Highlight the author’s conclusions:

p1:
answering the question of what constitutes a “good” species has long been a confusing and controversial exercise.

p4: 
Whatever the merits of each position, the species question undoubtedly has political and economic stakes.

Map the wording of the answers to the reference in the prompt, or to the author’s conclusions:

15. Which one of the following most accurately describes the main point of the passage?

Map the answers to the author’s conclusions.

(A) …thanks to the work of Charles G. Sibley and others.

“Sibley and others” don’t get a mention in either conclusion. The whole thing about Sibley was basically one long example meant to support the author’s overall conclusion.

(B) …most agree that all such classification systems contain…

This doesn’t sound at all like the author’s conclusions, and there’s no support for saying “most” scientists would agree with this.

(C) …is a controversial issue with practical implications…

This is just as general as the author’s conclusions, and all the wording maps. The “practical implications” are the “political and economic stakes” the author called out in their second conclusion.

(D) …these methods have been called into question by the work of Charles G. Sibley.

This is too specific, since Sibley was just an example, and it doesn’t capture the author’s conclusions well.

(E) …Sibley developed revolutionary methods…

Again, Sibley is only a case study, the main point isn’t about him. But in case you liked this one, they put that word “revolutionary” in there so you’d know this is wrong. The author said Sibley was part of a “revolution”, but didn’t describe his “methods” that way.

(C) is the correct answer.

16. According to the passage, which one of the following is true of the phylogenetic species concept?

Map the answers to the reference in the prompt. The right answer will map to a detail near the end of the first paragraph, where this “concept” gets introduced.

(A) It has effectively discredited…

Whoa, too strong. It only says it’s “increasingly popular”, and that the other method “until recently was the dominant approach”.

(B) Its popularity has declined since…

There’s nothing about a drop in its popularity in the passage.

(C) It is more useful in ornithology than in most other…

The author never makes this comparison. Ornithology is the only field we heard any details about.

(D) It has more proponents now than it had in the past.

That’s exactly what “increasingly popular” means. Boom.

(E) It was pioneered by Charles G. Sibley.

There’s nothing for “pioneered” to map to in the passage. The author never said Sibley was one of the first to apply the “concept”, only that he was “one of the fomenters of a controversial revolution”. That means he helped stir up trouble, but wasn’t necessarily the first to do anything.

(D) is the correct answer.

17. It can be inferred from the passage that Charles G. Sibley would have been most likely to agree with which one of the following?

Map the answers to the reference in the prompt. We heard a number of things about Sibley. He was a “splitter” who “might not have disagreed” that assigning species is “basically arbitrary” and that “the ‘species concept’ is slippery”.

(A) Splitters are somewhat more likely than lumpers…

This is much more specific than any comparison made in the passage between “splitters” and “lumpers”.

(B) The total number of animal species in the world today…

…never gets mentioned or referenced. This is much more specific than anything we see attributed to Sibley in the passage.

(C) A proper goal for ornithologists…

Stop. We never heard Sibley’s take on what ornithologists goal should be, just a description of the method he used.

(D) The degree of genetic difference…should have little bearing on the decision…

Sibley used a method “which compares DNA from different species”, so it’s fair to say he’d disagree with this.

(E) Disagreements about species classification are likely to persist…

This sounds pretty close to “the ‘species concept’ is slippery”, which the author quotes Sibley saying near the end of paragraph three.

(E) is the correct answer.

18. Which one of the following most accurately illustrates the biological species concept…

Map the answers to the reference in the prompt. This “concept” comes up in the middle of the first paragraph, where the author says its based on defining species as “reproductively isolated” groups.

(A) …share a common ancestor.

This doesn’t map to the reference, which is about “interbreeding”, not ancestry.

(B) …X and Y interbreed…, they should be classified as belonging to different species.

Wrong. The reference in the passage says if they “interbreed” then they’re the same species.

(C) …live in similar, though mutually isolated, habitats.

If this is true, they don’t interbreed, so they would not be the same species.

(D) …they nevertheless interbreed.

This matches the reference in the passage nicely.

