1 . The history of microbiology begins with Dutch cloth maker named Antoni van Leeuwenhoek, a man of no formal scientific education. In the late 1600s. Leeuwenhoek, inspired by the magnifying lenses（放大镜）he used to examine cloth, built some of the first-microscopes. He developed technique to improve the quality of tiny, rounded lenses, some of which could magnify an object up to 270 times. After removing some plaque from between his teeth and examining it under a lens, Leeuwenhoek found tiny twisting creatures, which he called “animalcules”.
His observations, which he reported to the Royal Society of London, are among the first descriptions of microbes（微生物）. Leeuwenhoek discovered an entire universe invisible to the human eye. He found different microbes in samples of pond water, rain water, and human blood. He gave the first description of red blood cells, observed plant tissue, examined muscle, and investigated the life cycle of insects.
Nearly two hundred years later, Leeuwenhock’s discovery of microbes helped French chemist and biologist Louis Pasteur to develop his “theory of disease”. This concept suggested that disease originates from tiny organisms attacking and weakening the body. Pasteur’s theory later helped doctors to fight infectious diseases including anthrax, diphtheria, polio, smallpox, tetanus, and typhoid. All these breakthroughs were the result of Leeuwenhoek’s original work. Leeuwenhoek did not foresee this legacy.
In a 1716 letter, he described his contribution to science this way: “My work, which I’ve done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a strong desire for knowledge, which I notice resides in me more than in most other men. And therefore; whenever I found out anything remarkable, I have thought it my duty to put down my discovery on paper, so that the scientific community might be informed thereof.”
1. Which of the following best describes Leeuwenhoek?| A．trained researcher with an interest in microbiology |
| B．A curious amateur who made pioneer studies of microbes |
| C．A talented scientist interested in finding a cure for disease |
| D．A bored cloth maker who accidentally made a major discovery |
| A．the discovery of microbes |
| B．Pasteur’s theory of disease |
| C．Leeuwenhoek’s contribution |
| D．the origin of the tiny organism |
| A．He admitted that many of his discoveries happened by chance. |
| B．He considered his work to be central to later medical breakthroughs. |
| C．He was greatly concerned with improving people’s living conditions. |
| D．He believed the sharing of knowledge was a key to scientific progress |
a. Magnifying lenses were built.
b. The “theory of disease” was put forward
c. Microbes were discovered in samples of waters.
d. Leeuwenhoek’s first microscopes were successfully developed.
e. Leeuwenhoek explained his thoughts upon his own contribution.
| A．a-d-c-e-b | B．d-a-c-e-b | C．a-c-d-b-e | D．d-a-e-b-c |
2 . Great work is work that makes a difference in people’s lives, writes David Sturt, Executive Vice President of the O.C. Tanner Institute, in his book Great Work: How to Make a Difference People Love. Sturt insists, however, that great work is not just for surgeons or special-needs educators or the founders of organizations trying to eliminate poverty in sub-Saharan Africa. The central theme of Great Work, according to Sturt, is that anyone can make a difference in any job. It’s not the nature of the job, but what you do with the job that counts. As proof, Sturt tells the story of a remarkable hospital cleaner named Moses.
In a building filled with doctors and nurses doing great life-saving work, Moses the cleaner makes a difference. Whenever he enters a room, especially a room with a sick child, he engages both patients and parents with his optimism and calm, introducing himself to the child and, Sturt writes, speaking “little comments about light and sunshine and making things clean.” He comments on any progress he sees day by day (“you’re sitting up today, that’s good.”) Moses is no doctor and doesn’t pretend to be, but he has witnessed hundreds of sick children recovering from painful surgery, and parents take comfort from his encouraging words. For Matt and Mindi, whose son McKay was born with only half of a heart, Moses became a close friend. As Sturt explains, “Moses took his innate (与生俱来的) talents (his sensitivity) and his practical wisdom (from years of hospital experience) and combined them into a powerful form of patient and family support that changed the critical-care experience for Mindi, Matt and little McKay.”
