dishes or paper plates
or paper plates
· White spoons
· Compost from local composter
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.
Redworms and Earthworms
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.
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.
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
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
a. provide the students with the trays of compost. This compost should have an assortment of types of organisms in it.
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)