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hhmi Biolnteractive
Some Animals Are More Equal than Others: Trophic Cascades and Keystone Species
Mean Leaf Area per Plant Over 18 Months
without beetle
with beetle
Leaf Area per Plant (cm²)
Control
Ecology
2400
2200
2000
1800
1600
1400
1200
1000
800
Experimental
0
T
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8 10 12
14 16
Months After Start of Experiment
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Refer to the figure to answer questions 12 through 17.
12. For both the plots with the beetles added and the control plots, state the mean
tree leaf area per plot that the scientists recorded after running the experiment for 18 months.
The mean tree leaf area per plot that the Scientist
recorded after running the experiment for 18 months wit
the beetles added is 1.7m², S 2.2m²
13. Compare the trends in mean tree leaf area per plot for both the plots with the beetles added and the
control plots over the 18 months of the experiment.
The area of the control plat for thinoceros beetles has d
has increased at a nearly constant rate, the other is a gradua
decrease at first, then a sudden decrease, and finally a dradua
18
Figure 2. Mean leaf area per
tree. Initial measurements
were taken before (0 to 2
months) and after (7 to 18
months) beetles were added
to 40 of 80 plants. The light
gray round markers represent
measurements taken of the
control plots, to which beetles
were not added. The black
square markers represent
measurements taken of the
experimental plots, to which
beetles were added.
Measurements were made on
all leaves to calculate the
mean leaf area per plant. Error
bars represent standard error
of the mean.
14. Draw two diagrams that show the food chains for both the experimental and control plots. Include increase.
interactions among predatory beetles (if present), ants, caterpillars, and piper plants.
Revised January 2018
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