Lesson 2 (Scavengers and Decomposers) in Unit 3, 4-6 ...

Lesson 2: Scavengers and Decomposers

Lesson’s Concept

Scavengers and decomposers are essential to the recycling of organic matter.

PURPOSE is transferred from one organism to 4–6 Module
Students study about scavengers and see ex- others in the food web, and between Unit 3
amples of the actions of decomposers. organisms and the physical environ-
ment.” (Science Content Standards,
OVERVIEW Grades K–12; Grade 6; Ecology, Stan-
In this lesson students will: dard 5b)
• Observe evidence of decomposition. - “Animals and plants sometimes cause
• Locate some scavengers on the school changes in their surroundings.” (Bench-
marks for Science Literacy, page 72)
grounds. • Students observe scavengers on the
• Make a mural of the scavengers they ob- school grounds and design habitats for
specific scavengers, such as earthworms,
served. sow bugs, beetles, and ants.
• Design a habitat in a container for a - “All organisms need energy and mat-
ter to live and grow.” (Science Content
specific scavenger, collect several scaven- Standards, Grades K–12; Grade 4; Life
gers from the school grounds, keep them Sciences, Standard 2)
for observation for 24 hours, and then - “By the end of the 5th grade, students
release them. should know that . . . Insects and vari-
• Conduct research, using reference books on ous other organisms depend on dead
a specific scavenger. plant and animal material for food.”
• Grow and compare colonies of decompos- (Benchmarks for Science Literacy, page
ers, such as molds, yeast, and bacteria. 116)
• Play a game to identify specific scavengers • Students write descriptions and facts
and decomposers. about specific scavengers. They also write
a song about decomposers or scavengers.
CORRELATIONS TO CALIFORNIA’S - Students “choose the form of writing
CONTENT STANDARDS AND (e.g., personal letter, letter to the editor,
FRAMEWORKS AND TO BENCH- review, poem, report, narrative) that
MARKS FOR SCIENCE LITERACY best suits the intended purpose.” (Eng-
• Students observe ways decomposers lish–Language Arts Content Standards for
California Public Schools, Kindergarten
change organic matter. Through Grade Twelve, page 37)
- “All organisms need energy and matter • Students sing a song about decomposers
or scavengers.
to live and grow. As a basis for under- - “Students sing or perform on instru-
standing this concept, students know . ments a varied repertoire of music.”
. . decomposers, including many fungi, (Visual and Performing Arts Framework,
insects, and microorganisms, recycle Music: Creative Expression Compo-
matter from dead plants and animals.” nent, Goal 3, page 64)
(Science Content Standards, Grades K–12;
Grade 4; Life Sciences, Standard 2c)
- “Organisms in ecosystems exchange
energy and nutrients among themselves
and with the physical environment. As
a basis for understanding this concept,
students know . . . over time, matter

4–6 Module, Unit 3: Lesson 2: Scavengers
Composting 459 and Decomposers

SCIENTIFIC THINKING PROCESSES the lesson; plus time a couple of weeks
observing, communicating, comparing, clas- later to observe the results of decomposers
sifying, relating growing

Time Vocabulary
30 minutes to prepare for the lesson; 45–60 decomposition, decomposers, organisms,
minutes per day for six days to implement scavengers

