LESSON 5: Decomposers in Different Environments -- Scientific Method
GRADE: 2
LEARNING TARGET: Compare the growth of decomposers in different
environments.
•
•
GLE: 2.2.3 Understand that similar investigations may not produce similar results.
o Observe the procedure of two similar investigations and explain that they
produced different results.
GLE: 2.2.5 Know that ideas in science change as new scientific evidence arises.
o Tell how scientific inquiry results in facts, unexpected findings, ideas, evidence,
and explanations.
LESSON OBJECTIVES:
• Groups of students will conduct mini-experiments to compare the growth of some
decomposers.
• Groups of students will practice the scientific method.
PROCESS SKILLS:
ACTIVITY TYPE
X Science
X Required
Human
Endeavor
Content
Integration
Inquiry Lesson
Optional
Individual or Extended
Reading Connection
X Cooperative Group Project
Writing Prompt
Research Project
Hands-on Science Activity
Culminating Project
Computer Lab Activity
KIT MATERIALS
•
•
•
30 Hand Lenses
• 1 Spray bottle
30 Self-closing bags
• 1 Teacher knife
Journal Pages: What
• 1 spoon
Rot! (4)
• 6 cotton balls
*The following items need to be ordered at 8479. Allow
2-3 days for delivery please:
• 2 Slices of bread
• 1 Banana
• 1 Citrus (lemon or orange)
• 2 packages of Yeast
NON-KIT MATERIALS
Refrigerator or other cool, dark
place
LESSON 5: Decomposers in Different Environments -- Scientific Method
VOCABULARY:
GRADE: 2
bacteria – one celled organism which can be seen only with a microscope;
some types of bacterium cause decay, others cause disease.
fungi – a large group of non-green plants that produce by spores
decomposer – an organism that breaks down cells of dead plants and animals into simpler
substances
mold – a downy or furry growth on the surface of organic matter
TEACHER BACKGROUND:
Fungi and bacteria are essential to the decay of plant material. Fungi (including molds) and
bacteria are decomposers working at the microscopic level to help plants break down into their
basic elements.
Moisture and darkness encourage rapid growth of fungi and some bacteria. Both of these
factors help fungi and bacteria thrive.
Set up your observations on a Friday and view the following M-F. This will give a couple
of days for things to start growing.
Preparation:
• Three days in advance order fresh items from 8479.
• One day in advance of the lesson, cut the citrus into quarters and rub each of them on the
floor to pick up bacteria. Let the quarters sit out overnight.
• Arrange to have a cool dark place to store several filled self-closing bags for one week.
A refrigerator is a good place.
• Locate a warm dark place to store several filled self-closing bags for one week. A
closet or covered box near a working heater is a good place.
• Put water in the spray bottle.
•
If you have less than 30 students in your class, invite another class to participate in a
cooperative science project. This will give you the multiple tests necessary to validate a
scientific experiment. Even numbers in the groups are easiest to cope with.
LESSON 5: Decomposers in Different Environments -- Scientific Method GRADE: 2
PROCEDURE
HELPFUL HINTS
1. Ask the class how they think plants decompose and
what factors effect decomposition.
2. Do things just decompose by themselves or do they
have help doing it? Discuss various ideas.
3. What conditions do they think are the best to help
decomposers grow? Accept various ideas.
2. Actually, no. Without various
decomposers, (many of which
we cannot see without a
microscope) things would
NOT decompose!
4. Explain they are going to test which environmental
conditions decomposers like mold, fungi and bacteria
will grow in the best.
4. Fungi, molds and bacteria are
not the only decomposers!
5. Divide the class into 5 groups. Even numbers are best.
To each student in the group give a self-closing bag.
5. Try to have 6 students per
group; four is an absolute minimum. If your class is too small
invite another 2nd grade class to
participate to get the multiple
tests required for the scientific
method.
6. On a piece of masking tape, instruct each student to
write the group number and their name and place the
tape on the bag.
