Name ________________________________________ per. ______ date ______________
Forest Food Webs (pp. 67-80)
Big Idea: Everything in nature is connected. You can’t change one part of an ecosystem without it having
some effect – large or small – on every other part.
1.
Suppose there was a decrease in the chipmunk population of the forest ecosystem shown below.
Describe an effect this would have on another population of animals shown in the food web. In your
description, be sure to

Identify a population from the food web diagram.

Describe an effect of decreased numbers of chipmunks on the identified population.
2.
What do you think would happen to the population of green plants eaten by chipmunks if all the
coyotes died or disappeared? Explain your answer.
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3.
Unintended consequences are bad things that happen because of something we did, even though we
didn’t expect or want those things to happen.
Invasive species are animals or plants from elsewhere that tend to outcompete and kill off native
species of animals or plants.
Suppose people who kept snakes from outside Washington state as pets released them into the forest
here because they didn’t want to take care of them anymore. Describe two unintended consequences
that could happen as a result.
4.
The Department of Wildlife is considering the possibility of re-introducing grizzly bears into the
North Cascades forest ecosystem.
a. Describe two factors the Department of Wildlife officials should consider about the forests
of the North Cascades before putting grizzly bears there.
b.
Ranchers in eastern Washington do NOT want the grizzly bears to be re-introduced because
the bears have been known to kill cattle. What scientific information would be needed to
solve the problem of how to protect the cattle without hurting the bears? How could that
information be gathered?
c.
Describe three possible solutions to the problem, including any useful scientific concepts.
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d.
5.
A criterion is something that is used to measure the success of a proposed solution to a
problem. Aside from the number of cattle killed by grizzly bears, what would be two other
criteria biologists could use to evaluate possible solutions to the above problem?
Nitrogen, a chemical element in our atmosphere, is needed by plants and animals to build cells and
tissues. Using the Nitrogen Cycle diagram shown below, explain how nitrogen moves from the body of
a cow out into the surrounding ecosystem. How is that nitrogen transferred to plants?
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6.
Using the Predator-Prey Populations graph shown below, explain how the population of prey affects
the population of predators and vice versa.
7.
Positive feedback loops are when increasing or decreasing one thing causes a continual increase or
decrease in another thing. Negative feedback loops are where increasing one thing causes an
alternating increase and decrease of the other thing. Is the predator-prey relationship shown above a
positive or negative feedback loop? Explain your answer.
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