Marta Coll and colleagues' 2010 Mediterranean Sea biodiversity census reported approximately 17,000 species, nearly double the number reported in Carl...
GMAT Information and Ideas : (Ideas) Questions
Marta Coll and colleagues' 2010 Mediterranean Sea biodiversity census reported approximately 17,000 species, nearly double the number reported in Carlo Bianchi and Carla Morri's 2000 census-a difference only partly attributable to the description of new invertebrate species in the interim. Another factor is that the morphological variability of microorganisms is poorly understood compared to that of vertebrates, invertebrates, plants, and algae, creating uncertainty about how to evaluate microorganisms as species. Researchers' decisions on such matters therefore can be highly consequential. Indeed, the two censuses reported similar counts of vertebrate, plant, and algal species, suggesting that ______
Which choice most logically completes the text?
Coll and colleagues reported a much higher number of species than Bianchi and Morri did largely due to the inclusion of invertebrate species that had not been described at the time of Bianchi and Morri's census.
some differences observed in microorganisms may have been treated as variations within species by Bianchi and Morri but treated as indicative of distinct species by Coll and colleagues.
Bianchi and Morri may have been less sensitive to the degree of morphological variation displayed within a typical species of microorganism than Coll and colleagues were.
the absence of clarity regarding how to differentiate among species of microorganisms may have resulted in Coll and colleagues underestimating the number of microorganism species.
Step 1: Decode and Map the Passage
Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Marta Coll and colleagues' 2010 Mediterranean Sea biodiversity census reported approximately 17,000 species, nearly double the number reported in Carlo Bianchi and Carla Morri's 2000 census" |
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| "—a difference only partly attributable to the description of new invertebrate species in the interim." |
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| "Another factor is that the morphological variability of microorganisms is poorly understood compared to that of vertebrates, invertebrates, plants, and algae, creating uncertainty about how to evaluate microorganisms as species." |
|
| "Researchers' decisions on such matters therefore can be highly consequential." |
|
| "Indeed, the two censuses reported similar counts of vertebrate, plant, and algal species, suggesting that ______" |
|
Passage Architecture & Core Elements
Main Point: The dramatic difference in species counts between two Mediterranean biodiversity censuses stems largely from different approaches to classifying microorganisms, since well-understood organism groups showed similar counts in both studies.
Argument Flow: The passage establishes a puzzling doubling of species counts between censuses, partially explains it through new discoveries, then focuses on microorganism classification uncertainty. It builds to the key evidence that well-understood groups had similar counts, suggesting the difference lies in microorganism classification approaches.
Step 2: Interpret the Question Precisely
This is a fill-in-the-blank question asking us to choose the best logical connector. The answer must create the right relationship between what comes before and after the blank.
Step 3: Prethink the Answer
- The logic here is crucial: if vertebrates, plants, and algae (the well-understood groups) had similar counts in both censuses, but the overall total nearly doubled from 2000 to 2010, then the increase must come from the problematic category—microorganisms
- Since we know microorganisms are hard to classify and researchers' decisions are "highly consequential," the difference likely reflects different classification approaches rather than actual species discovery
- So the right answer should explain how the similar counts of well-understood species, combined with the overall doubling, points to different treatment of microorganisms between the two studies
Coll and colleagues reported a much higher number of species than Bianchi and Morri did largely due to the inclusion of invertebrate species that had not been described at the time of Bianchi and Morri's census.
✗ Incorrect
- Focuses entirely on invertebrates causing the difference
- Contradicts the passage's explicit statement that invertebrates only "partly" explain the difference
- Ignores the microorganism classification issue that the passage emphasizes
some differences observed in microorganisms may have been treated as variations within species by Bianchi and Morri but treated as indicative of distinct species by Coll and colleagues.
✓ Correct
- Perfectly captures the logical inference: if well-understood groups had similar counts but totals doubled, the difference must be in microorganism classification
- Aligns with the passage's emphasis on classification uncertainty for microorganisms
- Explains why Bianchi and Morri had lower counts—they were more conservative in treating microorganism variations as separate species
Bianchi and Morri may have been less sensitive to the degree of morphological variation displayed within a typical species of microorganism than Coll and colleagues were.
✗ Incorrect
- Suggests Bianchi and Morri were less sensitive to variation than Coll
- This doesn't explain the count difference logically—if they were less sensitive, they might have missed distinctions, but the passage suggests they were more conservative
the absence of clarity regarding how to differentiate among species of microorganisms may have resulted in Coll and colleagues underestimating the number of microorganism species.
✗ Incorrect
- Claims Coll underestimated microorganisms, but Coll had the higher count (17,000 vs ~8,500)
- Contradicts the basic numerical relationship established in the passage