Determine the central idea of a scientific text and cite specific textual evidence to support objective analysis of ocean hydrothermal vents.
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Grade 6 · ela · Matching answer key included · US Letter and A4
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Summarize a paragraph without adding outside information.
The discovery of a hydrothermal vent is a detail; the central idea needs to explain the broader point about these ecosystems.
Write a central-idea sentence and connect two pieces of evidence to it.
This is an original practice passage, not a reproduction of a primary source. Read the answer explanations as interpretations of the provided text.
For centuries, marine biologists believed that all life on Earth fundamentally depended on sunlight and photosynthesis. In 1977, however, oceanographers aboard the submersible Alvin descended over 8,000 feet into the Galápagos Rift and made a breathtaking discovery: sprawling communities of giant tube worms, ghost-white crabs, and clams thriving in pitch-black water around boiling geothermal chimneys called hydrothermal vents.
Rather than capturing sunlight, these deep-sea organisms rely on chemosynthesis. Specialized bacteria absorb hydrogen sulfide—a toxic chemical spewing from the Earth's crust—and oxidize it to generate chemical sugars. These microscopic microbes form the foundational base of an entire alien-like food web miles beneath the reach of the Sun, completely revolutionizing humanity's understanding of where life can survive in the cosmos.
Which statement best captures the CENTRAL IDEA of the informational text?
Answer: B. The entire passage centers on the landmark 1977 discovery that revolutionized biology by demonstrating life powered by chemical synthesis rather than sunlight.
Intended curriculum references: CCSS.ELA-LITERACY.RI.6.1 · CCSS.ELA-LITERACY.RI.6.2. These references describe learning goals; they are not endorsements.
Published 2026-10-02; updated 2026-10-02. Original MakeWorksheet practice. Automated consistency checks support publication; independent subject-specialist review is not recorded. Read our editorial policy.
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