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Flatworms
- Observation
of a Live Planarian
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here for background
You
will receive a small petri dish with a flatworm inside it. The flatworm is
the freshwater planarian, also known as Dugesia.
1.
List 3 characteristics of flatworms.
2. What type of symmetry does this worm have?
3. Where do planarians live?
4.
Observe your worm, using a microscope or hand lens. Sketch the planarian below.
Label the eyespots. Label the anterior and posterior ends.
5.
Measure your planarian. This operation is best performed by removing some
of the water from the dish and waiting for the worm to stretch out.
Measure the length of the worm in millimeters. (Always replace the water;
you can use the dish lid to transfer water to and from the planarian
environment.)
Length of Planarian _______mm
Write
your length on the board and when all the lengths are down, determine the
average planarian size.
Average
____________ mm
6. Observe the planarian for five minutes. Does the planarian seem active or passive? How does it move? Does it swim or creep? Where in the dish does it spend most of its time? Make a current in the water with a pipette. How does the planarian react? Fill out the table below.
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Description |
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Movement |
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Worm
location |
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Reaction
to current |
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7.
Planarians actually display a "handedness" being right or left handed.
You can discover whether your worm is right or left handed by flipping the
planarian over on its dorsal (back) and seeing which way it recovers.
If it rolls to the right, it is right handed, if it rolls to the left, it is
left-handed. Do five trials to determine the handedness of
your planarian.
Fill out the data table:
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Which
way does it turn (left or right) |
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Trial
1 |
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Trial
2 |
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Trial
3 |
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Trial
4 |
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Trial
5 |
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Based
on your data, is your planarian right or left handed? ____________
8. Design an experiment to test the planarians reaction to light and dark. You will have flashlights and the room will be darkened for this part of the lab. Describe your experiment.
Conduct
your experiment to determine whether the planarian prefers light or dark.
Construct a data table
Write
your conclusions.
Make sure you answer the question: Does the planarian prefer a light or
dark environment and include your reasoning.
9.
Drop a piece of food into the petri dish with the planarian. Observe the
planarian's reactions. It may take a few minutes. How does it
eat the food? Where is its mouth? Use the space below to write
your observations.
Reaction
to food _______________________________________________________
How
does it feed?
Where is the mouth located?
What is the name of the tube used for feeding in the planarian?
Planarian Reproduction --Make sure your planarian has finished eating entirely and its pharynx is withdrawn, if it gets too close to the end of the hour, ask your teacher for a different planarian
Planarians
are hermaphrodites. Define hermaphrodite
Planarians
can also reproduce by regeneration. Define regeneration.
Is
this method of reproduction sexual or asexual?
Pour out some of the water, so that the planarian is mostly un-submerged. When it stretches out, use a razor blade to cut it cleanly in half. Replace the water and put the lid on it. Observe the two pieces of the planarian under the microscope.
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Movement (observations) |
Sketch |
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Anterior
end |
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Posterior
end |
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Label the lid with your NAME and HOUR.
Make a prediction: How long do you think (in days) will it take for your planarian to completely regenerate?
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