Decomposers are organisms that break down dead plant and animal matter into simpler
compounds. You can think of decomposers as the clean-up crew in an ecosystem. In forest communities,
consumers such as deer and insects eat a tiny fraction of the leaves on trees and shrubs. The leaves that
are left on the forest floor, as well as dead roots and branches, are eventually digested by fungi and
bacteria living in the soil. A pinch of soil may contain a half million fungi and billions of bacteria.
Kelly placed an orange peel in five beakers. Then he filled the beakers with dry soil. Finally, he
added different amounts of water to the beakers (see table 1). He measured the remaining orange peel
every day for a total of 28 days (see graph 1).
Beaker number
1
2
3
4
5
Table 1
Amount of water added
0 milliliters
25 milliliters
50 milliliters
75 milliliters
100 milliliters
Orange Peel Decomposition
100
90
Remaining orange peel, in percent
80
beaker 1
beaker 2
70
beaker 3
60
beaker 4
50
beaker 5
40
30
20
10
0
day 0
day 7
day 14
Days
Graph 1
day 21
day 28
1. Which beaker was the control group?
a. beaker 1
b. beaker 2
c. beaker 3
d. beaker 4
e. beaker 5
2. Which orange peel decomposed the most after 28 days?
a. The orange peel in beaker 1.
b. The orange peel in beaker 2.
c. The orange peel in beaker 3.
d. The orange peel in beaker 4.
e. The orange peel in beaker 5.
3. How much of the orange peel remained in beaker 3 after 14 days?
a. about 30%
b. about 35%
c. about 40%
d. about 45%
4. What is the independent variable in Kelly’s science experiment?
a. The amount of water he added to each beaker.
b. The amount of orange peel remaining in each beaker.
c. The number of fungi and bacteria in each beaker.
d. The amount of soil he added to each beaker.
5. About how many days did it take the orange peel in beaker 5 to decompose to 50% remaining?
a. about 5 days
b. about 12 days
c. about 16 days
d. about 25 days
6. What should Kelly do to improve his experimental design?
a. Make sure all of the beakers are kept at the same temperature during the experiment.
b. Put lids on beaker 1 and beaker 2, but keep beaker 3, beaker 4, and beaker 5 open to the air.
c. Add some water to beaker 1.
d. Put beaker 1 and beaker 2 in a dark room, but keep beaker 3, beaker 4, and beaker 5 in a well lit room
during the experiment.
7. Which organism is a decomposer?
a. deer
b. orange
c. trees
d. bacteria
8. After 28 days, which 2 beakers showed the most similar amounts of orange peel remaining?
a. beaker 1 and beaker 5
b. beaker 2 and beaker 5
c. beaker 2 and beaker 3
d. beaker 3 and beaker 4
9. Suppose Kelly filled beaker 6 with an orange peel, soil, and 125 milliliters of water. How much
remaining orange peel would you expect to find after 21 days?
a. about 5% remaining
b. about 20% remaining
c. about 30% remaining
d. about 60% remaining
Rainfall in inches
Amounts of rainfall in different biomes
200
180
160
140
120
100
80
60
40
20
0
grassland
desert
deciduous forest
tropical rainforest
Biome
Graph 2
10. In which biome would an orange peel decompose the most slowly?
a. Tropical rainforest, because it is the wettest biome.
b. Desert, because it is the driest biome.
c. Deciduous forest, because it is the second wettest biome.
d. Grassland, because it is the second driest biome.