Conodonts, the spiky phosphatic remains (bones and teeth composed of calcium phosphate) of tiny marine animals that probably appeared about 520million years ago, were once among the most controversial of fossils. Both the nature of the organism to which the remains belonged and the function of there mains were unknown. However,since the 1981 discovery of fossils preserving not just the phosphatic elements but also other remains of the tiny soft-bodied animals (also called conodonts) that bore them, scientists' reconstructions of the animals' anatomy have had important implications for hypotheses concerning the development of the vertebrate skeleton.
The vertebrate skeleton had traditionally been regarded as a defensive development, champions of this view postulating that it was only with the much later evolution of jaws that vertebrates became predators. The first vertebrates,which were soft-bodied, would have been easy prey for numerous invertebrate carnivores, especially if these early vertebrates were sedentary suspension feeders. Thus, traditionalists argued, these animals developed coverings of bony scales or plates, and teeth were secondary features, adapted from the protective bony scales. Indeed, externa! skeletons of this type are common among the well-known fossils of ostracoderms, jawless vertebrates that existed from approximately 500 to 400 million years ago.However,other paleontologists argued that many of the definitive characteristics of vertebrates, such as paired eyes and muscular and skeletal adaptations for active life, would not have evolved unless the first vertebrates were predatory. Teeth were more primitive than external armor according to this view, and the earliest vertebrates were predators.
The stiffening notochord along the back of the body, V-shaped muscle blocks along the sides, and posterior tail fins help to identify conodonts as among the most primitive of vertebrates. The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were moreprimitive than the armored jawless fishes such as the ostracoderms. It now appears that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton.
The second paragraph in the passage serves primarily to
A.outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton
B.contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains
C.contrast the characteristics of the ostracoderms with the characteristics of earlier soft- bodied vertebrates
D.explain the importance of the development of teeth among the earliest vertebrate predators
E.present the two sides of the debate concerning the development of the vertebrate skeleton
A（错），看懂了第二段就会明白这一段描述的是一个debate 而不是 contribution
B（错） 我们仔细看完第一段和第三段后会发现 来自于1981年的观点其实是支持传统观点的，而并非在拿这两种观点进行对比
C（错）这一问也是错的没边际， 文章并没有拿 ostracoderms的特点（这个名词仅仅是个例子）与软体动物的特点进行对比
D（错）development of teeth 仅仅只被作者视为一种特点而被提出，并没有说明这种development有多么多么重要
E（对）第二段其实讨论的就是 development of vertebrate skeleton， 然后通过争论 到底vertebrate一开始扮演的角色（是不是predator），所以 第二段从结构上来看，把观点一分为二，然后进行讨论
- 【OG18-P680-668题】In a review of 2,000 studies of human behavior that date back to the 1940s, two Swiss psychologists, declaring that since most of the studies had failed to control for such variables as social class and family size, none could be taken seriously.
- Following several years of declining advertising sales, the Greenville Times reorganized its advertising sales force two years ago. Before the reorganization, the sales force was organized geographically, with some sales representatives concentrating on city-center businesses and others concentrating on different outlying regions. The reorganization attempted to increase the sales representatives’ knowledge of clients’ businesses by having each sales representative deal with only one type of industry or of retailing. After the reorganization, advertising sales increased.In assessing whether the improvement in advertising sales can properly be attributed to the reorganization, it would be helpful to find out each of the following EXCEPT:
- The author of the passage would most likely agree with which of the following statements about the link between increased solar activity and certain seasonal weather changes on the Earth?
- The passage provides information to support which of the following statement about La Nina?
- X: In order to reduce the amount of plastic in landfills, legislatures should impose a ban on the use of plastics for packaging goods.Y: Impossible! Plastic packaging is necessary for public safety. Consumers will lose all of the safety features that plastic offers, chiefly tamper-resistant closures and shatterproof bottles.Which of the following best describes the weak point in Y's response to X's proposal?