Question

Difficulty: MediumParagraph Reordering and Placement

The paragraphs below are from a draft of an essay about the discovery of hydrothermal vents. Arrange these paragraphs in the most logical order to create a cohesive and well-structured essay.

  1. 1In 19771977, oceanographers aboard the research vessel *Alvin* made a startling discovery at the bottom of the Pacific Ocean: hydrothermal vents spewing superheated, mineral-rich water into the freezing depths.
  2. 2To their surprise, however, these pitch-black environments were teeming with complex life, including giant tube worms and ghost-white crabs. This thriving ecosystem challenged the long-held belief that all food chains must begin with sunlight.
  3. 3Instead of photosynthesis, these organisms relied on chemosynthesis, a process in which specialized bacteria convert the toxic chemicals from the vents into usable energy.
  4. 4Today, this discovery continues to reshape our understanding of life's adaptability and guides astrobiologists in their search for life on icy moons like Europa.

Answer

The paragraphs should be ordered: first, the introduction of the 19771977 discovery of hydrothermal vents; second, the description of the surprising ecosystem found in these dark environments; third, the explanation of chemosynthesis as the primary energy source for these organisms; and finally, the modern impact of this discovery on astrobiology.
The passage must flow chronologically and logically. The introduction establishes the 19771977 discovery of the vents. The second paragraph notes the surprising discovery of complex ecosystems within these vents. The third paragraph explains the mechanism (chemosynthesis) that supports these ecosystems, directly linking to 'these organisms' mentioned in the second paragraph. The final paragraph concludes by discussing the modern-day legacy and implications of this discovery.

Step-by-Step Solution

1
Identify the introductory paragraph.
The paragraph starting with 'In 19771977, oceanographers aboard the research vessel *Alvin*...' serves as the introduction because it establishes the time, setting, and main subject of the essay (the discovery of hydrothermal vents).
An essay must establish its central topic and setting before describing specific details or subsequent discoveries.
2
Determine the next logical step in the narrative.
The paragraph starting with 'To their surprise, however, these pitch-black environments...' must follow the introduction.
The phrase 'these pitch-black environments' directly references the 'freezing depths' and 'hydrothermal vents' established in the first paragraph, and the contrast word 'however' signals the unexpected discovery of life.
3
Link the explanation of the biological mechanism.
The paragraph discussing chemosynthesis ('Instead of photosynthesis, these organisms...') must follow the ecosystem description.
The pronoun reference 'these organisms' lacks an antecedent unless it immediately follows the introduction of 'giant tube worms and ghost-white crabs' in the ecosystem paragraph.
4
Identify the conclusion.
The paragraph starting with 'Today, this discovery...' is the final paragraph.
The time marker 'Today' transitions the essay to the present day and summarizes the ongoing significance of the discovery.

Key Concept

Paragraph Reordering and Placement
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