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Zorluk: ZorComparing and Contrasting Models

### Models of the Ediacaran Extinction

The Ediacaran biota were a group of multicellular, soft-bodied organisms that dominated Earth's oceans during the late Ediacaran period (roughly 635 to 541635\text{ to } 541 million years ago) and then abruptly disappeared. Scientists have proposed two models to explain their extinction.

Model 1 (Biotic Replacement Model)
This model proposes that the extinction of the Ediacaran biota was driven by the rapid evolution and diversification of early Cambrian metazoans (true animals). These new animals acted as "ecosystem engineers" that disrupted the benthic environments. Specifically, the evolution of motile burrowing organisms (bioturbators) destroyed the microbial mats on the seafloor that Ediacaran organisms depended on for food and stabilization. Additionally, the emergence of mobile predators and competitors actively outcompeted or preyed upon the immobile Ediacaran organisms, driving them to extinction.

Model 2 (Environmental Catastrophe Model)
This model proposes that the extinction of the Ediacaran biota was caused by a sudden, global environmental crisis, specifically a major ocean anoxia event (severe oxygen depletion in deep marine waters). The Ediacaran biota lacked specialized respiratory organs and relied on passive diffusion across their body surfaces, making them highly vulnerable to low oxygen levels. Under this model, the extinction of the Ediacarans occurred first due to these geochemical changes. The subsequent diversification and rise of Cambrian metazoans did not cause the extinction, but rather occurred because the demise of the Ediacarans freed up ecological niches and resources.

Based on the models, which of the following statements best describes how Model 1 and Model 2 differ regarding the relationship between the diversification of Cambrian metazoans and the extinction of the Ediacaran biota?

  1. Model 1 asserts that Cambrian metazoan diversification was the direct cause of the Ediacaran extinction, while Model 2 asserts that the extinction occurred first and created ecological opportunities that allowed Cambrian metazoans to diversify.Cevap
  2. B
    Model 1 asserts that the Ediacaran extinction occurred first and allowed Cambrian metazoans to diversify, while Model 2 asserts that Cambrian metazoan diversification was the direct cause of the Ediacaran extinction.
  3. C
    Model 1 asserts that ocean anoxia caused the extinction of the Ediacaran biota, while Model 2 asserts that the destruction of benthic microbial mats by burrowing organisms caused the extinction.
  4. D
    Both models assert that the diversification of Cambrian metazoans and the extinction of the Ediacaran biota were independent events driven by separate, unrelated geological changes.

Cevap

Model 1 asserts that Cambrian metazoan diversification was the direct cause of the Ediacaran extinction, while Model 2 asserts that the extinction occurred first and created ecological opportunities that allowed Cambrian metazoans to diversify.
The correct option accurately contrasts the causal structures of the two models. Model 1 asserts that the diversification of Cambrian metazoans was the cause of the Ediacaran extinction (biotic replacement), while Model 2 asserts that the Ediacaran extinction occurred first due to abiotic factors, creating empty ecological niches that subsequently allowed Cambrian metazoans to diversify.

Adım Adım Çözüm

1
Analyze Model 1 to determine the causal direction between Cambrian metazoan diversification and Ediacaran extinction.
Model 1 indicates that Cambrian metazoans diversified first, and their ecological activities (bioturbation, predation, competition) caused the Ediacaran extinction.
This establishes that Cambrian diversification is the cause of the extinction under Model 1.
2
Analyze Model 2 to determine the causal direction between Cambrian metazoan diversification and Ediacaran extinction.
Model 2 indicates that the Ediacaran extinction occurred first due to ocean anoxia, which then opened up niches and resources, allowing Cambrian metazoans to diversify.
This establishes that the extinction is the cause of the diversification under Model 2.
3
Compare the two models' causal pathways to identify the core difference.
Model 1 proposes that Cambrian diversification led to the extinction, whereas Model 2 proposes that the extinction led to Cambrian diversification.
This direct contrast matches the correct statement.

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Comparing and Contrasting Models
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Comparing and Contrasting Models

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