GRE考试

【单选题】The opposite of adaptive divergence is an
interesting and fairly common expression of evo-
lution. Whereas related groups of organisms take
Line on widely different characters in becoming
(5) adapted to unlike environments in the case of
adaptive divergence, we find that unrelated
groups of organisms exhibit adaptive convergence
when they adopt similar modes of life or become
suited for special sorts of environments. For
(10) example, invertebrate marine animals living firm-
ly attached to the sea bottom or to some foreign
object tend to develop a subcylindrical or conical
form. This is illustrated by coral individuals, by
many sponges, and even by the diminutive tubes
(15) of bryozoans.Adaptive convergence in taking this
coral-like form is shown by some brachiopods
and pelecypods that grew in fixed position. More
readily appreciated is the streamlined fitness of
most fishes for moving swiftly through water;
(20) they have no neck, the contour of the body is
smoothly curved so as to give minimum resis-
tance, and the chief propelling organ is a power-
ful tail fin. The fact that some fossil reptiles
(ichthyosaurs) and modern mammals (whales,
(25) dolphins) are wholly fishlike in form is an
expression of adaptive convergence, for these air-
breathing reptiles and mammals, which are highly
efficient swimmers, are not closely related to
fishes. Unrelated or distantly related organisms
(30) that develop similarity of form are sometimes
designated as homeomorphs (having the same
form).
It can be inferred that in the paragraph immediately preceding this passage the author discussedA．marine intelligence
B．adaptive divergence
C．air-breathing reptiles
D．environmental impacts
E、organisms with similar forms

网考网参考答案：B
网考网解析：
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