Mangroves typically grow in saltwater along coasts. But some mangroves live in freshwater along the San Pedro Mártir River of Mexico's Yucatán Peninsula. That's nearly 200 kilometers from the sea. Scientists wanted to know how these mangroves got trapped so far inland.
Carlos Burelo was among them. He became curious about these mangroves on a childhood fishing trip. there with his dad 35 years ago. Burelo saw that the roots of the mangroves grew above ground. This was different from the other trees, and it interested him so much. Today, Burelo works at Universidad Juárez Autónoma de Tabasco, Mexico. This biologist is part of a team that went on to discover where those mangroves came from.
Burelo's team first collected leaves from these mangroves. The scientists then compared their DNA to those of leaves from coastal mangroves. The coastal trees were growing along the Caribbean Sea and Gulf of Mexico. The DNA helped find the origins of the mangroves on the San Pedro Marir River. They had started along the Gulf of Mexico, some 170 kilometers away from the river. The river mangroves' DNA and their ages also contained clues about when they separated from their coastal relatives.
The team shared its findings in the Proceedings of the National Academy of Sciences on October 12-More than 100,000 years ago, the world was warmer and Sea levels higher. In fact, sea levels reached about 9 meters above today's levels. As a result, land on what is now the Yucatán Peninsula flooded. That allowed coastal mangroves to move inland. When the world cooled again, the mangroves were stuck for from the coast.
“The remarkable resilience of these trees is striking,” says Burelo.“Although they normally live in seawater, they've survived all this time inland. That is incredible.”
This discovery highlights how changes to the past climate have affected the world's coastlines. It also offers a chance to better understand how future sea level rise may affect these ecosystems .
1. What attracted Burelo's attention on the childhood fishing trip?| A．A typical kind of tree. | B．A trap on the coast. |
| C．A fishing net in the river. | D．A team of biologists . |
| A．To predict possible climate changes. | B．To find the substances they are rich in. |
| C．To separate them from their coastal relatives. | D．To get scientific evidence for the tree's origin. |
| A．Where the team carried out their research. |
| B．What once destroyed the Yucatán Peninsula. |
| C．When the sea level became higher than today's. |
| D．How the sea-loving tree ended up far from the coast. |
| A．Growing period. | B．Economic value. |
| C．Adaptive ability. | D．Ecological function. |
相似题推荐
【推荐1】Directions: Read the passage carefully. Then answer the questions or complete the statements in the fewest possible words.
While contact between adolescents (between the ages of fifteen and nineteen) and their peers (同龄人) is a universal characteristic of all cultures, the nature and the degree of such contact vary a great deal. In American contemporary society, adolescents spend much more time with their peers than with younger children or adults.
This pattern of age segregation (隔离) in American society did not become usual until the beginning of the industrialized society. Changes in the workplace separated children from adults, with adults working and children attending school. The dramatic increase of mothers in the workplace has further contributed to the reduction in the amount of time adolescents spend with adults. School reform efforts during the nineteenth century, which resulted in age-segregated schools and grades, have reduced the amount of time adolescents spend with younger children. Finally, the changes in population are considered a factor that may have contributed to the emergence of adolescent peer culture. From 1955 to 1975, the adolescent population increased dramatically, from 11 percent to 20.9 percent. This increase in the number of adolescents might be a contributing factor to the increase in adolescent peer culture in terms of growth in size.
Research supports the view that adolescents spend a great deal of time with their peers. Reed Larson and his colleagues examined adolescents’ daily activities and found that they spend more time talking to their friends than engaging in any other activity. In a typical week, high school students will spend twice as much time with their peers as with adults. This gradual withdrawal from adults begins in early adolescence. In sixth grade, adults (excluding parents) account for only 25 percent of adolescent social networks. Another important characteristic of adolescent peer culture is its increasingly autonomous (白治的) function. While childhood peer groups are conducted under the close supervision of parents, adolescent peer groups typically make an effort to escape adult supervision and usually succeed in doing so.
(Note: Answer the questions or complete the statements in NO MORE THAN EIGHT WORDS.)
1. “This pattern of age segregation” refers to the phenomenon that adolescents segregate themselves from
2. Besides changes in the workplace, what are the other two factors contributing to adolescent peer culture?
3. When do adolescents start to spend less time with adults?
4. How do adolescent peer groups differ from childhood peer groups?
【推荐2】Many people believe that there is some truth in the saying “Laughter is the best medicine.”
