There might be as many as 10 million species of complex life on this planet today —— a huge number. But add up all of the complex species that ever lived and some biologists think the grand total would be about five billion. The estimate leads to an astonishing conclusion: a staggering 99% of species are not around any more. They have been driven to extinction.
More species are joining the ranks of the extinct every year. Many scientists believe we are living through an episode of remarkably rapid extinction, on a scale that has been seen only five times in the last half a billion years.
They call this current episode the sixth mass extinction —— a large, global decline in a wide variety of species over a relatively short period of time. And they tend to agree that humans are the main cause.
Over-hunting, overfishing, and human-driven habitat loss are pushing many species to the brink. In fact, we have changed the planet so much that some geologists are now suggesting that we have entered a new phase in Earth’s history; an epoch they call the ＂Anthropocene＂. By 2100, it is expected that humans will have caused the extinction of up to half of the world’s current species.
Because we are living through this extinction, it is relatively easy for us to study the driving forces behind it. But how do we determine what caused other mass die-offs that happened long ago? To do so we have to look at what archaeologists, palaeontologists, geologists and other scientists have concluded from the evidence they have gathered.
The trouble is, those scientists do not always agree with one another —— even about the most recent extinction event. As well as the five-or six- mass extinctions, there have also been many smaller extinctions.
One of these mini extinction events happened towards the end of the Pleistocene, a few tens of thousands of years ago. It is sometimes called the ＂megafaunal＂ extinction because many of the species it claimed were particularly large animals, weighing more than 97lb (44kg). However, its cause remains a debate amongst scientists.
1. What can we learn about the sixth mass extinction？| A．Humans are the main cause of it. |
| B．It means a global decline over a long time. |
| C．It occurred towards the end of the Pleistocene. |
| D．Scientists still disagree about the cause of it. |
| A．99% of species will not be around any more by 2100. |
| B．By the 22nd century, there will probably be about five million on this planet. |
| C．About eight years later we will enter what is called the ＂Anthropocene＂. |
| D．It is not easy for us to figure out causes behind the＂Anthropocene＂. |
| A．Land animals. | B．Marine life. |
| C．Huge animals. | D．Flesh-eating creatures. |
相似题推荐
【推荐1】A remarkable variety of insects live on this planet. Insects have survived on earth for more than 300 million years, and may possess the ability to survive for millions more.
Insects can be found almost everywhere—on the highest mountains, in the cold South Pole and in bubbling hot springs. They dig through the ground, jump and sing in the trees, and run and dance in the air. They come in many different colors and various shapes. Insects are extremely useful to humans,pollinating (授粉) our crops as well as flowers in meadows,forests, deserts and other areas. But some insects, such as mosquitoes and fleas, can transmit disease.
There are many reasons why insects are so successful at surviving. Their amazing ability to adapt permits them to live in extreme ranges of temperatures and environments. They can survive on a wide range of natural and artificial foods - paint, books, grain, plants and animals. Because they are small, they can hide in tiny spaces.
A strong, hard but flexible shell covers their soft organs and is resistant to chemicals, water and physical impact. Their wings give them the option of flying away from dangerous situations or toward food or mates. Also, insects have an enormous reproductive capacity: An African ant queen can lay as many as 43,000 eggs a day.
Another reason for their success is the strategy of protective color. An insect may be right before our eyes, but nearly invisible because it is cleverly disguised (伪装) like a green leaf, lump of brown soil, a seed or some other natural object. Some insects use bright, bold colors to send warning signals that they taste bad. Others have wing patterns that look like the eyes of a huge predator, confusing their enemies.
1. What does the underlined word “transmit” in Paragraph 2 mean?| A．cure. | B．catch. |
| C．prevent. | D．spread. |
| A．Have a strong shell. | B．Fly away when necessary. |
| C．Hide in tiny spaces. | D．Change colors or shapes. |
| A．To look bad—tasting. | B．To send warning signals. |
| C．To avoid being discovered. | D．To frighten away their enemies. |
| A．How insects survive in different places. |
| B．Why insects can survive so successfully. |
| C．What insects can do to the environment. |
| D．Where insects can be found in quantity. |
【推荐2】In October, the wildlife group of Himachal Pradesh reintroduced bred-in-captivity (圈养的) Cheer Pheasants (彩雉) into the wild to increase the falling population of this endangered bird.
It is the first attempt of its kind in India. Already, the HP wildlife group is considering the experiment a success. “Out of the 18 birds set free past October-six adults and 12 young ones-11 are still surviving,” says Dr Savita, Chief Wildlife Warden, HP. “According to international standards, even if 20 percent survive for at least a year, the experiment is considered successful.” The birds have been in the wild for eight months now, still four months short of the critical one year period. But having survived the cold winters, survival now should relatively be a walk in the park for these birds.
