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. |
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 |
A.The weaker ferns and conifer. |
B.The larger nucleus. |
C.The stronger cell. |
D.The smaller genome. |
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? |
相似题推荐
【推荐1】Should We Create More National Parks
Don't you find it worrying that more and more species of animals are in real danger of becoming national parks extinct?
In addition, national parks protect animals from the danger of being hunted. A major reason why many species are endangered is that the animals are killed by hunters. They hunt animals to make money.
On the other hand, some people fight against the creation of national parks because they consider it wrong to interfere with nature. They believe that wild animals are happier living in their natural environment.
All in all, these disadvantages are far less important than the benefits of national parks, because these parks allow animals to live in a safe environment.
A.They say though the animals may face danger, they enjoy a free life. |
B.Firstly, national parks protect the animals' natural environment. |
C.To begin with, animals are important to humans. |
D.I personally believe that we must save these animals. |
E.There is a heated discussion about whether to create more national parks. |
F.In fact, they protect animals from their greatest enemies--human beings. |
G.Some hunters even hunt animals simply for sport. |
【推荐2】In 1973, when Melissa Greene was in 6th grade, her parents bought the first apartment on Hutchinson Island on the southeastern Atlantic cast. The first time she and her siblings ran down to the wild shore, they were shocked by the seashells there. Every tide left a wrack line of seashells. Today, on the same stretch of beach, she rarely finds the large, undamaged shells that were common in her childhood. “It’s a shocking difference,” she says, “what you don’t see any more are the deep piles of whole shells, quarter-sized and above, and the largest shells that we saw for years.”
Among the most admirable natural objects throughout human history, seashells contain both the surprise and wonder still promised by a trip to the beach and the profound changes underway on our coasts. Some of the largest and best-known marine mollusks (软体动物) have declined under fishing pressure. They are also harmed by rising ocean temperatures and acidifying waters and by other pollution. They can be reduced by the severe erosion-a persistent problem on Hutchinson Island.
With beaches seeing record tourism numbers, more people can mean fewer shells. “It is not as much individual collecting as the many ramifications of massive tourism,” says the paleo-biologist Michal Kowalewski at the Florida Museum of Natural History.“Mass tourism means more boats, more beach maintenance, more machinery, all contributing to changes in shorelines.”
Over twenty years ago, Sanibel became the first city in the U.S. to ban the practice of collecting and killing mollusks for their shells. Delaware’s state parks are among increasing numbers of state and national parks taking so-called low-impact beachcombing a step further: Asking visitors to leave empty shells alone, too. At Delaware Seashore State Park, signs advise visitors to “Leave shells where they lay or snap a photo of a marine critter in the sand. After all, the point of enjoying nature is because it is in a natural state.”
1. Why is the story of Melissa Greene mentioned in the first paragraph?A.To introduce readers to an Atlantic coast. |
B.To share Melissa’s attitude towards shells. |
C.To show an ocean village’s development. |
D.To lead in the topic of seashells’ disappearance. |
A.By comparing different conclusions. |
B.By collecting the supporting data. |
C.By listing the related factors. |
D.By quoting the opinions of experts. |
A.Consequences. | B.Industries. | C.Branches | D.Benefits. |
A.The common phenomenon of shell collecting. |
B.Different measures taken to protect the seashells. |
C.Future anticipation of seashells’ condition. |
D.The effectiveness of bans on seashells’ development. |
One night in the 1990s, we tidied up wrapping paper and toys while the lighted menorah stood on the kitchen table. When we were not there, as the many-colored candles broke, our long-haired black-and-white cat, Ladybug, jumped onto the kitchen table and brushed past them.
"Do you smell something?" asked my husband, Donny. "Is something burning?" asked Molly, our oldest, age ten.
It was Ladybug! The fur on her left side had been burnt. She wasn't hurt, but she wore an upset expression all evening, and for the rest of the week she hid whenever we began chanting the Hebrew(希伯来语)blessings over the candles. "
The following year, for fifth-grade homework about family traditions, Molly wrote about Ladybug's story with the Hanukkah candles. The teacher, Lynn Fink, a sporty and funny woman, enjoyed Molly's story and gave it an A.
Three years later, Seth got Ms. Fink for fifth grade. He also worked the burnt cat fur into a writing assignment, and he, too, got an A.
Our son Lee, three years later: the same teacher, the same story, the same A. We had no idea these retellings were piling up.
