Living Organisms As Indicators of Pollutants In Fresh Water Ecosystems
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Hubers, Hendriekje Chicago High School for
1. Use Hydra as a biological indicator of water pollution.
2. Learn about Hydra's natural environment, feeding behavior,
reproduction, and reactions to stimuli.
2-4 water samples from local ponds, streams, lakes, or rivers
1 glass culture dish (or depression slides)
Brine shrimp or Daphnea
4-6 droppers or pipettes
microprojector or microscopes
A Hydra population can be maintained and reproduced in the
classroom. If Brine Shrimp are fed to the Hydra, make sure the salt
water is rinsed off, otherwise you will kill your Hydra. Daphnea can
also be used as food for your Hydra.
1. With a dropper remove one Hydra (with some water) and place on a
culture dish or depression slide. If you use a culture dish, you
can prepare more than one Hydra for later observation. Place the
culture dish on the stage of the microprojector. Before turning
on the light source, place a heat filter above the culture dish (a
petri dish with water makes a good heat filter).
2. Observe and record the Hydra's structure and movements. You may
also want to discuss Hydra's reproductive behavior and how it
changes depending on the environmental conditions.
3. With a dropper place one Daphnea or Brine Shrimp (make sure you
have rinsed the salt water off) in the dish with the Hydra.
Observe and record your observations on the Hydra's feeding
4. Look at the pond and lake water samples. Discuss with students
which sample they think is the most contaminated and why, and what
effects they think each water sample will have on the Hydra when
added to the Hydra's environment. You can use as many water
samples as you want, just make sure that only one type of water is
added to each Hydra.
5. Add one drop of water from source A to one Hydra sample. Observe
and record your observations. Set this sample aside, you will
come back to observe it in about 10 minutes.
6. Repeat step 5 using water from source B. Repeat for as many water
samples as you want to study.
7. After 10 minutes for each sample, observe again and record if
there are any changes.
8. Write your conclusion on your observations.
1. Research other types of biological indicators and write a strategy
for how you could use this organism to determine the presence of
contaminants in any kind of ecosystem.
Note: Another demonstration which can be done in class is using Elodea
as an indicator. Use the same type of set-up you would use for