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Difficulty: EasyCentral Ideas

Prior to the 1977 discovery of deep-sea hydrothermal vents, scientists believed that all marine ecosystems ultimately depended on sunlight for energy, with photosynthesis forming the base of every food chain. However, researchers exploring the Galápagos Rift found diverse communities of crabs, clams, and giant tube worms thriving in total darkness near these volcanic vents. Instead of utilizing sunlight, specialized bacteria in these environments convert toxic chemicals from the vents into usable energy through chemosynthesis. This discovery proved that life can flourish in extreme environments entirely independent of solar energy, expanding our understanding of the conditions necessary to sustain life.

Which choice best states the main idea of the text?

  1. A
    Organisms living in extreme environments are generally more adaptable than those living in moderate climates.
  2. B
    Specialized bacteria near the Galápagos Rift use photosynthesis to survive in the deep ocean.
  3. The discovery of hydrothermal vent ecosystems demonstrated that biological communities can thrive without depending on sunlight.Answer
  4. D
    Future marine exploration will focus exclusively on finding new volcanic vents in the ocean.

Answer

The discovery of hydrothermal vent ecosystems demonstrated that biological communities can thrive without depending on sunlight.
The text describes how the 1977 discovery of hydrothermal vents challenged the previous scientific belief that all marine ecosystems rely on sunlight. Since these vent communities thrive in total darkness by using chemosynthesis instead of photosynthesis, the discovery proved that life can flourish entirely independent of solar energy. Thus, the idea that these ecosystems demonstrate that biological communities can thrive without depending on sunlight accurately states the main idea.

Step-by-Step Solution

1
Identify the transition in the passage that introduces the main shift in perspective.
The passage transitions from the old belief that all ecosystems depend on sunlight to the new finding of diverse communities thriving in total darkness near hydrothermal vents.
Central idea questions often focus on the contrast between an established belief and a new discovery.
2
Analyze how the organisms in the new discovery survive without sunlight.
Bacteria convert toxic chemicals into energy through chemosynthesis, allowing the community to thrive independent of solar energy.
Understanding the mechanism of survival explains why the discovery is significant to the main idea.
3
Select the option that summarizes this shift and its broader implication.
The correct choice summarizes that the discovery of these vent ecosystems proved that biological communities can thrive without depending on sunlight.
This directly aligns with the concluding sentence of the passage, which states that life can flourish independent of solar energy.

Key Concept

Identifying the central idea of a passage by analyzing the relationship between scientific claims and supporting evidence.
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