第29套
Tree Species Identification in Tropical Rain Forests
Identifying tree species in tropical rain forests may be harder than you think.Plant species identification can be difficult for all kinds of reasons even identification of trees,which are big and conspicuous.For example,for some willow trees,both leaves and flowers may be needed for identification,but the two may not be prent at the same time.Yet whatever problems may confront us in temperate climates,we can be sure that the tropics will po far wor difficulties.
1.The word conspicuous in the passage is clost in meaning to
A.clo to each other
<
C.easily noticed
我国的四大名著D.solitary
2.ln paragraph1,why does the author discuss willow trees
A.To provide an example of a tree that is unusually large
B.To explain the process of tree species identification
C.To support the idea that tropical trees can be more difficult to identify than temperate trees
D.To demonstrate one reason why it can be problematic to determine what species a tree belongs to
In tropical rain forests，the flowers of a given tree species are typically not in bloom and so cannot be obrved.In asonal rain forests(with a distinct wet ason and a distinct dry ason),many trees adjust their flowering to the rains,so flowering is to some extent predictable.But much rain forest(as in much of the Amazon region)is nonasonal,and trees may flower at any time.To be sure,different trees of the same species generally flower simultaneously,for if they did not,they could not pollinate each other.They must be responding to signals from the environment at large,or el (or in addition)they must be communicating with one another.But what tho signals are is unknown,at least to us.To the human obrver，the flowering ems random.In any ca,in a tropical forest(at least in a condary forest,which is forest that is regrowing after previous harvesting or clearance),the trees grow very clo together，and most are remarkably thin，like poles，and grow straight up and disappear into the gloom,twenty meters overhead.Even if there are flowers，you wo
uld not necessarily e them.抛弃的反义词
3.Paragraph2implies which of the following about tree flowering in asonal rainforests
A.It is less predictable than tree flowering in tropical rain forests
B.It results from an unknown means of communication between the individual trees
of each species.
C.It is more uful to rearchers trying to identify tree species than is the tree flowering in tropical rain forests.
D.It follows the same pattern that tree flowering follows in a tropical condary forest.
4.In paragraph2，why does the author discuss pollination
吐鲁番郡王府A.To provide evidence that in many tropical tree species flowering is at least somewhat predictable
B.To help explain why flowers on trees in tropical rainforests can be abnt most of the time
C.To help explain why different trees of the same species bloom at the same time
D.To suggest one reason why trees might benefit from adjusting their flowering to the rains
5.According to paragraph2，what is true about much of the Amazon region
A.It has tree species that adjust their pollination to rainfall.
B.It has not yet been harvested or cleared.
C.It has trees that typically flower during periods of rain.
D.It does not have parate wet and dry asons.
The leaves may not be accommodating either,at least when viewed from the ground. Rain-forest trees all face the same kinds of conditions and have adapted in the same general kinds of way.Rain forests are wet by definition.But in some there is a dry ason,and even when there is not,it doesn't rain all the time.Thus the forest floor may be moist，but the topmost leaves of the canopy are far above it and are expod to the fiercest sun.So the uppermost leaves must resist desiccation(drying out).Yet from time to time,and in due ason every day,they must also endure tremendous downpours.Leaves that can cope with such contrasts tend to be thick and leathery(to resist drought),oval in shape,and have a protection at the end known as a drip tip to let surplus rain run off
the leaf.Many hundreds of trees from dozens of only distantly related families have leaves of this general type.But even if you can distinguish individual leaves,it is hard to be certain if they belong to the tree you are interested in or to the one next to it or to some epiphyte(a plant that grows on other plants)or liana (vine)slung over its branches.Often,in short,rearchers must ba their identification of a tree on the bark of its trunk.The trunks of tropical trees are sometimes highly characteristic,being deeply furrowed or twisted,but in most species the bark is simply smooth and gray，dappled with lichen and moss.
6.The word endure in the passage is clost in meaning to withstand
A.benefit from
B.avoid
D.withstand
7.The word surplus in the passage is clost in meaning to
A.heavy
B.steady
C.sudden
8.Paragraph3offers an explanation for each of the following characteristics of rain-forest tree leaves EXCEPT
A.their having a drip-tip at the end
B.their thickness
C.their leathery texture
D.their oval shape
9.According to paragraph3,what is one reason that looking at leaves may not be very uful when trying to determine the species of a rain-forest tree
A.Leaves of rainforest trees often look very different when they are wet than when they are dry.
B.Leaves that are expod to the hot tropical sun dry out and lo their distinguishing characteristics.
C.It can be hard to determine whether a leaf has a drip tip or not.
D.It can be hard to determine whether a leaf belongs to a tree or to another plant growing on the tree.
