A Stream Ecosystem in the Classroom
To build a model of the world of nature is never an easy task. In this case the lotic ecosystem for the classroom is no exception. However, with the right materials, some time, and student involvement you can have an operational classroom ecosystem, complete with organisms, physical environment, interactions and relationships, and natural succession.
The purpose of this brief paper is to help you see the uses, challenges and advantages of building and maintaining a classroom lotic ecosystem. It will also provide you with directions and plans, and curricular applications.
Type of Activity:
The many activities which can be done with the stream model range from design problem solving activities to teacher guided labs and surveys, to student research in the classroom.
The target audience for this model and these activities is the General Biology student. However, I have used the model in Advanced Biology, and Chemistry successfully.
The stream ecosystem model is an effective classroom tool for developing students knowledge and abilities in the area of biology. This classroom tool has been used to study a wide variety of biological phenomena which many students don't have the opportunity to have first hand experience with. With the total investment of $150.00 to $200.00 a teacher can obtain the materials to build a model which will fit his or her classroom and be useful for the entire years biology curricula.
Building the Model
The plans for building the model can be found at http://www.augusta.k12.wi.us/HS/dept/sci/stream.htm. The plans which I have included were originally developed by Dave Meyers from Gale-Ettrick-Trempeleau High School in Galesville, Wisconsin.
Using the Model
There are many activities which can be carried out with this model. Since I set this model up at the start of the fall semester and use it in the study of Ecosystems many of these activities lend themselves to this area of biology.
Let me briefly describe a few.
ACTIVITY ONE -- Brainstorming what an ecosystem needs
To begin the use of the stream model (if you have built it, if not the first activity for the students could be to build it) a brainstorming session around the topic of "what an ecosystem needs to function" can be held in class. After the class has generated ideas on what the basic components of an ecosystem are, you can get to the task of having the class design the "parts" of your classroom stream ecosystem.
ACTIVITY TWO -- Stream flow
When the model is ready you need to have a few test runs with water in the system to check for leaks. During this time you can have your students calculate stream flow. I use the system while empty because it lends itself to cross-sectional measurements better this way, and you also don't have water moving through substrate materials this way.
To begin with I ask the students to consider what the physical environment in a stream is like. What types of conditions exist in the stream which influence the physical environment. Of course many will say its wet, but you will get a few who bring up the "amount of water" or "volume" and "how fast the water flows" or "rate". This will allow you to discuss how volume and rate are measured if you choose. I prefer to have the students form teams of two and design a method which they can use to measure these to factors using the stream model.
Many methods will result, including some who will want to measure the actual output of the pump. After some time and many calculations, the students will have some ideas about these two factors and you can guide them to the point of measuring cubic cm per second, or liters per minute using the model. The interesting thing about the model is that it will have areas of different rate and different volume measurements. This presents a great mystery for the students to solve.
Once you have calculated stream flow and defined one parameter in the physical factors affecting the developing ecosystem, you can begin the task of developing the substrate of the system.
One of the most important factors which will affect the development of your stream system is the substrate. I have traditionally obtained substrate materials directly from a local stream. Normally, two five gallon buckets full will be enough to distribute throughout the whole length of the stream. (My model is made of 4 runs of 10 feet.)
Before you introduce the material from the stream into the model it is helpful to define the sediment types. This can be done by conducting some simple soil texture tests using large test tubes or graduated cylinders. Observing the types of sediments obtained from the stream, and classifying them by type and percent composition of the sample is a good introduction stream sediments.
When you introduce the sediments and gravels into the stream you will want to be sure to let nature (the stream) distribute the types of particles. In this activity I have the students put small garden shovel fulls of stream sediments at the top of the first run under the pump. One or two shovel fulls at a time works well. Before we get to far I stop the process and ask the students to make some simple maps of the system and predict where they think the different particle types will end up. After they have made their maps and diagrammed the types of sediments and their locations (many students use a key based on our definition of the sediment samples) I have the students continue to add the material to the system until the whole thing has a good bottom substrate.
Sometimes the pump doesn't wash the materials down well enough, so we invent flood events using a 1/2 gallon plastic juice pitcher. This seems to work well as it helps the particles gain enough velocity to distribute themselves throughout the system.
As the sediments set up in locations the students can discuss their own explanations about the various stream substrate formations such as; runs, riffles, pools, point bars, channel bars, cut banks, and other physical features of the stream habitat.
ACTIVITY THREE -- Stream Organisms
For this activity you need access to a stream and some collection equipment. A D-frame net works well in collecting stream invertebrates for introduction into the system. Collecting organisms is a great activity if you can get to a creek with your students. If you can't, many of the organisms which take up residence in the stream can be found in ponds, lakes, and even temporary ponds and wet ditches. As a last resort you could get some from a biological supply company.
Once the organisms are in the stream the opportunities for investigations and observations are unlimited. Just let your curiosity and your students curiosity take hold. You'll be amazed at how many students will begin talking like biologists and gathering at the model before class.
ACTIVITY FOUR -- Classifying stream organisms
This is a simple variety of any classic taxonomic lesson where students build a key to the common organisms found in the stream. If the diversity of organisms is great, the activity may lend itself to comparative studies of organism types, classification, adaptations,
functional feeding groups, habitat and niche activities.
ACTIVITY FIVE -- Growth rate
The stream sections under the lights will soon grow algae. The types will depend on where you get your substrate materials and your stream samples. A simple way to get an idea of growth rate and algae colonization is to use microscope slides as growing substrates in the stream. Place the clean slides of known mass in different places in the stream and let the algae begin to grow on them. In a seemingly short period of time 1 to ???? weeks students will see growth on the slides, and be able to mass the slides and compare the different habitats and region of the slide for algae growth.
ACTIVITY SIX -- Photosynthesis investigations
One way to look at photosynthesis with this stream model is to use different color light sources and compare the condition of the growth under each light. A method which has shown some promise is to use clear colored plastic, (the gel type used in stage lighting or the colored clear acetate for overheads) and mount it in cardboard frames which wrap around and fit over the top stream sections. This creates a zone where only a single color light is available for the algae. By using several different colors of gels and a clear as the control students can make dramatic discoveries about the colors (then wavelengths) of light used by algae for photosynthesis.
Students have had opportunities to use the stream model for independent and small group research projects. Here is a sampling of just a few student ideas:
- Stream Organisms and their Habitats
- Dissolved oxygen in the Stream
- The pH of the Stream, Comparing the Sections
- Population Changes in Duckweed
- Snail Population Changes
- Organisms of the Sediment
- Phosphorous Levels in the Stream
This list represents some of the more traditional research projects students have attempted. All of the projects regardless of their level of sophistication were successful based on the fact that student research was conducted and results presented in classroom stream research symposiums.
The classroom stream ecosystem provides a focus for biology class projects, lessons, experiments and research. It provides students with a sense of ownership in the class if they are involved in the development of the system early in the school year. I have found students simply standing and observing, conversing about their ideas, and actively wondering what is going on in the stream on a daily basis. The model is a magnet for student curiosity. If you have a chance to build one and use it, I recommend it strongly, and wish you luck in your new quest to make biology real and relevant to your students. Remember, more information and a complete article on how to build and more details about the stream system can be found at http://www.augusta.k12.wi.us/HS/dept/sci/stream.htm.