How do people like Moses do great work when so many people just work? That was the central question raised by Sturt and his team at the O.C. Tanner Institute, a consulting company specialized in employee recognition and rewards system.
O.C. Tanner launched an exhaustive Great Work study that included surveys to 200 senior executives, a further set of surveys to 1,000 managers and employees working on projects, an in-depth qualitative study of 1.7 million accounts of award-winning work (in the form of nominations (提名) for awards from corporations around the world), and one-on-one interviews with 200 difference makers. The results of the study revealed that those who do great work refuse to be defeated by the constraints of their jobs and are especially able to reframe their jobs: they don’t view their jobs as a list of tasks and responsibilities but see their jobs as opportunities to make a difference. No matter, as Moses so ably exemplifies (例证), what that job may be.
1. According to Sturt, which of the following is TRUE?| A．It’s not the nature of the job, but what you do that makes a difference. |
| B．Anyone in the world is responsible to delete poverty and change the world. |
| C．Anyone can make a difference in people’s lives no matter what kind of job he does. |
| D．Surgeons, special-needs educators and founders of organizations can succeed more easily. |
| A．By keeping optimistic and calm when facing patients and their parents at hospital. |
| B．By showing his special gift and working experience when working at hospital. |
| C．By showing his sympathy and kindness to patients when entering their rooms. |
| D．By pretending to be a doctor or nurse when entering a room with a sick child. |
| A．demands | B．advantages | C．disadvantages | D．limitations |
| A．Great work is work that makes a difference in people’s lives no matter what you do. |
| B．If a boss has trouble recognizing his employees, he can ask O. C. Tanner for advice. |
| C．Moses makes a difference through his sensitivity and his practical wisdom. |
| D．Those who do great work are never defeated by others or their jobs themselves. |
3 . Hollywood’s theory that machines with evil(邪恶) minds will drive armies of killer robots is just silly. The real problem relates to the possibility that artificial intelligence(AI) may become extremely good at achieving something other than what we really want. In 1960 a well-known mathematician Norbert Wiener, who founded the field of cybernetics（控制论）, put it this way: “If we use, to achieve our purposes, a mechanical agency with whose operation we cannot effectively interfere(干预), we had better be quite sure that the purpose put into the machine is the purpose which we really desire.”
A machine with a specific purpose has another quality, one that we usually associate with living things: a wish to preserve its own existence. For the machine, this quality is not in-born, nor is it something introduced by humans; it is a logical consequence of the simple fact that the machine cannot achieve its original purpose if it is dead. So if we send out a robot with the single instruction of fetching coffee, it will have a strong desire to secure success by disabling its own off switch or even killing anyone who might interfere with its task. If we are not careful, then, we could face a kind of global chess match against very determined, super intelligent machines whose objectives conflict with our own, with the real world as the chessboard.
The possibility of entering into and losing such a match should concentrate the minds of computer scientists. Some researchers argue that we can seal the machines inside a kind of firewall, using them to answer difficult questions but never allowing them to affect the real world. Unfortunately, that plan seems unlikely to work: we have yet to invent a firewall that is secure against ordinary humans, let alone super intelligent machines.
Solving the safety problem well enough to move forward in AI seems to be possible but not easy. There are probably decades in which to plan for the arrival of super intelligent machines. But the problem should not be dismissed out of hand, as it has been by some AI researchers. Some argue that humans and machines can coexist as long as they work in teams—yet that is not possible unless machines share the goals of humans. Others say we can just “switch them off” as if super intelligent machines are too stupid to think of that possibility. Still others think that super intelligent AI will never happen. On September 11, 1933, famous physicist Ernest Rutherford stated, with confidence, “Anyone who expects a source of power in the transformation of these atoms is talking moonshine.” However, on September 12, 1933, physicist Leo Szilard invented the neutron-induced(中子诱导) nuclear chain reaction.
