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A Drop
in the Bucket
Program
Area
This activity
fits well into the Grade 10 Advanced Science, Core Unit 1: Interactions,
and Grade 10 Advanced Environmental Science, Core Unit 4: Population
Ecology. It may be used to introduce the concept of exponential
growth and to introduce or review graph-making skills in Grade
9. This activity may also substitute for yeast or fruit fly populations
in laboratory activities.
Learning
Outcomes
Teaching,
learning and evaluation will focus on the student's ability to:
- Estimate
and measure volume;
- Record
and graph data;
- Recognize
an exponential growth curve.
Classroom
Development
- Accuracy
is important when measuring and recording volumes. For an easier
set of initial measurements, a teaspoon may be used in place
of an eyedropper (1tsp = 15 ml). 50 L plastic garbage cans should
be used.
- A review
of volume measurement may be necessary.
- Students
should work in groups of 3 or 4, taking turns with each addition.
- After
performing this exercise, actual population data should be graphed
and discussed. Refer to the activity: Global Population Analysis
for follow-up analysis.
- The concept
of carrying capacity and limits to growth may also be introduced.
Timing
This activity
can be performed in half a period with subsequent periods spend
on examples and implications of exponential growth.
Resources
The Green
Teacher, Volume 21, December, 1990.
World Population
Video, 1990. A graphic simulation of the history of human population
growth. Zero Population Growth Inc. Southern Illinois University
of Carbondale.
Cross-disciplinary
Links
This activity
integrates Science and Mathematics. Extended discussion questions
on human population growth rate expands the linkage with other
disciplines in the Self and Society program.
Student
Activities
A
Drop in the Bucket
Purpose
To demonstrate
exponential growth.
Materials
- a large
plastic garbage can
- measuring
containers of various sizes
- water
- eyedropper
Method
- Place
1 drop of water from an eyedropper into an empty garbage can.
Assume 10 drops = 1 ml. Remember 1000 ml = 1 L. If the volume
of water added to this bucket is doubled at each turn, predict
how many turns it will take to fill this container.
- Double
the volume of water added on each successive turn until the
garbage can is full of water.
- Record
the turn and the volume you are adding.
- Plot
a graph of the volume of water added vs the turn. Plot the volume
of water on the y-axis, and turn numbers on the x-axis ( Remember
to keep the units consistent).
Observations
Prediction-the
number of turns it will take to fill this container is _______.
Construct
a table similar to the sample below.
| Turn |
Volume of water added |
| 1 |
0.1 ml |
| 2 |
0.2 ml |
| 3 |
0.4 ml |
Questions
1. Since
the rate of increase in volume remains the same, account for the
sharp upward curve?
2. The world
population growth curve has a similar appearance to the graph
drawn in this activity. Describe what you learned in this activity
about the growth rate of the human population.
Extension
To learn
more about human population growth, turn to the activity "Global
Population Analysis."
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