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Building an Ecosystem

By Charlotte C. Freeman

Type of Activity:

  • Hands-on
  • Group/Cooperative learning
  • Inquiry
  • Authentic assessment
  • Review/reinforcement
  • Interdisciplinary connections
    through time

Target Audience:

  • Integrated science
    level 1 and 2
  • Biology
  • AP Biology
  • Human Biology
  • Environmental Studies
  • Chemistry

A unit outline for one multi-science long term study

What Question Does This Unit Help Students Answer?

  • How can human activity harm an ecosystem?


Background Information:

This activity is designed to follow our students from grade 7 - 12. It uses a single aquatic ecosystem as a constant to be woven through the curriculum as the students progress through science. It is available to use for interdisciplinary activities. It is centered around a 400 gallon 4 tank system which is placed in sunlight in the lobby of our science building. It was seeded with water from nearby rivers, lakes, ponds, and creeks. It's only mechanical part is a pump which returns water from tank 4 back to tank 1. It was purchased from Ocean Arks International and is called a Living Machine.

Alternate systems more practical for smaller places could include the now commercially available River Tank System or a freshwater aquarium. Economy models can be created from 5- gallon plastic jugs or carboys begged from the school kitchen.

Class time required:

Class time needed can be customized by the year. Any teacher may choose to spend more or less time on this activity and can elect to give it a once-a-year treatment or return to the activity during the year as often as desired. Preparation time would vary according to the activities chosen. One person will have to assume the year long responsibility for maintenance of the system.


Naturally occurring microorganisms play a vital role in the recycling of materials within an ecosystem. These same microbes play a vital role in removing toxins and organic materials from aquatic systems. They can be "employed" by humans to restore polluted waters and prevent further damage. Using this as a recurring theme, I am maintaining a working ecosystem and emphasizing the need to understand ecosystems, their cycles and energy flow. From this idea I have moved into the idea of human impact on the ecosystem and water pollution from fertilizer run-off, industry, and other human activities. The year-by-year progression of this study will hopefully add additional meaning to the activity, result in increased retention, and show the connections between life and physical sciences. The stability and constancy over time can be observed and stresses on the system can be studied. This is an engineered simulated wetlands ecosystem.

Once the ecosystem is established, needed materials include magnifiers, microscopes, keys to the algae and plants, reference materials, soluble fertilizer, water quality test kits (i.e. Lamotte Kits) for testing dissolved oxygen, ammonia, nitrites, nitrates, hardness, pH, phosphates, chloride, etc., dip nets, sampling equipment, and supplemental food for larger organisms if the system does not produce adequate food. Lastly, continuous monitoring of temperature, pH, and light incidence by computer interfacing equipment (LEAP) and a computer gives a visual picture of the daily fluctuations in pH as a result of increased photosynthesis in the light and decreased photosynthesis in the dark. Conversely, the same graph shows the stability and constancy through time.

Examples of typical activities which might be included at each level:

  • Grade 7: Observations of the macroscopic invertebrates such as hydra, planaria, scuds, worms, Daphnia, and leeches which are attached to the transparent sides and can be observed in situ. Additional observations of fish behavior, algal blooms and declines, and the effect of covering the tanks with foil or cellophane to see the role of light are all within the realms of 7th grade expertise. This can be used for teaching observational skills, practicing questioning techniques, and creative writing exercises. For library research projects the students could choose a plant or animal and learn how to use library references to discover information on the natural history of that organism. Method of evaluation might include a portfolio of information accumulated by the student. Cooperative learning techniques could be used as the class shares observations, writings, and results of library research. Appropriate writing exercises might include 1st person stories written by the students from the perspective of becoming one of the inhabitants and describing what a typical day in their life would include, what they would see, eat, and do.

  • Grade 8: Continuation of the same activities begun in grade 7 with additional skills added such as pH testing, discovering the food chains operating, and watching the cyclic nature of the daily schedule. Simple problem solving activities such as trying to figure out how one would measure something like carbon dioxide in the water, the flow rate, evaporation rate, etc. would introduce the ideas of rate or indicators. Food chains and food webs could be based on what the students observe in this system. Students would continue to add to their portfolio and drawings. In a cooperative venture, sketches from art classes might focus on this machine or some part of it.

  • Grade 9/10 (Biology I): In this course we teach use of the microscope and students at this point could use scrapings from the side to see the microscopic life which occurs. In Biology I, communities and ecosystem studies occur early in the year and at this point food chains, food webs, predator-prey, and competition could be observed while constructing these webs. Biogeochemical cycles such as nitrogen, oxygen, carbon dioxide could be backed up with data from measurements with the test kits. Ammonia, nitrites, and nitrates could be tracked. This would emphasize the role of bacteria in the recycling of matter. The importance of the "microcosmos" segment of the ecosystem will be a major focus. The rapid pH response to light and non-light conditions could be used to reinforce the photosynthesis input and output. Living invertebrates are available for observation when studying classification. Simulation of fertilizer run-off projects by adding soluble plant fertilizer might be involved and include cooperation with another class. Observational activities and writing of observations could be used to sharpen skills of writing and observation. Individual projects could involve population counts, etc. Students could problem solve to determine how to collect samples from top, bottom, middle, etc.

  • Grade 10/11 (Chemistry): Building on previous information from biology experiences, the chemistry classes could look more closely at the reactions when carbon dioxide dissolves in water or examine the complex chemistry which occurs in a dissolved oxygen test. Indicators, electromagnetic spectrum and various water quality tests could be topics woven into this curriculum.

  • Grades 11/12 (Physics): Calculations of volumes, flow rates and studies of instruments such as photo-voltaic cells could be integrated into a physics course. The bending of light waves by water could become a hands on experience when students try to retrieve something from the tank using a dip net. Individual projects combining biology, chemistry, and physics would be appropriate here. Physics students could data onto a computer of CBL and then use that data for manipulations and graphing.

  • Advanced courses: AP Biology, Ecology/Environmental studies could use this as a focus for aquatic ecosystems and practice the use of testing equipment before going into the field. A fertilizer run-off project, algal response to phosphate and nitrate level, BOD studies, and productivity light/dark studies are facilitated by the presence of the system in house. Animal behavior and population studies of the invertebrates can become more sophisticated. The cycling of matter via photosynthesis, respiration, and its parallel in terrestrial plants and animals could be connected. Students could design ways to collect gaseous oxygen bubbling from the algae and submerged plants. By adding food scraps, the roles of detritivores and decomposers could become meaningful and the impact on the water chemistry could be monitored.

At the end of 3-5 courses of science a student will have yearly exposure to this system...a "constant" in the educational process. Each year would add to or build on the previous year. The student may have greater awareness of the role of detritivores and decomposers in the cycling of matter and understand how human activities may upset the balance in an ecosystem. Commercially, these machines are being used to clean up toxic sites and to process effluent from places such as ice cream manufacturers. The role of wetlands in making water suitable to sustain life has long been known. By giving students an up-close view of how an ecosystem works, I hope to have students buy into the idea of protecting our wetlands and waters from further damage. Another goal is to simply see the relationship between what is studied in a classroom and the real world.

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