Plant Evolution

Answer choices

1. A

   Correct80% picked this

   Some of them are the results of recent natural mutations

   Why this is right

   We're very attracted by the mild wording, "some". If we CTRL + F or scan for "mutations" we'll find it at the beginning of the second paragraph: Such [secondary] substances undoubtedly first appeared, and new ones continue to appear, as the result of genetic mutations in individual plants. If new secondary substances continue to appear as the result of mutations, then we can support that "some secondary substances are the results of recent mutations".

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

   80%
2. B

   Too Strong: typically1% picked this

   They typically contribute to a plant's taste or smell, but

   The end of the first paragraph says, "It is these secondary substances that give plants their distinctive tastes and smells". That's it. It doesn't give us any way to justify the quantitative specificity of saying "more than 50% of the time, a secondary substance does not contribute to both taste and smell". We have no idea with what frequency they contribute to taste, smell, both, or neither.

   1%
3. C

   Out of Scope: chemical reactions10% picked this

   Some of them undergo chemical reactions with substances produced by insects, thus altering the

   The "some" is very attractive, and this may sound reminiscent of the discussion in the 2nd and 3rd paragraphs where we hear about secondary substances evolving to solve an insect related problem. But we never hear about a secondary substance getting mixed together with a substance from the insects, undergoing a chemical reaction, and thereby changing the plants' chemical composition going forward. We just hear about plants mutating a new substance; the new substance proves to be useful in the survival battle with insects; the substance is thus selected for by evolution; and thus the secondary substance becomes a "conserved trait". So we could say that interactions with insects, over evolutionary time, alter the plant species' chemical composition. But that's miles away from plant juice + insect juice = chemical reaction.

   10%
4. D

   Too Strong: only one7% picked this

   Some species of plants produce only one

   We're told that "only a few [secondary] substances occur in any one species of plant". We never hear about plants that have only one secondary substance.

   7%
5. E

   Out of Scope: regulators of primary1% picked this

   A few of them act as regulators of plants' production of

   We only hear about primary substances in the first couple sentences, and we're told that secondary substances have "no known role in the internal chemical processes of plants' growth or metabolism", whereas primary substances are specifically required for growth and proper functioning. So since we're told that secondary substances have no known role in doing what primary substances are doing, it's nearly contradicted to say that "some secondary substances regulate the production of primary substances".

   1%