Scientists have long puzzled over how iguanas, a group of lizards(蜥蜴) mostly found in the Americas, came to live in the isolated Pacific islands of Fiji and Tonga. Some scientists used to suppose that they must have traveled there on a raft, a journey of around 5,000 miles from South America to the islands. There are documented cases of iguanas reaching remote Caribbean islands and the Galapagos Islands on floating logs. But new research in January by Brice Noonan and Jack Sites suggested that iguanas may have simply walked to Fiji and Tonga when the islands were still a part of an ancient southern supercontinent.
The ancient supercontinent was made up of present-day Africa, Australia, Antarctica and parts of Asia. If that’s the case, the island species would need to be very old. Using “molecular (分子) clock” analysis of living iguanas’ DNA, Noonan and Sites found that, sure enough, the lineage of iguanas has been around for more than 60 million years—easily old enough to have been in the area when the islands were still connected by land bridges to Asia or Australia.
Fossils (化石) uncovered in Mongolia suggest that iguanid ancestors did once live in Asia. Though there’s currently no fossil evidence of iguanas in Australia, that doesn’t necessarily mean they were never there. “The fossil record of this continent is surprisingly poor and cannot be taken as evidence of true absence,” the authors write.
So if the iguanas simply walked to Fiji and Tonga from Asia or possibly Australia, why are they not also found on the rest of the Pacific islands? Noonan and Sites say fossil evidence suggests that iguana species did once inhabit other islands, but went extinct right around the time when humans settled in those islands. But Fiji and Tonga have a much shorter history of human presence, which may have helped the iguanas living there to escape extinction.
The researchers say that their study can’t completely rule out the rafting theory, but it does make the land bridge theory “far more reasonable than previously thought.”
1. What did some scientists previously believe about the iguanas?
A. They were once discovered in America.
B. They traveled by raft to Fiji and Tonga.
C. They could survive in poor living conditions.
D. They moved to Fiji and Tonga from Australia.
2.According to Noonan and Sites, 60 million years ago ____.
A. the land of the world was a supercontinent
B. Fiji and Tonga were connected to Asia or Australia
C. Africa, Australia and America were a continent
D. iguanas walked to Fiji and Tonga from Africa
3.The underline word “lineage” in Paragraph 2 probably refers to ____.
A. conditions in which creatures can survive
B. the change in ancient plants and animals.
C. the line of generations of an ancestor
D. the habitat of a type of an ancient animal
4. What is the main topic of this passage?
A. The life span of animals living on the ancient supercontinent.
B. The two islands being home to several iguana species in the Pacific region.
C. The fossil evidence suggesting iguanas’ ancestors’ swimming to Fiji and Tonga
D. By raft or by land — how did iguanas reach the tiny Pacific islands?
高三英语阅读理解中等难度题
Scientists have long puzzled over how iguanas, a group of lizards(蜥蜴) mostly found in the Americas, came to live in the isolated Pacific islands of Fiji and Tonga. Some scientists used to suppose that they must have traveled there on a raft, a journey of around 5,000 miles from South America to the islands. There are documented cases of iguanas reaching remote Caribbean islands and the Galapagos Islands on floating logs. But new research in January by Brice Noonan and Jack Sites suggested that iguanas may have simply walked to Fiji and Tonga when the islands were still a part of an ancient southern supercontinent.
The ancient supercontinent was made up of present-day Africa, Australia, Antarctica and parts of Asia. If that’s the case, the island species would need to be very old. Using “molecular (分子) clock” analysis of living iguanas’ DNA, Noonan and Sites found that, sure enough, the lineage of iguanas has been around for more than 60 million years—easily old enough to have been in the area when the islands were still connected by land bridges to Asia or Australia.
Fossils (化石) uncovered in Mongolia suggest that iguanid ancestors did once live in Asia. Though there’s currently no fossil evidence of iguanas in Australia, that doesn’t necessarily mean they were never there. “The fossil record of this continent is surprisingly poor and cannot be taken as evidence of true absence,” the authors write.
So if the iguanas simply walked to Fiji and Tonga from Asia or possibly Australia, why are they not also found on the rest of the Pacific islands? Noonan and Sites say fossil evidence suggests that iguana species did once inhabit other islands, but went extinct right around the time when humans settled in those islands. But Fiji and Tonga have a much shorter history of human presence, which may have helped the iguanas living there to escape extinction.
The researchers say that their study can’t completely rule out the rafting theory, but it does make the land bridge theory “far more reasonable than previously thought.”
