CERR Student Exemplar: Ecological Relationships
Figure 1
Food web from http://king.portlandschools.org/
The food web depicted above was recorded on Haiku Island 50 years ago. About 45 years ago, a
biotechnology company was testing a product they hoped would act as a fertilizer. Unfortunately, the
product decimated the primary producers and rendered the soil untillable for several years. What is the
fate of the predators on this island? Respond to the prompt using the Claim, Evidence, Reasoning, Rebuttal
(CERR) framework for constructing a scientific explanation. Develop a claim as to the fate of the predators.
Support your claim with evidence and explain how the evidence supports your response. Rebut alternative
explanations. See “What to include in your argument” for further information.
What to include in your argument:
Write an argument in order to persuade another biologist that your claim is valid and acceptable. As you
write your argument, remember to do the following:
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•
•
•
•
•
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State the claim you are trying to support
Include genuine evidence (data + analysis + interpretation)
Provide a justification of your evidence that explains why the evidence is relevant and why it
provides adequate support for the claim
Include a rebuttal that provides counter evidence and reasoning for why the alternative
explanation(s) is not the appropriate explanation for the question or problem.
Organize your argument in a way that enhances readability
Use a broad range of words including vocabulary that we have learned
Correct grammar, punctuation, and spelling errors
CERR Student Exemplar: Ecological Relationships
Question: What is the fate of the predators on this island?
The fate of the food web mirrored the fate of the primary producers, or plants, that form the base
of the food web. Therefore, the fate of most of the predators on the island was extinction. The primary
consumers (rabbits, squirrels, etc.) feed on the plants (see Figure 1). Because these animals will have
nothing to eat, they will die out first. Figure 1 shows that as the number of primary producers begin to
shrink, the predators will have less and less food. The reduction in food will lead to starvation and
ultimately extinction of the fox and snake population. Unlike the fox and snake, the birds of prey may be
able to fly to other islands. If any birds were able to reach other destinations, they may have survived and
succeeded in other ecosystems. An alternative claim might be that the predators are unaffected because
they do not feed upon the plants, however, this fails to account for the fact that predators eat animals that
eat plants and with no food source, the entire web will collapse.
Key to paragraph deconstruction bellow:




Claim
Evidence
Reasoning
Rebuttal
The fate of the food web mirrored the fate of the primary producers, or plants, that form the base
of the food web. Therefore, the fate of most of the predators on the island was extinction. The primary
consumers (rabbits, squirrels, etc.) feed on the plants (see Figure 1). Because these animals will have
nothing to eat, they will die out first. Figure 1 shows that as the number of primary producers begin to
shrink, the predators will have less and less food. The reduction in food will lead to starvation and
ultimately extinction of the fox and snake population. Unlike the fox and snake, the birds of prey may be
able to fly to other islands. If any birds were able to reach other destinations, they may have survived and
succeeded in other ecosystems. An alternative claim might be that the predators are unaffected because
they do not feed upon the plants, however, this fails to account for the fact that predators eat animals that
eat plants and with no food source, the entire web will collapse.
RUBRIC FOR GENERATING AN ARGUMENT
Point Value
Aspect of the Argument
0
1
Comments or Suggestions
The claim
The claim is sufficient
The claim is accurate
The evidence
Includes data
The data is sufficient to support the claim
The justification of the evidence
Explains why the evidence is important or why it is relevant
Links the evidence to an important concept or principle
Rebuttal - The challenge (May be optional, ask your teacher)
The alternative explanation(s) being challenged is (are) explicit
Explains why the alternative explanation is inaccurate
Language of science
Appropriate use of scientific terms
Used phrases that are consistent with the nature of science
Mechanics
The order and arrangement of the sentences enhances the
development of the main idea (organization)
The author used complete sentences, proper subjectverb agreement, and kept the tense constant (grammar)
The author used appropriate spelling, punctuation,
and capitalization (conventions)
Total score
/11 or /13
Adapted from Scientific Argumentation in Biology, Copyright © 2013 NSTA. All rights reserved.
Graphic Organizer for Generating an Argument
The Research Question: What is the fate of the predators on this island? Respond to the
prompt using the Claim, Evidence, Reasoning, Rebuttal (CERR) framework for constructing a scientific
explanation. Develop a claim as to the fate of the predators. Support your claim with evidence and
explain how the evidence supports your response. Rebut alternative explanations.
Your Claim: The fox and the snake went extinct on the island, while the birds of prey likely migrated
to other islands or the mainland.
Your Evidence:
Your Justification
of the Evidence:
1. Primary producers or autotrophs form the base
of the food web on this island because they
make food from sunlight, CO2 and water.
2. The primary consumers (rabbits, squirrels, mice,
seed-eating birds, herbivorous insects) feed
exclusively on plants and vegetation
3. The snake and the fox feed exclusive on other
animals and are landlocked
4. Birds of prey feed on other animals but they are
mobile and some can fly long distances
1. Primary producers produce, or plants, the food
that primary consumers feed upon
2. Rabbits, squirrels, mice, seed-eating birds,
herbivorous insects will die out first because
their only food source is plants.
3. As the number of herbivores quickly decline,
food will become scarcer for the predators,
especially the snake and fox, and they will go
extinct with nothing to eat.
4. The birds may survive if they are able to migrate
to another island or the mainland if they are
close enough.
Rebuttal:
An alternative hypothesis or claim is that the predators are unaffected because they do not feed on
primary producers. This claim fails to account for the fact that if the primary consumers have nothing to
eat, they will all starve and because there are no animals to eat, the predators will starve too.
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