Living Organisms As Indicators of Pollutants In Fresh Water Ecosystems

Hubers, Hendriekje Chicago High School for
Agricultural Sciences
(312) 881-5000

Objectives: 1. Use Hydra as a biological indicator of water pollution. 2. Learn about Hydra's natural environment, feeding behavior, reproduction, and reactions to stimuli. Materials: 2-4 water samples from local ponds, streams, lakes, or rivers 1 glass culture dish (or depression slides) Hydra population Hydra medium Brine shrimp or Daphnea 4-6 droppers or pipettes microprojector or microscopes heat filter Strategies: 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 behavior. 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. Evaluation: 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 demonstrating photosynthesis.
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