(E) …never been known to interbreed…

Then the “biological species concept” would say they’re not the same species.

(D) is the correct answer.

19. If valid, Charles G. Sibley’s findings, as described…

Map the answers to the reference in the prompt.

(A) A stork population from Europe…

The reference only mentions “storks” as one big group, so we have no way of comparing the ones “from Europe” to the ones “from North America”.

(B) A stork population from South America…

Same issue as (A).

(C) …likely to be of the same species as one from Europe.

The reference says American vultures are “more closely related to storks”, so this could be evidence to “seriously challenge” that.

(D) …likely to be of a different species than one from Europe.

This aligns with what Sibley says in the reference in the passage. But we’re looking for something to “challenge” it.

(E) …likely to be of the same species as one from South America.

The “vultures found in North and South America” are one big group in the reference, so we aren’t looking for a comparison between them.

(C) is the correct answer.

20. The passage provides information sufficient to answer which one of the following questions?

Map the answers to the author’s conclusions. The answer will probably rely on a detail, but the prompt doesn’t tell us where to look. So it’s typically best to eliminate what you can tell is wrong first, then do any searching and re-reading if you still need to.

(A) When did Charles G. Sibley begin…

There are no dates mentioned anywhere in the passage except the quote from Sibley “In 1996”.

(B) What are two continents on which storks are found?

It’s only “vultures” that get described as “found in North and South America” and “European”. We don’t get any geographic info about storks.

(C) What common traits…

The passage only says scientists argue these birds are “closely related”, but not a single “common trait” gets mentioned.

(D) What is one objection to applying Sibley’s work…

This maps to the opening of the third paragraph, where the author explains that “Sibley’s work has not been widely accepted.” The author brings in a “critic” who calls his work “arbitrary”.

(E) What is one non-avian animal population…

The passage only got into details about birds.

(D) is the correct answer.

21. It can be inferred from the passage…

Map the answers to the reference in the prompt. Another one about the “biological species concept”. Make sure you see the answer will “disagree” with this take.

(A) There are considerably more bird species…than are currently recognized.

Love this. The “concept” we’re disagreeing with is what “the lumpers employ”. They would tend to undercount since they “group separate but very similar populations of birds into a single species”.

(B) …might nevertheless belong to the same species.

The “biological species concept” would totally agree with this, since these birds could still interbreed. That’s their basis for deciding who’s part of the same species, not “physical characteristics”.

(C) …that are considered extinct in fact have surviving members.

Totally out of scope. There’s nothing in the passage about who’s “extinct” or “surviving”.

(D) There is less biodiversity…

There’s no mention of increasing or decreasing “biodiversity” or what was up “50 years ago”.

(E) …motivated by political rather than by scientific concerns.

Not even close. We have no info on what anyone thinks the debate is “motivated by”.

(A) is the correct answer.

22. Which one of the following, if true, would provide the strongest support for the author’s assertion…

Map the answers to the reference in the prompt.

(A) It is becoming increasingly difficult to enact international agreements…

The passage says absolutely nothing about “international agreements”.

(B) …more likely to result in new avian species than in new mammalian species.

The reference is only about the overall “number of species”, so a comparison between birds and mammals wouldn’t support it at all.

(C) …economic considerations often outweigh scientific ones.

The reference doesn’t make any comparison between “economic” and “scientific” factors, so this info wouldn’t support it at all.

(D) …will probably favor the efforts of…

This might be a fair assumption to make based on the author’s argument, but it has nothing to do with “the number needing protection”, so it doesn’t support the specific reference we’re being asked about here.

(E) …if none of the biological populations involved is endangered.

Alright, let’s play the game here. (A) is the only other answer that maps to species “needing protection”, but it brought in a totally new subject. Everything in this answer maps to statements in the passage. If you need to totally “get it”, you’ll likely waste time thinking this through, even though it should be clear it’s the right answer anyway.

That said, if this is true, then the “splitters” would only want the species count to increase when at least one of the “populations involved is endangered”. And that means the reference in the passage is probably true: increasing the number of species would be directly related to increasing the number “needing protection”.

(E) is the correct answer.