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Difficulty: MediumPart-to-Whole Rhetorical Function

Deep-sea hydrothermal vent ecosystems are typically characterized by their reliance on chemosynthesis, where microbes convert chemical energy from vent fluids into organic matter. However, marine biologist Marcus Vance has identified several vent sites where photosynthetic microbes utilize geothermal radiation—the faint infrared glow emitted by superheated water��to perform a form of non-solar photosynthesis. This discovery challenges the long-held paradigm that photosynthesis is strictly dependent on sunlight reaching the photic zone. Consequently, Vance's research suggests that primary production in the deep ocean may be more diverse and widespread than previously assumed, requiring a revision of ecological models for aphotic environments.

Which choice best describes the function of the underlined sentence in the text as a whole?

  1. A
    It outlines the study's ultimate conclusion regarding the need to revise existing ecological models of aphotic zones.
  2. B
    It supports the opening assertion that deep-sea ecosystems are defined by their exclusive reliance on chemosynthetic microbes.
  3. It introduces a specific finding that challenges a prevailing assumption about the types of biological processes occurring in deep-sea environments.Answer
  4. D
    It explains the biochemical mechanism by which geothermal radiation is converted into energy during non-solar photosynthesis.

Answer

The choice that states the underlined sentence introduces a specific finding that challenges a prevailing assumption about the types of biological processes occurring in deep-sea environments.
The correct answer is correct because the passage begins by stating a common characteristic of hydrothermal vents (their reliance on chemosynthesis). The underlined sentence introduces Marcus Vance's discovery of photosynthetic microbes at these vents, which utilize geothermal radiation rather than sunlight. This finding directly challenges the general assumption that photosynthesis cannot occur in the deep, lightless ocean. Therefore, the sentence functions to introduce a discovery that challenges a prevailing assumption about biological processes in this environment.

Step-by-Step Solution

1
Analyze the context before the underlined sentence.
The opening sentence establishes a typical baseline or prevailing assumption: that deep-sea hydrothermal vent ecosystems are defined by their reliance on chemosynthesis.
To understand how the underlined sentence functions, we must first understand the context it responds to.
2
Analyze the content and function of the underlined sentence itself.
The underlined sentence introduces a counter-example or new finding: the discovery of microbes at vent sites performing non-solar photosynthesis using geothermal radiation.
This step determines the direct meaning and immediate logical role of the sentence.
3
Analyze the context after the underlined sentence and determine the relationship between the parts.
The subsequent sentences explain that this discovery 'challenges the long-held paradigm' and suggest revisions to current ecological models. Therefore, the underlined sentence serves to introduce the specific finding that drives this shift away from the traditional assumption mentioned at the start.
This final step integrates the part into the whole structure of the text to identify its rhetorical purpose.

Key Concept

Analyzing how a specific sentence or part of a text contributes to the development of the author's overall argument or explanation.
Estimated Time:1m 30s
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Topics

Part-to-Whole Rhetorical Function

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