|
OBJECTIVE
This
activity page will offer:
-
An operational definition in alien invasion
- Hands-on
activity in the inadvertent transfer of organisms
- An
opportunity for microscopic observation
MATERIALS
- Two large test tubes, labeled "A" and "B"
- Dropper pipette
- Distilled water
- Sprig of Elodea (also called Anacharis)*
- Forceps
- Microscope
- Slides
- Coverslips
- Sterile
Cotton Ball
Teacher
Note:
Prior
to this activity, sprigs of Elodea should be maintained
in a standard, non-sterile aquarium tank that has sufficient
aeration to support a rich aquatic community. A tank overgrown
with algae is ideal. You can also obtain these or similar
plants at most tropical fish stores.
PROCEDURE
- Use a clean pipette to transfer a drop of distilled water
onto a glass slide.
- Gently position a coverslip over the drop.
- Examine this drop with a microscope using both low and
high power magnifications. Record the presence of any observed
organisms. If applicable, use classroom resources to identify
these organisms. Include a sketch of what you see.
- Fill both sterile test tubes "A" and "B" two-thirds full
with distilled water. Make sure not to contaminate either
of these tubes with unwanted organisms.
- Use forceps to transfer a sprig of Elodea to test
tube "A".
- Set both test tubes aside. Both tubes should be exposed
to sufficient light to meet the photosynthetic needs of
the plant.
- Plug the mouth of each tube with a sterile cotton ball.
- Each day examine the appearance of the tube walls, water,
and plant surface. Record the appearance of any additional
life forms.
- Use a sterile pipette to remove several drops of water
from each tube. Examine these droplets using a microscope.
Note the appearance of any microorganisms.
- After recording your observations for one week, compare
and contrast the appearance of the water in both tubes "A"
and "B".
QUESTIONS
- Why did this activity require two test tubes, if only
one was needed for the Elodea sprig?
- What happened to tube "A", into which the Elodea
sprig was introduced?
- What happened to tube "B"?
- What types of organisms were transferred along with the
Elodea sprig?
EXTENSIONS
On Your Own
Contact
a local pet store that maintains tropical fish. Discuss the
different types of species that are common invaders to local
fish tanks. Identify the preferred means of dealing with each
of these unwanted organisms. What types of techniques are
biological controls? Which ones are chemical controls?
Sterile
Transfer
Suppose you wanted to introduce Elodea, and only Elodea,
into a new environment. How could you improve the transfer
technique so that few if any unwanted organisms were imported
into the new environment?
Art
Extension
Imagine if you were the size of a tiny protozoan species.
How might the surface of an aquarium plant appear to you?
Think about the nooks, crannies and other types of microorganisms
you'd uncover. Use classroom resources to investigate the
flora and fauna common to such environments. Working in a
team, create a classroom mural that depicts this microscopic
universe.
WEB
CONNECTION
Noxious,
Invasive, and Alien Plant Species
Government site that addresses alien species infringing
on wetlands.
Anacharis-Elodea
densa
Description and great image of Elodea sprigs.
Basics
of Fish Care
Basic fish care with a section on quarantine of newly
acquired individuals from the Minnesota Branch of the American
Association for laboratory Animal Science Inc. website.
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 Teacher Mentor, Cambridge Public Schools,
Cambridge, MA
Anne E. Jones, Science Department, Wayland Middle School,
Wayland, MA
|
