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Name ______________________________ Per. ____ Assign# _____ Date _______ Score _____

Population Dynamics of Duckweed

Truman Holtzclaw



You and a partner will be given one duckweed plant in a 10 oz.,wide rim,plastic cup filled with pond water. These plants may include one to seven "leaves". Each leaf can break off to become its own plant. Your job for the next two month's will be to count and record the population growth of your "leaves" on the back of this paper. Make a neat and simple graph with the population on the vertical (#"s of leaves) and the 60 days on the horizontal. You should count your population at least twice a week (Mondays and Fridays?) You will also need to replace the water as it evaporates. Use clear pond water if possible.


You and your partner will team up with another pair to try out a variable between your population and their population. One of your populations (cup of water and Duckweed) will be the "control" and the other will have the one variable or "experimental factor". Some variables that you might want to consider are: A. closeness to the light; B. a fertilizer; C. carbon dioxide content; D. temperature, E. light source, F. kind of water or another variable of your choice. Please check with your instructor about the variable you have chosen. We will to try to use a variety variables.

Some questions for thought:

  1. What are the life needs of the Duckweed?

  2. What effect did you expect that your variable might have on the Duckweed?

  3. What, if any, effect did your variable have on the Duckweed population?

  4. On a cellular level, can you explain the effect(s) of your variable?

  5. How does the Duckweed's cup of water compare and contrast to the planet Earth? Give some of the major differences and similarities.

  6. How does your Duckweed population compare and contrast to the Homo sapiens population? Give some of the major differences and similarities.

  7. What control do you have over your Duckweed population and what control do you have over the human population?

  8. Describe the growth of the Duckweed population. Did the rate of increase, remain about the same, or did it increase or decrease?

  9. What factor(s) do you believe limited the growth of the Duckweed population?

  10. Why do plants require an outside source Nitrogen, while animals must continually give off Nitrogen?

  11. In terms of complexity & energy potential what are the major differences between the molecules that plants take in and the molecules that animals take in?


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