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Lab Activity 7.1
Responses to Light
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Directions
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Study
the instructional material below. Be sure to click on each of the photographs
for an enlarged view in a separate window. The
larger version is necessary to complete the assignment.
It opens in a separate window which can be resized by grabbing the bottom
right corner and dragging it. It
can also be moved by
grabbing the top heading bar and dragging it.
Be sure to close the extra window by using the X in IBM, or the close box
in MAC when you are finished using them. |
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Introduction
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Studying
the behavior of aquatic organisms can be fascinating. Their basic activities
are similar to our own and include seeking favorable conditions. When we
directly observe them carrying out their daily activities we get a chance
to understand them more fully. Directional movements are examples of behavioral
responses to envirnmental factors. Mobile organisms can move in a way that
will allow them to enjoy favorable environmental conditions. In this lab
activity you will study the behavior of two simple, aquatic organisms. Ask
yourself if their behavioral responses increase their probability of survival. |
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Instruction
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Study
the information and photographs in the experiment that follows. Be sure
to complete the observations, formulate answers to the questions you're
asked, and write them in your notebook.
Be sure
to write about what you are learning in the lab section of your notebook.
You will be expected to answer questions about the lab activity during
the lab self test and lab quiz. It helps to have your text and coloring
books open beside you for support.
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| Supporting
Information |
| Refer
to the Assigned Readings Below: |
| Marine
Biology Textbook |
None |
| Marine
Biology Coloring Book |
None |
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Response
to Light by Planarian Flatworms
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In this experiment
we will observe the effects of light on a small flatworm called
Planaria . We will use the organisms' movements to determine
the nature of its responses. Movement toward a source of light is
called a positive phototaxis. Movement away from a source of light
is called a negative phototaxis.
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Observe the photograph
of a Planaria .
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Experimental
Set Up:
- We obtained a
plastic petri dish and a piece of thick paper. We
cut the paper in a half circle to fit half the cover of the petri
dish and taped it on the cover surface.
- We transferred
a planarian flatworm into the petri dish and covered the dish.
- We turned the
cover until the edge of the paper lay near the flatworm and recorded
the flatworms movements. We repeated the process ten times giving
the flatworm a choice between the shaded and unshaded portions
of the petri plate.
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Observe the photograph
of the experimental set up.
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Observations:
- Which part of
the petri plate does the Planaria choose most often?
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What type of
phototaxis does the Planaria display (positive or negative)?
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