7. Inform the class that each group will be conducting a
mini-experiment. Each group will write its own
question to answer with an experiment. All of us
together are exploring which conditions a decomposer
(mold, fungi and bacteria) will grow in the best.
8. Into the bag
o Group 1 will place a half slice of bread
o Group 2 will place a half slice of bread sprayed
with two squirts of water from the spray bottle.
o Group 3 will place a one-inch slice of banana
and ½ spoonful of yeast.
o Group 4 will place a quarter of citrus in the bag.
o Group 5 will place a quarter of citrus in the bag
along with a cotton ball moistened with water.
9. Instruct the groups to zip the bags shut. Leave air in
the bags.
8.
o Inform group 4 and 5 that
yesterday you rubbed their
citrus quarters on the floor
to pick up bacteria.
LESSON 5: Decomposers in Different Environments -- Scientific Method
PROCEDURE
10. Take a few minutes to discuss the concept of variables
with the class. A variable is something that can be
changed in an experiment. Science rules say that we
can only change one variable at a time.
11. Place half of the bags from group 1,2,3,4, and 5 in a
cool dark place.
GRADE: 2
HELPFUL HINTS
10. This lesson is really several
small experiments combined.
Don’t let students get
confused! The only variable
that we are changing is
temperature.
12. Place the other half of the bags from group 1,2,3,4, and
5 in a warm dark place.
13. Help students to write the question they are trying to
find the answer to:
o Group 1 will ask the question: Will bread mold
grow best in warm/dry or cool/dry conditions?
o Group 2 will ask the question: Will bread mold
grow best in warm/wet or cool/wet conditions?
o Group 3 will ask the question: Will fungi
(yeast) on a banana grow best in cool or warm
conditions?
o Group 4 will ask the question: Will bacteria on
citrus grow best in warm/dry or cool/dry
conditions?
o Group 5 will ask the question: Will bacteria
grow best in warm/wet, or cool/wet conditions?
14. Have students hypothesize what will happen and record
in the space provided on the Journal Page: What Rot!
15. Speculate as a class. What will the yeast do? What
affect will temperature have? Is moisture important?
16. Everyday during the week have students observe their
group’s bags and carefully record their observations on
the Journal Page: What Rot!
16. Have a hand lens available.
Keep the bags closed.
17. After one week the bread and banana should be well on
their way to decomposing. Allow the students to
observe the structures of mold and the decomposition
of the bananas.
17. The citrus may take a week or
longer to turn into bluish-green
fuzz balls. If so, continue the
experiment an extra week.
18. Invite students to draw what they see on the Journal
Page: What Rot!
LESSON 5: Decomposers in Different Environments -- Scientific Method GRADE: 2
PROCEDURE
HELPFUL HINTS
19. Instruct students to write a conclusion about their
experiment.
20. As a class discuss what has happened in each bag. Did
all of the bread, banana, citrus decompose at the same
rate? Why or why not? What role did the yeast play?
What role did temperature play? What role did
moisture play?
21. Were their any surprises? Remind the students that
even though an experiment may produce an unexpected
result, scientists should report things as they actually
happened. No erasing!
21. Unexpected results from
experiments have resulted in
very exciting information like
the discovery of penicillin!
22. Guide students to come to some conclusions about
which conditions affect the rate of growth of bread
mold, fungus on bananas and bacteria on citrus fruit.
23. Does it appear that decomposers mostly like it warm,
moist and dark?
23. Low and behold, those are the
conditions of your worm bin!
Molds, fungi, bacteria, and
worms are all type of
decomposers.
24. Decide as a class if you need to repeat this experiment
in light conditions instead of in the dark to verify your
assumption.
24. Call 8479 for more supplies if
you choose to do this again!
25. Toss the still closed bags into the trash.
25. Bread mold produces an
antibiotic that is not friendly to
worms. Too much citrus in a
worm bin also can make worms
sick. Bananas and yeast are OK in
the bin.
26. Have students wash up.