1. Paragraph 1 mainly tells us that artificial intelligence may .| A．run out of human control |
| B．satisfy human’s real desires |
| C．command armies of killer robots |
| D．work faster than a mathematician |
| A．prevent themselves from being destroyed |
| B．achieve their original goals independently |
| C．do anything successfully with given orders |
| D．beat humans in international chess matches |
| A．help super intelligent machines work better |
| B．be secure against evil human beings |
| C．keep machines from being harmed |
| D．avoid robots’ affecting the world |
| A．It will disappear with the development of AI. |
| B．It will get worse with human interference. |
| C．It will be solved but with difficulty. |
| D．It will stay for a decade. |
It’s common knowledge that the woman in Leonardo da Vinci’s most famous painting seems to look back at observers, following them with her eyes no matter where they stand in the room. But this common knowledge turns out wrong.
A new study finds that the woman in the painting is actually looking out at an angle that’s 15. 4 degrees off to the observer’s right-well outside of the range that people normally believe when they think someone is looking right at them. In other words, said the study author, Horstmann, “She’s not looking at you. “ This is somewhat ironic, because the entire phenomenon of a person’s gaze (凝视) in a photograph or painting seeming to follow the viewer is called the “Mona Lisa effect” . That effect is absolutely real, Horstmann said. If a person is illustrated or photographed looking straight ahead, even people viewing the portrait from an angle will feel they are being looked at. As long as the angle of the person’s gaze is no more than about 5 degrees off to either side, the Mona Lisa effect occurs.
This is important for human interaction with on-screen characters. If you want someone off to the right side of a room to feel that a person on-screen is looking at him or her, you don’t cut the gaze of the character to that side-surprisingly, doing so would make an observer feel like the character isn’t looking at anyone in the room at all. Instead, you keep the gaze straight ahead.
Horstmann and his co-author were studying this effect for its application in the creation of artificial-intelligence avatars(虚拟头像) when Horstmann took a long look at the “Mona Lisa” and realized she wasn’t looking at him.
To make sure it wasn’t just him, the researchers asked 24 people to view images of the “Mona Lisa” on a computer screen. They set a ruler between the viewer and the screen and asked the participants to note which number on the ruler intersected(和……相交) Mona Lisa’s gaze. To calculate the angle of Mona Lisa’s gaze as she looked at the viewer, they moved the ruler farther from or closer to the screen during the study. Consistently, the researchers found, participants judged that the woman in the “Mona Lisa” portrait was not looking straight at them, but slightly off to their right.
So why do people repeat the belief that her eyes seem to follow the viewer? Horstmann isn’t sure. It’s possible, he said, that people have the desire to be looked at, so they think the woman is looking straight at them. Or maybe the people who first coined the term “Mona Lisa effect” just thought it was a cool name.
1. It is generally believed that the woman in the painting “Mona Lisa”___________.| A．attracts the viewers to look back |
| B．seems mysterious because of her eyes |
| C．fixes her eyes on the back of the viewers |
| D．looks at the viewers wherever they stand |
A． | B． | C． | D． |
| A．confirm Horstmann’s belief |
| B．create artificial-intelligence avatars |
| C．calculate the angle of Mona Lisa’s gaze |
| D．explain how the Mona Lisa effect can be applied |
| A．Horstmann thinks it’s cool to coin the term “Mona Lisa effect”. |
| B．The Mona Lisa effect contributes to the creation of artificial intelligence. |
| C．Feeling being gazed at by Mona Lisa may be caused by the desire for attention. |
| D．The position of the ruler in the experiment will influence the viewers’ judgement. |
5 . I read somewhere that we spend a full third of our lives waiting. But where are we doing all of this waiting, and what does it mean to an impatient society like ours? To understand the issue, let’s take a look at three types of “waits”.
