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Difficulty: EasyEvaluating the Impact of New Evidence

Two students discuss the energy source of a newly discovered bacterium, *Bacterium X*, which lives near deep-sea hydrothermal vents.

Student 1 Hypothesis
*Bacterium X* is a photoautotroph. It utilizes the faint geothermal light emitted by the hot vent fluids to perform photosynthesis.

Student 2 Hypothesis
*Bacterium X* is a chemoautotroph. It obtains energy by oxidizing hydrogen sulfide (H2SH_2S) dissolved in the vent fluids and does not require light.

Researchers subsequently cultured *Bacterium X* in a completely dark laboratory environment rich in hydrogen sulfide and found that the bacteria grew and reproduced at normal rates. Which of the following statements best describes how this new finding affects the students' hypotheses?

  1. A
    The finding is consistent with Student 1's hypothesis but contradicts Student 2's hypothesis.
  2. The finding contradicts Student 1's hypothesis but is consistent with Student 2's hypothesis.Answer
  3. C
    The finding is consistent with both Student 1's hypothesis and Student 2's hypothesis.
  4. D
    The finding contradicts both Student 1's hypothesis and Student 2's hypothesis.

Answer

The finding contradicts Student 1's hypothesis but is consistent with Student 2's hypothesis.
The correct answer is correct because the bacteria's ability to grow in total darkness contradicts the photoautotrophic model (which requires light), while its normal growth in a hydrogen sulfide environment aligns with the chemoautotrophic model.

Step-by-Step Solution

1
Identify the key requirements of each student's hypothesis.
Student 1's hypothesis requires light for photosynthesis, whereas Student 2's hypothesis requires hydrogen sulfide (H2SH_2S) and does not require light.
To evaluate how new evidence affects hypotheses, one must first establish the predictions or requirements of each proposed model.
2
Analyze the conditions and outcomes of the new experiment.
The bacteria grew normally in a dark environment containing hydrogen sulfide.
Determining the conditions of the new finding is necessary to compare them against the requirements of the hypotheses.
3
Determine the impact of the findings on each hypothesis.
Growth in darkness directly contradicts Student 1's requirement for light, while successful growth using hydrogen sulfide supports Student 2's chemoautotrophic model.
Comparing the experimental outcomes to the requirements of both hypotheses reveals which model is supported and which is refuted.

Key Concept

Evaluating how new experimental findings support or contradict competing scientific hypotheses.
Estimated Time:45s
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Topics

Evaluating the Impact of New Evidence

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