托福阅读真题+题目+答案：Origins of the Deciduous Forests

托福阅读真题+题目+答案：Origins of the Deciduous Forests

Forests dominated by deciduous trees (trees with leaves that fall off at the end of the growing season) are found around the world.▋ But they were not always so widespread, and there are unanswered questions about their evolution. ▋The ancestors of deciduous trees can be traced back to the Cretaceous Period, 113-65 million years ago, when dinosaurs ruled the land and the continents occupied different positions from today.▋ At this time, extensive deciduous forests existed only at very high latitudes, near the north and south poles.▋

1.The word “extensive” in the passage is closest in meaning to

A.widespread

B.early

C.developing

D.dense

Alaska was closer to the North Pole during the late Cretaceous than it is today, but the climate was milder, reflecting higher temperatures for the entire planet. This can be deduced from the shape of fossil leaves. There is a remarkably consistent relationship between leaf shape and mean annual temperature for modern plant species. For example, the proportion of species with toothed leaves consistently increases as one moves from warm to cold climates Based on statistical analyses of a large number of such leaf characteristics, temperatures in the Cretaceous Arctic generally hovered above freezing during the winter. This is confirmed by the lack of geological evidence of permafrost, a layer of earth that is permanently frozen. However, fossilized tree trunks at Ellesmere Island in northern Canada display damaged sections (growth interruptions) consistent with damage caused by severe frost indicating that occasional frosts occurred. Also, although the winters were generally mild, they were-like modern Arctic winters--very dark. Because of the tilt of Earth's axis, very little sunlight reaches high northern latitudes for several months each year, so trees and shrubs of the ancient Arctic could not photosynthesize (produce chemical energy from sunlight) for several weeks or even months, depending on the latitude. This is apparent from growth rings from fossilized wood of the period; the annual growth rings end abruptly, evidence of a rapid interruption of photosynthesis and plant growth with the onset of winter darkness.

2.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

A.Trees and shrubs in the ancient Arctic could not photosynthesize during those months of the year when little sunlight reaches high latitudes due to the tilt of Earth's axis.

B.Because of the tilt of Earth's axis. very little sunlight was needed for trees and shrubs to produce the chemical energy necessary for photosynthesis at high northern latitudes.

C.Arctic trees and shrubs photosynthesized between several weeks and many months each year, depending on the latitude and the tilt of Earth's axis.

D.High northern latitudes receive little sunlight because of the tilt of Earth's axis, which required ancient Arctic trees and shrubs to produce all the energy they needed in only a few months.

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