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  3. A reconstruction of an ancient tree from one of Earth’s first forests reveals that the plants were topped with fronds(蕨类植树物的叶子)

A reconstruction of an ancient tree from one of Earth’s first forests reveals that the plants were topped with fronds(蕨类植树物的叶子)

admin2009-04-23  40
问题     A reconstruction of an ancient tree from one of Earth’s first forests reveals that the plants were topped with fronds(蕨类植树物的叶子) and not leaves. The crown(树冠) of an ancient tree found in a place from which stone is dug out in New York has shed light on the look of the world’s earliest forests believed to have thrived about 390 million years ago.
    The discovery of this 390-million yes, old, six-foot upper portion of an ancient tree trunk allowed  scientists to create a composite picture of the entire plant when they put it together with fragments of a trunk found in the same site a year before and with tree stumps recovered more than 130 years ago. The remains have been widely reported as "evidence of the Earth’s oldest forest," according to a paper published in this week’s Nature.
    "The basic point of this paper is two things," says lead author William Stein. "We now have clear evidence what these stumps really were", and we also have "real strong evidence of the structure of these forms."
    From the fossil reconstruction, the team of scientists determined that a tree comprising all these parts could grow about 30 feet tall. According to Stein, the base would have been massive— on the order of 2.5 feet in diameter—and a large, single trunk with vertical ridges, topped by a leafless crown of a material resembling fronds on ferns(蕨类) and palms.
    By piecing together the fragments, the team was able to get an idea of what forest might have looked like 390 million years ago. Stein estimates these trees would have been "fairly closely spaced," about 3 to 16 feet apart, and that they would have dropped a load of fronds from their branches onto the forest floor. Amongst these trees were likely smaller plants and shrubs. These trees likely let more sunlight through than modern-day counterparts, for their branch structures did not fan out as far, forming an umbrella-like shape.
    Stein notes that the rise of forests with trees like these caused the removal of CO2 from the air and temperatures to drop, creating climates like those experienced today. The drop CO2 in levels, he says, likely led to the evolution of flat leaves on trees to attract and retain more of the gas, which plants need. Up next, he says: research will focus on "the internal structure of the plants to work out how they grew" as well as "how they functioned physiologically, particularly the relationship with CO2."
选项 A、It helps people know that ancient trees have no trunk.
B、It provides us new information about the appearance of the earliest forest.
C、It provides evidence for the existence of trees 397 million years ago.
D、It provides evidence for the bloom of trees 397 million years ago.
答案B
解析 根据题干中the crown of an ancient tree found in New York，可以定位到第一段的最后一句话。该句提到一个古树树冠在纽约的一个采石的地方被发现，这为了解三亿九百万年前世界早期森林的样子提供了新的信息。文章没有提到这个古树树冠的出土使人们知道古树没有树干，故可排除A；三亿九百万年前有树木这一事实也不是以这个古树树冠的出土为证据的，故排除C；人们所认为三亿九百万年前树木很茂盛，但这个古树树冠的出土并未证明这一点，故可排除D。
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