Population densityAverage tadpole body mass (milligrams)Average number of distinct bufadienolide toxins per tadpoleAverage amount of bufadienolide per...
GMAT Information and Ideas : (Ideas) Questions
| Population density | Average tadpole body mass (milligrams) | Average number of distinct bufadienolide toxins per tadpole | Average amount of bufadienolide per tadpole (nanograms) | Average bufadienolide concentration (nanograms per milligram of tadpole body mass) |
|---|---|---|---|---|
| High | 193.87 | 22.69 | 5,815.51 | 374.22 |
| Medium | 254.56 | 21.65 | 5,525.72 | 230.10 |
| Low | 258.97 | 22.08 | 4,664.99 | 171.43 |
Ecologist Veronika Bókony and colleagues investigated within-species competition among common toads (Bufo bufo), a species that secretes various unpleasant-tasting toxins called bufadienolides in response to threats. The researchers tested B. bufo tadpoles' responses to different levels of competition by creating ponds with different tadpole population densities but a fixed amount of food. Based on analysis of the tadpoles after three weeks, the researchers concluded that increased competition drove bufadienolide production at the expense of growth.
Which choice uses data from the table to most effectively support the researchers' conclusion?
The difference in average tadpole body mass was small between the low and medium population density conditions and substantially larger between the low and high population density conditions.
Tadpoles in the low and medium population density conditions had substantially lower average bufadienolide concentrations but had greater average body masses than those in the high population density condition.
Tadpoles in the high population density condition displayed a relatively modest increase in the average amount of bufadienolide but roughly double the average bufadienolide concentration compared to those in the low population density condition.
Tadpoles produced approximately the same number of different bufadienolide toxins per individual across the population density conditions, but average tadpole body mass decreased as population density increased.
Step 1: Decode and Map the Passage
Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Ecologist Veronika Bókony and colleagues investigated within-species competition among common toads (Bufo bufo), a species that secretes various unpleasant-tasting toxins called bufadienolides in response to threats." |
|
| "The researchers tested B. bufo tadpoles' responses to different levels of competition by creating ponds with different tadpole population densities but a fixed amount of food." |
|
| "Based on analysis of the tadpoles after three weeks, the researchers concluded that increased competition drove bufadienolide production at the expense of growth." |
|
Table Data Analysis: High density: 193.87 mg mass, 374.22 ng/mg concentration; Medium density: 254.56 mg mass, 230.10 ng/mg concentration; Low density: 258.97 mg mass, 171.43 ng/mg concentration. Pattern: As density increases, mass decreases, concentration increases.
Passage Architecture & Core Elements
Main Point: Research on toad tadpoles shows that increased competition leads to higher toxin production but reduced growth.
Argument Flow: The passage introduces a study on toad competition, describes the experimental methodology of varying population density while keeping food constant, and presents the conclusion that competition drives a trade-off between toxin production and growth.
Step 2: Interpret the Question Precisely
What's being asked? Which answer choice uses the table data most effectively to support the researchers' conclusion
What type of answer do we need? Evidence that demonstrates the trade-off between toxin production and growth under increased competition
Any limiting keywords? "most effectively support" - we need the strongest evidence for the specific conclusion stated
Step 3: Prethink the Answer
- The researchers concluded that "increased competition drove bufadienolide production at the expense of growth."
- To support this, we need data showing: As competition increases (higher density), toxin production increases; As competition increases, growth decreases; These two changes happen together, suggesting a trade-off.
- Looking at our table pattern: high density = lowest body mass + highest toxin concentration; low density = highest body mass + lowest toxin concentration.
- So the right answer should highlight this inverse relationship - showing that higher competition correlates with both increased toxin production AND decreased growth.
The difference in average tadpole body mass was small between the low and medium population density conditions and substantially larger between the low and high population density conditions.
- Focuses only on body mass differences between conditions
- Completely ignores toxin production data
- Doesn't demonstrate the trade-off that's central to the researchers' conclusion
Tadpoles in the low and medium population density conditions had substantially lower average bufadienolide concentrations but had greater average body masses than those in the high population density condition.
- Shows both sides of the trade-off relationship
- Low/medium density: lower toxin concentrations BUT greater body masses
- High density: higher toxin concentrations BUT lower body masses
- Directly supports the "at the expense of" conclusion by showing the inverse relationship
Tadpoles in the high population density condition displayed a relatively modest increase in the average amount of bufadienolide but roughly double the average bufadienolide concentration compared to those in the low population density condition.
- Mentions both toxin amount and concentration but doesn't clearly connect to growth
- "Modest increase in amount" doesn't effectively support increased production claim
- Fails to highlight the trade-off aspect that's key to the conclusion
Tadpoles produced approximately the same number of different bufadienolide toxins per individual across the population density conditions, but average tadpole body mass decreased as population density increased.
- Shows body mass decreased with density (supports growth part)
- But states toxin variety stayed "approximately the same"
- Doesn't demonstrate increased toxin production, missing half the conclusion