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Duckweed Bioassay

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Duckweed Bioassay

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  1. Duckweed Bioassay Ms. Molstad East High School Chemistry in the Community Class

  2. Pre-Test • Determining Prior Knowledge • Assess what you learn during lab • 10 Points • Do the best you can

  3. What is a Bioassay? • Involves use of a biological organism to test for chemical toxicity • Ex: Canary in the coal mine • Test effects of compound being considered for use in drugs • Environmental testing

  4. Dose/Response Experiment • Expose organisms to various levels of a chemical and then measure their response • Duckweed is the bioassay organism • Place duckweed in various concen. of chemical, you monitor growth and health over a period of 7 days.

  5. What is Duckweed? • Small aquatic plant • Found on surface of ponds, wetlands, and nutrient rich lakes. • Lemna minor • Food source for some animals • Fast growing

  6. Is Duckweed Bad for Waterways? Increased nutrients = Increased duckweed Lake Eutrophication: Increased P & N Causes algal blooms Reduced dissolved O Kills other organisms

  7. Where do the Increased Nutrients Come From? • Human activity at home • Agricultural runoff • Golf courses • Untreated sewage • Industrial runoff

  8. Duckweed Bioassay Lab • Test the affect of various concentrations of fertilizer on an aquatic plant • Predict • Hypothesis • Conduct Experiment • Analyze results • Form Conclusion

  9. Duckweed Reproduction • By budding-new fronds grow from buds on parent plant • Measure growth rate by counting how many new fronds develop • Frond Counting

  10. Lab Procedures Lab Set Up/Participation Data Collection & Analysis • Lab Participation • Set Up • Filling in table • Graph • Questions

  11. Happy Counting!

  12. Last Day of Counting!

  13. Question #4 TC50 • TC50 • The Toxic Concentration that kills 50% of Duckweed OR • The Toxic Concentration that causes Duckweed to grow ½ as well as those in the control group • 1. Look at Control • Day 1 – 20 fronds • Day 8- ___ fronds 2. Look at Day 8 Which soln. had ½ as many fronds as the control? If no ½, then list a range

  14. Determining Doubling Time • Question #6 in Packet • Should have 3 soln. conc. to determine doubling time for. • Some might show negative growth • To Calculate Duckweed Growth Rate: • n = the number of days over which growth is measuredFo = the number of fronds at day 0Fn = the number of fronds at day nD = the doubling time of duckweed (in days)D = {(nlog2) divided by (logFn - logFo)} days • Ex: If at day 0 there are 8 fronds and at day 4 there are 18 fronds, thenD = {(4 x log2) divided by (log18 - log 8)}= {(4 x 0.301) divided by (1.255 - 0.903)}= 3.4 days

  15. Why Use a Bioassay? • Use of a biological organism to test for chemical toxicity • Examples of use: • Test effects of compound being considered for use in drugs • Environmental testing

  16. Tuesday: • Turn in Lab Packet • Post Test