Preparation ___ Soil, rocks, and other materials for habitats
(for scavengers) in containers
___ 1. Read the “Background Information for
the Teacher” at the end of this lesson. For “Part II, Growing Decomposers”
___ One resealable plastic sandwich bag for each
___ 2. Locate an area in the school’s neighbor-
hood and/or on the school grounds group of two or three students
where students can find scavengers, such ___ Masking tape and marker
as ants, sowbugs, slugs, and worms. Lo- ___ Half cup of garden soil
cate rocks, pieces of wood, or paper that ___ Piece of bread and pieces of fruits and veg-
students can look under. If your school
grounds do not have any rocks or pieces etables
of wood, you will need to find an empty ___ Wet paper towels
lot within walking distance where these ___ Two slices of a banana
things are present. You could also place ___ Teaspoon of active yeast
(approximately two weeks in advance) ___ Four tablespoons of cottage cheese
some rocks or pieces of wood on the soil, ___ Magnifying lenses (one for each pair of stu-
in a planter, or near a corner of a lawn
area on the school grounds. (Tell the cus- dents)
todian what you are doing, so the items ___ Students’ journals or a copy of the “Decom-
will not be moved.)
posers Investigation Sheet” for each student
___ 3. Make two (or more) copies and cut
apart the “Scavengers and Decompos- For “Part III, Playing a Game About Scavengers
ers Cards” to provide one card for each and Decomposers”
student (pages 468-471). ___ Two or more copies of “Scavengers and

___ 4. Decide whether you want students to Decomposers Cards” (to provide one card for
write the results of their investigations in each student)
their journals in an open format or have ___ Masking tape or a clothespin to tape or pin a
student use the “Decomposers Investiga- card on the back of each student
tion Sheet.” If you decide to use the “De-
composers Investigation Sheet,” make a PRE-ACTIVITY QUESTIONS
copy for each student (page
472). Day 1

Materials A. Tell students that in this lesson they will
learn more about decomposers, the organ-
For “Pre-Activity Questions” isms that decompose organic material. They
___ Examples of nutrients or things that can will also learn about scavengers, animals that
eat dead things or the wastes of living things.
represent nutrients, such as compost, plant Ask students:
fertilizer, vitamins, a protein drink, a piece of • What are nutrients? Show examples of
fruit, a leaf, and a stuffed animal to represent nutrients that you obtained (see “ma-
a dead animal terials” list). Nutrients include protein,
___ Butcher paper for a mural vitamins, minerals, and carbohydrates and
For “Part I, Learning About Scavengers” provide nourishment to keep an organism
___ Quart-sized jar or other transparent contain- alive.
er with lid for each group of students • How do plants get the nutrients that they
need in order to grow? They get them from
the soil.

CLOSING THE LOOP 460 4–6 Module, Unit 3:
Composting

• How do the nutrients get into the soil? and other debris. Look for sow bugs, mil- 4–6 Module
Through the work of scavengers and decom- lipedes, worms, and beetles. Tell students to Unit 3
posers. (Students might not know this at pay particular attention to each scavenger’s
this time. Record their answers and refer habitat (area where it lives), because they
to their answers at the end of this lesson.) will be designing a habitat for them in a
container.
B. Lead students on a walk around the school’s D. Back in the classroom, ask how many more
neighborhood and/or on the school grounds scavengers students found the second time.
to locate organisms (living things) that live Why did they see more scavengers? They
under leaves, rocks, or pieces of wood. knew where to look and what to look for.
Students should record in their journals what E. Have students add drawings of scavengers
they see. Was there anything growing on any to the mural.
of the rotting or decomposing things; e.g., Homework Assignment: Ask students to begin
mold? designing a habitat in which to keep some scav-
engers. They can draw these, labeling what they
Note: Ask students not to pick up the organisms will put in the container to make certain that
but, instead, to point out to other students what their scavenger is provided with its basic needs
they found. (i.e., air, food, water, and shelter).
C. Go back in the classroom and ask students
Day 3
to draw what they saw, which could include
animals, such as ants, sow bugs, and milli- F. Ask students to share their homework as-
pedes. signments. Tell students that they will work
D. To illustrate what the students observed, in groups to design habitats, where they
have them make a mural on a piece of will keep some scavengers for 24 hours.
butcher paper, using the drawings of what
they observed on the school grounds. Note: The 24-hour rule of keeping an organism
provides opportunities for students to observe
PROCEDURE closely an animal in a humane manner (without
causing the animal undue stress or death) and
Day 2 teaches students to respect other living things.
Part I, Learning About Scavengers After 24 hours each animal should be released in
the exact spot where it was found.
A. Ask students, “What are scavengers?” They
are animals that eat dead things. Have students • Have students use quart jars or other
look up the word scavenge in the dictionary. containers with lids in which to design a
They should find out that “to scavenge” habitat for their scavengers. Lids should
means to clean away or feed on carrion or have holes punched in them to allow air
refuse; therefore, scavengers feed on dead into the containers.
things. Ask students to name some scaven-
gers and to describe what they eat. Vultures, • Ask groups of students to select a spe-
crows, seagulls, coyotes, and ants eat dead animal cific scavenger and to make a habitat for
bodies. Some scavengers, like earthworms, eat and this organism in the container. Students
break down dead plant parts. must make certain that the scavenger
is provided with air, food, water, and
B. Ask students to look at the mural of the shelter.
organisms they observed on the school
grounds. Tell them that most of the animals • Tell students that they cannot collect
they saw are called scavengers. They scav- their scavengers until all the habitats
enge through organic matter and eat it. These they created have been approved by
include worms, beetles, sow bugs, milli- you.
pedes, slugs, and ants. Where do scavengers
live? In and on top of soil, in logs, under rocks, G. When all groups have completed design-
in damp places. ing the habitats, lead them on a collecting
expedition on the school grounds and allow
C. Lead students on a walk on the school each group to collect two to five scavengers.
grounds to look for additional scavengers Students should record in their journals
under pieces of wood, newspapers, rocks, the exact location where they found their

