ms. molstad east high school chemistry in the community class
TRANSCRIPT
Ms. MolstadEast High School
Chemistry in the Community Class
Pre-TestDetermining Prior Knowledge
Assess what you learn during lab
10 PointsDo the best you can
What is a Bioassay?Involves use of a
biological organism to test for chemical toxicityEx: Canary in the coal
mineTest effects of
compound being considered for use in drugs
Environmental testing
Dose/Response ExperimentExpose 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.
What is Duckweed?Small aquatic plant Found on surface of
ponds, wetlands, and nutrient rich lakes.
Lemna minor Food source for
some animalsFast growing
Is Duckweed Bad for Waterways?Increased nutrients =
Increased duckweed
Lake Eutrophication: Increased P & N Causes algal bloomsReduced dissolved OKills other organisms
Where do the Increased Nutrients Come From?Human activity
at homeAgricultural
runoffGolf coursesUntreated
sewageIndustrial runoff
Duckweed Bioassay LabTest the affect of
various concentrations of fertilizer on an aquatic plant
PredictHypothesisConduct ExperimentAnalyze resultsForm Conclusion
Duckweed Bioassay Data
Solution Concentration
# Duckwee
d Fronds/C
up
Avg. #
Fronds
Comments about Plant
Health
Control
Fertilizer Concentration ( %)
Fertilizer Concentration ( %)
Fertilizer Concentration ( %)
Duckweed ReproductionBy budding-new
fronds grow from buds on parent plant
Measure growth rate by counting how many new fronds develop
Frond Counting
Lab ProceduresLab Set Up/Participation Data Collection &
AnalysisLab ParticipationSet Up
Filling in tableGraphQuestions
Last Day of Counting!Duckweed Frond Counts-Class Averages
Day 1 Day 3 Day 5 Day 8
Control
100%
10%
1%
0.10%
0.01%
0.001%
Question #4 TC50TC50The Toxic
Concentration that kills 50% of Duckweed
ORThe Toxic
Concentration that causes Duckweed to grow ½ as well as those in the control group
1. Look at ControlDay 1 – 20 frondsDay 8- ___ fronds
2. Look at Day 8Which soln. had ½ as many fronds as the control?If no ½, then list a range
Determining Doubling TimeQuestion #6 in
PacketShould 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
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
Tuesday:Turn in Lab PacketPost Test