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Decomposer Identification |
OBJECTIVES:
MATERIALS: · Microscope
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Petri
dishes
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White
spoons · Compost from local composter
BACKGROUND:
Bacteria and fungi digest organic matter and convert it into different
chemical forms that are used by other microbes, invertebrates and plants.
During thermophilic composting the populations of various types of
microorganisms will change as conditions change. The world of microbes in
compost is diverse and mysterious.
The energy that they release during their struggle to stay alive,
creates another ecosystem that helps to further digest and change organic
material.
There is always a challenge in compost in that your mixture produces an
end product that has carbon and nitrogen in balance.
Making compost at the beginning can produce “smells” but once it
gets an “earthy smell” then the compost is ready.
In this lesson we will have the student explore the different microbes
that they can find. It is not
important what their names are, but that students look for organisms that
help this complex chemical process.
Below are some of the organisms the students may see.
Drawing pictures can help them look at the organism careful.
Nematodes
Springtails
Redworms and Earthworms
Ground Beetles
Wolf Spiders
Centipedes PROCEDURE:
Before the lab
Collect a sample of compost that has various types of organisms.
You can get the compost from the black compost bin behind the composter in
the garden or from the composter directly. The bin in the back will have a
greater variety of cool compost organisms.
To get a good assortment of organisms, one method of collecting
invertebrates is to take grab samples of compost from various locations in
the heap. Some organisms such as centipedes and sowbugs will be more
likely to be found near the surface. Others will be found deeper in the
heap.
For the heat loving decomposers you will need to look for actinomycetes in
the compost. These look like
white and fuzzy.
Lab intro:
Tell them today they are going to learn about and examine organisms found
in the various phases of composting
1.
Go over the compost powerpoint.
Be sure to point out that there are two phases, a hot thermophilic
(heat producing phase) and a cool phase.
2.
ACTIVITY:
a.
provide the students with sets of
compost food chain sheets and the cards
(students should work in teams of two or three) and ask them to
look for the ones that are thermophilic (heat loving).
These are the organisms from the first phase (includes
actinomycetes, mold, bacteria, protozoa).
Have them set those cards aside separate from the rest.
b.
Ask them how are these thermophilic organisms similar:
(all are tiny simple organisms)
c.
pass out the trays of compost with actinomycetes on them.
Have them use magnifying lens to look.
they should be able to see the strands that are formed by the
bacteria
3.ACTIVITY
a.
ask them to review the other cards
(the ones that are NOT thermophilic)
b.
ask them to look for separate primary consumers--the ones that eat the
compost residue from secondary and tertiary consumers.
c.
put the cards to one side on the table but keep them handy so students can
use them to figure out their organisms
4.ACTIVITY
a.
provide the students with the
trays of compost. This
compost should have an assortment of types of organisms in it.
b.
Students should look for a variety
of organisms. They can use
wooden tongue depressors, plastic spoons, or other instruments that will
not hurt the organisms, to sort through the compost. Flashlights and
magnifying lenses can be used to enhance the observation. The larger
organisms, such as worms, centipedes, millipedes, sowbugs, earwigs,
spiders, ants, beetles, snails, slugs, some mites, etc., can be observed
with the naked eye. To get a closer look, they can pull the organism out
and put them in the petri dish for closer observation.
You can also allow them to place samples of the compost in petri
dishes or watch glasses and observe them under a microscope.
c.
Have students use the Decomposer Worksheets and cards to identify
different organisms that they find. Have them observe the organisms with
their magnifying glasses or microscope and then draw some of their
organisms on the worksheet. Tell
them to draw as many details as possible.
(Some students are very detail oriented and will only draw one or
two. For those that draw
quickly, ask them first to put in more details and then to keep drawing
other organisms.) They can
color the drawings as well.
d.
When they are done, have them carefully put their organisms in the petri
dishes back in the dirt for the next class.
5. Wrap up (5 minutes)
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