Reading Comprehension

PT7 · S3 · P3 · Q16 Crop Bacteria

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Cultivation of a single crop on a given tract of land leads eventually to decreased yields.

Topic

Using bacteria — including genetically altered ones — to suppress plant pathogens and improve crop yields.

Framework

Present Debate. The author lays out the technique, walks through the genetic-alteration extension, and presents proponents' and opponents' arguments before closing with a hopeful note.

Main Point

Beneficial soil bacteria like Pseudomonas fluorescents already improve crop yields by suppressing pathogens; proponents argue genetic alteration of bacteria could extend these benefits, while opponents worry about deliberate release. Proponents counter that specific alterations (like removing the frost-damage gene from P. syringae) make the altered strain safer than the original.

P1: Beneficial bacteria suppress pathogens

Continuous cultivation increases harmful soil bacteria; rotation breaks this. Even without rotation, soils become "suppressive" — partly because bacteria like P. fluorescents outcompete the pathogens. Treating wheat (and sugar beets, cotton, potatoes) seeds with these bacteria increases yields.

P2: Genetic alteration as the next step

Proponents suggest genetically altered bacteria could be even more useful — for example, releasing nonpathogenic P. syringae to crowd out the frost-damage variety. Opponents object to large-scale releases of altered bacteria. Proponents counter that the alteration is just removing the gene for frost damage, making the strain safer than the original.

P3: Even more ambitious uses

Some proponents go further: combining traits from different bacteria (e.g., transferring insecticidal-compound genes into corn-root pseudomonads). Such bacteria are hard to develop and may struggle in natural soil. Still, proponents see excellent prospects, and many hope risk-assessment efforts will satisfy opponents and let research go forward.

16.

The author discusses naturally occurring Pseudomonas fluorescens bacteria in the first paragraph primarily in order to do which one of the following?

  1. prove that increases in the

    Too Strong

    Too Strong: prove / sole Contradicted (if anything) The verb "prove" is super suspicious from the jump. Authors rarely think they are full-on proving something. Saying that P-f is the sole cause of suppressivity contradicts the clause that says, "While there may be many reasons for this [suppressive soil] phenomenon".

    2% picked this

  2. explain why yields increased after

    Out of Scope: altered Pseudo-fluor

    The passage never discusses altering Pseudomonas fluorescens. We only hear about the naturally occurring version. The passage only discusses altering Psuedomonas syringae.

    8% picked this

  3. detail the chemical processes that

    Out of Scope: chemical processes

    This answer is grabbing some relevant nearby keywords, but at no point does the passage give us any details about any chemical process. We're at the stage of suspecting that P-f suppresses phytopathogens and helps crops such as sugar beets, cotton, and potatoes grow better, but the author isn't presenting any knowledge we have of how this would chemically take place.

    4% picked this

  4. Correct

    provide background information to support

    Why this is right

    This answer reinforces the broader takeaway that follows the discussion of Pseudo-fluor, in the first sentence of the 2nd paragraph. This answer is a little atypical for most Local Purpose questions, in that it really ends up explaining the pivot point of how the first paragraph transitions into the rest of the passage. (usually the correct answer isn't so connected to the big picture) But we can see how the beginning of the 2nd paragraph is basically the author saying, "As you can see from my discussion of P-f, it seems like crops could benefit from genetically altered bacteria". This is a very weird transition, since the P-f discussion was a situation in which naturally occurring bacteria benefited crops. So how does it suggest that genetically altered bacteria would help crops? It's a thin connection, logically, but it explicitly IS the connection the author is offering.

    Skill tested: Local Purpose · how this choice captures the passage's function is the move to repeat next time.

    80% picked this

  5. argue that crop rotation is

    Too Strong: disappear

    This is tempting, since it does seem to reinforce the sentence right before P-f, but the author isn't trying to convince us that crop rotation is unnecessary. Even if that's something we can infer from the discussion of P-f, there's no reason to think the author is trying to distance us from crop rotation. More importantly, she never says that diseases brought on by phytopathogens will eventually disappear on their own. "Suppressing" something doesn't mean that the thing no longer exists, just that it is prevented from taking over.

    6% picked this

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