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Difficulty: Very hardRhetorical Synthesis: Supporting Claims

While preparing a presentation on the diet of the extinct Madagascar lemur *Megaladapis*, a student takes the following notes:
* *Megaladapis* was a genus of giant lemurs that went extinct approximately 500500 years ago.
* Some researchers hypothesized that as Madagascar’s climate became drier, *Megaladapis* adapted to feeding on plants in open grasslands.
* Plants using C3C_3 photosynthesis (dominant in closed canopy forests) have low stable carbon isotope ratios (δ13C\delta^{13}\text{C}), while plants using C4C_4 photosynthesis (dominant in open grasslands) have high δ13C\delta^{13}\text{C} ratios.
* Paleontologist Dr. Karen Samonds measured the δ13C\delta^{13}\text{C} levels in fossilized *Megaladapis* tooth enamel.
* The analysis revealed that *Megaladapis* enamel had consistently low δ13C\delta^{13}\text{C} levels, matching those of modern leaf-eating lemurs that live in closed canopy forests.

The student wants to support the claim that *Megaladapis* fed on canopy forest plants rather than adapting to grassland vegetation. Which choice most effectively uses information from the notes to support this claim?

  1. A
    Although some researchers hypothesized that *Megaladapis* adapted to drier climates by feeding on grassland plants, Dr. Karen Samonds analyzed fossilized tooth enamel to study the extinct lemurs' dietary habits.
  2. B
    Because modern leaf-eating lemurs in closed canopy forests have low δ13C\delta^{13}\text{C} levels, *Megaladapis* likely avoided grasslands to prevent competition with other species that consumed high-δ13C\delta^{13}\text{C} plants.
  3. Dr. Karen Samonds's analysis of fossilized *Megaladapis* tooth enamel showed consistently low δ13C\delta^{13}\text{C} levels, which match those of modern canopy-dwelling lemurs and suggest that *Megaladapis* fed on canopy forest plants rather than grasslands.Answer
  4. D
    Dr. Karen Samonds found that fossilized *Megaladapis* tooth enamel had high δ13C\delta^{13}\text{C} levels, which are characteristic of canopy-dwelling plants that utilize C3C_3 photosynthesis.

Answer

Dr. Karen Samonds's analysis of fossilized *Megaladapis* tooth enamel showed consistently low δ13C\delta^{13}\text{C} levels, which match those of modern canopy-dwelling lemurs and suggest that *Megaladapis* fed on canopy forest plants rather than grasslands.
The correct option effectively uses the data from the notes by stating that the consistently low carbon isotope levels in the tooth enamel of Megaladapis match those of modern canopy-dwelling lemurs, which directly supports the claim that the extinct lemurs fed on canopy forest plants rather than adapting to grasslands.

Step-by-Step Solution

1
Identify the target claim to be supported.
The claim is that Megaladapis fed on canopy forest plants rather than adapting to grassland vegetation.
This defines the specific rhetorical goal the correct option must accomplish.
2
Examine the scientific notes regarding carbon isotope ratios and vegetation types.
Plants in closed canopy forests (C3C_3) have low δ13C\delta^{13}\text{C} ratios, while plants in open grasslands (C4C_4) have high δ13C\delta^{13}\text{C} ratios.
Establishing this relationship is necessary to connect the chemical signatures in the fossils to their dietary habitats.
3
Analyze the findings from the tooth enamel study.
Megaladapis tooth enamel showed consistently low δ13C\delta^{13}\text{C} levels, matching those of modern leaf-eating lemurs in closed canopy forests.
This links the fossil evidence to the canopy forest signature.
4
Evaluate the options to find the one that directly supports the claim using only the provided facts.
The option mentioning that the consistently low stable carbon isotope levels in Megaladapis tooth enamel match modern canopy-dwelling lemurs directly supports the claim that they fed on canopy forest plants rather than grasslands.
This choice satisfies the prompt's rhetorical goal using only the stated facts from the notes.

Key Concept

Rhetorical Synthesis: Supporting Claims
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Rhetorical Synthesis: Supporting Claims

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