Read the passage excerpt:
'Wetland ecosystems act as nature’s biological kidneys, filtering suspended particulates, heavy metals, and excessive agricultural nutrients such as nitrates and phosphates through complex biochemical assimilation by hydrophytic vegetation and rhizosphere microbial colonies. When wetlands are drained for agrarian conversion, these accumulated pollutants leach into adjacent fluvial systems, triggering catastrophic eutrophication and hypoxia in downstream aquatic basins.'
Why does the author metaphorically describe wetlands as 'nature’s biological kidneys'?
Answer and explanation
Correct answer: D. They filter out harmful dissolved nutrients and pollutants through plant and bacterial action
- Step 1: The passage explicitly explains the metaphor: wetlands filter 'suspended particulates, heavy metals, and excessive agricultural nutrients... through complex biochemical assimilation by hydrophytic vegetation and rhizosphere microbial colonies'.
- Step 2: This natural filtration mirrors renal blood purification.
Answer
They filter out harmful dissolved nutrients and pollutants through plant and bacterial action.
Why not the others: 'They produce biological enzymes that regulate terrestrial mammalian hydration' is scientifically irrelevant; 'They store large reserves of underground fossil aquifers...' describes deep aquifers rather than surface wetlands; 'They absorb excess atmospheric nitrogen...' misidentifies nitrogen fixation mechanics.
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