, and reporting their findings.

The goals of this activity are to allow students to:

1. use scientific methods to investigate biological phenomena.
2. use laboratory equipment to study isopods.
3. understand the processes which define life.
4. understand the relationship between structure and function as they relate to living things.
5. apply biological principles to situations in daily life.

The teams are observed in laboratory activities and are tested by holistic rubrics. They are responsible for experimenting and drawing conclusions from the experiments. The scientific paper is also used to determine whether students are using the scientific method correctly as well as correct grammar and usage.

Lab Activity 1:

Observe the activities of your isopods for approximately 15 minutes. Make a record of what they did after placing them in the container. How can you explain their behavior after placing them in the container?

Now that you have your isopod colony set up, you are to find out as much as you can about these animals. Are they really animals? Consult any references that you can find and determine what kind of organism they really are. Where do they fit in the classification system of living organisms?

Examine their body from both the ventral and dorsal aspects. What do the terms dorsal and ventral mean? Does it have an anterior and posterior end? What kind of body symmetry does it have? What are the various appendages on the body? What function do the various appendages serve? Does the organism breathe? If so, how does it obtain oxygen? Does it have a mouth?

Prepare a drawing showing the organism from the dorsal view. This drawing is to be made directly from one of your specimens. A stereomicroscope will help in viewing some of the small structures. Do the same from the ventral view.

Your first lab will include a complete description of the body form of the isopod. Your drawings will be a part of this report. In this report not only are you to describe the body, but also determine functions of the various parts. You are expected to use the library to obtain additional information about isopods. All references or sources of information must be included in your bibliography at the end of the report .

Lab Activity 2:

In this activity you are to study the means by which isopods move around. Design a procedure which will determine how fast your isopod moves and also what affects its rate and direction of movement. You are to collect as much data as needed to answer the questions below. Your data is to be presented in tabular form in your report.

After determining the rate of movement of your isopods, design a procedure along with other members of the class for conducting an isopod race. First, design the race course to be used. The instructor may have some suggestions for this. Second, determine what rules are to be followed, and third, determine who has the fastest isopod. Repeat the race a second time making any modifications in the course and rules that seem to be needed. Do it a third time if you wish.

Some of the questions that are to be answered in this activity are as follows:

1. How do the isopods move?
2. Do all legs move together?
3. Describe the pattern of leg movement.
4. Does the kind of surface make any difference as to its rate of movement?
5. Is there any way that you can stimulate it to go faster? Slower?
6. Does the light or darkness cause it of move faster or slower?
7. Does it make a difference whether the surface is level or hilly?

Lab Activity 3:

In this activity you are to determine what isopods eat. Design and carry out an experiment which tells you something about the food preferences of isopods. This activity should be carried out with other members of the class in order to obtain more data than with yours alone.

Some of the questions that are to be answered in this exercise are as follows:

1. What foods do isopods eat?
2. How do they take food into the body?
3. Does it make a difference whether it is wet or dry?
4. Do they show a food preference?
5. Should the food be in a light or dark place?

Lab Activity 4:

You are to design a procedure which will tell you how strong an isopod is in proportion to its weight. As a part of this activity you are to find out something about the anatomy of the legs and body of an animal and without dissecting your organism. This would kill your specimen. Refer to various references to get an idea as to how the internal anatomy may possibly appear. The fact that the organism is a member of the Arthropoda should give you an idea of its internal anatomy.

Finally, along with other members of the class, design and carry out a contest to determine who has the strongest isopod.

The following are questions which are to be answered by your report.

1. Are the legs all the same? If not, how do they differ?
2. Do the muscles show through its body covering as human muscles do? Explain.
3. Are the legs jointed? If so, how many joints are there?
4. How do the legs secure traction?
5. What kind of surfaces provide the best traction? The poorest traction?
6. What proportion of its body weight can it carry or pull? In order for you to pull or carry the same proportion, how much would you have to weigh?
7. Are there any environmental conditions which seem to affect its strength?

Lab Activity 5:

In this, the final activity of the series on isopods, you are to determine whether chemicals will affect its activity in any way.

Design a procedure to expose your isopods to a volatile substance such as airplane glue. Care should be taken to not overexpose your organisms as they may die. Use very short exposure times to begin with. Be sure that you establish the normal pattern of behavior of your isopods before exposing them to the chemical substances.

The following are questions which you are to answer in your report:

1. How does the substance enter the body of the animal?
2. Does the size of the body make any difference on the effect of the chemical?
3. What is the normal pattern of behavior of the isopod?
4. How is the pattern of behavior altered as a result of its exposure to the chemical?

All data to support your conclusions should be presented in some kind of table or graph.