The year Lily got Ms. Fink for fifth grade, she also felt inspired to write down what happened that night. By now, we were very fond of Ms. Fink. We invited her to join us for a night of Hanukkah. It was her first time to experience the Jewish holiday. Happily, she ate her potato pancakes. Gamely, she spun the dreidel. Delightedly, she opened the small gift of home-made cookies the children had prepared for her. As the evening seemed to be winding down, she clapped her hands, rubbed them together as if before a big dinner, and said excitedly," So! When do we torch the cat?"
1. What happened to Ladybug when the family celebrated Hanukkah that year?
A.She was seriously hurt that night. |
B.She broke the candles on the menorah. |
C.She had some of her fur burnt. |
D.She got a surprising present from the family. |
A.Hanukkah lasts for only one night. |
B.The writer has at least four children. |
C.The family saw Ladybug jump onto the kitchen table that night. |
D.Frying potato pancakes is not a tradition to celebrate Hanukkah. |
A.It's easy to be wise after the event. |
B.Where there is a will, there is a way. |
C.He that falls today may be up again tomorrow. |
D.Once bitten, twice shy. |
A.forgot the story of Ladybug |
B.came to the writer's home unexpectedly |
C.knew all the traditions of Hanukkah well |
D.thought people would torch the cat to celebrate Hanukkah |
【推荐1】English is fast becoming the language of science around the world, but what is its future among everyday speakers? One expert points out that the percentage(比率) of native English speakers is declining(降低) globally while the languages of other rapidly growing regions are being spoken by increasing numbers of people. But English will continue to remain widespread and important.
However, British language scholar David Graddol says English will probably drop in dominance(主导) by the middle of this century to rank, after Chinese, about equally with Arabic, Hindi, and Urdu. “The number of people speaking English as a first language continues to rise, but it isn’t rising nearly as fast as the numbers of many other languages around the world, simply because the main population group has been largely in the less developed countries where languages other than English have been spoken,” he says.
In a recent article in the journal Science, Mr. Graddol noted that three languages that are not near the top of the list of the most widely spoken now might be there soon. These are Bengali, Tamil, and Malay, spoken in south and Southeast Asia.
David Crystal, the author of the Cambridge Encyclopedia of the English Language, says about 1.5 billion of the world’s six billion people speak it as a second tongue compared to the 400 million native speakers. But another expert on the English language says Mr. Graddol underestimates (低估) the future of its dominance. “Nobody quite knows what’s going to happen because no language has been in this position before. But all the evidence (证据) suggests that the English language snowball is rolling down a hill and is getting faster,” he said.
1. In David Graddol’s opinion, English will _______.A.remain widespread and important |
B.be more important than any other language |
C.lose its dominant position |
D.die away in the near future |
A.2. | B.3. | C.4. | D.5. |
A.Malay. | B.Arabic. | C.Urdu. | D.German. |
A.English Remaining the Dominant Position |
B.The Future of English? Who Knows? |
C.Opinions from Different Experts |
D.The English Language Snowball Rolling Down |
【推荐2】Have you ever complained why life is so tiring? Does the sky sometimes seem dark to you? Are your studies sometimes not successful? Well, friends, cheer up and smile all the time. If you see the world with your warm heart, you’ll find that the whole world smiles to you.
While in school, sometimes you are tired of your lessons, but have you ever noticed the happy smile on your teacher’s face when you did a good job?
One day it is fine. Just before you go out, it suddenly starts to rain. Maybe you would feel very sad and start to complain about the weather. But dear friends, why don’t you sit down and listen to the free concerts that the nature offers you? And with the timely rain, crops in the fields will grow better and better and farmers will have a good harvest.
Although everyone wants to succeed in what he tries to do, sometimes failure can’t be avoided. I think failure is not terrible, and the terrible thing is that we are afraid of it and give up hope. When we face failure, we must be confident in ourselves, draw a useful lesson from it and try our best to finish what we have decided to do. As a popular saying goes, “Failure is the mother of success”.
Attitude decides everything. With an optimistic attitude life is easy and pleasant. Let’s smile to whatever we meet and the whole world will smile to us.
1. People sometimes complain _________.A.the sky is always dark |
B.their studies are successful |
C.they see the world with their heart |
D.life is tiring |
A.must be confident in ourselves |
B.shouldn’t be afraid of it |
C.shouldn’t give up hope |
D.All of the above |
A.Smile and the World Smiles to You |
B.Complaining about Life |
C.Failure is the Mother of Success |
D.It is Very Hard to Succeed |
【推荐3】Some people think if you are happy, you are blind to reality. But when we research it, happiness actually raises every single business and educational outcome for the brain. How did we miss this? Why do we have these social misunderstandings about happiness? Because we assumed you were average. When we study people, scientists are often interested in what the average is.
