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【单选题】
Disaster struck 250 million years ago, when the worst devastation in the earth's history occurred. Called the end-Permian mass extinction, it marks a fundamental change in the development of life. The history of life on the earth is replete with catastrophes of varying magnitudes. The one that has captured the most attention is the extinction of the dinosaurs and other organisms 65 million years ago—between the Cretaceous and Tertiary periods—which claimed up to half of all species. As severe as that devastation was, it pales in comparison to the greatest disaster of them all: the mass extinction some 250 million years ago, at the end of the Permian period. Affectionately called 'the mother of mass extinctions' among paleontologists (with apologies to Saddam Hussein), it yielded a death toll that is truly staggering. About 90 percent of all species in the oceans disappeared during the last several million years of the Permian. On land, more than two thirds of reptile and amphibian families vanished. Insects, too, did not escape the carnage: 30 percent of insect orders ceased to exist, marking the only mass extinction insects have ever undergone. But from catastrophes, opportunities arise. For several hundred million years before the end-Permian event, the shallow seas had been dominated by life-forms that were primarily immobile. Most marine animals lay on the seafloor or were attached to it by stalks, filtering the water for food or waiting for prey. In the aftermath of the extinction, many once minor groups-active, predatory relatives of modern-day fish, squids, snails and crabs—were able to expand. Some completely new lineages appeared. This ecological reorganization was so dramatic that it forms a fundamental boundary in the history of life. Not only does it demarcate the Permian and Triassic periods, it also establishes the close of the Paleozoic era and the start of the Mesozoic era. The modern tidal pool reflects what lived and what died 250 million years ago. Over the past few years, exciting new insights into the causes and consequences of the end-Permian mass extinction have poured in from virtually every branch of the earth sciences. Some of these findings include detailed studies of rapid changes in ocean chemistry, more thorough documentation of extinction patterns and new analyses showing that large volcanic eruptions occurred at the Permo Triassic boundary. How much do mass extinctions contribute to the evolution of a group as compared with long-term adaptive trends? For examples sea urchins are ubiquitous in modern oceans but were relatively uncommon during the Permian. Only a single genus, Miocidaris, is known for certain to have survived the extinction. Did Miocidaris survive by pure chance, or was it better adapted? Would sea urchins today look any different had it not been for the end Permian extinction? To resolve such questions, we need to learn more about the causes of the catastrophe and how those species that survived differed from those that disappeared. The key sources for this information are rock layers and fossils. Unfortunately, samples from the late Permian and early Triassic are notoriously difficult to come by. The fossil record across the boundary is plagued by poor preservation, a lack of rock to sample and other problems, including access. An extensive drop in sea level during the late Permian limited the number of marine rocks deposited on land, and many areas where the best rocks were preserved (most notably, in southern China) have been relatively hard for some geologists to reach. As such, it has proved difficult to ascertain just how quickly life was snuffed out or if the deaths were subject to any regional variations. Some creatures, especially those sensitive to changes in the environment, died off rapidly, as shown by Erik Flugel and his colleagues at the University of Erlangen, who arrive
A.
two thirds
B.
half
C.
90%
D.
30%
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【单选题】以下关于垃圾邮件给EMAIL营销带来的影响叙述有误的是()
A.
降低了用户对EMAIL营销的信任
B.
有价值的信息淹没在大量的垃圾邮件中
C.
垃圾服务商屏蔽
D.
垃圾邮件含有大量有价值信息,是许可邮件营销的有益补充
【单选题】园路面层定额中 干硬性水泥砂浆垫层厚度按( )考虑,若实际厚 度与定额不同时,可按本章有关子目进行调整。
A.
2cm
B.
3cm
C.
4cm
D.
5cm
【单选题】计算机的主机由哪些部件组成?
A.
CPU、外存储器、外部设备
B.
CPU和内存储器
C.
CPU和存储器系统
D.
主机箱、键盘、显示器
【多选题】许可Email营销在主题设计上应遵循的基本原则有
A.
要体现内容的精华
B.
要体现出发件人信息中无法包含的内容
C.
要体现出品牌或产品信息
D.
不宜过于简单或过于复杂
【多选题】营销的目标群体确定后,接下来就要针对目标群体进行Email营销内容的策划,包含( )
A.
确定方向
B.
精确定位
C.
重点推送
D.
全部发送
【单选题】计算机系统的“主机”由【】构成.
A.
CUP、内存储器及辅助存储器
B.
CUP和内存储器
C.
存放在主机箱内部的全部器件
D.
计算机的主板上的全部器件
【单选题】根据老师的作文要求充分想象,这时的想象是( )。
A.
无意想象
B.
有意想象
C.
幻想
D.
妄想
【单选题】计算机系统的“主机”由()。
A.
CPU,内存储器及辅助存储器
B.
CPU和内存储器
C.
存放在主机箱内部的全部器件
D.
计算机的主板上的全部器件
【判断题】PC的内部存储器由ROM、RAM和Cache(缓冲存储器)。
A.
正确
B.
错误
【单选题】以下关于垃圾邮件给Email营销带来的影响叙述有误的是( )
A.
降低了用户对Email营销的信任
B.
有价值的信息淹没在大量的垃圾邮件中
C.
邮件服务商屏蔽
D.
垃圾邮件含有大量有价值信息,是许可邮件营销的有益补充
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