Reading Comprehension

PT109 · S2 · P3 · Q21 Atmospheric CO2

A free, expert breakdown of this official LSAT Reading Comprehension question.

  • Save & drill this skill — build targeted practice sets from questions like this one

  • Video walkthroughs — watch every question solved step by step

  • 81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

Experts anticipate that global atmospheric concentrations of carbon dioxide (CO2) will have doubled by the end of the twenty-first century.

Topic

The potential effects of elevated CO2 levels on agriculture and global warming.

Framework

Challenge Position

Main Point

While some initially believed that increased CO2 levels could lead to lush agricultural growth and aid in decreasing global warming, research suggests that it might actually disrupt ecosystems, decrease crop yields, and exacerbate global warming. *The Most Valuable Sentence: (start of paragraph 3).*

P1: Introduction to CO2's Anticipated Impact

This paragraph sets up an initial optimistic view that increased CO2 levels might boost plant growth and lessen global warming by enhancing photosynthetic rates and trapping more carbon.

P2: Challenge to the Optimistic View

Recent studies show that while plant growth could increase with more CO2, it would vary between species, potentially reducing agricultural yields and harming ecosystem stability. For example, certain crops might suffer compared to weeds, leading to ecological changes and increased wildfire risks.

P3: Doubts About CO2 Reducing Global Warming

The paragraph discusses how in some conditions, such as warming tundras, enhanced plant growth won’t offset CO2 emissions from decomposing peat, hence the increased uptake of CO2 might not significantly curb global warming.

21.

Which one of the following, if true, is LEAST consistent with the hypothesis mentioned in the second sentence of the second paragraph?

  1. The roots of a certain

    Consistent

    This tells us a story of a plant that used to be dominated by a high-efficiency plant now being able to compete better in a CO2 rich world. This matches the story of crabgrass, which used to get dominated by high-efficiency corn and sugarcane, now being able to steal some territory from those crops in a CO2 rich world.

    5% picked this

  2. When grown in an atmosphere

    Consistent

    This tells us a story of a plant with low / average efficiency that ends up being more powerful and more competitive in a CO2 rich world. This matches the 2nd paragraph.

    6% picked this

  3. Correct

    When trees of a species

    Why this is right

    This is telling a story about a high CO2 world in which the high efficiency plant is doing better than the lower efficiency plant. That's a mismatch. In our current world, high efficiency plants beat out the lower efficiency ones. But in the CO2 rich world, we're expecting the lower efficiency plants to do better.

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

    73% picked this

  4. When two different species of

    Consistent

    This story doesn't exactly match what the 2nd paragraph was talking about, but it doesn't mismatch like the correct answer does. This is talking about two species with comparable efficiency. In a high CO2 world, one of them outperforms the other. That would only go against the passage if we thought that "the only thing that affects how fast you grow / how well you compete against other local plants is your photosynthetic efficiency". But there could be other factors that also affect growth rates. The 2nd paragraph would predict that the richer CO2 world wouldn't favor either plant based on their photosynthetic efficiencies. But it wouldn't necessarily predict that they will grow at equal rates, because other factors could influence growth rate too.

    7% picked this

  5. The number of leguminous plants

    Consistent

    This answer has nothing to do with differences in how high-efficiency vs. lower-efficiency plants respond to a world with more CO2. This is just talking about leguminous plants (legumes, like lentils or beans) doing worse in an atmosphere rich in CO2, but we don't know if they are high or low when it comes to photosynthetic efficiency.

    8% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill
LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free