PrepTest 157 - Section 4 - Passage 3 - Question 17

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

Context · What's a "species"? Arguments about biodiversity assume we know this.

Debate among ornithologists · Lumpers vs. splitters

Lumpers group separate, but similar bird populations into a single species. Splitters divide those populations into different species.

Lumpers' perspective · Biological species concept

A species is a group that is reproductively isolated from other groups (not a lot of interbreeding in the wild between the groups).

Splitters' perspective · Phylogenetic species concept

A species is a population which has a pattern of ancestry and descent. Members of a species have a distinctive, genetically traceable feature.

Intro to Sibley · Part of splitters. Used DNA-DNA hybridization.

This technique compares DNA to determine relationships between different groups birds.

Sibley's perspective · Many earlier bird classifications were wrong

Examples: American vultures are more related to storks than European vultures. Loons and grebes aren't closely related.

One criticism of sibley (not by author) · DNA analysis still requires arbitrary interpretation

DNA shows differences between groups. But there's no clear line when those differences signify different species.

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Sibley's potential response · Acknowledges that "species concept" is slippery

However, for practical reasons, we have to limit the number of species we recognize. (If we said you were a different species from your mom, because you have slightly different DNA, that would lead to billions of different "species" in the world. That's impractical.)

Implications of debate · How we answer the species question has political and economic consequences

Example: Increasing number of species would likely increase number of endangered species.

Passage Style

Critique or debate

17.

It can be inferred from ███ ███████ ████ ███████ ██ ██████ █████ ████ ████ ████ ██████ ██ █████ ████ █████ ███ ██ ███ █████████ ██████

Question Type

Implied

Other’s perspective

This is an Inference question about the perspective of Sibley. We learn about Sibley’s perspective in P2 and P3. In general, we know that Sibley used the process of DNA-DNA hybridization to classify bird species, and we know that his work hasn’t been widely accepted.

Splitters are somewhat ████ ██████ ████ ███████ ██ ██ █████████ ██ █████████ ███ █████████ ██████ ████ ██████ ███████████ █████████

Unsupported. Sibley doesn’t say which perspective is more likely to be motivated by political and economic concerns.

The total number ██ ██████ ███████ ██ ███ █████ █████ ██ ████████ ██████████ ██████████

Unsupported. We see in P3 that Sibley recognizes that there are many examples of populations that don’t neatly fit scientists’ classifications. Additionally, Sibley’s work was about classification of bird species in particular, not the total number of animal species. The passage doesn’t suggest that Sibley thinks that the estimated number of total animal species is accurate.

A proper goal ███ ██████████████ ███████ ██ █████████ ████████ ██ ██ ████████ ███ ██████████████ ██████ ██ ██ ██ ██████ ███ █████ ██████ ██ ████████

Unsupported. Sibley does recognize that scientists need to limit the number of species that are recognized, but the passage doesn’t indicate that Sibley thinks that reducing the total number of species should be the goal for taxonomic research.

20%

The degree of ███████ ██████████ ████ ███ ███████████ ███████ ████ ███████ ██ ████ █████ ██████ ████ ██████ ███████ ██ ███ ████████ █████ ███████ ██ ████████ ████ ██ █████████ ██ ███ ████ ████████

Anti-supported. Sibley is a splitter, and his method compares the DNA from different species to determine relationships. Sibley’s method is based on studying genetic differences, so he wouldn’t think that the degree of genetic difference should have little bearing on species classification.

17%

Disagreements about species ██████████████ ███ ██████ ██ ███████ ████ ██ ██████████ ████ ███████ █████████████ ███ ███████ ████████

This is supported in Sibley’s writings that we see in P3. Sibley acknowledges that evolution produces all degrees of genetic differences. This means that, at some point, lines must be drawn to distinguish one species from another. This shows that, even if techniques are further refined, scientists will still need to make subjective decisions about species classification, so these disagreements are likely to persist.

60%

PrepTest 157 - Section 4 - Passage 3 - Question 17

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