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Pond-water Populations
Task with Student Directions
Contributed by: Oregon State Department of Education


  • jars with lids
  • graduated cylinder or measuring cup
  • eye droppers
  • microscopes
  • tap water
  • thermometer
  • a light source
  • a heat source
  • aquarium water
  • slides & cover slips
  • liquid fertilizer
  • reference book for identification of protists, algae (optional)
  • materials from home


Have you ever seen an aquarium grow greener and greener? What could course algae to grow rapidly in some water, turning ponds and aquariums green?

Your task is to plan, design, and conduct an experiment to answer a scientific question. The question is: "In your investigation, how does changing one factor affect the growth of organisms." You have 50 minutes to set up your investigation. You will then observe your algae for two weeks.

  1. Under the heading "DESIGN" list, in order, the steps you will use to answer the question. You may include a diagram to help illustrate your plans for the investigation. Include any safety procedures you would follow. Make your procedure detailed enough, so someone else could follow it easily.
    • Construct a data table or chart or indicate any other method you could use to record your observations and results that will be obtained.
    • Transform your data into a graph or some other appropriate display.
  2. Perform the experiment by following the steps outlined in your procedure. Be sure to note any changes to your listed procedures and tell why.
    • Under the heading "DATA" record your observations and measurements in an organized manner. Then write statements or paragraphs or use tables and graphs to help with "ANALYSIS".

  3. Under the heading "ANALYSIS," write an interpretation and analysis of your results. Note any limitations to your investigation and sources of error.

  4. Under the heading "FRAMING a (NEW) INVESTIGATION," based on what you learned in your investigation, write your own question that can be answered with further scientific inquiry using the same classroom materials that you had for this investigation.

  5. Ask a new question and explain what observations or scientific information lead you to this question.



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