题目内容
9. No bird and no beast _____ in the lonely island.
A. are seen B. is seen C. see D. Sees
B
小学期末标准试卷系列答案Everywhere man is altering the balance of nature．He is facilitating the spread of plants and animals into new regions, sometimes deliberately, sometimes unconsciously．He is covering huge areas with new kinds of plants, or with houses, factories, slag-heaps and other products of his civilization．He exterminates some species on a large scale, but favors the multiplication of others．In brief, he has done more in five thousand years to alter the biological aspect of the planet than has nature in five million．
Many of these changes which he has brought about have had unforeseen consequences．Who would have thought that the throwing away of a piece of Canadian waterweed would have caused half the waterways of Britain to be blocked for a decade, or that the provision of pot cacti for lonely settlers’ wives would have led to Eastern Australian being overrun with forests of Prickly Pear? Who would have prophesied that the cutting down of forests on the Adriatic coasts, or in parts of Central Africa, could have reduced the land to a semi desert, with the very soil washed away from the bare rock? Who would have thought that improved communications would have changed history by the spreading of disease-sleeping sickness into East Africa, measles into Oceania, very possibly malaria into ancient Greece?
These are spectacular examples; but examples on a smaller scale are everywhere to be found．We make a nature sanctuary for rare birds, prescribing absolute security for all species; and we may find that some common and hardy kind of bird multiplies beyond measure and ousts the rare kinds in which we were particularly interested．We see, owing to some little change brought about by civilization, the starling spread over the English country-side in hordes．We improve the yielding capacities of our cattle; and find that now they exhaust the pastures which sufficed for less exigent stock．
【小题1】The following examples except _______________ reflect man altering the balance of nature．
| A．man is covering huge areas with new kinds of plants |
B．man is fa cilitating the spread of animals into new regions． |
| C．man is killing some species on a large scale |
| D．man is getting to know the importance of keeping the balance of nature． |
| A．Eastern Australian was overrun with forests． |
| B．Half the waterways of Britain blocked for a decade． |
| C．In parts of central Africa, the land reduced to a semi desert． |
| D．Disease-sleeping has been caused． |
| A．Disease-sleeping sickness． | B．Measles． |
| C．Improved communications． | D．Malaria． |
| A．some common and hardy kind of bird multiplies |
| B．rare kinds multiply |
| C．all bird multiply |
| D．no bird multiply |
| A．that man is deliberately destroying the balance of nature |
| B．that man has foreseen the consequences of altering the balance old nature |
| C．that improved communications have changed history |
| D．that man is altering the balance of nature |
Birds that are half-asleep—with one brain hemisphere (半球) alert and the other sleeping—control which side of the brain remains awake, according to a new study of sleeping ducks.
Earlier studies have documented half-brain sleep in a wide range of birds. The brain hemispheres take turns sinking into the sleep stage characterized by slow brain waves. The eye controlled by the sleeping hemisphere keeps shut, while the wakeful hemisphere’s eye stays open and alert. Birds also can sleep with both hemispheres resting at once.
Decades of studies of bird groups led researchers to predict extra alertness in the end-of-the-row sleepers which tend to be attacked more easily. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.
Also, birds napping at the end of the line depend on single-hemisphere sleep, rather than total relaxation, more often than inner ducks did. Turning 16 birds through the positions in a four-duck row, the researchers found that compared with 12 percent for birds in internal spots, outer birds half-asleep during some 32 percent of napping time.
“We believe this is the first evidence for an animal behaviorally controlling sleep and wakefulness at the same time in different regions of the brain,” the researchers say.
The results provide the best evidence for a long-standing assumption that single-hemisphere sleep evolved as creatures scanned for enemies. The preference for opening an eye on the lookout side could be widespread, he predicts. He’s seen it in a pair of birds napping side-by-side in the zoo and in a single pet bird sleeping by a mirror. The mirror-side eye closed as if the reflection were a companion and the other eye stayed open.
Useful as half-sleeping might be, it’s only been found in birds and such water animals as dolphins, whales, and seals. Perhaps keeping one side of the brain awake allows a sleeping animal to surface occasionally to avoid drowning.
Studies of birds may offer unique insights into sleep. Jerome M. Siegel of the UCLA says he wonders if birds’ half-brain sleep “is just the tip of the iceberg.” He supposes that more examples may turn up when we take a closer look at other species.
【小题1】According to the passage, birds often half sleep because ______.
| A．they have to watch out for possible attacks |
| B．their brain hemispheres take turns to rest |
| C．the two halves of their brain are differently structured |
| D．they have to constantly keep an eye on their companions |
| A．An imagined companion gives the bird a sense of security. |
| B．Birds prefer to sleep in pairs for the sake of their security. |
| C．The phenomenon of birds napping in pairs is widespread. |
| D．A single pet bird enjoys seeing its own reflection in the mirror. |
| A．alert themselves to the approaching enemy |
| B．emerge from water now and then to breathe |
| C．be sensitive to the ever-changing environment |
| D．avoid being swept away by rapid currents |
| A．half-brain sleep has something to do with icy weather |
| B．the mystery of half-brain sleep is close to being solved |
| C．most birds living in cold regions tend to be half sleepers |
| D．half-brain sleep may exist among other species |