June 2007 PrepTest, Section 3, Question 11
Feathers recently taken from seabirds stuffed and preserved in the 1880s have been found to contain only half as much mercury as feathers recently taken from living birds of the same species. Since mercury that accumulates in a seabird's feathers as the feathers grow is derived from fish eaten by the bird, these results indicate that mercury levels in saltwater fish are higher now than they were 100 years ago.
Feathers recently taken from seabirds stuffed and preserved in the 1880s have been found to contain only half as much mercury as feathers recently taken from living birds of the same species. Since mercury that accumulates in a seabird's feathers as the feathers grow is derived from fish eaten by the bird, these results indicate that mercury levels in saltwater fish are higher now than they were 100 years ago.
Feathers recently taken from seabirds stuffed and preserved in the 1880s have been found to contain only half as much mercury as feathers recently taken from living birds of the same species. Since mercury that accumulates in a seabird's feathers as the feathers grow is derived from fish eaten by the bird, these results indicate that mercury levels in saltwater fish are higher now than they were 100 years ago.
Feathers recently taken from seabirds stuffed and preserved in the 1880s have been found to contain only half as much mercury as feathers recently taken from living birds of the same species. Since mercury that accumulates in a seabird's feathers as the feathers grow is derived from fish eaten by the bird, these results indicate that mercury levels in saltwater fish are higher now than they were 100 years ago.
The argument depends on assuming that
the proportion of a seabird's diet consisting of fish was not as high, on average, in the 1880s as it is today
the amount of mercury in a saltwater fish depends on the amount of pollution in the ocean habitat of the fish
mercury derived from fish is essential for the normal growth of a seabird's feathers
the stuffed seabirds whose feathers were tested for mercury were not fully grown
the process used to preserve birds in the 1880s did not substantially decrease the amount of mercury in the birds' feathers
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