Many people think happiness is genetic. That’s only half the story, because the average person does not fight their genes. When we stop studying the average and begin researching positive outliers —people who are above average for a positive aspect like optimism or intelligence —a wildly different picture appears. Our daily decisions and habits have a huge impact upon both our levels of happiness and success.
Scientifically, happiness is a choice. It is a choice about where your single processor brain will devote its limited resources as you process the world. If you scan for the negative first, your brain really has no resources left over to see the things you are grateful for or the meaning embedded(嵌入) in your work. But if you scan the world for the positive, you start to acquire an amazing advantage.
I wrote the cover story for the Harvard Business Review magazine on “Happiness Leads to Profits.” Based on my article called “Positive Intelligence” and my research in The Happiness Advantage, I summarized our researched conclusion: the single greatest advantage in the modern economy is a happy and busy workforce.
A decade of research in the business world proves that happiness raises nearly every business and educational outcome: increasing sales by 37%, productivity by 31%, and accuracy on tasks by 19%, as well as a number of health and quality-of-life improvements.
1. The underlined word “this” in the first paragraph refers to .A.the fact that people are happy |
B.the connection between happiness and educational outcome |
C.the fact that people often misunderstand happiness |
D.the fact that most people are average |
A.Scientists are only interested in what the average is. |
B.You can choose to be happy or not. |
C.The average are not happy at all. |
D.Our decisions and habits have nothing to do with happiness. |
A.To advertise himself. |
B.To arouse the readers’ interest. |
C.To support his point about happiness. |
D.To attract the readers to read his articles. |
A.To explain what is happiness. |
B.To describe the misunderstandings about happiness. |
C.To show people the importance of happiness. |
D.To make the point that happiness promotes business and educational outcome. |
【推荐1】The Amazon Clipper
Join the Amazon Clipper for an exciting journey through the world's most plentiful river and largest typical jungle. The river is surely an excellent way to get to know the complex secrets of the Amazon rainforest.
Day 01 Wednesday: Departure
The boat departs from the Tropical Experience Hotel at 11:30 am. Once on board, you'll be introduced to the staff and to your room.The hotel will be ready to serve some delicious food for lunch. You'll then navigate towards the Pagodao River.
Day 02 Thursday: Amazon
In the morning you'll have a hike in the forest with a specialist guide. You'll have the chance to know the local vegetation(植物) ,as well as spend some time with a native family. You'll see how they prepare manioc (树薯) flour, very typical of the Amazon dietary culture. You'll then sail through Anavilhanas, the largest fresh water archipelago (群岛)in the world.
Day 03 Friday: Amazon
Today you'll sail to Praia Grande or another white sand beach. Hopefully there will be some time to swim! Then, you'll take a canoe trip on Lake Acajatuba, to observe the typical vegetation. Then, you'll stop at Paricatuba to see some abandoned buildings from the rubber growing age.
1. When will you learn about the local food culture?A.On Wednesday. | B.On Thursday. | C.On Friday. | D.On Saturday. |
A.Fresh water. | B.Typical plants. |
C.White sand beach. | D.Traditional culture. |
A.Have a bird watching. | B.See some rare animals. |
C.Learn about specific plants. | D.Get a chance to swim. |
【推荐2】How Your Money Helps
Membership activities made a contribution of over £3 million to the Museum last year. Your support plays a vital role, thank you.
In 2015 Members responded to an appeal to acquire the Stoney Waterloo Album. Through their extraordinary generosity, and that of the American Friends of the British Museum, the Museum secured this historic album in 200th anniversary year of the Battle of Waterloo. Visit info.museum.org.uk.
Designed by Sir Robert Smirke and completed in 1857, the Grade I listed Bloomsbury building requires frequent and painstaking work to maintain it. For much of the past year regular work has been undertaken to the main portico(门廊) as part of ongoing, vital repairs to the stonemasonry(石雕).
The British Museum is a museum of the citizen — its collection is for the whole of the UK. Last year 3 million visitors saw British Museum objects on display in museums and galleries across the UK. The Sikh fortress turban tour has been the most popular, reaching over 350,000 visitors and nine museums across the country. Visit citizen.britishmuseu,.org to learn more.
One of the most ambitious building developments in the British Museum’s history — the World Conservation and Exhibitions Centre — was completed with the support of our Members. The building in the northwest corner of the Museum site houses new state-of-the-art conservation and science laboratories, new storage facilities, and the Sainsbury Exhibitions Gallery.