Laughter therapy has become very popular in recent years and as a result, more and more laughter clubs are starting to open up in cities and towns all over the world. At a laughter session, a trained therapist instructs the group to perform a series of exercises which are designed to produce laughter.
So next time you feel ill, stressed out or depressed, try watching a funny film or try remembering an amusing incident in your life. You will soon feel better.
| A．Laughter helps you focus. |
| B．This finding has led to so-called clown doctors. |
| C．Some people may find the idea embarrassing at first. |
| D．Laughter makes the world a better and more colorful place. |
| E．Using laughter therapy in children’s hospitals has proven to be invaluable. |
| F．If one person starts laughing, it is unavoidable that someone else will be drawn in. |
| G．In fact, research done by scientists has shown that laughter has a lot of health benefits. |
【推荐3】All living things need energy to move and grow. Energy can come in many different forms.
Where do plants get their energy? They get their energy from the sun. Plants absorb sunlight with their leaves.
Plants are called producers because they produce their own food. Producers form the base of every food chain in an ecosystem. Plants are eaten by animals, which are eaten by larger animals. For example, a plant takes in energy from the sun and turns it into plant food.
The food humans eat provides us with energy. When we chew and digest food, a chemical reaction takes place.
| A．The energy produced from this reaction fuels our bodies. |
| B．Eater, that plant might be eaten by a rabbit, giving the rabbit energy. |
| C．Notice how you feel when you eat whole foods like vegetables and fruits. |
| D．Through this process, energy from the sun is moved from one living thing to another. |
| E．They use the sun’s energy to change water and carbon dioxide into plant food and oxygen. |
| F．The amount of energy we get from food depends on which nutrients are in the food we eat. |
| G．For example, light energy, heat energy, and chemical energy are all different forms of energy. |
【推荐1】Heart in your throat. Butterflies in your stomach. Bad courage feeling. These are all phrases many people use to describe fear and anxiety.
You have likely felt anxiety inside your chest or stomach, and your brain usually doesn’t hurt when you’re scared. Many cultures tie weakness and bravery more to the heart or the guts than to the brain. But science has traditionally seen the brain as the birthplace and processing site of fear and anxiety. Then why and how do you feel these emotions in other parts of your body? Research confirms that while emotions do begin originally in your brain, it’s your body that carries out the orders. While your brain gradually changed and developed to save you from a falling rock or speeding man-eating animals, the anxieties of modern life are often a lot more abstract. Fifty-thousand years ago, being rejected by your tribe could mean death, but not doing a great job on a public speech at school or at work doesn’t have the same consequences. Your brain, however, might not know the difference.
There are a few key areas of the brain that are heavily involved in processing fear. Amygdala (杏仁体) is a small area of the brain located near your ears which detects obvious features, or the emotional connection of a situation and how to react to it. Threat search is a vital part of this process, and it has to be fast.
The hippocampus (海马体) is near and tightly connected to the amygdala. It’s involved in memorizing what is safe and what is dangerous, especially in relation to the environment — it puts fear in conditions.
The prefrontal cortex (前额叶皮质), located above your eyes, is mostly involved in the realization and social aspects of fear processing. For example, you might be scared of a snake until you read a sign that the snake is not poisonous or the owner tells you it’s his friendly pet.
As is described by a singer in his song “Lose Yourself”, the reason his hands sweated, his knees got weak and his arms became heavy was that his brain was nervous.
1. What can we learn from paragraph 2?| A．Emotions can lead to reactions in the body. |
| B．The brain keeps up with the pace of modern life. |
| C．Fear and anxiety do much damage to the brain. |
| D．Nowadays people have more anxieties than before. |
| A．Receiving outside information. |
| B．Storing memories. |
| C．Identifying different features. |
| D．Adjusting emotions. |
| A．To show the singer’s love for music. |
| B．To present a common phenomenon. |
| C．To illustrate the singer’s physical condition. |
| D．To explain physical discomfort originates from brain. |
| A．The response to fear and anxiety |
| B．A study about sense of fear |
| C．What negative emotions affect your body |
| D．What is the root of fear and anxiety |
Stressed? It is shown in recent research that walking or cycling to work calms you down (traveling by bus or train is also better than driving).
Walking to work reduces stress and improves brain power, researchers say. Adults who stopped driving the car and started walking or cycling became calmer and found it easier to concentrate. A study of 18,000 Britons found that going to work by train or bus improved their wellbeing compared with driving.
