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Earth Systems Science Core
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Changing Ecosystems

What will happen if seeds are watered with salty water instead of fresh water? Are plants growing at cool temperatures capable of storing as much energy as similar plants growing at warm temperatures? What happens to an ecosystem when one group of organisms increases or decreases in number?

Try it!

Your goal is to sprout seeds, comparing two different types of water in the process.



  • Seeds (any type that sprout quickly, such as alfalfa or chia)
  • Plain water
  • Salty water (make up your own and compare the amount of salt used with friends)
  • Paper towels
  • Two zip closure bags
  • Marking pen
Safety concerns: Be sure to keep all chemical safety rules. As with all science lab activities, the most important safety rule is to follow all teacher directions.


  1. Place 20 seeds in salty water and 20 seeds in fresh water overnight.
  2. The next day prepare two different paper towels as follows:
    • Moisten one with the salty water.
    • Moisten one with the plain water.
  3. Remove the seeds from the salty water and place them on top of the paper towel soaked in the salty water.
  4. Fold the paper towel over the top of the seeds so they are covered (if possible, fold it again so it is in quarters).
  5. Slide the paper towel into a zip closure bag.
  6. Label the bag "salty water."
  7. Remove the seeds from the plain water and place them on top of the paper towel soaked in the plain water.
  8. Fold the paper towel over the top of the seeds so they are covered (if possible, fold it again so it is in quarters).
  9. Slide the paper towel into a zip closure bag.
  10. Label the bag "plain water."
  11. Place both bags in a warm (not too hot or too sunny) location.
  12. After three to five days, open the bags and count the number of sprouted seeds in each.


  1. What differences in sprouting did you observe?
  2. Was the factor being tested in this experiment biotic or abiotic?
  3. What was the factor?
  4. Do you think all kinds of seeds would react the same way to a change in salt concentration?

Click here to check your answers.


Data Interpretation:

Now you get to analyze how another abiotic factor can change what goes on in an ecosystem.

Plot the following data on graph paper.  Place the temperatures on the x-axis across the bottom of the graph and the mg glucose/hour on the y-axis at the left of the graph.

Compare your graph with a sample graph.


  1. What is the abiotic factor shown in the graph?
  2. What is the biotic factor that changes when the abiotic factor changes?
  3. What does an increase in temperature do to the rate of sugar (glucose) production?
  4. Why do you think the graph drops sharply at higher temperatures?

Check for our answers.



The photo below shows slices of a mat of microorganisms found in a hot spring at Yellowstone National Park. If you look closely, you will notice layers of green, red and tan. Each layer contains different microorganisms. The organisms in each layer work with those in other layers to provide each other with the things they need to stay alive. In this situation, what do you think might happen if one kind of organism was suddenly destroyed? Could similar things happen in larger ecosystems?

Photo courtesy Evan Whitaker

You were correct if you guessed that the other microorganisms would be greatly affected if one kind was destroyed. Changes in populations, no matter how large or small, will have an effect on other populations and communities in the ecosystem.


Try it!

Design an experiment to test the effect of changing an abiotic or biotic factor on an ecosystem of your own. Explore the following sites for "Bottle Biology." Get some ideas to see what other people have done.



Write two Cinquains, one for abiotic and one for biotic.

Cinquain is a form of poetry that has a total of five lines. The lines depend on parts of speech and syllables rather than rhyme. The pattern for a cinquin is:

Line 1 = One noun of 2 syllables
Line 2 = Adjective(s) with total of 4 syllables that describe the noun
Line 3 = Words showing action and having a total of 6 syllables (-ing words work well)
Line 4 = Words with a total of 8 syllables that tell how you feel about the noun
Line 5 = Another noun of 2 syllables that makes you think of the first noun

Heaven’s light
Melting, shining, tempting
Succulent, delicious, pure ambrosia
Review science lab safety rules here.

Get the plug-ins: Get Adobe Acrobat Reader and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE Earth Systems Science core.


Updated October 24, 2008 by: Glen Westbroek

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