Visit buildings.british.org.uk.
The Portable Antiquities Scheme (PAS), managed by the British Museum, recently announced the discovery of a significant Viking store of valuables in Oxfordshire. The PAS offers the only mechanism for recording such finds, which are made publicly available on its online database at finds.org.uk.
1. This passage is most probably from ________.A.an announcement about the British Museum |
B.a science magazine about the British Museum |
C.the homepage of the British Museum |
D.a newspaper advertisement on the British Museum |
A.finds.org.uk. |
B.citizen.britishmuseu,.org |
C.info.museum.org.uk. |
D.buildings.british.org.uk |
A.The Battle of Waterloo happened in the year 1915. |
B.Three million visitors saw British Museum objects on display in museums in 2015. |
C.The Grade I listed Bloomsbury building can be visited in Oxfordshire. |
D.Membership activities push forward the development of the British Museum. |
【推荐3】Now many young people are traveling around the world on their own, not because they have no one to travel with, but because they prefer to go alone.
Kristina Wegscheider from California first traveled alone when she was at college and believes that it is something everyone should do at least once in their life. “It opens up your mind to things and pushes you out of your comfort zone.” Wegscheider has visited 46 countries covering all seven continents.
In foreign countries, with no one to help you read a map, look after you if you get ill, or lend you money if your wallet is stolen, it is challenging. This is what drives young people to travel alone. It is seen as character building and a chance to prove that they can make it on their own.
Chris Richardson decided to leave his sales job in Australia to go traveling last year. He set up a website, The Aussie Nomad, to document his adventures. He says he wished he had traveled alone earlier. “The people you meet, the places you visit, or the things you do, everything is up to you and it forces you to grow as a person.” said the 30-year-old man.
Richardson describes traveling alone like “a shot in the arm”, which “makes you a more confident person that is ready to deal with anything”. He said, “The feeling of having overcome something on my own is a major part of what drives me each day when I’m dealing with a difficult task. I walk around with my head up because I know deep down inside that nothing is impossible if you try.”
The great 19thcentury explorer John Muir once said. “Only by going alone in silence can one truly get into the heart of the wilderness.
1. Which of the following will Kristina Wegscheider agree with?A.Traveling alone is a necessary experience for everyone. |
B.It is more meaningful to travel in foreign countries. |
C.It is comfortable to travel around without a friend. |
D.Traveling abroad helps people to find new things. |
A.you have to make things on your own. |
B.it is hard for you to prove yourself to others. |
C.you can only depend on yourself whatever happens. |
D.it will finally build your character. |
A.He started traveling alone at an early age. |
B.He was once shot in the arm. |
C.He used to work as a salesman. |
D.His website will inspire others to travel alone. |
A.Travel Abroad | B.Travel Alone |
C.Travel Light | D.Travel Wide and Far |
【推荐1】Definition of adult learning vary, but according to the European Commission, it is defined as all forms of learning undertaken by adults after having left initial education and training, however far this process may have gone.
Education and training are important factors in achieving the strategic goal of raising economic growth, competitiveness and social inclusion. However, with some expectations, implementation(实现,履行) remains weak. Most education and training system still largely focus on the education and training of young people and limited progress has been made in changing systems to mirror the need for learning throughout the life span. An additional 4 million adults would need to participate in lifelong learning. Recent research confirms the importance of investing in adult learning. Research on older adults indicates that those who engage in learning are healthier, with a consequent decrease in health care costs.
Europe’s key economic challenge is to raise its growth and employment performance while preserving social cohesion(凝聚力). Rapid progress in other regions(地区) of the world shows the importance of innovative (创新的), advanced and quality education and training as a key factor in economic competitiveness. General levels of competence must increase, both to meet the needs of the employment market and to allow citizens to function well in society.
Europe is facing unheard-of demographic changes that will have a major impact on society and on the economy and consequently on education and training provision and needs. The European population is aging: over the next 30 years the number of younger Europeans(up to 24 years old)will fall by 15%. One in three Europeans will be over 60 years old, and about one in then will be over 80.
Raising the overall level of skills of the adult population by offering more and better learning opportunities throughout adult life is important for both efficiency and equity reasons given the challenges identified above. Not only does adult learning help make adults more efficient workers and, better-informed and more active citizens, it also contributes to their personal well-being.
