Reading Comprehension

PT157 · S4 · P3 · Q17 Definition of Species

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Political arguments about biodiversity and the preservation of endangered species generally assume we know what a species is.

Topic

The challenge and controversy of defining what counts as a "species," especially in ornithology, and the implications of different definitions.

Framework

Present Debate

Main Point

There is an ongoing debate among scientists about how to define a species, with significant practical and political consequences, especially for conservation. ( — opening sentences, and the summary of practical stakes at the end.)

P1: Debate Over What Constitutes a Species

This paragraph introduces the ongoing debate about what a "species" actually is, focusing on the classic divide between "lumpers" (who group similar populations) and "splitters" (who separate populations into more species). Lumpers use the biological species concept (reproductive isolation), while splitters prefer the phylogenetic species concept (diagnosable populations with unique, genetically traceable traits).

P2: Example of a "Splitter" – Sibley's Contributions

Here we get an example in ornithology: Charles G. Sibley, a splitter, used DNA technology to challenge conventional classifications of bird species, arguing for unexpected relationships among birds (like American vultures being closer to storks than to other vultures).

P3: Pushback and the Limits of Classification

Sibley's ideas faced significant criticism. A critic argues that interpreting genetic differences is arbitrary, and even Sibley concedes that species definitions are inherently slippery because many populations don’t fit our tidy definitions.

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 views?

  1. Splitters are somewhat more likely

    Out of Scope

    The idea of political / economic concerns comes from the final paragraph. It's not reinforcing any of the details we have about Sibley in the 2nd and 3rd paragraphs. And the passage provides no evidence for the idea that one group is more politically / economically motivated than the other group.

    2% picked this

  2. The total number of animal

    Contradicted

    Since Lumpers have been in charge thus far (the dominant approach to categorization), and since Splitters want to take some of these populations that are lumped together as one species and split them up according to genetic differences, the Splitters would create a world with a bigger number of species if they had their way.

    1% picked this

  3. A proper goal for ornithologists

    Contradicted

    Just like (B), this is the opposite of what a Splitter would say. The goal of a Splitter like Sibley is to actually increase the number of species, because they want to take an animal population that is currently being lumped together as 1 species and split it up into multiple species. Their system is less simple than Lumpers'. Lumpers just ask whether or not two populations interbreed frequently in the wild. Splitters have to study the DNA of populations and compare them.

    19% picked this

  4. The degree of genetic difference

    Contradicted

    Sibley is a Splitter and splitters specifically use the degree of genetic difference that two populations display with respect to each other, in order to help determine whether or not they should be considered to belong to the same species.

    18% picked this

  5. Correct

    Disagreements about species classification are

    Why this is right

    This builds off Sibley's concessions in the 3rd paragraph, where he says that "the species concept is slippery because there are so many examples in nature of populations that refuse to fit our limited set of definitions and names". Earlier in that paragraph the author suggests that Sibley would also agree, at least in part, to the notion that DNA-DNA can give you an approximation of how different two animals' sets of genes are from each other, "but how you interpret those differences is basically arbitrary". An arbitrary interpretation or a decision made on a somewhat arbitrary basis is likely to have people who disagree with it. If someone were to disagree with this answer, they would say, "Nuh-uh ... if techniques like DNA-DNA hybridization are further refined, it will be unlikely for there to be any disagreements about species classification". That's a pretty implausible position, that disagreements about species classification will just stop entirely. So agreeing that disagreements will still take place, even in an improved future, is a very safe idea.

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

    61% picked this

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