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OBJECTIVE
This
activity page will offer:
- Assemble
a worm collection device called a Baermann Funnel
- Collect
Caenorhabditis elegans or other active nematodes from local
soil samples
-
Observe the appearance and behaviors of these worms
MATERIALS
- Paper toweling
- Fine mesh screen (metal)
- Small wire basket (or plastic food basket)
- Funnel
- Tubing (that fits the base at the bottom of the funnel)
- Clamp
- Microscope, slides, cover slips and petroleum jelly (for
observing specimens)
PROCEDURE
Extracting
Nematodes
- Obtain several samples of local soil.
- Separate the soil in each sample by passing it through
the fine mesh screen.
- Once the larger chunks have been broken down, spread the
sample on a paper tissue. The soil should form a layer about
1-cm thick.
- Wrap up the soil within this tissue and place it within
the wire basket or plastic fruit basket.
- Slip a hose with a clamp onto the neck of a large funnel.
Position the basket and soil in the funnel. SEE DIAGRAM
- Make sure that the clamp is set on the hose. Fill the
funnel with enough water so that the bottom of the soil
is positioned beneath the surface of the water.
- Leave undisturbed for 2-3 days. You may have to refill
the funnel to replace water lost to evaporation.
- During this time, active nematodes will move out of the
soil and into the water. They'll fall to the bottom of the
funnel and collect in the tube. To retrieve these specimens,
release the clamp allowing water to flow through the hose
into a collection beaker.
- Use a microscope to examine the worms living in the water.
Describe their appearance and behavior. Can you identify
young and old individuals? What factors will you use to
differentiate these animals? Do you think all soils will
contain similar populations of nematodes? Explain.
THINK
ABOUT IT
Baermann Limits
Although the Baermann Funnel
can be used to collect active nematodes, it is not an effective
tool for extracting inactive species.
Why? Can you design a collection tool that will extract nematodes
that are immobile? Share your thoughts and design with classmates.
With your instructor's approval, assemble and test this device.
EXTENSIONS
Critically Examining Human Aging
Identify
ten different changes you associate with human aging. Which
are the most critical changes? Which changes have the most
social impact? Which changes might have the greatest impact
to prehistoric human ancestors? Why? Do you think males and
females "age" at the same rate? How do societal images affect
our concept of aging?
The
Big Picture - Future Shock
Write
a futuristic science fiction story about a civilization in
which the wealthy have the technology available to arrest
their aging process. In contrast, the poor have accelerated
aging due to the environmental toxins created by the industries
of the richer and more powerful class.
Use
the Web!
What
is the typical life expectancy of a person in the United States?
Is life expectancy the same for males and females? If not,
what social and genetic factors might affect life span? How
does life expectancy in the US compare with life expectancies
in other nations? Research how average life span has changed
over the centuries. Which advances in science and medicine
had the greatest impact on life span? Were genetic factors
also responsible for any observed increase?
WEB
CONNECTION
Worm
Links
This site provides links to the laboratory use of Caenorhabditis
elegans.
Phylum
Nematoda
An introduction to the phylum Nematoda
Genetics
of Aging
Learn more about aging in this Science Friday piece. Listen
to it in real audio!
Scientists
Discover Cellular Fountain of Youth
A CNN overview of aging and genes.
For
more Web links on this topic - visit our Resources
Section.
The
activities in this guide were contributed by Michael DiSpezio,
a Massachusetts-based science writer and author of "Critical
Thinking Puzzles" and "Awesome Experiments in Light & Sound"
(Sterling Publishing Co., NY).
Academic Advisors for this Guide:
Corrine Lowen, Science Department, Wayland Public Schools,
Wayland, MA
Suzanne Panico, Science Department, Fenway High School, Boston,
MA
Anne E. Jones, Science Department, Wayland Middle School,
Wayland, MA
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