1. What dose the author say about adult learning?A.It reduces health care costs greatly. |
B.The young need take it seriously. |
C.It hasn’t been given enough attentions. |
D.More adults have realized its importance. |
A.Upgrade(提高) general levels of our abilities |
B.Face various challenges bravely. |
C.Copy what other regions have done. |
D.Be sensitive to the labour market. |
A.Change in the education system | B.Changes in the job market |
C.Changes in the population | D.Changed in society |
【推荐2】Seventeen-year-old Lindsey Stoefen loves to play tennis, softball and run until last October when a rare disorder paralyzed her legs and left her in a wheelchair. But in late April after becoming an in-patient at Marianjoy Rehabilitation Hospital in Chicago, the teen climbed into a specially designed exoskeleton (外骨骼) which supported her body and moved her legs.
“Yes, I'm gonna be a robot! And I was scared at first. Am I gonna like it? Is it gonna be okay? And then once I got into it, I loved it." Lauren Bularzik, Lindsey s physical therapist, says the exo robots help to accelerate the recovery process.
For someone who takes a lot of energy to only walk a few feet, exo can get them up and get them moving. Besides speeding up recovery time, these robotic skeletons are especially helpful for those with paralysis, from spinal cord injuries and strokes.
Using the machine can help some patients rewire their brains to use secondary muscles, so they can eventually walk again without the device. But Patrick Wensing, assistant professor at the University of Notre Dame says exoskeletons have one big drawback. While existing exoskeletons are very powerful, right now they don t understand what the user wants to do. So in order to switch between activities in daily life, you often have to press a button interface to tell the exoskeleton “I would like to stand up now".
Wensing and his team are cooperating with Ekso Bionics, a leading developer of wearable robots, to create a machine that can understand what its user wants to do without implanted sensors and complicated control panels.
Taylor Gambon has spent the last year analyzing data from exoskeleton users and comparing them to models of everyday walking. Later this year, the team will travel to Ekso Bionics' California headquarters, where they will work directly with exoskeletons to design programs that interact with users of various disabilities, so that more people like Lindsey Stoefen can get back on their feet again.
1. What's the purpose of the story about Stoefen in the first paragraph?A.To prove Stoefen's bravery against disability. |
B.To explain Stoefen's misfortune in life. |
C.To introduce advanced medical skills in Chicago. |
D.To introduce the topic of robotic skeleton. |
A.They can improve the recovery speed. |
B.They can replace the real person. |
C.They can't understand the intention of users. |
D.They can help patients do everything in life. |
A.Disappointed. | B.Critical. |
C.Indifferent. | D.Optimistic. |
A.An advertisement. | B.A science fiction. |
C.A product handbook. | D.A popular science magazine. |
【推荐3】Apple Seeds
Circulation (发行量):1 Year, 9 Issues
Cover Price: $44. 55
Price For You: $33. 95
Product Description: Apple Seeds is an award-winning magazine filled with stories for kids aged from 7 to 9. The cover is very soft, providing durability (耐用性) that allows each issue to be enjoyed for many year to come. Besides, there is a big surprise for you --- it’s being sold at a more favorable discount than usual.
Better Life
Circulation: 1 Year, 12 Issues
Cover Price: $44. 55
Price For You: $15. 00
Product Description: Designed for those who have a strong interest in personal lifestyle, Better Life is America’s complete home and family service magazine. It offers help with food, recipes, decorating, building, gardening, family health, money management, and education.
Humor Times
Circulation: 1 Year, 12 Issues
Cover Price: $36. 00
Price For You: $11. 95
Product Description: Humor Times Magazine is for those who love to laugh! Full of cartoons and humor columns, it shows up in your mailbox once a month and keeps you smiling all year round! In today’s world, you need a reason to laugh. So let’s find it in Humor Times.
News China
Circulation: 1 Year, 12 Issues
Cover Price: $47. 88
Price For You: $19. 99
Product Description: News China Marine is the English edition of China Newsweek. The magazine covers the latest Chinese domestic news in politics, business, society, environment, culture, sports and travels, etc. It is the first comprehensive news magazine for readers interested in China.
1. What do we know about Apple Seeds?A.The soft cover enables it to be read and kept long. |
B.It can be purchased as an award for your children. |
C.It offers the biggest discount among all the magazines. |
D.The magazine is going to surprise for many years. |
A.People who have an interest in personal lifestyle of the Chinese. |
B.People who have a strong sense of humor and love to laugh. |
C.People who want to enlarge the knowledge of their kids. |
D.People who are interested in China’s politics, business and culture. |
A.beautifying your house. |
B.finding interesting stories for your kids |
C.ordering food from restaurants. |
D.learning about sports and travels. |