4–6 Module, Unit 3: Lesson 2: Scavengers
Composting 461 and Decomposers

organisms and the type and number of Part II, Growing Decomposers
organisms they collected. Day 5
Note: The containers should be kept away from
direct sunlight. A. Set out the materials, including pieces of
H. Back in the classroom, organize a view- bread, fruit, and vegetables, yeast, cottage
ing and explanation exhibit. Make sure to cheese, and plastic resealable sandwich bags.
allow time for students to observe all of the
scavengers that were collected. B. Ask students whether they have found food
in the refrigerator that had mold or slimy
Day 4 stuff on it. Explain that these are decompos-
ers eating and decomposing the food.
I. On the following day have the students
observe their scavengers, sketch them, • Tell students that they will try to grow
and write two descriptive sentences about different decomposers in a plastic bag.
them.
• Separate the class into groups of two or
J. Then ask students to release their organ- three students.
isms in the exact location where they were
collected. • Provide a plastic resealable sandwich
bag to each group of students and a piece
K. Decide with the class what to do with the of tape on which students should use
soil and plastic containers. Reuse the soil; a marker to write their names and the
reuse or recycle the plastic containers. numbers of their bags.

C. Assign one or two groups to each bag and
give them directions (listed below) on how

Picture intentionally deleted.

Two students from Janet Cohen’s
sixth-grade class at Gold Trail
Elementary School place bread in
a plastic bag to observe how the
bread will change over time.

Two students from Janet Picture intentionally deleted.
Cohen’s sixth-grade class at 4–6 Module, Unit 3:
Gold Trail Elementary School
place soil in a plastic bag to 462 Composting
observe evidence of decom-

posers growing in the soil
over time.

