Self-study
P1
Every culture that has adopted the cultivation of maize—also known as corn—has been radically changed by it. ███
intro topic ·
Influence of maize
explain significance ·
of maize
Contributed to development of agrarian and urban societies, and European population growth
hypothesis ·
Maize's influence is due to its productivity
phenomenon ·
Productivity of maize
Intro to hypothesis ·
Biochemistry provides the answer
P2
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Context ·
Explanation of photosynthesis
Water splits into hydrogen and oxygen, hydrogen produces energy. Meanwhile, carbon dioxide builds sugars with help from enzyme (rubisco).
Problem ·
Too much oxygen interferes with photosynthesis
Enzyme supposed to work with carbon dioxide, but oxygen binds to enzyme instead, meaning less enzyme available to work with carbon dioxide
P3
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Solution (hypothesis) ·
Different method of photosynthesis
Enzyme (rubisco) is kept separate from atmospheric gases (e.g., oxygen and carbon dioxide)
Complication with hypothesis ·
Carbon dioxide cannot reach enzyme as gas
Solution: Carbon dioxide becomes nongas molecule (C-4) in order to reach enzyme and drive photosynthesis
Strengthen hypothesis ·
Other highly productive crops use this method of photosynthesis
Passage Style
Phenomenon-hypothesis (RC)
Single position
21.
Which one of the following ████ ██████████ ██████ ███ ████ █████ ██ ███ ████████
a
The greater productivity ██ ██████ ██ ████████ ████ ████ █████ ██████ ██ ███ ██ ███ ███ ██████████████ ████████ ██ █████ ███ █████████ ████ █████ ██████ ███ █████████ ████ ███ ███████ ██ ██████ ███████
This is an accurate summary of the main point. P2 introduces a constraint that most crops have (the reactions that build sugars are hindered by excess oxygen), and the author spends the rest of the passage explaining how the C-4 process allows maize to be more productive than those crops.
b
Because of their ███████ ██ ███████ ███████ ██████████ ███ ██████ █████████ ██ ██████████ █████ ███████ █████████ ██████ ████ ███ █ ███ ██████████████ ███████ ████ ██████ ██ █████ ███ ███████████ ██ ████ █████ █████████
Unsupported. Although the author states that
c
C-4 photosynthesis, which ██████ ██ ██████ ████████ █ ███████ ████████ ██ ████████ █████████ ████ █████ ████ █████████ ███ ██ █████████ ███████████ ████████ ████ ██ ██████████████ █████████ ██ ███████ ███████
Unsupported. C-4 photosynthesis makes more efficient use of the enzyme rubisco, not atmospheric hydrogen.
d
The presence of ███ ██████ ███████ ██ █ ███ ██████ ██ ███ ███████ ██ ███ ███████ █████████ ██████ ██ ██████████ ███ ████████ ███████ ██ █████ ████ ██ ██████ ██ ███ ██████████ ██ ██████ ██ ███████████████
Anti-supported. Rubisco isn’t what helps C-4 plants to circumvent any negative effects; rubisco is the target of those negative effects. Those negative effects are circumvented in C-4 plants by the process of separating rubisco from oxygen.
e
Some of the ███████ ████ ██████████ ████ ███████ █████████ ██████ ████ ███████ ████████ █████████ ██████████ ██ ███████ ███████████ █████ ████ █████ ████ █████████████ ██ ███████ ████ ████████ ███ ███████ ███████
This (inaccurately) describes how the mechanism works, but the main point isn’t simply that some productive crops have this mechanism—it’s that this mechanism is precisely what allows these crops to be so productive. And (E)’s description of the C-4 mechanism is wrong, anyway; atmospheric gases still enter the leaves. The oxygen within the leaf is just kept separate from rubisco.