Reintroduction of any species into the wild requires painstaking efforts, and this experiment is no exception. The first step of the experiment was setting up a conservation breeding facility (繁殖设施) in Chail. The next step was their pairing. “Before the pairing, the genetic analysis was carried out,” says Dr Savita. “Besides, they were often screened for diseases and infections (感染) before they were set free.” Even one diseased bird could infect the entire population in the habitat.
Eventually, three pairs and their 12 chicks were chosen for a flight into the wild. The site chosen for their release (放飞) was a small hill in village Seri. Throwing them straight into the deep end could have proved a disaster, so soft-release was planned. For a month, the birds were kept in-three enclosed pens at the release site. Each pen mirrored their habitat with branches and bushes inside.
A month later, they were allowed to move out to live the life they were actually supposed to. The surviving 11 birds were closely tracked and they seem to have adapted well to the new surroundings. In another four months, the hill in village Seri could become a striking place on the wildlife map.
1. Which of the following best describes “a walk in the park” underlined in paragraph 2?| A．Alarming. | B．Meaningful. | C．Challenging. | D．Easy |
| A．They lived in the park for some time. |
| B．They suffered from disasters. |
| C．They learned to fit in with the wild life. |
| D．They were examined on a daily basis. |
| A．Returning to the Wild |
| B．Saving the Wild Birds |
| C．A Soft Release of Birds |
| D．A Successful Bird Research |
A． | B． | C． | D． |
【推荐3】Batesian mimicry (模仿) where a harmless species mimics a harmful one to escape enemies is widespread in animals. But most recorded examples of the phenomena are visual. For instance, the kingsnakes have evolved to look like a poisonous species, while the flower-loving flies have adopted the appearance of wasps (黄蜂). Now, for the first time, researchers have uncovered a kind of bat that has developed this trick related to sound to scare away enemies.
Danilo Russo first discovered the greater mouse-eared bat’s genius while working on his Ph. D. paper report on bats. “I noticed that when we handled the bats to take them out of the net or process them, they produced sounds just like wasps,” he said.
Years later, the animal ecologist at the University of Naples Federico II and his team set out to investigate if the sound was a coincidence or a way to frighten away enemies. The researchers recorded the cries of the bats when they were being caught. They then compared the sounds to four wasps. The similarities in the sounds convinced the scientists the bats were copying the insects to scare off enemies.
Russo and his team tested their theory on eight wild owls and eight human-raised owls. When the scientists played normal bat sounds, all the owls flew towards the speaker in search of the insects. However, the birds instantly flew away when exposed to the bat’s bee-like sound.
The researchers who published their findings observed that the wild birds showed greater fear than the ones brought up by humans. This indicated that the owls had previously been stung(叮) by the wasps and knew to clear away when they heard the buzzing sound.
“Birds tend to avoid stinging insects,” Russo says. “When nest boxes or tree holes are occupied by hornets, birds do not even attempt to explore them, not to mention nest there.”
1. Why were the king snakes mentioned in the text?| A．To prove they are scary. | B．To confirm a phenomenon. |
| C．To show they are poisonous. | D．To compare them with flies. |
| A．They can make sounds. | B．They can copy wasps. |
| C．They can poison insects. | D．They can escape from nets. |
| A．Owls like the bat’s bee-like sound. |
| B．Human-raised owls don’t like to eat bats. |
| C．Wild owls have a stronger ability to survive. |
| D．Wild owls have been attacked by wasps before. |
| A．Sounds Can Help Bats and Owls Escape |
| B．Clever Insects Learn Skills from Each Other |
| C．Some Animals Can Learn from Their Enemies |
| D．Bats Make Sounds like Wasps to Escape Owls |
【推荐1】The use of cellphones by students at school has become a widespread and controversial issue in recent years. On one hand, cellphones can provide students with many benefits, such as access to information, ability to communicate with others, and opportunities to complete schoolwork.
To address this issue, many schools have established policies to control the use of cellphones by students.
In addition to the potential for distraction, there are also serious safety concerns related to students’ use of cellphones at school. Students are at risk of being exposed to cyberbullying (网络霸凌) and other online dangers if they are not careful with their devices.