CLOSING THE LOOP

to set up each bag. Ask students to describe Day 12 4–6 Module
in their journals the appearance of the items Unit 3
in the bag and predict how these items will Safety Caution: Do not to open the plastic
change over time. bags. These bags may contain high concentra-
Bag 1: Place a piece of bread or pieces of veg- tions of spores, which may be harmful if inhaled
etables and a wet paper towel in the plastic or exposed to an open cut or abrasion. Students
bag. Seal the contents, describe the appear- should be cautioned not to open or puncture
ance of the items in your journals, and store the bags. Students should report any accidental
the bag in a dark place. opening to the teacher.
Bag 2: Either drag some pieces of food scraps E. At the end of a week, redistribute the bags
in the dirt outside or add a half teaspoon of
soil to the bag. Moisten the contents. Seal and have students describe what they see
the contents, describe the appearance of the without opening the bags.
items in your journals, and store the bag in a • Provide magnifying lenses for students
dark place.
Bag 3: Place a slice of a banana inside a plas- to take a closer look at the contents of
tic bag and sprinkle the banana with a half the bags through the plastic.
teaspoon of active yeast. Seal the contents, • Ask students to draw and describe in
describe the appearance of the items in your their journals what they see. Or distrib-
journals, and store the bag in a dark place. ute the “Decomposers Investigation
Bag 4: Sprinkle some garden soil or dirt from Sheet” for student to complete. If using
the school grounds on a couple of table- the investigation sheets, collect these for
spoons of cottage cheese in a plastic bag. Seal students to use in a week.
the contents, describe the appearance of the • Place the bags back in the box or hang
items in your journals, and store the bag in a the bags back on the hooks and leave
dark place. them for another week.
Bag 5: Add a half cup of garden soil to a • Advise students to wash their hands
plastic bag. Add water to make the soil after returning their bags.
moist, but not soggy. Seal the contents,
describe the appearance of the items in your Day 19
journals, and store the bag in a dark place.
Note: The bags can be kept in the dark by stor- F. At the end of week two, redistribute bags
ing them in a box with a lid. The bags can also and magnifying lenses and have students
be stored on a board in which small hooks are make their final observations of the con-
affixed. A hole can be punched in each bag and tents of their bags without opening them.
the bags hung on the hooks. The entire board can • Ask students to draw and describe in
be placed in a dark area or covered with cloth or their journals what they see. Or redis-
butcher paper. tribute the “Decomposers Investigation
Sheet” for student to complete.
D. After students have described the items in • Direct students to carefully return their
the bags, place the bags back in a box or unopened bags to the teacher for proper
hang the bags on the hooks and leave them disposal. If the contents of the bags are
undisturbed for a week. not to be composted, then it would be
prudent to attach a note for the janitor to
read informing him or her that the trash
bags contain student projects of decom-
posing food, which may contain high
concentrations of spores that should not
be inhaled.

G. Tell students that they may not be certain
what decomposers are growing in their
bags, but most likely there will be some of
the following:

• Mold. Mold is a thread-like organism;
some threads will have dark round sacs

4–6 Module, Unit 3: Lesson 2: Scavengers
Composting 463 and Decomposers

that contain spores. Spores make new 1. You will need to model the kinds of ques-
cells. tions to ask that will lead students to guess
• Yeast. Yeast cells are shaped like an egg. the identity of the organism on a student’s
Some have little bumps on them called back. Students should not try to guess the
buds. These buds grow bigger and break name right away by saying, “Am I a red
away to become new yeast cells. worm?” Instead they should ask questions
• Bacteria. Although mold and yeast will that will begin to eliminate some of the
also grow in the cottage cheese, there organisms. For example, “Do I have legs?”
might be small colonies of bacteria that “Am I microscopic in size?”
are yellow, cream-colored, or red that
look shiny and moist. The grayish cob- 2. Using tape or a clothespin, place a card on
web-like look in soil indicates the pres- the back of each student. Have students
ence of actinomycetes, a type of bacteria. ask questions of other students to guess
H. Have students describe in their journals what decomposer or scavenger cards are
what they saw in their bags and compare on their backs.
their findings to what they predicted would
be in the bags. 3. When students have guessed what cards
I. Conduct a discussion on what the students were on their backs, they can return their
observed. cards and get new ones.