The very purest form of waiting is the Watched-Pot Wait. It is without doubt the most annoying of all. Take filling up the kitchen sink(洗碗池) as an example. There is absolutely nothing you can do while this is going on but keep both eyes fixed on the sink until it’s full. During these waits, the brain slips away from the body and wanders about until the water runs over the edge of the counter and onto your socks. This kind of wait makes the waiter helpless and mindless.
A cousin to the Watched-Pot Wait is the Forced Wait. This one requires a bit of discipline. Properly preparing packaged noodle soup required a Forced Wait. Directions are very specific. “Bring three cups of water to boil, add mix, simmer three minutes, remove from heat, let stand five minutes.”I have my doubts that anyone has actually followed the procedures strictly. After all, Forced Waiting requires patience.
Perhaps the most powerful type of waiting is the Lucky-Break Wait. This type of wait is unusual in that it is for the most part voluntary. Unlike the Forced Wait, which is also voluntary, waiting for your lucky break does not necessarily mean that it will happen.
Turning one’s life into a waiting game requires faith and hope, and is strictly for the optimists among us. On the surface it seems as ridiculous as following the directions on soup mixes, but the Lucky-Break Wait well serves those who are willing to do it. As long as one doesn’t come to rely on it, wishing for a few good things to happen never hurts anybody.
We certainly do spend a good deal of our time waiting. The next time you’re standing at the sink waiting for it to fill while cooking noodle soup that you’ll have to eat until a large bag of cash falls out of the sky, don’t be desperate. You’re probably just as busy as the next guy.
1. While doing a Watched-Pot Wait, we tend to ___________.| A．keep ourselves busy |
| B．get absent-minded |
| C．grow anxious |
| D．stay focused |
| A．The Forced Wait requires some self-control. |
| B．The Forced Wait makes people passive. |
| C．The Watched-Pot Wait needs directions. |
| D．The Watched-Pot Wait engages body and brain. |
| A．It is less voluntary than the Forced Wait. |
| B．It doesn’t always bring the desired result. |
| C．It is more fruitful than the Forced Wait. |
| D．It doesn’t give people faith and hope. |
| A．Take it seriously. |
| B．Don’t rely on others. |
| C．Do something else. |
| D．Don’t lose heart. |
| A．exploring various causes of “waits”. |
| B．describing detailed processes of “waits”. |
| C．analyzing different categories of “waits” |
| D．revealing frustrating consequences of “waits” |
6 . If you wear glasses, chances are you are smarter. Research published in the famous British journal Nature Communications has found that people who displayed higher levels of intelligence were almost 30 percent more likely to wear glasses.
The scientists studied the genes of thousands of people between the ages of 16 and 102.The study showed intelligence can be connected to physical characteristics. One characteristic was eyesight. In out of 10 people who were more intelligent, there was a higher chance they needed glasses. Scientists also said being smarter has other benefits. It is connected to better health.
It is important to remember these are connections which are not proven causes. Scientists call this correlation. Just because something is connected to something else does not mean one of those things caused the other. And it’s worth noting that what constitutes intelligence is subjective and can be difficult, if not impossible, to measure.
Forget genes though. Plenty of proof shows wearing glasses makes people think you are more intelligent, even if you do not need glasses. A number of studies have found people who wear glasses are seen as smarter, hard-working and honest. Many lawyers use this idea to help win their cases. Lawyer Harvey Solves explained this. Glasses soften their appearance. He said Sometimes there has been a huge amount of proof showing that people he was defending broke the law. He had them wear glasses and they weren’t found guilty.
Glasses are also used to show someone is intelligent in movies and on TV. Ideas about people who wear glasses have begun to shift. People who do not need glasses sometimes wear them for fashion only. They want to look worldly or cool. But not everyone is impressed by this idea, though. GQ magazine said people who wear glasses for fashion are trying too hard to look smart and hip (时髦的). However, that hasn’t stopped many celebrities from happily wearing glasses even if they do not need them. Justin Bieber is just one high-profile fan of fashion glasses.