1. What did some scientists previously believe about the iguanas?
A. They were once discovered in America.
B. They traveled by raft to Fiji and Tonga.
C. They could survive in poor living conditions.
D. They moved to Fiji and Tonga from Australia.
2.According to Noonan and Sites, 60 million years ago ____.
A. the land of the world was a supercontinent
B. Fiji and Tonga were connected to Asia or Australia
C. Africa, Australia and America were a continent
D. iguanas walked to Fiji and Tonga from Africa
3.The underline word “lineage” in Paragraph 2 probably refers to ____.
A. conditions in which creatures can survive
B. the change in ancient plants and animals.
C. the line of generations of an ancestor
D. the habitat of a type of an ancient animal
4. What is the main topic of this passage?
A. The life span of animals living on the ancient supercontinent.
B. The two islands being home to several iguana species in the Pacific region.
C. The fossil evidence suggesting iguanas’ ancestors’ swimming to Fiji and Tonga
D. By raft or by land — how did iguanas reach the tiny Pacific islands?
高三英语阅读理解中等难度题查看答案及解析
Scientists have been puzzled by the phenomenon that migrating birds fly not just in groups all the time, but in "V" formations and they have tried to figure out what benefit birds get from this particular formation. Now, a research group from University of London may have found the answer ― migrating birds fly in a "V" to save energy, according to a study published in the journal Nature.
When a bird flaps(振翅) its wings, it stirs the air around it and causes it to move indifferent directions. Scientist found in the study that the air creates an upward-moving wave at the tips of the wings, which means that if a bird flies around the wingtips of another bird, it can get a boost(抬高) from the rising air and therefore use less energy to stay in the air.
Apart form the "free ride" strategy, scientists were also surprised to observe that migrating birds timed their wing beats and adjusted their positions in a very precise way to maximize the lifting effect while avoiding areas where the air move downward.
"They're able to sense what's going on from the bird in front, where this 'good air' is coming from and now how to position themselves perfectly in it," lead researcher Steven Portugal told BBC.
In fact, the "V" formation has long thought to help birds fly more efficiently(效率搞地). A previous study showed that birds' heart rates went down when they were flying together in a "V" formation. Jet fighters were also found to be able reduce their energy use by up to 18% by staying near the wingtips of other jet fighters. Both of these findings led scientists to suspect that the "V" formation had an efficiency purpose, but until now they still lack proof.
"For scientists, the new study provides an insight into an interesting natural phenomenon. But it could mean even more for aircraft companies — helping them understand how they can imitate that with their plane formations to save fuel, said Portugal."
1.What is the author's purpose in writing this article?
A. To explain how birds benefit from migration.
B. To introduce how migrating birds find their way.
C. To tell some applications of migrating birds' "V" formations.
D. To report new findings about migrating birds' "V" formations.
2. According to the recent study, when birds migrate .
A. they don't change their lead birds during the whole journey
B. they fly in "V" formations to protect themselves against enemies
C. they form the shape of a "V" to make best use of the lifting effect
D. the air they stir around makes it hard for the birds behind to fly fast
3.What is the significance of the new study according to this article?
A. It might inspire aircraft companies to think of ways to improve efficiency.
B. It has proved that the "V" formation can improve in efficiency in many fields,
C. It has led scientists to discover that birds' heart rates go down when they fly in a "V".
D. It shows that the best formation of jet fighters in battle should be a "V" formation.
4. The underlined word "imitate" in the last paragraph most probably means " ".
A. use B. copy C. change D. learn
高三英语阅读理解中等难度题查看答案及解析
Scientists say they have found key clues(线索)into how long we will live. One of them is a firm __21___. British researchers believe a firm strong handshake is not just a __22___ of confidence but also an indicator of a long life. Lead author Dr Rachel Cooper of University College London said her study looked __23___ 33 different reports on the __24___ of handshakes. The research involved more than 50,000 men and women and __25___ 40 years. Dr Cooper concluded that __26___ with weaker handshakes were 70 per cent more likely to die earlier than those with the __27___ handshakes. She concludes that people with a firm strong handshake __28___ from a happy childhood that __29___ a healthy diet and __30___ of exercise.
The new study, __31___ in the British Medical Journal, also found other signs of living a longer life. These 'measures of __32___ capability' include walking at a faster pace, getting out of a chair quickly, and being able to __33___ on one leg. The study showed that slow walkers were almost three times __34___ to die at a younger age than those who walked quickly and actively. Those who __35___ to get up from their armchairs were twice as likely to die earlier than those who sprang __36___ their chairs. Dr Cooper believes there __37___ more research into the link __38___ physical capability and a long life. “Research that helps people to __39___ a long and healthy life is ever more important to help provide for an ageing __40___.” she said.
