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BIO-MONITORING DATA SHEET How Healthy is my Stream? Determining Pollution Tolerance Index Date: ______ Period: ______ Table #: _______ Introduction: Ecologists can assess the “health” of an ecosystem by the presence or absence of particular species. Macroinvertebrates are often used to assess the health of rivers and streams. These are animals with no backbones that are visible without the aid of a microscope. Team Member Names: ___________________________________________ Procedure: 1. Use the macroinvertebrate key to identify and classify the species in your stream sample. Group 1 ____ Pouch Snail ____ Tubifex Worm ____ Blood Midge ____ Rat-tailed Maggot Larva ____ Riffle Beetle Group 2 ____ Midge (except Blood Midge) ____ Blackfly Larva ____ Flatworm ____ Leech ____ Water Mite _____ Total present x 1 = _____ Total present x 2 = _____ Index value for Group 1 _____ Index value for Group 2 Group 3 ____ Damselfly Nymph ____ Dragonfly Nymph ____ Aquatic Sowbug ____ Scud ____ Cranefly Larva ____ Clam Group 4 ____ Stonefly Nymph ____ Mayfly Nymph ____ Caddisfly Larva ____ Dobsonfly Nymph ____ Riffle Beetle ____ Water Penny ____ Gilled Snail _____ Total present x 3 = _____ Total present x 4 = _____ Index value for Group 3 _____ Index value for Group 4 2. On the Bio-monitoring Data Sheet, place a check mark next to each type of organism that was found in your sample. (NOTE: We are not counting individuals, we are counting types of animals.) 3. Multiply the number of species in each group by its group number to determine its index value. 4. Add the index values of all four groups and divide by the total number of species found in your sample to determine the Pollution Tolerance Index (PTI) for your stream. 5. Discuss the answers to the questions with your group members. Take notes on your discussion in your science journal. 6. Write the answers in your journal in complete sentences that restate the question and are supported with your data. ______________________________________________________________ Discussion Questions: 1. Describe the process your group used to identify organisms and assess your stream sample. 2. Which animals were the most common in your sample? 3. Which animals were the least common in your sample? 4. What is the PTI of your stream according to your results? Explain. 5. Infer: which of the organisms are the most tolerant to pollution? 6. Which organisms must be present to indicate a healthy stream? PTI = Sum of index values divided by total number of different animals in sample = ___________ PTI KEY: 4 = excellent quality 3 = good quality 2 = fair quality 1 = poor quality