問題詳情
Passage 2 Life Life originated in the early seas less than a billion years after the Earth was formed. Yetanother three billion years were to pass before the first plants and animals appeared on thecontinents. Life’s transition from the sea to the land was perhaps as much of an evolutionarychallenge as was the genesis of life.What forms of life were able to make such a drastic change in lifestyle? The traditional viewof the first terrestrial organisms is based on megafossils—relatively large specimens ofessentially whole plants and animals. Vascular plants, related to modern seed plants and ferns, leftthe first comprehensive megafossil record. Because of this, it has been commonly assumed thatthe sequence of terrestrialization reflected the evolution of modern terrestrial ecosystems. In thisview, primitive vascular plants first colonized the margins of continental waters, followed byanimals that fed on the plants, and lastly by animals that preyed on the plant-eaters. Moreover, themegafossils suggest that terrestrial life appeared and diversified explosively near the boundarybetween the Silurian and the Devonian periods, a little more than 400 million years ago.Recently, however, paleontologists have been taking a closer look at the sediments belowthis Silurian Devonian geological boundary. It turns out that some fossils can be extracted fromthese sediments by putting the rocks in an acid bath. The technique has uncovered new evidencefrom sediments that were deposited near the shores of the ancient oceans—plant microfossils and microscopic pieces of small animals. In many instances the specimens are less than one-tenth of amillimeter in diameter. Although they were entombed in the rocks for hundreds of millions ofyears, many of the fossils consist of the organic remains of the organism.These newly discovered fossils have not only revealed the existence of previously unknownorganisms, but have also pushed back these dates for the invasion of land by multi-cellularorganisms. Our views about the nature of the early plant and animal communities are now beingrevised. And with those revisions come new speculations about the first terrestrial life-forms.
【題組】46. According to the theory that the author calls “the traditional view,” what was the first form oflife to appear on land?
(A) Bacteria
(B) Meat-eating animals
(C) Plant-eating animals
(D) Vascular plants
參考答案
答案：D
難度：適中0.461538
統計：A(3),B(1),C(1),D(6),E(0)