In conclusion, the use of cellphones by students at school is a complex issue that requires careful consideration of both the benefits and disadvantages. Clear policies should be established to balance student safety with their educational needs.
| A．However, students can use cellphones to help with their learning. |
| B．Schools have a responsibility to educate students about these risks. |
| C．Students sometimes constantly ask why schools are so strict with them. |
| D．For students, it is essential to realize the negative effects of cellphone use. |
| E．However, cellphones can also be a major source of distraction in the classroom. |
| F．Some require students to turn their cellphones off or put them away during class. |
| G．Schools can help students make the most of this technology by providing guidance. |
【推荐2】Young people's career expectations have become more concentrated in fewer occupations(职业) over the past two decades though social media and technologies like Artificial Intelligence(Al) are developing rapidly, according to a report form the Organization for Economic Cooperation and Development (OECD). Traditional occupations from the 19th and 20th centuries, such as lawyers and police officers, continue to trap(使陷入) the imaginations of young people around the world as they did nearly 20 years ago.
The report, based on a latest survey of the 15-year-olds in 41 countries,said the career expectations of youngsters may be “antiquated and unrealistic”.Nearly half of young people around the world wish to work in just 10 of the most common professions. The surveys show that too many teenagers are ignoring, or don't know, new types of jobs that are coming up,particularly as a result of digitalisation(数字化). It is a concern that more young people than before appear to be picking their dream job from a small list of the most popular, traditional occupations, like teachers, lawyers or business managers.
The report found that among boys and girls who perform similarly in science, boys are more likely to expect to work in science and engineering. The top 10 occupations preferred by boys have changed very little since 2000-but girls are now more likely to want to be architects, police officers, and designers rather than hairdressers or writers.
The report also found a broader range of career expectations in countries with strong and firm occupational training for teenagers. For example, in Germany teenagers show a much wider range of career interests that better reflect patterns of labour market demands. More than a third of students in the UK report a lack of career advice at schools and colleges. Young people's wishes are set as young as age seven, and do not change enough over time to meet demands.
1. What does the underlined word “antiquated”in paragraph 2 probably mean?| A．Outdated | B．Uncertain. | C．Purposeful. | D．Demanding. |
| A．Puzzled. | B．Surprised . | C．Satisfied. | D．Worried. |
| A．Strengthening the occupational training for teenagers. |
| B．Offering more new types of occupations with high pay. |
| C．Advertising new types of occupations on social media. |
| D．Enriching the occupation imaginations of young people. |
| A．New Occupations for Young People |
| B．Young People's Career Expectations |
| C．The Occupational Training for Teenagers |
| D．The Different Demands in Labour Market |
【推荐3】The American Psychological Association(APA) has issued its first advisory on social media use in adolescence (青春期). What’s most striking in its data based on recommendations is how little we really know about how these apps affect our kids.
The relative newness of platforms like Snapchat and Tik Tok means little research is available about their long-term effects on teen and tween brains. Getting better data will require significant funding—and much more openness from tech companies.
“What little evidence we do have unsurprisingly suggests that social media trades on motivators that aren’t great for young brains. Many kids’ first exposure to social media occurs at the worst possible time when it comes to brain development,” says Mitch Prinstein, a psychologist and neuroscientist at the University of North Carolina(UNC).
“Things like ‘button and artificial intelligence(in general)’ are going to affect young people’s brains in a way that’s very different from adult brains when it comes to the desire to stay online and to say or do almost anything to get followers.” When it comes to social interactions, he compares kids’ brains to a car with a huge gas pedal and weak brakes (刹车).
Earlier this year, Prinstein and his UNC colleagues published the results of one of the first studies of how the adolescent brain reacts to social media. The team surveyed a group of middle schoolers to understand their social media habits, and then stuck them in an MRI machine to watch their brains as they reacted to social rewards or punishments. They found that 12-year-olds who habitually checked social media had distinct neural patterns, with more activities over time in parts of the brain associated with motivation, salience(or where attention is focused) and cognitive control.
The team didn’t weigh in on whether those differences were good or bad, or whether the relationship was causal or correlational. But their work points to the need for more research. It should also remind parents of the need to be keenly aware of social media’s hidden influence on still-developing brains.
1. What issue regarding social media apps does the APA report highlight?| A．Their addictive nature. | B．The lack of data on their influence. |
| C．The dishonesty of their developers. | D．The ineffectiveness of their incentives. |
| A．Uncontrolled. | B．Sensitive. | C．Unpredictable. | D．Productive. |
| A．They are usually highly motivated. | B．They find it difficult to concentrate. |
| C．They have greater cognitive control. | D．Their brains show unique features. |
| A．Empowering Teens in the Digital Age |
| B．How to Guide Teens’ Social Media Engagement |
| C．The Hidden Influence of Social Media on Young Minds |
| D．The Importance of Healthy Social Media Habits |
