Archaeopteryx and Bird Evolution
During the late Jurassic period, about 150 million years ago, the animal many consider to be the first bird left a fossil record. ⬛At that time the climate of Europe was tropical and palm-like trees surrounded shallow bodies of water (lagoons). ⬛The ancient bird met its death in one of these lagoons and there, in the fine mud at the bottom of the lagoon, it formed an exquisite fossil to be unearthed in the limestone quarry at Solnhofen, Germany, in 1861.⬛ This specimen was called Archaeopteryx lithographica . It was remarkable on two counts.⬛ First, it had features of both birds and reptiles and so formed the “missing link” in the evolutionary branch from reptiles to birds. Second, it was discovered just two years after Charles Darwin published his book On the Origin of Species , outlining the theory of evolution.
Archaeopteryx had reptilian jaws and teeth and a reptile-like tail. It also had feathers remarkably similar to those of modern birds. The fine grain of the Solnhofen Limestone preserved in great detail their well-developed flight feathers. These feathers made wings and they were also present on the tail. In many ways Archaeopteryx resembled the present-day pheasant coucal (a species of cuckoo bird) of Australia and New Guinea, not only in size but also in general bone and feather construction. The structure of the tail was, however, different in Archaeopteryx: the feathers projected out from a long tail. Archaeopteryx also had three clawed fingers on the leading side of its wings and these were movable. It might have used these claws in climbing trees just as the young hoatzin birds of South America do today. If a nestling hoatzin falls out of the nest, it uses its claws to climb back to safety. In fact, wing claws are not uncommon in modern tree-climbing birds (e.g., woodpeckers), especially at nestling stage.
It seems that Archaeopteryx was not a strong flier, although it was no larger than a pigeon or a chicken. Its rather small size should have assisted flying, but all the fossils of Archaeopteryx, except one, lack the sternum of birds that evolved later. The sternum is the breastbone, a large bone extending from the chest to the abdomen. The powerful flight muscles (pectoral muscles) are anchored to the sternum in modern birds. These extremely large muscles enable birds to fly by flapping their wings. One fossil of Archaeopteryx, believed to be the least ancient of the seven fossils, has a sternum to which pectoral muscles could have been attached. This specimen of Archaeopteryx may well have had powered flight.
Some pectoral muscles are also attached to the furcula, the forked bone in front of the breast bone formed by fusion of the collarbones. Archaeopteryx had a furcula but, although this might have meant that it had some pectoral muscles for flight, it would not have provided sufficient anchorage for large pectoral muscles. Archaeopteryx also lacked the air sacs characteristic of flying birds. These are bags of air extending from the lungs and into the bones through small openings, and they are used to supply oxygen during the extreme energy demands of flight.
Archaeopteryx, therefore, did not have all the characteristics necessary for flight as seen in modern birds, even though it had feathers. It has even been suggested that the feathers were merely for insulation and not used in flying at all. Birds are able to maintain their body temperature in ways that reptiles cannot, but the fossil records cannot tell us whether Archaeopteryx was bird-like or reptilelike in this characteristic. Having feathers is not the ultimate clue to the ability to fly. Although it used to be thought that Archaeopteryx was the very first feathered creature to evolve, recently discovered fossils show that dinosaurs—probably quite unrelated to the ancient birds—also had feathers. These dinosaurs walked the Earth in the late Jurassic and early Cretaceous periods. They did not fly, as can be seen by their bone structure, particularly the bones of the hind limbs. Therefore, having feathers and being able to fly are two characteristics that need not always go together. Feathers might well have evolved in the first instance to provide insulation or to fulfill some function other than flight. Then, later, they were used for flight.
1.The word “consider” in the passage is closest in meaning to
A.argue
B.believe
C.agree
D.determine
2.According to paragraph 1, why was the discovery of the Archaeopteryx lithographica fossil significant?
A.It provided clues about the climate of Europe in the late Jurassic period.
B.Its existence was predicted by Darwin.
C.It provided insight into how birds evolved from reptiles.
D.It was the earliest known fossil from the Jurassic period
3.According to paragraph 2, the Archaeopteryx fossil discussed in the passage had so much detail because
A.it was preserved with the feathers projecting out from the tail
B.the properties of the limestone where it was found were suitable for preservation
C.feathers were present on the tail as well as on the wings
D.its wing claws had not been used
4. According to paragraph 2, Archaeopteryx differed from the modern pheasant coucal in
A.body size
B.tail features
C.bone structure
D.feather construction
5. What can be inferred from paragraph 3 about the evolution of Archaeopteryx?
A.Archaeopteryx probably got smaller as it evolved.
B.Archaeopteryx may have become better at flying as it evolved.
C.Archaeopteryx probably lost its sternum as it evolved.
D.Archaeopteryx may have developed smaller flight muscles as it evolved.
6. In paragraphs 3 and 4, all of the following are given as reasons why Archaeopteryx was probably unable to fly well EXCEPT:
A.Its furcula could not support large pectoral muscles.
B.It did not possess a sternum in most cases.
C.It did not have air sacs.
D.It was too small to power flight.
7. The word “fusion” in the passage is closest in meaning to
A.curving
B.enlargement
C.extension
D.merging together
8. What is the author’s purpose in discussing feathered dinosaurs in paragraph 5 ?
A.To support the argument that the presence of feathers does not necessarily indicate the ability to fly
B.To suggest that dinosaurs relied on feathers for insulation
C.To argue that Archaeopteryx was more similar to dinosaurs than to birds
D.To argue that some dinosaurs living at the same time as Archaeopteryx were also closely linked to birds
9. Look at the four squares [⬛] that indicate where the following sentence could be added to the passage.
The dead bird remained in one piece because the low oxygen levels in lagoons discouraged other organisms from feeding on it.
Where would the sentence best fit?
10. Prose summary
The sauropod dinosaurs had a long neck and tail and were the largest animals ever to live on land.
Answer Choices:
A) Even though the tropical climate of the Jurassic period was favorable to the evolution of new species, Archaeopteryx did not survive.
B) Archaeopteryx was reptile-like in some respects but was similar to a modern bird in its overall bone structure, feathers, and wing claws.
C) Feathers have a number of functions, including temperature regulation, but scientists can only theorize about the true function of Archaeopteryx feathers.
D) Similarities between Archaeopteryx and the modern pheasant coucal of Australia and New Guinea provide clues about the part of the world where birds first evolved.
E) Archaeopteryx was the right size for flying but lacked several other essential requirements for flight.
F) Although other dinosaur fossils found before Archaeopteryx showed the presence of feathers, these feathers were attached to the tail and were used mainly to assist in walking.
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