Atmospheric CO2

Answer choices

1. A

   Consistent5% picked this

   The roots of a certain tree species grow more rapidly when the amount of CO2 in the atmosphere increases, thus permitting the trees to

   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%
2. B

   Consistent6% picked this

   When grown in an atmosphere high in CO2, certain weeds with low photosynthetic efficiencies begin to thrive in cultivated farmlands

   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%
3. C

   Correct74% picked this

   When trees of a species with a high photosynthetic efficiency and grasses of a species with a low photosynthetic efficiency were placed in an

   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.

   74%
4. D

   Consistent8% picked this

   When two different species of grass with equivalent photosynthetic efficiency were placed in an atmosphere high in CO2, one species grew much more rapidly

   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.

   8%
5. E

   Consistent8% picked this

   The number of leguminous plants decreased in an atmosphere rich in CO2, thus diminishing soil fertility and limiting the types of plant species

   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%