Blend-A-Plant

A Demonstration About Levels of Organization

Donald Cronkite

Overview

This short demonstration illustrates the ideas of "levels of organization" and "emergent properties." Students consider the differences in the properties of a plant before and after it has been subjected to a kitchen blender. The approach employs a combination of small group discussion and interaction among all the members of the class.

Biological Concepts

• levels of organization

• emergent properties

• hierarchies

Class time

This short introductory exercise can take from 15 to 30 minutes.

Background Information

Organization is an essential feature of life. Organisms are not just piles of cells of various types, but highly patterned and organized systems. We can study these systems in terms of the object itself (an organism, for example), or in terms of its parts (organ systems such as the nervous, cardiovascular or digestive systems) or in terms of systems of which the object is a part (in this case, populations or species). Understanding each level is important because it focuses on the importance of structure to living things and because it gives us a more complete picture of the object being studied. Properties of one level may not be seen at other levels. For example, it makes sense to speak of the average height or weight of a population of organisms, but individual organisms cannot be said to have an average height or weight. Often the first chapter of biology texts has a short discussion that considers this idea.

Materials

• Handouts with the questions with space to record answers. (See Student Activity Sheet.)

• Small potted plant, preferably with flowers. Small begonias work well, but any plant without woody tissue will do. (Geraniums work poorly because they have woody stems.)

• Kitchen blender ("Waring Blender" or "Osterizer", for example)

• Stout pair of scissors for cutting up the plant before blending.

• 500 ml beaker with at least 300 ml of water.

• Container to catch the dirt when the roots are cleaned off. (If there isn't too much dirt, just spread out a newspaper on the desk or lab bench.)

• Blackboard or other such place for recording lists of answers to questions

Teacher Preparation

At the beginning of class, have the plant on the front desk or lab table covered with a layer of newspaper. The demonstration is more effective if the blender and beaker are kept out of sight until it is time to use them.

When it is time to do the exercise, tell the students that we can study any object of interest to biologists at three different levels -- in terms of the object itself, it terms of what the object is made of, or in term of what the object is a part of. Break the students into groups of three, and ask them to list what the three levels would be if we were studying atoms. If we were studying species? (See Student Work Sheet.) [For atoms: atoms are made of elementary particles; they make up molecules. For species: species are made of populations or individuals; they make up communities or genera -- there is more than one way to go on that last one.]

Call attention to the plant. Carry it around so that everyone gets a good look at it. Then ask each group to take one minute to make as large a list as they can of all the things that plant is doing. Then ask the groups to call out things from their list as you make a list of these responses on the board. [Many answers are possible including: photosynthesizing; reproducing; mitosis and meiosis; moving liquids through the vascular tissue; transpiring; respiring; metabolizing; active transport of minerals; moving sugar in the phloem; looking pretty; attracting insects; etc.]

Then pull out the blender, remove the plant from its pot, knock off as much soil as possible -- even rinse it off if you have a handy faucet, cut the plant into pieces and put the pieces in the blender. Add a few hundred ml of water and blend the plant into a homogenous mass. This part can be fun if you let it.

Pour the homogenized plant into the beaker. Ask the groups now to think of all the things on the list that the plant no longer is doing. [It may still be carrying on some metabolic reactions including photosynthesis if the chloroplasts survived the blender, but it won't be transporting or doing many other things on the list.]

Ask the whole group why the plant is doing less things. After all, it is still composed of the same chemicals as before it was blended. [It now lacks organization, and how the parts are organized in time and space makes many functions possible.]

Now is the time to discuss emergent properties. Point out that the plant has properties when it is organized that it lacks after blending even if it has the same molecules. These properties found at one level of organization but not at less organized levels are called "emergent properties." Water movement by transpiration, for example, requires an intact system of roots, vascular tissue and leaves. The phenomenon is a property that only emerges at a certain level of organization. Likewise, water, made of two hydrogens and an oxygen, freezes at 0 degrees, boils at 100 and is most dense at 4 degrees. These are not properties of hydrogen and oxygen except when they are organized as water molecules.

Extensions/Variations

1. You can blend anything that loses properties when disorganized. There is a Jell-O mold that makes a replica of the brain, for example. It would be interesting to blend a brain and then think why a brain can think before being blended but not after.

2. Other questions to consider include:

How is the classification scheme used by biologists an example of levels of organization?

What could you learn about schooling behavior in fish by studying the molecular biology of fish? What would you not be able to learn?

Resources

Most college level introductory biology texts include comments on levels of organization and emergent properties.

About The Author

Donald Cronkite is a Professor of Biology at Hope College in Holland, MI. His address is Biology Department, Hope College, Box 9000, Holland, MI 49422-9000. His e-mail address is cronkite@hope.edu

NAME:__________________________ DATE:__________ PERIOD:_______________

Levels of Organization

Form groups of three to discuss the following questions. You will discuss some of the questions as a group and then as a whole class. Don't get ahead, but work at the pace of the whole class.

1. After you have heard about levels of organization, think about that with respect to atoms: What are atoms made of? What do atoms make up?

2 What about individual organisms? What are they made of? What do they make up?

----------- Now discuss this as a whole group ----------

3. Make a list of all the things the plant at the front of the room is doing.

----------- Combine the group lists to make one large class list ----------

----------- Observe as the plant is moved to a different level of organization ----------

4. After the teacher has "moved the plant to another level of organization," draw a line through all the things on the previous list that the plant is no longer doing.

----------- Discuss #4 as a whole class -----------

5. What is an emergent property?

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