Examkin

Question

Difficulty: EasyInferences and Implicit Meaning

For decades, marine biologists assumed that deep-sea hydrothermal vent communities depended entirely on chemosynthetic bacteria that oxidize hydrogen sulfide emitted by the vents. However, recent analyses of lipid biomarkers in deep-sea vent fauna reveal significant concentrations of compounds synthesized exclusively by methane-oxidizing archaea. This finding indicates that methane oxidation contributes far more to the primary production of these ecosystems than previously recognized. Furthermore, because methane emissions fluctuate independently of hydrogen sulfide discharges, ecosystems reliant on both metabolic pathways exhibit greater ecological resilience to sudden geochemical shifts in vent fluid composition than do ecosystems dependent on a single chemical energy source.

Based on the passage, which of the following statements regarding deep-sea hydrothermal vent ecosystems can be inferred? Consider each of the three choices separately and select all that apply.

  1. Some deep-sea vent ecosystems are less vulnerable to fluctuations in hydrogen sulfide emissions than biologists had previously assumed.Answer
  2. B
    Methane-oxidizing archaea have completely replaced hydrogen-sulfide-oxidizing bacteria as the primary energy source in deep-sea vents.
  3. The chemical composition of fluid discharged from deep-sea hydrothermal vents is subject to change over time.Answer

Answer

The correct selections are the statement that vent ecosystems are less vulnerable to fluctuations in hydrogen sulfide emissions than previously assumed and the statement that vent fluid chemical composition changes over time.
The inference stating that vent ecosystems are less vulnerable to hydrogen sulfide fluctuations than previously assumed is correct because the passage reveals that biologists originally thought vents relied exclusively on hydrogen sulfide, but the presence of methane oxidation provides an additional metabolic pathway that buffers against chemical shifts. The inference stating that vent fluid composition changes over time is also correct because the text explicitly references independent gas emission fluctuations and sudden geochemical shifts in vent fluid composition.

Step-by-Step Solution

1
Analyze the passage evidence regarding historical assumptions versus current findings.
Biologists initially believed vent life depended entirely on hydrogen sulfide. The discovery of methane oxidation providing secondary energy means these communities do not rely solely on hydrogen sulfide, making them more resilient to its fluctuations than previously thought.
Establishes support for the inference regarding reduced vulnerability.
2
Evaluate claims of complete replacement.
The text explicitly states ecosystems are 'reliant on both metabolic pathways,' directly contradicting any claim of complete replacement.
Identifies an overstatement distractor unsupported by the text.
3
Analyze passage references to fluid composition stability.
The passage discusses independent fluctuations in gas discharges and 'sudden geochemical shifts in vent fluid composition,' which logically necessitates that the chemical composition varies over time.
Establishes support for the inference regarding changing fluid composition.

Key Concept

Making valid implicit inferences grounded strictly in passage claims without overstating author conclusions.
Rate this question

Topics

Inferences and Implicit Meaning

More questions from this topic