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Tadpole Body Mass and Toxin Production after Three Weeks in Ponds
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 Bokony 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?
Difficulty: Hard

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.

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