10.According to paragraph3,one reason that rearchers in tropical forests must often rely on a tree’s bark for species identification is that
A.distinct species of tree often have similar kinds of lichens and moss growing on their trunks
卵胎生鱼B.the leaves of many different tropical tree species are very similar to each other in appearance
C.many rainforest trees have neither epiphytes nor lianas
D.the bark of the trees is less affected by changes in light and moisture than leaves are
【In a temperate forest you can be fairly sure that any one tree is the same species as the one next t
o it or,at least，it will be one of a list that is unlikely to exceed more than half a dozen(oak with ash in much of Britain;lodgepole pine with aspen in the northernmost reaches of North America;alder,Scottish pine,and spruce in the Baltic; and so on).】But in the Amazon in particular，you can be fairly sure that any one tree is not the same species as the one next to it.Often there is a third of a mile between any two trees of the same species,and there can be up to120different species of trees in any one acre.So the task,often,is to identify an individual tree that may be not much thicker than your arm from the appearance of its bark,out of a total list of veral hundred(or thousand)possibilities which may well include some that have not
been described before,so that there is nothing to refer back to.
11.Which of the ntences below best express the esntial information in the highlighted ntence in the passage Incorrect choices change the meaning in important ways or leave out esntial information
【In a temperate forest you can be fairly sure that any one tree is the same species as the one next to it or,at least，it will be one of a list that is unlikely to exceed more than half a dozen(oak with ash in much of Britain;lodgepole pine with aspen in the northernmost reaches of North America;alder,Scottish pine,and spruce in the Baltic; and so on).】
A.Different temperate forests contain different combinations of tree species but in all such forests,all the trees of any one species are likely to be found clo together.
B.Temperate forests rarely contain more than about six species of tree,and trees growing next to each other tend to be of the same species.
C.You can easily make a list of all the tree species that are likely to be found in temperate forests,and if one tree is not on that list，you can be confident that the tree next to it will be.
D.Forests in Britain,in North America,and in the Baltic generally contain no more than half a dozen tree species,and all the species can be found on lists.
12.The word task in the passage is clost in meaning to
灶王A.difficulty
B.job
女人婚姻
C.strategy
对闺蜜的称呼
13.Look at the four squares that indicate where the following ntence could be added to the passage.
As a result,the topmost level of a rainforest can be dert-like.
Where would the ntence best fit.Click on a square to add the ntence to the passage.
The leaves may not be accommodating either,at least when viewed from the ground. Rain-forest trees all face the same kinds of conditions and have adapted in the same general kinds of way.Rain forests are wet by definition.【A】But in some there is a dry ason,and even when there is not,it doesn't rain all the time.【B】Thus the forest floor may be moist,but the topmost leaves of the canopy are far above it and are expod to the fiercest sun.【C】So the uppermost leaves must resist desiccation (drying out).【D】Yet from time to time,and in due ason every day,they must also endure
忆往事14.Drag your choices to the spaces where they belong.To review the passage，click on View Text Answer Choices
A.In tropical forests different trees of the same species flower at different times so
they are not able to pollinate one another.
B.Flowering in tropical trees is often unpredictable and when it occurs,the flowers themlves tend to be too high up to be clearly visible.
C.Many tropical tree species have leaves that look very similar from the ground,and becau the trees often grow clo together，correctly matching a leaf with a particular tree can be difficult.
D.The leaves and bark of a single rain forest tree are often very different at different heights due to the need to adapt to different conditions,which adds to the difficulty of species identification.
E.Becau trees in rain forests are spaced cloly together，it is easy to tell whether neighboring plants are the same species,but that is not much help in determining which species they are.
F.Often,a rain-forest tree has to be identified by its bark,but trees of like species are widely scattered,the list of possible species is very long,and many have similar-looking bark.
The Extinction of the Dinosaurs
Paragraph1:Geologists define the boundary between diment layers of the Cretaceous period(144-
65million years ago)and the Paleocene period(65-55million years ago)in part by the types and amounts of rocks and fossils they contain or lack. Before the limit of65million years ago，marine strata are rich in calcium carbonate due to accumulations of fossils of microscopic algae deposited on the a floor.Above the65-million-year limit，a-floor diments contain much less calcium carbonate, and fossils of veral families of mollusks are no longer found.In continental diments,dinosaur fossils,though frequent before65million years ago,are totally abnt.By contrast,new families of mammals appear,including large mammals for the first time.
1..According to paragraph1，which of the following is true of Paleocene diments ○They lack fossils from some families of mammals found in Cretaceous diments.○They contain fossils of dinosaurs.
○They contain fossils of some animals that did not exist during the Cretaceous.
○They contain fossils of more kinds of mollusks than are found in Cretaceous diments.
Paragraph2:Scientists wondered for many years about what could have caud the dinosaurs'rapid disappearance at the end of the Cretaceous period,coming up with a great variety of theories and scenarios.For some,it could have been due to unfavorable genetic changes triggered by a dramatic i
ncrea by a factor of10，100，1，000in cosmic-ray particles reaching the Earth after a supernova explosion somewhere in the neighborhood of the solar system.For the high-energy particles to affect life，they would have to get through the protective barrier of the Earth's magnetosphere,the region of the upper atmosphere controlled by Earth's magnetic
