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Botanist: Mycorrhizal fungi networks (MFNs) connect the root systems of various plants in a forest environment. In a recent five-year study of a mature Douglas fir forest, isotopic carbon tracing revealed that significant amounts of carbon moved continuously from mature, canopy-dominant Douglas firs to nearby shaded Douglas fir seedlings via these MFNs. Furthermore, the seedlings connected to the MFN exhibited a 30 percent higher survival rate than similarly shaded seedlings that were isolated from the fungal network. Therefore, it is clear that mature trees actively allocate resources through MFNs specifically to ensure the survival of their own species' offspring in light-limited environments.

Which of the following statements, if true, most strongly weaken the botanist's argument? (Select all that apply)

  1. Studies on mixed-species forests indicate that carbon transferred through MFNs flows from canopy-dominant trees to nearby shaded seedlings of entirely different plant species at the same volume and rate.Cevap
  2. B
    When researchers experimentally severed the MFN connections between mature Douglas firs and their seedlings, the mature trees demonstrably altered their root exudation patterns to compensate for the lost pathway.
  3. The fungi comprising the network actively extract carbon from mature trees to fuel their own subterranean expansion, with seedlings merely passively absorbing excess carbon that the fungi excrete into the surrounding soil.Cevap
  4. D
    Advances in soil analysis have shown that isotopic tracing can sometimes miscalculate the precise origin point of carbon if the surrounding soil contains exceptionally high levels of decaying organic matter.
  5. E
    Douglas fir seedlings cultivated in controlled laboratory settings without any fungal networks demonstrate significantly faster vertical growth than seedlings grown in natural, mature forests.

Cevap

The correct statements are the one indicating carbon flows to different species at the same rate, and the one indicating fungi actively extract the carbon while seedlings passively absorb it.
The conclusion makes two distinct causal claims based on the observed correlation: that the mature trees 'actively allocate' the resources, and that they do this 'specifically to ensure the survival of their own species'. The correct answers introduce new evidence that dismantles both claims. The statement about mixed-species forests shows that the transfer is indiscriminate, destroying the 'own species' motive. The statement about fungal extraction shows that the fungi, not the trees, are driving the mechanism, destroying the 'actively allocate' claim.

Adım Adım Çözüm

1
Analyze the structure of the argument.
Premises: Carbon moves from mature trees to shaded seedlings via MFNs. Connected seedlings survive 30% more. Conclusion: Mature trees actively allocate resources specifically to ensure their own species' survival.
Deconstructing the argument into premises and conclusion is necessary to identify the logical gap.
2
Identify the logical gaps and assumptions.
The author assumes that the transfer of carbon implies 'active allocation' by the tree (rather than passive diffusion or fungal action) and assumes the intent is 'specifically to ensure the survival of their own species'.
Finding assumptions reveals the vulnerabilities where the argument can be weakened.
3
Evaluate the options for statements that attack these specific assumptions.
One correct choice attacks the 'own species' assumption by showing cross-species transfer. The other correct choice attacks the 'active allocation' assumption by showing the fungi are the active agents.
Correct weaken answers often introduce new information that severs the causal link assumed by the author.

Anahtar Kavram

Identifying alternative explanations and severing assumed causal relationships in a correlation.
Tahmini Süre:2m 30s
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