Part III, Playing a Game About E. After the game is over, discuss what type of
Scavengers and Decomposers questions were asked most often to find out
Day 6 about what organisms’ cards were on their
backs. Have students verbally share something
A. Use the cards in this lesson and go over each with the class that they learned in this game.
living thing with the class. Then ask students to write in their journals one
fact that they did not know before about one of
B. Provide one card to each student and ask the organisms.
students to find out two facts about their or-
ganisms. For example, what does this organ- DISCUSSION/QUESTIONS
ism eat and where does it live? Ask students
to write the facts on the backs of their cards. A. Ask students:
• Allow students to go to the library or • How do the nutrients get into the soil?
provide books for students to use in their Through the work of scavengers and decompos-
research (see “Resources” at the end of ers. Have students compare their answers
this lesson). to the answers to the same question re-
• If students have access to the internet, corded at the beginning of this lesson.
they can obtain information on the com- • What is the role of scavengers and decom-
puter. posers in nature? They break down or decom-
• If two students have the same organism, pose organic material.
they can work together, but they will • What would happen if there were no
need to research a total of four facts about scavengers or decomposers? We would be
their organism. surrounded by dead animals and plants.
• How do decomposers help plants? They
C. After students have completed their re- decompose organic materials into simpler parts
search, ask them to report the information to that plants can use for growth.
the class.
B. Remind students of the story, The Fall of Fred-
D. Gather all the scavenger and decomposer die the Leaf, that they heard in Lesson 1. Ask
cards and shuffle them. Tell students that students what will happen to Freddie. (Older
they will now play a game. Each student will students can write their responses in their
get a card placed on his or her back. Students journals.) He will be eaten by scavengers and
will need to ask questions from other stu- decomposed by decomposers and will become part of
dents to try to determine what decomposer the soil.
or scavenger cards they have on their backs.
C. Discuss with students:
• Why do metals, plastics, and other hu-
man-made things not decompose? They

CLOSING THE LOOP 464 4–6 Module, Unit 3:
Composting

Submitted by Janet Cohen, sixth-grade teacher, Gold matter. Also, ask students to place back in its
Trail Elementary School, Gold Trail Union School original position any rocks or pieces of wood
District. they overturned while looking for scavengers.
That way the scavengers will still have their
are usually not organic. There are no known shelter. Students can draw or describe in writing
living things that can eat them and break what they saw.
them down. (This topic will be addressed
in Lesson 3.) Day 7
• How could people use scavengers and
decomposers to reduce the amount of B. The following day ask students to share
waste going into landfills? (Older stu- their homework assignments.
dents can write their responses in their
journals.) People can keep organic waste EXTENSIONS
out of the landfills and have scavengers and
decomposers decompose the organic waste by A. Read with students the book, A Log’s Life
composting. by Wendy Pfeffer. Ask students to help you
list the scavengers that lived in the log and
Application what they eat, as described in the book.
Pillbugs eat dead leaves; millipedes eat decaying
A. Ask students to write a song about decom- plants.
position, decomposers, or scavengers, using
B. Read with students the book, The Magic
School Bus Meets the Rot Squad by John May
and Jocelyn Stevenson. Have students write
and draw a similar story about their own
class.

C. Have students participate in a science fair
by doing a project on scavengers or decom-
posers.

D. Organize a decomposer and scavenger ap-
preciation day.

E. Have students compare a red worm to a
night crawler.

Submitted by Janet Cohen, sixth-grade teacher, Gold Resources 4–6 Module
Trail Elementary School, Gold Trail Union School Unit 3
District. Videos

a tune everyone in the class knows, such as Life on the Forest Floor. New York: BFA Educa-
“Three Blind Mice” or “Old McDonald Had tional Media, 1989 (12 minutes).
a Farm.”
For example: The importance of the forest floor and its
inhabitants is explained.
Decomposition Soil and Decomposition. New York: BFA Educa-
tional Media, 1986 (16 minutes).
(Sung to the tune of “Three Blind Mice”) Shows how plant fertilizer is made by nature
De-compo-sition, de-compo-sition, and how it is manufactured by people. Time-
See how things rot, lapse photography shows the decomposition
See how things rot. process of dead leaves changing to fertilizer.
There’s mold, bacteria, and yeast around. Soil and Water: A Living World. Irwindale, Calif.:
They decompose things into the ground. BARR Films, 1984 (16 minutes).
They can create a big soil mound. Shows animals that live in the soil.
De-compo-sition. Worm Bin Creatures Alive Through a Microscope.
Kalamazoo, Mich.: Flowerfield Enterprises, 1998
Homework Assignment: Ask students to look (31 minutes).
for signs of decomposition and of scavengers on
their way to and from school or in their neighbor-
hoods. Caution students not to touch decaying