The study, published in the journal Preventive Medicine, also found that the longer people spent walking or cycling, the happier or less stressed they were. However, stress levels and inability to concentrate worsened if they spent more time in the car.
Lead researcher Adam Martin, from the University of East Anglia's Norwich Medical School, said that despite the crowds and disruption, walking to bus stops or stations and being able to relax on the journey “cheer people up”. Two thirds drive to work, 18 percent use public transport, 11 percent walk and 3 percent cycle.
A research earlier this year found that commuters (乘公共车辆往返者) had small but statistically significant lower scores on all measures of wellbeing. The worst effects were witnessed in those whose journeys last between 61 and 90 minutes. But when commuting time reaches three hours or more, the negative effects disappear, the report said.
“The effects of commuting on personal wellbeing are the greatest for anxiety and happiness, suggesting that commuting affects daytoday emotions more than overall evaluations of satisfaction with life or the sense that daily activities are worthwhile，” the report stated.
Dr Daniel Newman, from Cardiff University's Sustainable Places Research Institute, said, “This report says that many of us, who spend mornings and evenings sitting in traffic jam, already know: commuting can be a chore.”
1. What can be learned from Paragraph 1?
| A．Driving for long drives people crazy. |
| B．Feeling stressed can be predicted. |
| C．Walking to work helps reduce stress. |
| D．Travelling by bus makes people excited. |
| A．preferred by most people |
| B．easier to perform in daily life |
| C．making people more creative |
| D．beneficial to the sense of happiness |
| A．Tiresome task. |
| B．Amazing challenge. |
| C．Meaningless thing. |
| D．Financial trouble. |
| A．A scientific report. |
| B．A transportation guide. |
| C．A policy announcement. |
| D．A new lifestyle introduction. |
【推荐3】It’s important for children to take part in social activities during their summer holidays. “Kids should have a break during the summer. They’ve worked hard during the school year and this is their time to relax, but they should continue communicating with their friends and meeting new people,” said Dr. Jin Han. He’s a professor at Baylor College of Medicine in Houston.
Spending time with friends and meeting new people by doing fun and educational activities such as music, arts and sports programs in summer help with their development. “If children spend a lot of time alone on their electronic equipment, then they will fail to communicate with others,” Han said. “In today’s world, it’s very easy for kids to stay indoors all day and keep in touch with others, but that is not a good way to connect with others. Face-to-face communication is necessary and important. Parents should restrict the time their children spend on electronic equipment. For example, the time they spend on their phones cannot be more than one hour a day.”
It’s also important for children to spend quality time with their parents and sisters or brothers. “It’s not the length of time, but the quality of time that families spend together that is really valuable,” Han said. “This type of communication is not something that you can get from anywhere else. It doesn’t matter how old the child is, because family bonding (人与人之间的关系) experiences can happen at any time.”
Having children spend time with friends and families doesn’t have to spend money in the wallet, either. For example, going to the neighborhood swimming pool or having a picnic is a great way to spend quality time together.
1. What does Dr. Jin Han think about the summer holidays according to the first paragraph?| A．It is necessary for children to have a rest during summer holidays. |
| B．Children should relax as much as possible during summer holidays. |
| C．Making new friends in summer holidays is difficult for children. |
| D．Children should prepare for schoolwork in summer holidays. |
| A．Increase. | B．Control. | C．Spend. | D．Employ. |
| A．How long children spend with families matters. |
| B．What to do with families depends on the parents. |
| C．When to spend time with families makes a difference. |
| D．How to enjoy the time with families is of great importance. |
| A．The importance of friends and families. | B．The introduction of some social activities. |
| C．The suitable ways to spend summer holidays. | D．The necessity of face-to-face communication. |
【推荐1】A new report by a British plant protection group says that almost 30 percent of the world’s tree species (物种) are at risk of dying out. The State of the World’s Trees report shows that 17,500 tree species are at risk of extinction. And 440 species have fewer than 50 trees left in the wild. The report was recently published by Botanic Gardens Conservation International (BGCI).
In a statement, BGCI Secretary General Paul Smith said, “This report is a wake-up call to everyone around the world that trees need help.”
Trees help support the natural environment and are considered important for fighting the world’s warming and climate (气候) change. The extinction of a single tree species could mean losing many others. “Every tree species is important to millions of other species that depend on trees all over the world,” Smith said.
