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Difficulty: MediumCentral Ideas

For years, marine biologists assumed that the deep-ocean hydrothermal vent ecosystems, which exist in perpetual darkness under extreme pressure, depended solely on chemosynthesis by local bacteria for energy. However, recent analyses of organic matter collected from several Pacific vent sites have revealed traces of photosynthetic byproducts. Researchers hypothesize that these materials originate from surface waters, drifting downward as 'marine snow' and supplementing the vents' primary energy output. This suggests that deep-sea vent communities, far from being completely isolated biological enclaves, maintain a subtle ecological connection to the sunlit upper layers of the ocean.

Which choice best states the main idea of the text?

  1. Deep-sea hydrothermal vent ecosystems are not entirely isolated and receive supplementary energy from the ocean's sunlit surface layers.Answer
  2. B
    All marine ecosystems, regardless of depth, are primarily dependent on nutrients that sink from the ocean surface.
  3. C
    Chemosynthetic bacteria in deep-sea vents are capable of producing their own energy through photosynthesis.
  4. D
    Fluctuations in surface sunlight are causing hydrothermal vent communities to abandon chemosynthesis in favor of marine snow.

Answer

The statement that deep-sea hydrothermal vent ecosystems are not entirely isolated and receive supplementary energy from the ocean's sunlit surface layers.
The correct option correctly states the main idea of the passage. The text details how researchers found photosynthetic byproducts in hydrothermal vent sites, indicating that these deep-sea ecosystems receive supplementary nutrients from the surface. Thus, they are not completely isolated but instead maintain an ecological connection to the sunlit upper layers of the ocean.

Step-by-Step Solution

1
Read the passage to determine the primary topic and key supporting details.
Identified that deep-ocean vents, previously thought to rely solely on local chemosynthesis, actually receive organic matter with photosynthetic byproducts from surface layers.
Establishes a foundation for understanding the main argument.
2
Analyze the conclusion of the passage.
Found that the connection to the surface suggests vent communities are not completely isolated biological enclaves.
Synthesizes the supporting evidence with the author's primary takeaway.
3
Compare the synthesized main idea with the given choices to find the one that matches without overgeneralizing or speculating.
The option stating that hydrothermal vent ecosystems are not entirely isolated and receive supplementary energy from the surface accurately represents the passage's central theme.
Ensures the selected option is neither too narrow nor too broad.

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Central Ideas
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