Exploring Decomposition
By Sarah Hinners
Grade Level: 6th
Inquiry Question: What is decomposition, and where, when and how does it occur?
Objectives:
 The student will understand the importance of decomposers in ecosystems.
 The student will be able to identify factors that enhance decomposition.
 The student will become familiar with different types of organisms that are
decomposers.
BVSD Standards and Benchmarks Addressed:
Science Standard 3.2.03 The student will describe the role of organisms in decomposition
and recycling of nutrients.
Science Standard 3.3.01 The student will recognize that interrelationships exist among
organisms (e.g. predator/prey, population dynamics).
This activity also ties in nicely with:
Standard 2.1.03: The student will classify and describe matter in terms of categories (e.g.
atoms, molecules, elements, compounds, mixtures, solutions).
Background Information:
All living things are made up of just a few elements. In fact, just 4 elements –
carbon, nitrogen, oxygen and hydrogen – make up about 96% of living matter. The
remaining 4% is almost all accounted for by 4 more elements: sulfur, phosphorus,
calcium, and potassium. Another 17 elements are present in trace amounts in organisms.
Individual atoms of these 25 elements combine in different ways to form the
organic molecules and compounds that are the building blocks of life. However, there is a
finite quantity of elements on this planet with which to make living things. When a
building is torn down, we often recycle some of the wood and stone of which it is built in
order to build something else. Similarly when an organism dies it is essential that its
valuable materials be recycled and used to build another organism. Decomposers are
organisms that specialize in eating dead tissues. As they consume these tissues, they
break them back down into compounds. This process makes the compounds available for
use in another organism. If decomposition stopped, life on this planet would stop, as there
would be no more materials with which to make new organisms.
Decomposers act at all trophic levels in an ecosystem. All living matter, be it
plant or animal, is subject to decomposition. The individual atoms that make up your
body now could next be used to make a tree, a snail, or an alga. In this way, the process
of decomposition is the most direct link between all living things.
All consumers perform decomposition to some extent. When we eat food, we
excrete a broken-down form of the original matter. However, decomposers specialize in
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eating dead tissue and they consist primarily of fungi and bacteria. Because most
decomposers are not visible to the naked eye, we don’t think often about the process of
decomposition and if we do, it seems somehow mysterious or magical. The purpose of
this activity is to get students thinking about decomposition: to recognize it when they see
it and to be familiar with factors that enhance the decomposition process.
Concepts Addressed: Decomposition, food webs, the chemical makeup of living things,
interdependence.
Possible Misconceptions to Address:
1. fungi=mushrooms
(Mushrooms are just the most visible form of fungi. Most fungi exist primarily as a
mycelium: a network of invisible threads that permeate soils, compost piles, etc. If you
find some really good decaying leaf litter, you may be able to detect the mycelium, or
other examples of fungi, like mold.)
2. Only food decomposes.
(Most students’ experience with decomposition may be primarily based on what happens
to leftovers in their refrigerators. This activity is a way to get them to see more broadly,
that decomposition is happening all around us.)
Vocabulary Words: decomposer, decay, constituents, microbes, fungi, mold, atoms,
elements, compounds.
Time and Location: How long, i.e. 1 or 2 hours. and anywhere outdoors with some
moist areas.
Materials:
Outdoor portion: Zip-lock™ bags, Sharpies™, trowels, a few pairs of work gloves.
Indoor portion: wide flat sorting trays, magnifying glasses, dissecting microscopes and/or
simple compound microscopes, forceps or other pointed tools students can use to pick
through their samples.
Procedure:
1. In the classroom: To engage the students, you may present the class with a variety
of materials in various stages of decomposition. Ask the class what is happening
to these materials. Take a few minutes and have them write down in their
journals/notebooks some questions they have about decomposition. Ask for
volunteers to share some of their questions with the class and write these on the
board. These questions can be revisited after returning to the classroom.
2. Outdoors: Have students divide into groups of 2-3 and give each group a couple
of bags, a marker, and a trowel or other digging/scooping implement. Suggest
that using their sense of smell in addition to sight may be useful in this activity.
You may want to start out by getting students’ initial suggestions of good places
to look (wet, shady, among trees, etc.)
3. Send them off in search of decomposing matter. Each group should collect at least
a couple of samples, place the matter in their bags, and label the bag with the
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marker. Each bag should have the following information: names of people in
group, date, general location (ex. Waneka Lake) and specific location (ex. under
shrubs, at water’s edge, wetland soil, etc.) Suggest that using their sense of smell
in addition to sight may be useful in this activity. You may want to start out by
getting students’ initial suggestions of good places to look (wet, shady, among
trees, etc.)
4. Return to classroom and place samples in sorting trays. Let the students explore
their samples for awhile using the forceps, magnifying glasses and microscopes.
5. In journals, students should record a description of their sample. Is it wet/dry?
How does it look/smell? How advanced is the decomposition? Can you tell what
it originally was? What sort of organisms do you think are present?
6. As a class, summarize groups’ findings by listing:
Conditions that seem to encourage decomposition.
Characteristic organisms found in decaying matter (this may lead to an extension
where students learn more about these organisms and how to identify them.)
Characteristics of decaying matter: do some materials break down more easily
than others?
You may also want to revisit the students’ initial questions about decomposition
at this time.
** This part of the activity has the potential for a variety of extension activities.
For example, students could conduct experiments looking at the decomposition
rates of different materials (ex wood, leaf, eggshell, fruit, etc.) , or of the same
material in different conditions (ex. Wet, dry, damp, light, dark), or designing inclass composting projects.
Assessment:
This activity is primarily meant to be completed in one day as part of the ecology portion
of the 6th grade curriculum. Therefore, assessment is primarily based on students’ journal
entries (initial questions, recording of observations). It would also be possible, time
permitting, to have groups report their findings to the rest of the class.
Additional assessment for the activity may consist of questions on decomposition
included in the final chapter test/review.
References:
1. http://compost.css.cornell.edu/Composting_homepage.html (see especially
“Composting in Schools section”)
2. http://www.offwell.free-online.co.uk/decompos.htm
(good general description of the process of decomposition, plus slide show of decaying
rabbit)
3.http://www.frostvalley.org/programs/environ_ed/environ_edart/DecompositionForestTr
ees.pdf
(diagram of decomposition in a forest)
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Related Reading:
1. See reference #2.
2. Literacy component: Read the following poem as a class and discuss the meaning and
relevance to decomposition. Extension: have students write their own decomposition
poems based on their experiences in this activity.
If I should die before I wake,
All my bones and sinew take;
Put me in the compost pile,
And decompose me for a while.
Wind, water, rain will have their way,
Returning me to common clay!
All that I am will feed the trees,
and little fishes in the seas.
On radishes and corn you munch-You might be having me for lunch!
And then excrete me with a grin-Chortling, "There goes Lee again!!"
-Lee Hays, The Weavers
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