1. What does the new study show?| A．People wearing glasses are smarter. |
| B．People wearing glasses are healthier. |
| C．Wearing glasses can make people cleverer. |
| D．Wearing glasses is associated with higher IQ. |
| A．Shift. | B．Link. | C．Proof. | D．Consequence. |
| A．Because it can create a moral image. |
| B．Because it can mislead the witnesses. |
| C．Because it can highlight clients’ qualities. |
| D．Because it can prove the clients’ innocence. |
| A．Positive. | B．Negative. | C．Mixed | D．Indifferent. |
7 . Oxygen, I'm sure you'd agree, is pretty important for life on Earth. We breathe it in, our cells survive on it and without it, we hardly live. Basically all multicellular life on Earth evolved over millions of years to make use of oxygen.
But take a deep breath, because we need to talk about Henneguya salminicola, a tiny parasite(寄生虫) containing fewer than100 cells that lives within the muscle tissue of salmon, a large fish with silver skin and pink flesh. The strange-looking parasite does not busy itself with such small matters as breathing oxygen. Nope, it seems that H. salminicola is the first multicellular animal we've found that survives without the stuff.
“Aerobic respiration(有氧呼吸) was thought to be commonly found in animals, but now we confirmed that this is not the case, "said Dorothee Huchon, a zoologist at Tel Aviv University in Israel, in a press release.
Huchon and a team of international researchers examined and sequenced(排序) all of. salminicola's' genes in their study, published in the journal Proceedings of the National Academy of Sciences. They found that the parasite, which is closely related to jellyfish, lacks the DNA machinery necessary to“breathe”---it doesn't' have mitochondria(线粒体), often called the "powerhouse" of the cell, because they use oxygen to make energy. It's like a little factory inside almost all cells, and DNA detectives can find mitochondrial genes during sequencing.
The discovery came as something of an accident for the team, who were examining the genome (the complete set of genes) of the species. When they went searching for the mitochondrial genes, they came up empty-handed. "Our discovery shows that evolution can go in strange directions, ”Huchon said. "Aerobic respiration is a major source of energy, and yet we found an animal that gave up this important pathway.”
Some single-celled life forms have evolved the ability to survive without oxygen and do not have mitochondria, either. Plenty of bacteria can exist without oxygen at all. Instead of oxygen, they get their energy from fermentation(发酵) or use other molecules like iron.
But how H. salminicola produces energy is still unclear. Huchon suggests it could draw oxygen from the cells in salmon or it could have evolved similar methods to those of single-celled organisms which scientists have documented in the past.
1. What can we learn about Henneguya salminicola?| A．It is an animal consisting of a cell. |
| B．It can still survive without oxygen. |
| C．It takes on a normal appearance. |
| D．It has a longer lifespan than salmon. |
| A．To make cells breathe fast. |
| B．To help to produce oxygen. |
| C．To provide energy for cells. |
| D．To help cells absorb oxygen. |
| A．Interested. | B．Satisfied. | C．Astonished. | D．Frightened. |
| A．The natural evolution of animal cells |
| B．Different kinds of life forms on earth |
| C．A research on single-celled organisms |
| D．A creature that doesn't breathe oxygen |
8 . Financial regulations in Britain have imposed a rather unusual rule on the bosses of big banks. Starting next year, any guaranteed bonus of top executives could be delayed 10 years if their banks are under investigation for wrongdoing. The main purpose of this “clawback” rule is to hold bankers responsible for harmful risk-taking and to restore public trust in financial institution. Yet officials also hope for a much larger benefit: more long-term decision-making not only by banks but also by all corporations, to build a stronger economy for future generations.
“Short-termism” or the desire for quick profits, has worsened in publicly traded companies, says the Bank of England’s top economist, Andrew Haldane. He quotes a giant of classical economies, Alfred Marshall, in describing this financial impatience as acting like “Children who pick the strawberries out of their pudding to eat them at once” rather than putting them aside to be eaten last.
