Thomas Henry Huxley (1825−1895), one of Charles Darwin’s earliest and most staunch defenders, as well as an influential naturalist in his own right, first observed the many similarities between reptiles and birds. Huxley noted, for example, that the wings of a bird hid reptilian fingers. Today, few scientists challenge not only the link between birds and reptiles in general, but between birds and theropods, a group of bipedal saurischian dinosaurs. Hundreds of structural similarities exist, including elongated arms, large eye openings, swiveling wrists, three forward-facing toes, and hollow bones.
The most diverse theropod group is the coelurosaurs, a carnivorous bipedal group that includes the Tyrannosaurus rex and the Velociraptor, the latter of which is quite similar to the oldest known bird, the Archaeopteryx. Coelurosauria, in fact, is the clade that contains all theropods more closely related to birds than to carnosaurs, and all coelurosaurs have been thought to possess feathers.
However, a recent find of what seems to be an entirely new—and apparently featherless—coelurosaur has complicated the subject. Several suggestions have been made as to why this particular chicken-sized dinosaur from the Late Jurassic period lacked feathers.
One possibility is that, in some creatures, feathers were replaced by scales because the feathers were not needed for warmth, recognition of family members, or mating rituals—uses that feathers were thought to have had for dinosaurs that did not fly. It is also possible that some coelurosaurs had feathers in only certain geographic areas. Another idea is that this particular coelurosaur was so young that it had not yet grown feathers.
A more fundamentally profound alternative is that, contrary to conventional scientific thought, birds and feathered dinosaurs developed feathers independently of each other rather than from a common ancestor. This would certainly not be the first case of what is known as convergent evolution. Fish and certain mammals can swim ,but have evolved this attribute separately. Likewise, insects have wings, but developed them independently from birds. Luckily, the new fossil of what has been named a Juravenator is well-preserved almost in its entirety. More insights into why it did not have feathers will likely lead to new insights into how other animals did develop this trait.
1. In the passage, the author is primarily interested in:
(A) presenting possible solutions to a problem that has troubled scientists for years
(B) providing background information and possible explanations for a curious discovery
(C) answering critics of a controversial theory that is supported by a new finding
(D) showing how an established idea can become too entrenched in conventional scientific thought
(E) presenting historical background to a current phenomenon
2. According to the passage, the Archaeopteryx _______________________ .
(A) had feathers but did not fly
(B) is the oldest known coelurosaur
(C) was approximately the size of a chicken
(D) shares some similarities with carnivorous dinosaurs
(E) and the Juravenator developed feathers from a common ancestor
3. According to the passage, feathers on dinosaurs .
(A) were not used for flight
(B) were not always present at birth
(C) were first noted by Huxley
(D) might have evolved from scales
(E) were a characteristic of all coelurosaurs
4. Which of the following can be inferred from the passage?
(A) All adult coelurosaurs possessed feathers.
(B) Coelurosaurs who did not need feathers for warmth or mating rituals shed those feathers for scales.
(C) Scientists have reached a consensus that certain birds and dinosaurs are evolutionarily linked.
(D) Thomas Henry Huxley believed in the idea of convergent evolution.
(E) Coeulurosaurs that did not have feathers instead had scales.
5. According to the passage, convergent evolution __________.
A. had not been thought to apply to a common trait found in birds and other animals prior to the discovery of the Juravenator fossil
B. has not been shown to apply to humans
C. was not always thought to apply to birds and coelurosaurs
D. was first noticed by Thomas Henry Huxley
E. explains why some dinosaurs developed feathers for warmth
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发表于 2021-10-9 22:22:53
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