Biology COE Task Version
September 2014
The Moths and the Trees
The Forest Ecosystem diagram shows part of a forest ecosystem. Tussock moths are
native to the forest ecosystem. In the fall, tussock moths lay eggs on Douglas fir trees.
In the spring, tussock moth larvae eat the needles of the Douglas fir trees.
Moths and Trees COE Task Example
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Biology COE Task Version
September 2014
1. Students used a greenhouse with Douglas fir trees as a model of a forest ecosystem to
predict the effects of tussock moths on a forest ecosystem.
a) Describe two ways the greenhouse model might be unable to reliably predict the
effects of tussock moths on the forest ecosystem.
In your description, be sure to:
• Identify two differences between the model and the forest ecosystem, other than
temperatures.
• Describe how each difference can prevent scientists from making accurate
predictions about the effects of tussock moths on forest ecosystems.
One difference:
Another difference:
Moths and Trees COE Task Example
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Biology COE Task Version
September 2014
Task Title: The Moths and the Trees
Item number: 4 Cognitive Complexity: 2 (page 1 of 2)
Performance Description
A 4-point response demonstrates the student understands:
Content Standard SYSA: Feedback is a process in which the output of a system provides information
used to regulate the operation of the system. Positive feedback increases the disturbance to a system.
Negative feedback reduces the disturbance to a system.
Item Specification 2: Determine whether a given system involves positive feedback or negative
feedback.
AND
Content Standard SYSC: In complex systems, entirely new and unpredictable properties may emerge.
Consequently, modeling a complex system in sufficient detail to make reliable predictions may not be
possible.
Item Specification 1 and 2: 1. Given a model of a complex system that is lacking sufficient detail to
make reliable predictions about that system, describe inadequacies of the model. 2. Predict the possible
consequences of a change in a given complex system and/or describe why a simplified model may not
be able to reliably predict those consequences.
Item and example response
SYSC(1)
a) The response describes two ways the greenhouse model might be unable to reliably
predict the effects of tussock moths on the forest ecosystem by:
• Identifying two differences between the model and the forest ecosystem other than
temperatures AND
• Describing how each difference can prevent scientists from making accurate
predictions about the effects of tussock moths on forest ecosystems
Examples:
Identify differences:
There are many more types of trees in
the forest than in the greenhouse
Humidity/rainfall/acid rain/forest
fires is much more varied in the
forest
Prevents accurate predictions:
Scientists won’t know the variety of different trees
that tussock moths can eat and damage
Populations of moths fluctuate more in the forest, so
moths can eat more or less needles at different times.
Points
2
• Scientists can’t predict how populations of moth
Many more interactions between
competitors are affected by moth populations.
animals/other organisms in the forest • The moth population in the forest will grow more
slowly with predators and more trees will survive.
• Moths in the forest can move in and out. More tree
damage than what really happens will be shown in
the greenhouse.
Moths can’t escape the greenhouse.
• The moths in the forest have a greater genetic
variation, increasing the biodiversity of the forest.
Note: Responses identifying only one difference between the model and the forest ecosystem
other than temperatures and describing how that difference can prevent scientists from
making accurate predictions about the effects of tussock moths on forest ecosystems may be
credited one point.
Moths and Trees COE Task Example
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document. All other individuals wishing to reproduce this document must contact OSPI.
Biology COE Task Version
September 2014
Student Responses
Response A-2 points
One difference:
The weather in a greenhouse is stable, there is no snow in a greenhouse.
Weather conditions, such as snow, can kill larvae on tree branches and
affect populations growth.
Another difference:
Other animals such as birds or grogs are not in a greehouse. The
absense of preditors can increase the population of moths and make
observations unreliable.
Response B-1 point
One difference:
Inside a green house the moths will not have any preditors like they do in a
forest ecosystem Without preditors, less moths will die, changing
the results.
Another difference:
In a green house students will only be changing the temp. There is rain
in the forest which also effects the moth population so the greenhouse
will not have all of the limiting factors that effect the moths population
in forest ecosystem
Moths and Trees COE Task Example
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document. All other individuals wishing to reproduce this document must contact OSPI.
Biology COE Task Version
September 2014
Response C-0 points
One difference:
The data is unreliable because you can’t grow the trees in the
greenhouse so its harder to produce eggs
Another difference:
The needles of the larvae will get dry and then the bugs wont eat them
which if they don’t eat they will die and the population of the bugs will go down
and wont be as many
Response D
One difference:
The greenhouse can limit the amount of trees the moths can find and use,
resulting in fewer larvae and fewer trees eaten.
Another difference:
The greenhouse prevents birds that eat moths from coming in changing the
amount of moths that stay alive throughout the year to use the trees.
Response E
One difference:
In a greenhouse, there are many less animals and plants contributing to the
ecosystem. With less animals, they won’t be able to get a very accurate
prediction.
Another difference:
The atmosphere is different in a greenhouse. There is a different moisture level
and moth’s may not be able to produce as many moths.
Moths and Trees COE Task Example
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Biology COE Task Version
September 2014
Response F
One difference:
In a greenhouse the temperature is always greater then outside so that’s one
way the students could get unreliable information.
Another difference:
Another way is in a greenhouse there is protection so the moth’s have a less
likely chance to be ruined because in the forrest no one is monitoring.
Response G
One difference:
A forest ecosystem has more organisms than a greenhouse. More organisms could
mean more danger to the moths. In a normal ecosystem there are things that eat
moths or accidentally crush them. A greenhouse could not account for these
fatalities and will show more moths eating trees than there really are.
Another difference:
A greenhouse is fairly still, sterile air. An ecosystem has wind, rain, and other
weather patterns that could hinder the moths growth and flight abilities.
Moths and Trees COE Task Example
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document. All other individuals wishing to reproduce this document must contact OSPI.
Biology COE Task Version
September 2014
Response H
One difference:
Moths can’t get out of the greenhouse, even when they get overpopulated. All the
needles on the green house trees will get eaten by huge numbers of larvae more
than a real forest.
Another difference:
A forest has more than just Douglas Fir Trees. Maybe moths will lay their eggs
on other kinds of trees in a real forest ecosystem. You won’t know what other
kinds of trees moths eat if you can only study the kind in the greenhouse.
Response I
One difference:
There is no wind in a greenhouse.
Another difference:
There are other kinds of moths in a forest
Moths and Trees COE Task Example
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document. All other individuals wishing to reproduce this document must contact OSPI.