1.A.childhood B. relationship C.hardship D.handshake
2.A.sign B. symbol C.trip D.sigh
3.A.at B. into C.to D.on
4.A.strength B. length C.likeliness D.confidence
5.A.last B. past C.lasted D.passed
6.A.women B. they C.those D.men
7.A.weaker B. strongest C.weakest D.strong
8.A. must benefit B.could have lived C. should come D. may have benefited
9.A.concluded B. consisted C.included D.including
10.A.plentiful B. plenty C.a number D.the number
11.A.published B. being published C.publishing D.having published12.A.physician B. physics C.physiology D.physical
13.A.stand B. balance C.live D.shake
14.A.likely B. likelier C.likelihood D.liking
15.A.wanted B. hoped C.struggled D.were dying
16.A.out of B. in front of C.ahead of D.away from
17.A.needs to be B. need to be C.ought to be D.must be
18.A.from B. among C.between D.beneath
19.A.benefit B. involve C.make D.enjoy
20.A.popularity B. pollution C.population D.publication
高三英语完型填空简单题查看答案及解析
Scientists think they have the answer to a puzzle that confused even Charles Darwin: How flowers evolved and spread to become the most important plants on earth.
Flowering plants, or angiosperms (被子植物), make up about 90% of all living plant species,but how they did this has been a mystery. New research suggests it is due to genome (基因组) size.
Hundreds of millions of years ago,the earth was dominated by ferns (蕨类)and conifers(针叶树) - they were the main plants on the earth. Then, about 150 million years ago, the first flowering plants appeared on earth. They quickly spread to all parts of the world.
Why angiosperms were successful and diverse on earth has been debated for centuries.Charles Darwin himself called it a "mystery", fearing this apparent sudden change might challenge his theory of evolution.
Kevin Simonin from San Francisco State University in California US and other researchers analyzed data held by the Royal Botanic Gardens, Kew, on the genome size of hundreds of plants, including flowering plants, gymnosperms (a group of plants including conifers) and ferns. They then compared genome size with anatomical (结构上的) features. This provides "strong evidence" that the success and rapid spread of flowering plants around the world is due to "genome downsizing".
By reducing the size of the genome, which is contained within the nucleus (核) of the cell, plants can build smaller cells. The researchers say genome-downsizing happened only in the angiosperms, and this was "a necessary condition for rapid growth rates among land plants".
1.What do we know about angiosperms? ______
A.They are superior in number among all living plant species.
B.They controlled the earth for hundreds of millions of years.
C.They challenge Charles Darwin's theory.
D.They are extinct plants in the world.
2.It can be implied that ______ .
A.Simonin works in the Royal Botanic Gardens Kew
B.Simonin is probably an American biologist
C.Darwin was confident of his theory of evolution
D.Darwin succeeded in figuring out the flower evolution
3.What contributed to the success and diversity of angiosperms? ______
A.The weaker ferns and conifer.
B.The larger nucleus.
C.The stronger cell.
D.The smaller genome.
4.What can be a suitable title of this passage? ______
A.Why were gymnosperms successful on earth?
B.What puzzle confused even Charles Darwin?
C.Why angiosperms dominated the earth?
D.When angiosperms outnumbered conifers and Ferns?
高三英语阅读理解中等难度题查看答案及解析
._________life began on the earth is one of the biggest puzzles to scientists.
A.How B.What C.Where D.That
高三英语单项填空简单题查看答案及解析
________life began on the earth is one of the biggest puzzles to scientists.
A.How B.What C.Where D.That
高三英语单项填空中等难度题查看答案及解析
A global group of scientists have reduced the time it takes to find and introduce disease-resistance genes from wild plants into domestic crops such as rice, wheat and potato, a research revealed on Tuesday.
Scientists from the John Innes Center in Britain, along with colleagues from Australia and the United States, have created a database known as AgRenSeq, where researchers can easily search for resistance genes already discovered in wild relatives of modern crops.
The study was co-authored by a global expert Professor HarbansBariana from the University of Sydney, who said that this technology will support the discovery and characterization of new sources of disease resistance in plants. Once researchers have identified resistance genes using AgRenSeq, they can clone them and introduce them to domestic crops to protect against diseases and pests,
“We have found a way to scan the genome(基因组)of a wild relative of a crop plant and pick out the resistance genes we need and we can do it in record time,” Dr. Brande Wulff, a project leader from the John Innes Centre, said.
