1998 WWLPT Biology Institute:
Motion
Lesson Title
Measuring the Displacement Distance from a Fixed Origin
of Flatworms of the Genus Dugesia
Summary/Abstract
Instructor's Objectives
Target Age or Ability Group Audience
Teacher Instructions/Special Precautions
Materials & Equipment Needs
Background [Prior Knowledge
or vocabulary necessary to complete activity]
The Student Lab
Method of Evaluation/Assessment
Extension/Reinforcement/Additional
Ideas
Summary/Abstract to
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Planaria is a common flatworm found in freshwater and damp soil.
Planaria belong to the order Tricladia of the class Turbellaria
and the genus Dugesia. A single planarian was placed into
three temperature environments and the motion of the planarian was recorded.
The motion recorded was the displacement (mm) value from an origin point.
Our results indicated that there was an increase in the displacement of
the planaria at 27 degrees C vs. 23 degrees C and that there was a decrese
in the displacement of the planaria at 19 degrees C than 23 degrees C.
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Instructor's Objectives
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Does temperature effect the motion (displacement) of a Planarian ?
Null Hypothesis: Average displacement in mm at 23C will
be equal to the average displacement at 19C and 27C
Alternate Hypothesis: Average displacement in mm at 23 C will not be
equal to the average displacement at 19C and 27C
Students also participate in elucidating a scientific problem that
can be investigated and in working together to design a method to investigate
the problem.
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Target Audience or Age Group
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This activity would be appropriate for students at the middle school or
high school level.
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Notes to the Teacher: to
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This lab is designed for a lab groups of three to four students.
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Teacher should order planaria cultures from a biological supply house (Carolina,
Nasco, etc.) so that cultures arrive the week of the lab.
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Planaria may also be obtained from local streams or freshwater ponds by
using liver as a lure in attracting the planaria.
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Planaria cultures may be maintained if the water is kept clean (use distilled
water not tap water), and the planaria are fed small amounts of
raw liver occasionally.
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The preparation time required for this lab is allocated to obtaining the
materials.
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The time allocated for this lab should be 20 minutes for an introduction
on invertebrates and flatworms as well as the potential difficulties students
may encouter.
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Students may measure the displacement (point of origin to place where planaria
are located at the end of the time allotted) or they may plot the location
of planaria at various times during the experiment by feeding an image
from a flex cam into a video monitor and tracing the path using overhead
transparencies and overhead pens.
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Materials & Equipment
Needs to top
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Basic Equipment:
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Planaria Hot Water
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Graph paper Petri plates
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Ice
Optional Equipment:
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Flex-camera
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Video Monitor
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VCR
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Background to
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Planaria is a common flatworm found in freshwater and damp soil.
Planaria belong to the order Tricladia of the class Turbellaria and
the genus Dugesia. The abyss between primordial organic molecule and protozoan
was at least as great as that between protozoan and man, and took perhaps
as long to span. With the advent of true multicellular organisms,
ever more complicated animal structures became practicable in the struggle
for existence. The planaria is a true flatworm. These organisms
are related to the gutless flatworm containing the first nervous system
and the first brain.
This activity helps students answer:
- How do environmental factors affect the movements of organisms?
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The Student Lab to
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1) Place a flex camera above the petri dish at a measured distance
2) Attach the flex camera to a video monitor
3) Connect VCR to camera and monitor to capture planaria motion on
video tape
(Optional)
Experimental
Protocol:
1) Place a single planarian into a petri dish with enough water to fully
cover the
organism.
2) Record the temperature of the water in the petri dish (this will serve
as the control
environment).
3) Place the petri dish onto a piece of grid paper.
4) Mark a central point on the graph paper (origin point).
5) Position the planarian into the center of the petri dish.
6) Move the petri dish to position the head of the planarian on the origin
point.
7) Mark the final position of the head of the planarian at the conclusion
of one minute
interval.
8) Record the displacement, within that one minute interval, from the origin
point (tail of
the vector) to the location of the head of the planarian at the end (head
of the vector) .
9) Repeat the above in sequences of three (3) trials.
10)Repeat steps 1-9 at various water temperatures (19C and 27C)
Mathematical Calculations:
1) Measure the distance between a line on the graph
paper.
2) Measure the distance between a line on the video
monitor screen.
3) Calculate a ratio between the above two values:
Example: 5.00mm (graph paper) = 5.5 cm (on
monitor)
5.00mm = “
x” mm
5.50cm
distance measured from monitor in cm
4) Use Dimensional Analysis to solve for “x”
to determine the calculated
displacement in mm
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Methods of Evaluation/Assessment
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A written lab report could require that the students be required
to:
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Collect data on appropriate data tables
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Display data on appropriate charts or graphs.
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Analyze data and make written conclusions.
Students could be asked to present their results to the entire
class and submit themselves to
"peer review."
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Extension/Reinforcement/Additional
Ideas to top
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What method does the planaria use for motion?
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Does time of day effect the motion of planaria?
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What is the effect of light on planaria motion?
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How should the motion that is not in a straight line be recorded?
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References Including Web Addresses
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