Examkin

Question

Difficulty: HardRhetorical Structure and Sentence Function

Read the passage below:

For decades, evolutionary biologists operated under the assumption that phylogenetic trees could be constructed solely by mapping vertical gene transfer, wherein genetic material passes strictly from parent to offspring. However, the discovery of widespread horizontal gene transfer (HGT) among single-celled organisms disrupted this paradigm, revealing that genetic sequences frequently jump across disparate lineages. Some taxonomists initially posited that HGT was merely an evolutionary anomaly confined to extremophilic archaea, exercising minimal influence on the broader architecture of life's tree. Yet, recent comparative genomic analyses have demonstrated that HGT-derived sequences constitute up to twenty percent of the functional genome in several terrestrial bacterial clades, playing a pivotal role in metabolic adaptation. While these empirical findings do not entirely invalidate the utility of traditional phylogenetic models for multicellular eukaryotes, they do necessitate a profound conceptual shift from a bifurcating tree to a reticulated web when conceptualizing early microbial lineage relationships. Consequently, maintaining a strict vertical-transmission model for prokaryotic systematics risks distorting our understanding of early evolutionary dynamics.

In the context of the passage, the sentence "Some taxonomists initially posited that HGT was merely an evolutionary anomaly confined to extremophilic archaea, exercising minimal influence on the broader architecture of life's tree" serves primarily to:

  1. characterize an initial attempt to minimize the broader significance of a phenomenon prior to the introduction of evidence that refutes that viewAnswer
  2. B
    summarize the primary theoretical framework that the author ultimately seeks to defend throughout the passage
  3. C
    present empirical data that directly invalidates traditional phylogenetic models for all living organisms
  4. D
    qualify the scope of recent genomic findings by highlighting a methodological limitation in microbial systematics
  5. E
    offer a concession to researchers who argue that horizontal gene transfer operates as the primary driver of eukaryotic evolution

Answer

The correct option is the choice stating that the sentence serves to characterize an initial attempt to minimize the broader significance of a phenomenon prior to the introduction of evidence that refutes that view.
The correct response accurately identifies the sentence's structural role: it articulates an early, restrictive viewpoint held by some taxonomists—that horizontal gene transfer was an insignificant anomaly—which sets up the subsequent contrast ('Yet...') introduced by the author using recent genomic data.

Step-by-Step Solution

1
Analyze the local context and immediate surrounding transition signals of the highlighted sentence.
The sentence describes a perspective from 'some taxonomists' who viewed horizontal gene transfer (HGT) as 'merely an evolutionary anomaly' with 'minimal influence.'
Understanding the content of the target sentence isolates the specific claim being made.
2
Examine the sentence that follows to determine the structural relationship.
The following sentence begins with the pivot word 'Yet' and introduces 'recent comparative genomic analyses' demonstrating that HGT constitutes up to twenty percent of functional genomes in bacterial clades.
The contrast word 'Yet' indicates that the subsequent sentence presents empirical evidence overriding or refuting the initial view.
3
Synthesize the overall rhetorical function of the target sentence.
The sentence introduces a restrictive, early hypothesis regarding HGT's significance in order to set up the contrast with newer evidence showing HGT's widespread role.
This structural setup aligns directly with characterizing an attempt to minimize a phenomenon before presenting refuting evidence.

Key Concept

Rhetorical Role of Counter-Hypotheses and Structural Pivots
Rate this question

Topics

Rhetorical Structure and Sentence Function

More questions from this topic