“This used to be a process that took l0 Or 15 years and was like searching for a needle in a haystack(干草堆),” Wulff said. “We have perfected the method so that we can clone these genes in a matter of months and for just thousands of dollars instead of millions.”
The team are highly optimistic about their work, predicting it to be utilized in protecting many crops with wild relatives including soybeans, pea, cotton, potato, wheat, rice, banana and cocoa. “Using speed cloning and speed breeding we could deliver resistance genes into the best varieties within a couple of years, like a phoenix(凤凰) rising from the ashes,” Wulff added.
1.How have the researchers developed the resistance genes?
A.By reducing the research time.
B.By introducing them to wild plants.
C.By cloning them from domestic crops.
D.By getting resistance genes from wild plants.
2.What will be the use of the study in the future?
A.It will protect crops from being damaged by pests.
B.It will create a database for researchers to search.
C.It will protect domestic crops for 10 to 15 years.
D.It will contribute to reducing the wild plants.
3.Which of the following best explains “utilized” underlined in Paragraph 6?
A.Produced. B.Made.
C.Used. D.Studied.
4.What can we infer from what Brande Wulff said?
A.The resistance genes cost millions of dollars.
B.The resistance genes were found in a haystack.
C.It took the researchers ten years to find the resistance genes.
D.Disease-resistance genes will be put into practice soon.
高三英语阅读理解中等难度题查看答案及解析
Scientists have been studying how people use money for long. Now they’re finding some theories may apply to one group of monkeys.
Researchers recently taught six monkeys how to use money. They gave the monkeys small metal disks(圆片) that could be used like cash and showed them some yummy apple pieces. The monkeys soon figured out that if they gave one of the disks to a scientist, they d receive a piece of apple in return.
If you think that is all the monkeys can figure out, you are wrong. Two researchers, Jake and Allison, acted as apple sellers in the experiments. The monkeys were tested one at a time and had 12 disks to spend in each experiment. Jake always showed the monkeys one apple piece, while Allison always showed two pieces. But that’s not necessarily what they gave the monkeys. The number of apple pieces given for a disk was determined at random.
Experiment One: Allison showed two pieces of apples but gave both pieces only half the time. The other half, she took one piece away and gave the monkey just the remaining piece. Jake, on the other hand, always gave exactly what he showed: one piece for each disk. The monkeys chose to trade more with Allison.
Experiment Two: Allison continued to sometimes gave two pieces and sometimes one piece. But now, half the time, Jake gave the one apple piece he was showing, and half the time he added a bonus. Guess what? The monkeys chose to trade more with Jake.
In the first experiment, the monkeys correctly figured out that if they traded with Allison, they’d end up with more treats. In the second one, when a monkey received two pieces from Jake, it seemed like again. When Allison gave the monkey only one piece instead of the two she showed, it seemed like a loss. The monkeys preferred trading with Jake because they’d rather take a chance of seeming to win than seeming to lose.
We also sometimes make silly business decisions just to avoid the feeling that we’re getting less, even when were not. Would you have made the same choices?
1.What conclusion might experts draw from the first experiment?
A. The monkeys show certain business sense.
B. Business theories can apply to all monkeys.
C. People are smarter in terms of finance.
D. It’s easy to teach monkeys how to trade.
2.What does a bonus in paragraph 5 refer to?
A. A metal disk.
B. An apple piece.
C. A chance.
D. A coin.
3.Why did the monkeys choose to trade more with Jake in the second experiment?
A. Because Jake always gave them two apple pieces.
B. Because the apple pieces from Jake were yummy.
C. Because they didn’t like the feeling of losing.
D. Because they get more apple pieces from Jake.
4.What could be the best title for the passage?
A. People’s Business Decision: Lose or Gain?
B. Moneky’s Business Sense: Smart or Silly?
C. Shopping for Bargain: Same or different?
D. Disk for Apple: Who to Trade with?
高三英语阅读理解中等难度题查看答案及解析
Scientists also have no idea how long it will be before all wild animals in the cages _____.
A. should be set free B. will be set free
C. are set free D. would be set free
高三英语单项填空中等难度题查看答案及解析
Scientists also have no idea how long it will be before all wild animals in the cages _____.
A. should be set free B. will be set free C. are set free D. would be set free
高三英语单项填空中等难度题查看答案及解析