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Inquiry-based Investigations into Pond Water Microorganisms

By Marie Doucet


The following lessons are part of a unit investigating the abundant life found in pond water and is used to develop scientific, technological, and critical thinking skills in biology students. The nature of the activities focuses on exploration, invention, and application and provides students with attitudes of discovery and curiosity into their natural, physical world. Much attention is given to scientific process skills and higher-order thinking as students learn problem-solving, graph construction, graphical analysis, and application.


I use these activities during my study of pond ecology with extensions into the protist kingdom. Follow-up activities and extensions involve the "adoption" of a specific microbe from pure cultures on which cooperating groups are to research and design test methods of specific factors that affect the growth of their organism (for example, pH, salinity, light, etc). At the conclusion of the unit, student groups direct and produce a presentation using appropriate software and multimedia applications.

I have found that these activities heighten student capabilities and interest in further projects involving field monitoring of area water quality. They are comfortable and feel confident in their scientific discoveries.

This project idea is of my personal design. However, collaboration of ideas was gained with two of my colleagues, A.J. and Cathy Reon, biology teachers at Barbe High School in Lake Charles, Louisiana.


Pond water is alive with a diverse array of organisms and many are microscopic. These microorganisms are essential to the balance of the pond ecosystem. You may already be familiar with some of these, like the amoeba, paramecium, and euglena.


In this inquiry lab, you will become familiar with common microorganisms and experienced in exploring the microbial world.


Pond water, compound light microscope, slides, cover slips.


  1. 1. You will work in teams of 2.

  2. You have been provided with a diagram of common pond water microorganisms that you should look over and study.

  3. Prepare wet mounts and use your microscope to search and find at least 10 of the microbes on your list.

  4. For each microorganism you find, provide the following information:
  • a. name
  • b. classification (kingdom, phylum, etc.)
  • c. sketch/description
  • d. description of movement, if any
  • e. approximate population count (devise a method) graph this data


    1. Which organisms seem to be most abundant?

    2. Of those organisms found, name those that are photosynthetic.

    3. Name those that are heterotrophic.

    4. Name some abiotic factors affecting the populations of microorganisms.

    5. Predict a possible outcome resulting from an increase in the population of Paramecia.

    6. Draw some conclusions about the biodiversity of the pond ecosystem.


    Culturing organisms simply means to grow them. By providing the necessary nutrient and environmental requirements, you can grow cultures of organisms for further investigation or study.


    In this inquiry lab, you will design an experiment to test the effectiveness of various culture techniques for microorganisms.


    pond water, compound light microscope, microscope slides, cover slips, rice grains, hay stalks, well water, hot plate, beakers, pipettes, baby food jars, dehydrated yeast, egg yolk, balance


    1. You will work in pairs.

    2. Choose one microbe to investigate (i.e., Paramecium or Euglena).

    3. After forming your hypothesis about the effectiveness of specific culture techniques, you will design a controlled experiment testing this hypothesis. You must have this design approved by your teacher.

    4. You must test at least two methods (discussed and researched).

    5. Tables and graphs must be used to illustrate your data and observations.

    6. You will be given two weeks to conduct this investigation.

    7. You must submit an individual lab report with graphs and answers to analysis questions.


    Design a flow chart diagraming your procedure with results.

    Which culture technique seemed to be the most effective?

    What criteria did you use to arrive at this conclusion?

    Assume that the population of Paramecia has peaked in a sample culture. Predict the future growth of this sample population if its growth is allowed to grow unchecked.

    When the population of a microorganism begins to decline after a rapid growth period, what measure(s) can you take in the lab to insure a continued stock of that organism?

    Include a discussion of sources of error in your culturing techniques.


    Morholt, Evelyn and Paul F. Brandwein, A Sourcebook for the Biological Sciences,
    San Diego: Harcourt Brace Jovanovich, Publishers, 1986.

    Pendergrass, William R., Carolina Protozoa and Invertebrates Manual,
    Burlington: Carolina Biological Supply Company, 1980.

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