|
Teaching Tips
 One
of the best things about Life Science is how easy it is to bring the
living world into the classroom. If your
students are exploring
the diversity of life on Earth through classification, you’ll
have no difficulty providing an array of plants and animals
for firsthand study. Terrariums and aquariums—such as those
seen in the video in Stephanie Selznick’s first-grade classroom—are
excellent small-scale study systems. The TerrAqua
Column, which is
described
in Bottle Biology on this Web site, provides a similar opportunity.
As
your students understandings of plants and animals grows, you
may wish to introduce other groups of living things featured
in the video—the fungi, protists, bacteria, and archaea. Some
suggestions for bringing these life forms into your classroom are provided
below.
Fungi
Your students are likely to be familiar with typical
examples of fungi—the mushrooms— and many will consider them to
be plants. One way to help students distinguish between these
two groups is to bring examples in and compare them side by side. The
supermarket
is a great source of these familiar fungi with most carrying
a variety of types.
You might also start a field collection of fungi. During warmer
and wetter months, a walk through the woods or a park can provide
an astounding variety of specimens. Decaying plants and dead
trees are
great sources of fungi in the “wild”. Of course, no field
specimen should ever be tasted!
Molds and yeasts are also examples
of microscopic fungi that can be brought into the classroom.
One way to collect molds is
to use unpreserved bread to swipe different surfaces. The bread
can be put
into a plastic baggie and left for observation over time, with
slightly moist bread being more likely to yield results more
rapidly.
A more sophisticated way to culture both molds
and yeasts is to purchase Petri plates with prepared media from
a biological supply company. A type that contains “Sabouraud
Dextrose Agar” selects
for fungi, although “Trypticase Soy Agar” or “Nutrient
Agar” will also work. These plates, which are sterilized when
they are prepared, provide a food source for molds and yeasts.
All you have to do is rub a cotton-tipped swab (which can also
be purchased sterile if you wish) on a surface of interest and then
apply
it as
a “streak” onto the plate, which is then incubated upside-down.
The molds generally appear “fuzzy”, while the yeast colonies
appear as “dots”.
There are few precautions in culturing
fungi in this way—they
grow in a closed container and are types that are already present
in the environment. To dispose of the plates, spray with disinfectant
solution, seal, and throw away. The only thing to be careful
about
is opening the plate—every time you do, you can introduce new
microbes!
An example of culturing fungi in this manner can be seen in a
Bottle Biology activity using the EcoColumn called “Basically,
I’m a Fungi”.
Protists
The first time a student looks under a microscope
at a drop of pond water is likely to hook them on the world of
protists. This
is what enthralled Anton Van Leuwenhoek, the inventor of the
first microscope. There are few special “tricks” to
observing these creatures—a compound light microscope,
glass slides (depression slides are best), cover slips, and droppers
are the basic supplies. You can also purchase solutions to slow
them down, such as “ProtoSlo” or… if you don’t
have a microscope, borrowing one from a middle or high school
and sharing views of your samples with colleagues and administrators
may even be a way of making a case for purchasing one. It’s
even possible to distinguish between the plant-like forms, which
are characteristically green, and the animal-like forms, which
move in various ways.
Bacteria
Perhaps the most ubiquitous organisms
on Earth are the bacteria. Your students are likely to be familiar
with the word, and it
is easy to bring meaning to it by culturing bacteria in your
classroom—they’re on every surface. Like molds and
yeasts, bacteria can be cultured on Petri plates with prepared
media. “Trypticase Soy Agar” or “Nutrient Agar” will
yield excellent results. Bacteria are cultured in the same way
as fungi, by swabbing a surface of interest, applying it in a
streak to the surface of the plate, and incubating it upside-down.
Bacterial colonies will appear as tiny “dots” on
the surface of the medium—each dot represents the offspring
of one bacterium. To dispose of the plates, spray with disinfectant
solution, seal with tape, and throw away.
An example of culturing
bacteria in this manner can be seen in a Bottle Biology activity
using the TerrAqua Column called “What
is It?”
Archaea
One reason that the archaea are fascinating
is that they characteristically grow in extreme environments.
For this reason, they are not good
candidates for bringing into the classroom as live cultures—even
microbiologists are challenged with getting them to grow out
of their natural habitats. If you’re interested in introducing
your students to this group, this Web site may be useful: http://www.ucmp.berkeley.edu/archaea/archaea.html
|
Teaching
prev:
taxonomic classification
