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Difficulty: MediumLogical Inferences

The hydrothermal vent worm *Alvinella pompejana* is known for its remarkable tolerance to extreme heat. Scientists hypothesized that the dense layer of filamentous bacteria coating the worm’s back acts as a protective thermal blanket, insulating it from the scalding vent water. To test this, researchers placed worms with intact bacterial layers and others with their bacterial layers removed into chambers that simulated fluctuating vent temperatures. If the bacteria functioned as an insulator, the worms without bacteria would show more rapid internal temperature fluctuations. However, the researchers found that internal temperature changes occurred at the same rate in both groups of worms. Which choice most logically completes the text?

  1. A
    the bacteria instead protect *Alvinella pompejana* by detoxifying heavy metals in the vent water
  2. the bacterial layer does not serve as a thermal barrier protecting the worm from environmental heatAnswer
  3. C
    the worms with the intact bacterial layers were better able to regulate their internal temperature than the worms without bacteria
  4. D
    hydrothermal vent conditions are too unstable for symbiotic relationships between worms and bacteria to develop

Answer

the bacterial layer does not serve as a thermal barrier protecting the worm from environmental heat
The correct option is supported because the passage states that if the bacteria functioned as an insulator, worms without bacteria would show more rapid internal temperature fluctuations. Since the researchers found that internal temperature changes occurred at the same rate in both groups of worms, it can be logically inferred that the bacterial layer does not act as a thermal barrier.

Step-by-Step Solution

1
Identify the researchers' hypothesis and the experimental setup.
The hypothesis is that the bacteria insulate the worm from heat. The experiment tests this by comparing the temperature change rates of worms with and without the bacteria.
This establishes the logical condition: if the hypothesis is true, the two groups must perform differently.
2
Analyze the results of the experiment.
The researchers found that both groups of worms experienced internal temperature changes at the exact same rate.
This direct observation contradicts the prediction that the groups would show different rates of temperature shifts.
3
Formulate the logical conclusion.
Because the presence of the bacteria did not slow down or alter temperature changes, the bacterial blanket does not function as a thermal insulator.
This conclusion completes the text by directly matching the logical outcome of the experimental findings.

Key Concept

Logical Inferences
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Topics

Logical Inferences

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