4–6 Module, Unit 3: Lesson 2: Scavengers
Composting 465 and Decomposers

Through a video microscope, a variety Landry, Sarah B. Urban Wildlife. Peterson First
of decomposers (e.g., various fungi and Guides series. New York: Houghton Mifflin
bacteria) and scavengers (e.g., red worms, Company, 1994.
nematodes, sow bugs, and millipedes) are
shown. Contains a section that describes the king-
doms of life on Earth. Provides information
Slide Set and colored pictures of many invertebrates
that can be found in soil. Also describes
“The Decomposer Food Web.” D.L. Dindal, vertebrates commonly found in an urban
1990. Available from J. G. Press, Inc., 419 State setting.
Ave., Emmaus, PA 18049; (610) 967-4135. Lavies, Bianca. Compost Critters. New York:
Dutton Children’s Books, 1993.
Contains 70 slides and a script on scaven- Colored photographs and text describe
gers and decomposers. organisms that live in compost.
May, John, and Jocelyn Stevenson. The Magic
Books School Bus Meets the Rot Squad: A Book About
Decomposition. New York: Scholastic, Inc., 1995.
Anderson, Lucia. The Smallest Life Around Us: Ms. Frizzle’s class learns about decomposi-
Exploring the Invisible World of Microbes with tion.
Eight Easy at-Home Experiments. Illustrated by Milne, Lorus J., and Margery Milne. A Shovel-
Leigh Grant. New York: Crown Publishers, ful of Earth. Illustrated by Margaret LaFarge.
Inc., 1978. New York: Henry Holt and Company, Inc.,
1987.
Colored illustrations and text (suitable for Describes soil; useful as a reference.
upper elementary school students) describe Mound, Laurence, and Stephen Brooks. Insects.
various types of microbes, such as molds, DK Pockets series. New York: Dorling Kinder-
yeast, and bacteria. sley Publishing, Inc., 1995.
Donahue, Mike. The Grandpa Tree. Boulder, Colored photographs and text describe
Colo.: Roberts Rinehart, 1988. a variety of insects. This book contains
Describes the life cycle of a tree and the ani- chapters on specific habitats and associated
mals that live in and around it. At the end animals.
when grandpa tree falls, the animals make Pfeffer, Wendy. A Log’s Life. Illustrated by
homes in it and the “sawdust mixed with Robin Brickman. New York: Simon & Schuster
dirt becomes food for flowers.” Books for Young Readers, 1997.
Forey, Pamela, and Cecilia Fitzsimons. An Describes the life cycle of a tree and focuses
Instant Guide to Insects. New York: Bonanza on the life that a log supports.
Books, 1987. Pringle, Laurence. The Hidden World. New
Colored illustrations and text describe York: Macmillan, 1977.
insects, including many scavengers. Describes and illustrates some animals that
Henwood, Chris. Earthworms. Keeping Mini- live in soil.
beasts series. London: Franklin Watts, 1988. Silver, Donald M. One Small Square Backyard.
Other titles in the Keeping Minibeasts series Illustrated by Patricia J. Wynne. New York:
include: Ants; Beetles; and Snails and Slugs. W.H. Freeman and Company, 1993.
Jaspersohn, William. How the Forest Grew. Il- Colored illustrations and text describe
lustrated by Chuck Eckart. New York: William plants and animals that can be present in a
Morrow & Company, Inc., 1980. yard, including those found in soil.
Describes the succession from a grassland Viorst, Judith. The Tenth Good Thing About
to a forest. Also describes the process of de- Barney. Illustrated by Erik Blegvad. New York:
composition that occurs on the forest floor. Macmillan Publishing Company, 1987.
Kalman, Bobbie, and Tammy Everts. Bugs and
Other Insects. New York: Crabtree Publishing
Company, 1994.
Provides information on insects, such as
beetles, flies, ants, and termites. Shows the
life cycle of a butterfly.