The average time for holding a stock in both the United States and Britain, he notes, has dropped from seven years to seven months in recent decades. Transient(短期的) investors, who demand high quarterly profits from companies, can hold back a firm’s efforts to invest in long-term research or to build up customer loyalty. This has been called “quarterly capitalism”.
In addition, new digital technologies have allowed more rapid trading of equities( 股 票 ), quicker use of information, and thus shortens attention spans in financial markets. “There seems to be an advantage of short-term thinking at the expense of long-term investing,” said Commissioner Daniel Gallagher of the US Securities and Exchange Commission in speech this week.
In the US, the Sarbanes-Oxley Act of 2002 has pushed most public companies to delay performance bonuses for senior executives by about a year, slightly helping reduce “short-termism.” In its latest survey of CEO pay, The Wall Street Journal finds that “a substantial part” of executive pay is now tied to performance.
Much more could be done to encourage “long-termism,” such as changes in the tax code and quicker disclosure(披露) of stock acquisitions. In France, shareholders who hold onto a company investment for at least two years can sometimes earn more voting rights in a company.
Within companies, the right compensation design can provide motivation for executives to think beyond their own time at the company and on behalf of all shareholders. Britain’s new rule is a reminder to bankers that society has an interest in their performance, not just for the short term but for the long term.
1. According to Paragraph 1, one reason for imposing the new rule is the _______.| A．enhance banker’s sense of responsibility |
| B．help corporations achieve larger profits |
| C．build a new system of financial regulation |
| D．guarantee the bonuses of top executives |
| A．indirect | B．negative |
| C．favorable | D．temporary |
| A．the obstacles to preventing “short-termism”. |
| B．the significance of long-term thinking. |
| C．the approaches to promoting “long-termism” |
| D．the popularity of short-term thinking. |
| A．Failure of Quarterly Capitalism |
| B．Patience as a Corporate Virtue |
| C．Decisiveness Required of Top Executives |
| D．Frustration of Risk-taking Bankers |
9 . It is an honor for me to deliver this speech and on behalf of the graduating students, welcome you to this special ceremony 2020.
This is a unique moment. We are stepping up to another phase of our lives at a time of great hardship and global difficulties. Hope this ceremony will help erase sad memories, refresh beautiful ones and add more splendid memories into our lives.
I was born in the middle of war, which caused my family to move to Serbia for three years. When the war ended, we returned to Bosnia. My mother, who is and will ever be my heroine, was the only figure who guided me, provided for me and kept me on the right track, in the hope for a better life. I owed her so much as she is responsible for huge part of my success. I will always remember her teachings “to complain less and always find solutions at the price of whatever it takes” ， which brought me to China, an ancient land of new hopes.
During the COVID-19 outbreak, I got the best opportunity to understand China. I saw millions of people united with one goal-to win the battle against this epidemic. I have never seen such a collective dedication from a nation, turning things for the better by sacrificing personal convenience on a grand scale. China's governance and health care system proves to be one of the most efficient in the world. With a population of 1.4 billion, China not only has successfully controlled the transmission of the corona-virus but also assisted many other countries across the globe.
Everyone has a role to play in the battle against the virus. In Tsinghua, I played a tiny but necessary role: Staying on campus, studying online, cooperating during temperature checks and respecting social distancing measures. The rules set by the university and Chinese government had everyone's health and safety as first priority. This made me feel safe and confident that China was on the right track towards victory. Throughout this time, despite the immense challenges, Tsinghua has facilitated many online conferences, which helped me nurture more skills in my field of study.
Friends, we are now graduating from one of the world’s most prestigious universities. Tsinghua has been like a mother to us over the past months and years, guiding and nurturing us along the way, providing us with great vision and placing on us high expectations. So what comes next? Actions speak louder than words. Let us accept new challenges, think beyond our limits and keep in mind the ethics of life.
