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APPENDIX H-1
Example of an Inquiry-Based
Laboratory Exercise
LAB 1: ECOLOGY OF DUCKWEED
NAME PER DATE DUE
GRADED
INTRODUCTION
FIX/FINISH/RETURN
Have you spent any time collecting samples of plants in ponds and streams?
Ponds are an interesting aquatic ecosystem with numerous forms of life to study.
One of the plants common to this ecosystem is a plant called duckweed.
If you have a pond or stream near your home or school, collect some of these
plants for the class experiment. You could also compare the plant structure of
duckweed to that of the pond or stream algae. Think about the function of the
various plants in the freshwater ecosystem.
Many aquatic ecosystems have become endangered by human interference.
When the pond or marsh is filled in or polluted, there is no longer a balance
within that habitat and many organisms are endangered or killed.
You will be using duckweed in the lab. In the first demonstration lab, you will set
up a growth culture and graph the growth of the duckweed under normal con
221
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222
PROFESSIONAL DEVELOPMENT OF SCIENCE TEACHERS
ditions.In the second part of the lab, you will design an approach that will test
some variables that affect the growth of duckweed.
Which of the following growth curves do you think will illustrate the growth
pattern of a small population of duckweed introduced into a container and left to
grow for two weeks? Discuss this with your team.
Growth of
Duckweed
Time
Growth of
Duckweed
Growth of
Duckweed
in In
O ~QO
O / O
. I
o 1 o
Z I Z J
J
Time
l
/
Time
The following are some questions that you can discuss in you group before your
start the lab:
· Can you name some biotic and abiotic factor that would influence the rate of
growth of the duckweed in a pond or in the classroom?
· Can you think of some natural or human induced factors in the environment
that could alter the rate of growth of the duckweed population?
· What economic factors relate to environmental pollution such as acid rain?
· What political factors are involved in preventing or cleaning up environmen-
tal pollution?
SAFETY NOTES
Use care when working with glassware.
· Wash your hands before and after the lab.
Use care when working around electrical sources.
Use care when using any chemicals in the lab.
PART A:
Materials:
Each team should have/obtain:
· 400-ml beaker or similar container to hold the initial culture of duckweed.
· Light source.
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AN INQUIRY-BASED LABORATORY EXERCISE
223
· 10 duckweed structures. Each unit includes several lobes attached and roots
growing beneath. Try to have structures with 3 lobes/structure or a total of 30
lobes per container.
Pond water.
Inoculating loop or similar device to pick up and transfer duckweed from
source to team vessel.
· Graph paper.
Procedure for Part A of the Investigation:
Microscopic examination under stereo microscope or hand lens.
Take a "plant" from the pond water provided or that you collected yourself.
The duckweed floats on the surface of the water and is made of 1-4 lobes. It
usually occurs as a three-lobed structure. Each lobe is considered a separate
plant.
Note the arrangement and structure of the lobes.
Note the roots that extend into the water.
Can you find any invertebrates living on the duckweed?
Sketch the arrangement of the lobes on the duckweed.
2. Set up a culture of duckweed to observe over 1-2 weeks, depending upon the
instructions of your teacher.
Obtain a 400-ml beaker or similar container.
Add 300-ml of pond water to the beaker/container.
· With the inoculating loop or similar device, select 10 "plants" from the stock
of duckweed. Remember that each "plant" is made of several real plants that
look like lobes.
· Set up a chart to record your observations of the population of lobes of
duckweed over the period of the lab. The chart should include the total number of
lobes from all "plants" added together.
· Record the number of lobes in your original sample of duckweed.
· Label your beaker/container with your team members.
.
Place the container in the light source provided by the teacher.
DATA ANALYSIS AND INTERPRETATION
· Make daily observations and count the lobes. Record these data.
· At the end of the 1-2 weeks, make a final count of the lobes and record on
your chart.
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PROFESSIONAL DEVELOPMENT OF SCIENCE TEACHERS
· Graph your results with the independent variable on the x axis (days) and the
dependent variable on the y axis (number of lobes).
.
PART B
Explain your results.
HYPOTHESIS OR PREDICTION
Now that you have completed the preliminary part of this lab and have recorded
the growth patterns of duckweed, design a procedure for testing one factor that
would influence the growth of the duckweed.
From the information that you have about this topic, develop a hypothesis that
could be tested in a controlled experiment that will gather quantitative data.
Explain the reasoning behind your hypothesis.
Answer the following questions to develop your hypothesis:
What is the question you are investigating?
2. What variables are you testing?
3. What are the controls for the experiment?
4. What hypotheses could you propose?
PLAN OF INVESTIGATION
Design a controlled experiment based on your hypothesis. Make a number list of
steps, similar to a recipe, that anyone could follow. Design a table that will be
convenient for recording your data. Answer the following list of questions as you
design your experiment:
What procedures would you use to test your hypothesis?
2. What will you measure?
3. How will you show your results in graphs?
QUESTIONS/ANALYSIS
How do your data relate to your hypothesis?
2. What caused any errors in your experiment?
3. What other questions came from your results?
4. To what other biology topics is this lab related? Explain.
5. What did you learn from this activity?
6. How does this lab relate to topics studied in the classroom?
Representative terms from entire chapter:
science teachers
