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Zorluk: OrtaSuggesting Experiments to Resolve Viewpoints

A team of marine biologists is investigating the source of organic carbon that supports the food web in the Mariana Trench, located at a depth of over 10,000 meters. The scientists propose three different hypotheses to explain where the organic carbon originates.

* Hypothesis 1: The organic carbon in the trench is derived from dead photosynthetic plankton sinking from the sunlit surface waters.
* Hypothesis 2: The organic carbon is produced locally in the trench by chemosynthetic bacteria that utilize geothermal chemical energy from deep-sea hydrothermal vents.
* Hypothesis 3: The organic carbon consists of terrestrial plant debris transported from land down the slopes of submarine canyons during storm events.

Match each hypothesis with the experimental observation that would most directly invalidate (disprove) it.

  • Hypothesis 1Sediment samples show that the organic matter contains no chlorophyll degradation products (such as pheophytin).
  • Hypothesis 2The rate of local organic carbon production remains constant after a tectonic event seals all deep-sea hydrothermal vents in the trench.
  • Hypothesis 3Chemical analysis shows a complete absence of vascular plant polymers (such as lignin) in the trench sediment.

Cevap

Hypothesis 1 matches the absence of chlorophyll degradation products; Hypothesis 2 matches the constant organic carbon production after hydrothermal vents are sealed; Hypothesis 3 matches the complete absence of vascular plant polymers.
Hypothesis 1 relies on surface-dwelling photosynthetic organisms. The correct pairing matches this to the absence of chlorophyll breakdown products (pheophytin), which must be present if surface plankton are the main source. Hypothesis 2 relies on geothermal vents for chemosynthesis; thus, a constant rate of carbon production after vents are sealed disproves it. Hypothesis 3 relies on land plants; thus, a complete lack of lignin (a vascular plant polymer) disproves it.

Adım Adım Çözüm

1
Identify the key source of organic carbon proposed by Hypothesis 1 and find a biological tracer associated with it.
Hypothesis 1 proposes photosynthetic plankton, which contain chlorophyll. The complete absence of chlorophyll degradation products (pheophytin) directly invalidates this claim.
Photosynthetic organisms must leave behind traces of chlorophyll when they die and sink.
2
Identify the key energy source for the carbon production proposed by Hypothesis 2 and determine how to block it.
Hypothesis 2 proposes local chemosynthesis at hydrothermal vents. If sealing all vents has no effect on carbon accumulation, hydrothermal chemosynthesis cannot be the source.
If local production is dependent on vent emissions, stopping the vents must decrease carbon production.
3
Identify the key source of organic carbon proposed by Hypothesis 3 and identify its unique terrestrial chemical marker.
Hypothesis 3 proposes land-based plant debris. Terrestrial vascular plants contain lignin, so the complete absence of lignin invalidates this runoff source.
Lignin is a diagnostic biomarker for terrestrial vegetation and does not originate from marine microbes or phytoplankton.

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Suggesting Experiments to Resolve Viewpoints
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