III. Reading Comprehension: Choose the best answer for the question（20 分）
Part A.
Perhaps no destination has inspired more great naturalists than Brazil.
Charles Darwin first made landfall at Bahia in 1832; Alfred Russel Wallace
and Henry Walter Bates arrived at Pará in 1848 and Fritz Müller in 1852.
Wallace roamed the Amazon for four years and the indefatigable Bates for
11.
While Darwin and Wallace would conceive of the theory of evolution by
natural selection, its acceptance was aided by Bates and Müller. And thanks
to Bates and Müller, no creatures contributed more to the early growth of
evolutionary science than butterflies.
Bates noticed species whose wing patterns resemble those of other
butterfly families in the area. In puzzling this out, he realized that harmless
butterflies were mimicking noxious species that were unpalatable to birds
and lizards, and therefore not attacked by predators.
A few years after Darwin published “On the Origin of Species,” Bates
suggested that this sort of mimicry—now called “Batesian”—was proof of
the principle of natural selection.
Müller crucially observed that unpalatable butterflies were also
mimicking other species of unpalatable butterflies. If they were already
unpalatable, he wondered, what added advantage was there to mimicking
other species? It dawned on him that unpalatable mimics would enjoy
strength in numbers: Their unpalatability had to be learned by predators, and
species would share the cost of those lessons, whereas a uniquely patterned
unpalatable species would bear the full cost.
Natural selection thus explained why different species’ wing patterns
would converge. But how were such similar but complex wing color patterns
generated by different species? The answer eluded scientists for nearly 150
years, until an international team of researchers recently revealed mimicry’s
innermost secrets.
There were two ways in which what is still called “Müllerian mimicry”
would evolve: Either each species independently evolved mutations that led
to very similar wing patterns, or patterning genes were exchanged among
species. By analyzing the DNA sequences in two mimicking Heliconius
species in South America, researchers could determine that each species had
independently evolved up to 20 different patterns. But in more closely related
mimicking species, they found that color-controlling genes had been
exchanged.
It is astonishing that so many patterns could be independently generated and
replicated in different species. And it is surprising to have species swapping
genes. After all, the inability to breed successfully with other groups has long
been an operational definition of species. Even if such interspecies matings
are rare, a gene that confers a strong advantage, like mimicry, can spread
quickly through a population.
【題組】52. According to the passage, why do unpalatable butterflies mimic other species
of unpalatable butterflies?
(A) To become even more unpalatable.
(B) To attract mates from other species.
(C) To minimize the cost of being eaten.
(D) To enjoy more colorful wing patterns.
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