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OG-1
Passage 19
When marine organisms called phytoplankton photosynthesize, they absorb carbon dioxide dissolved in seawater, potentially causing a reduction in the concentration of atmospheric carbon dioxide, a gas that contributes to global warming. However, phytoplankton flourish only in surface waters where iron levels are sufficiently high. Martin therefore hypothesized that adding iron to iron-poor regions of the ocean could help alleviate global warming. While experiments subsequently confirmed that such a procedure increases phytoplankton growth, field tests have shown that such growth does not significantly lower atmospheric carbon dioxide. When phytoplankton utilize carbon dioxide for photosynthesis, the carbon becomes a building block for organic matter, but the carbon leaks back into the atmosphere when predators consume the phytoplankton and respire carbon dioxide.
For the following question, consider each of the choices separately and select all that apply.
1. It can be inferred from the passage that Martin’s hypothesis includes which of the following elements?
A. A correct understanding of how phytoplankton photosynthesis utilizes carbon dioxide
B. A correct prediction about how the addition of iron to iron-poor waters would affect phytoplankton growth
C. An incorrect prediction about how phytoplankton growth would affect the concentration of atmospheric carbon dioxide
2. It can be inferred that the author of the passage mentions predators (line 10) primarily in order to
A. help explain why Martin’s hypothesis is incorrect
B. identify one effect of adding iron to iron-poor waters
C. indicate how some carbon dioxide is converted to solid organic matter
D. help account for differences in the density of phytoplankton between different regions of the ocean
E. point out a factor that was not anticipated by the scientists who conducted the field tests mentioned in the passage
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