CLOSING THE LOOP 466 4–6 Module, Unit 3:
Composting

A child’s cat, Barney, dies and his father Magazine Article
asks the child to determine ten good things
about Barney. The tenth good thing is that Johnson, Cecil E. “The Wild World of Com-
Barney will enrich the soil in which plants post,” National Geographic, Vol. 158 (August,
will grow. 1980), 272–84.

Audiocassette Contains photographs of a variety of scav-
engers.
Dirt Made My Lunch, recorded by the Banana
Slug String Band, 1989. Distributed by Music
for Little People.

Includes the song “Decomposition” by
Steve Van Zandt.

4–6 Module
Unit 3

4–6 Module, Unit 3: Lesson 2: Scavengers
Composting 467 and Decomposers

Scavengers and Decomposers Cards�

1. Bacteria 2. Fungus—mushroom

3. Fungus—mold 4. Actinomycetes

CLOSING THE LOOP 468 4–6 Module, Unit 3:
Composting

Scavengers and Decomposers Cards—continued 6. Red worm

5. Termite

7. Night Crawler 8. Fruit fly

4–6 Module
Unit 3

4–6 Module, Unit 3: Lesson 2: Scavengers
Composting 469 and Decomposers

Scavengers and Decomposers Cards—continued 10. Sow bug

9. Millipede

11. Slug 12. Scarab Beetle

CLOSING THE LOOP 470 4–6 Module, Unit 3:
Composting

Scavengers and Decomposers Cards—continued 14. Crow

13. Ant

15. Turkey vulture 16. Gull

4–6 Module
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4–6 Module, Unit 3: Lesson 2: Scavengers
Composting 471 and Decomposers

Student’s Page

Name:

Decomposers Investigation Sheet

A different type of decomposer has been introduced into each of the bags. Each decomposer
has specific characteristics that scientists use to figure out their type. Use the hand lens, and
without opening the plastic bag, observe the contents in each bag. Try to see any difference
in growth patterns among the types of decomposers. Record the date and what you
observed today on the lines below. Use the back of this sheet if you need more room to write.

Bag 1. Date:
Date:
Date:

Bag 2. Date:
Date:
Date:

Bag 3. Date:
Date:
Date:

Bag 4. Date:
Date:
Date:

Bag 5. Date:
Date:
Date:

CLOSING THE LOOP 472 4–6 Module, Unit 3:
Composting

Background Information
For The Teacher

There is no waste in nature; the wastes or dead Some species, called aerobic bacteria, require ox- 4–6 Module
bodies of one form of life become food or nu- ygen to live and others, called anerobic bacteria, Unit 3
trients for other forms of life. When something do not. Bacteria are eaten by protozoa, worms,
dies, decomposers use the dead material as food. snails, arthropods, and other small organisms.
Decomposers include microscopic organisms, Bacteria are abundant in air, water, soil, and in or
such as bacteria and fungi (e.g., yeast, mold, on other organisms. Although some can transmit
mildew). diseases, most act as decomposers and get the
Most decomposers cannot be seen with the nutrients they need by breaking down complex
naked eye, but their colonies can be observed. organic compounds in the tissues of living or
For example, the grayish cobweb-like material in dead organisms. Bacteria break these organic
compost indicates the presence of a type of bac- compounds into simple chemical substances that
teria called actinomycetes (pronounced “ak-tin’- can be recycled into other organisms.
o-my-cee’-tees). Actinomycetes and fungi work Some bacteria multiply by a simple division of
together to decompose the toughest organic ma- cells (each cell divides into two). Some species
terial, such as cellulose and even lignin, which is reproduce by budding (a bud forms on a parent
the main component in paper. cell and then detaches to become a new cell).
Fungi (pronounced “fun-guy”) are not plants Still others reproduce by generating spores,
or animals; they belong to their own kingdom: which grow into new bacteria cells.
Fungi. Fungi means “more than one fungus.” All living things need nutrients to live. Ani-
Fungi cannot produce their own food because mals get nutrients from the plants and/or other
they have no chlorophyll, so they grow on animals they eat. Waste excreted by organisms is
organic materials to survive. Fungi help break high in nutrients. When living things die, their
down organic matter, such as dead leaves and bodies are also high in nutrients. Decomposers
grass, and turn them into rich dark compost. can release these nutrients into the soil where
Molds, mildews, and yeast are fungi. Most fungi they might be held in solution by water. Plant
have a nucleus (genetic materials surrounded root hairs absorb this moisture full of nutrients,
by a membrane) and several other internal parts and the nutrients are transported into the stems
surrounded by membranes. and leaves of the plant. When leaves and other
Threads of mold, a type of fungi, can be seen plant parts fall to the ground, their nutrients
with a magnifying lens. Some threads will have are returned to the soil by decomposers. When
dark round sacs that contain spores. Spores are something organic, like a leaf, decomposes, it is
like seeds. They are often spread by wind or by actually recycled.
an insect to a favorable area, where they will All previously living things decompose. If noth-
open and a new thread will grow. A mold colony ing decomposed, the Earth would be covered
is formed as the threads become longer and with dead animals and plants. In addition, the
branch into more threads. Molds feed on organic soil would not get back the nutrients that plants
wastes and help to break them down. This action need to grow.
releases nutrients contained in the organic waste Decomposition does not happen all at once. It in-
to the soil. volves many steps in which many living things
Yeast is also a type of fungi. They also depend participate. Organic material is consumed,
on other organisms for food. The yeast feeds excreted, and eaten again by different life forms.
on organic matter, causing it to decay or break Scavengers can be seen with the naked eye
down into smaller parts. A yeast cell is shaped and are called macroorganisms. Most of these
like an egg. Some have little bumps on them animals cannot eat fresh organic material, like
called buds. These buds grow bigger and break leaves, until it has been broken down by mi-
away to become a new yeast cell. croorganisms, such as fungi and bacteria. Once
Bacteria are single-celled microscopic organ- the organic matter is softened, scavengers, such
isms. They are placed in a classification kingdom as red worms, night crawlers, sow bugs, milli-
called Monera. They have no distinct nucleus or pedes, slugs, mites, and various types of insects,
other internal parts surrounded by membranes.

4–6 Module, Unit 3: Lesson 2: Scavengers
Composting 473 and Decomposers

such as beetles, termites, and ants, break down The type of soil, moisture content of the soil,
the substances into smaller parts. Then decom- temperature, and kinds of organisms present
posers eat these smaller parts and break them all contribute to the rate of decomposition in
down further into simpler components, like soil. Ideal conditions for aerobic (oxygen-requir-
nutrient compounds (protein, vitamins, miner- ing) bacteria, fungi, and other microorganisms
als, and carbohydrates). These simpler materials, include the presence of water and air. Most
which are essential for life, can now be absorbed decomposers live in the soil or leaf litter. How-
from the soil by plants. Note that only decom- ever, some molds travel through the air and can
posers actually decompose organic material into decompose fruit and other organic matter that
simpler components. are not in or on top of soil.
There are larger animals that play the role of Sunlight, water, and air can also break down
scavengers by eating waste that has begun to both organic and inorganic substances. This
decay. These scavengers include crows, turkey lesson focuses on living things (scavengers and
vultures, magpies, gulls, and coyotes. They can decomposers) that break down organic matter.
be called “nature’s clean-up crew.”

CLOSING THE LOOP 474 4–6 Module, Unit 3:
Composting