Let's undertake everything we can for the sake of unity, humanity and the international community. Let's work together for a more promising future and prosperous world.
1. In the author's eyes, the special ceremony 2020 should| A．be a unique moment to mourn the sacrificed |
| B．be a time to wave a heartfelt goodbye to adversities |
| C．be a moment to open a new chapter of life |
| D．be a glorious time to embrace a beautiful past |
| A．The author came to China so as to escape from wars |
| B．The author witnessed how the original virus spread swiftly |
| C．The author was requested to supply medical aid to the fight against COVID-19 |
| D．Owing to dozens of timely measures,China had a ideal control of the virus |
| A．The strict rules of the government. |
| B．The joint commitment of the nation. |
| C．The harsh circumstance in China. |
| D．The great transformation of the school. |
10 . Modern medicine’s ability to keep us alive makes it tempting to think human evolution may have stopped. But if we look at the rate of our DNA’s evolution, we can see that human evolution hasn’t stopped – it may even be happening faster than before.
Evolution is a gradual change to the DNA of a species over many generations. It can occur by natural selection, when certain traits created by genetic changes help an organism survive or reproduce. Such genes are thus more likely to be passed on to the next generation, so they increase in frequency in a population. Gradually, these changes and their associated traits become more common among the whole group.
By looking at global studies of our DNA, we can see evidence that natural selection has recently made changes and continues to do so. Though modern healthcare disrupts a key driving force of evolution by keeping some people alive longer, in countries without access to good healthcare, populations are continuing to evolve. Survivors of infectious disease outbreaks drive natural selection by giving their genetic resistance to offspring. Our DNA shows evidence for recent selection for resistance of killer diseases like Lassa fever and malaria. Selection in response to malaria remains in regions where the disease remains common.
Humans are also adapting to their environment. Gene change allowing humans to live at high altitudes have become more common in populations in Tibet, Ethiopia, and the Andes. The spread of genetic changes in Tibet is possibly the fastest evolutionary change in humans, occurring over the past 3,000 years. This rapid increase in frequency of a mutated gene that increases blood oxygen content gives locals a survival advantage in higher altitudes, resulting in more surviving children.
Diet is another source for adaptations. Studies show that natural selection favoring a change allowing adults to produce lactase – the enzyme (酶) that breaks down milk sugars – is why some groups of people can digest milk. Over 80 per cent of northwest Europeans can, but in parts of East Asia, where milk is much less commonly drunk, an inability to digest lactose is the norm. Like high altitude adaptation, selection to digest milk has evolved more than once in humans and may be the strongest kind of recent selection.
Yet, despite these changes, natural selection only affects about 8 per cent of our genome. But scientists can’t explain why some genes are evolving much faster than others. We measure the speed of gene evolution by comparing human DNA with that of other species. One fast-evolving gene is human accelerated region 1 (HAR1), which is needed during brain development. A random section of human DNA is on average more than 98 per cent identical to the chimp comparator, but HAR1 is so fast evolving that it’s only around 85 per cent similar. Though scientists can see these changes are happening – and how quickly – we still don’t fully understand why fast evolution happens to some genes but not others.
1. Which of the following statements may the author agree with?| A．Evolution occurs among several people overnight. |
| B．Genes may change and some are beneficial to people’s lives. |
| C．Evolution is done when the whole population possesses a certain gene. |
| D．The changed genes leading to higher survival rates are chosen deliberately. |
| A．explains | B．causes | C．upsets | D．heals |
| A．some people can resist infectious diseases like malaria |
| B．children in Tibet tolerate living environments with thin air |
| C．northwestern Europeans digest lactose better than East Asians |
| D．the human gene HAR1 resembles that of a chimp to a lesser extent |
| A．What Is Natural Selection? |
| B．Are Humans Still Evolving? |
| C．Why Will Certain Genes Evolve? |
| D．How Do Mutated Genes Function? |