The report shows that thousands of kinds of trees in the world’s top six countries for tree-species diversity (多样性) are at risk of dying out. The greatest single number is in Brazil, where 1,788 species are at risk. The other five countries are Indonesia, Malaysia, China, Colombia and Venezuela.
Now tree species are facing many challenges. The most worrying thing is that climate change and terrible weather are growing dangers. The report adds that at least 180 tree species are in danger because of rising seas and terrible weather. It points out that island tree species are more at risk than other trees because many islands have species of trees that can be found nowhere else. .
1. What does the underlined word “extinction” probably mean in paragraph 1?| A．Growth. | B．Disappearing. | C．Introduction. | D．Planting. |
| A．They really need to be protected badly. |
| B．Many more kinds of them will be found. |
| C．The problem of their dying out isn’t serious. |
| D．They are not very important to human beings. |
| A．Their main functions. | B．Their economic value. |
| C．Their environmental advantages. | D．Their living places. |
| A．Challenging Environment | B．Increasing Temperature |
| C．The Result of Terrible Weather | D．Tree Species at Risk |
【推荐2】As the weather turns colder in some parts of the world, signs of autumn begin to appear. At this time of the year depending on your location, you may also see a familiar flower: chrysanthemums ( 菊花). We often call them “mums,” for short.
In parts of the United States, many people use chrysanthemums as decorations. The flowers sit next to pumpkins for Halloween, October’s famous holiday. But then the mums are thrown away along with rotting jack o’lanterns.
This yearly tradition bothered plant expert Jessica Damiano. In a recent article, she wanted to know why people simply threw away their mums. So, she asked some of her neighbors in Long Island, New York.
Everyone had the same answer: They thought the flowers were annuals — flowers that only last for one season.
Damiano explained that there are annual and perennial (多年生的) mums. Perennials come back for several growing seasons. Garden chrysanthemums, she adds, are actually perennials. Annual chrysanthemums are often sold in stores as potted gift plants. Special plant stores usually sell perennial mums.
If the plants are not labeled at a store, Damiano said to look at the leaves. The large, flat leaves of perennial mums have deep cuts around the edges. The narrow leaves of annuals do not.
Perennial mums are hardy flowers. But they cannot survive freezing temperatures. They also cannot survive extreme summer heat. So, that means about half of the United States is good for growing mums.
Perennial chrysanthemums come from China. Kaifeng, a city in China’s Henan province, is famous for its mums. Each year, the city holds a popular festival to celebrate the flowers. Chrysanthemum festivals are also held in other countries — like Pakistan, Germany, South Korea, Japan, and the United States, to name a few.
Chrysanthemums come in shades of orange, red, rust, pink, purple, yellow, cream, and white. Some can grow to nearly one meter in height. They reach their mature size in about three years. In warmer climates, they bloom again in spring.
1. Why did people throw away their chrysanthemums?| A．They don’t like the mums. |
| B．They don’t think the mums can flower again. |
| C．They mistake the mums as lanterns. |
| D．They throw away the mums by accident. |
| A．By observing the leaves. | B．By looking at the pot. |
| C．By asking others. | D．By referring to books. |
| A．Freezing. | B．Extremely hot. | C．Warm. | D．Wet. |
| A．Pakistan. | B．Germany. | C．Japan. | D．China. |
【推荐3】A new report by a British-based plant protection group says almost 30 percent of the world’s tree species are at risk of extinction. The State of the World’s Tree report warns that 17,500 tree species are at risk of dying out. And 440 species have fewer than 50 individual trees left in the wild. The report was recently published by Botanic Gardens Conservation International (BGCI).
The report says the number of threatened tree species is double the number of threatened mammals, birds, amphibians and reptiles combined. In a statement, BGCI Secretary General Paul Smith said, “This report is a wake-up call to everyone around the world that trees need help.”
Among the most at-risk trees are species including magnolias and dipterocarps. These trees are commonly found in Southeast Asian rainforests. The report says oak and maple trees also face threats.
Trees help support the natural environment and are considered important for fighting global warming and climate change. The extinction of a single tree species could mean the loss of many others. “Every tree species matters, to the millions of other species that depend on trees all over the world,” Smith said.
The report shows that thousands of kinds of trees in the world’s top six countries for tree-species diversity are at risk of extinction. The greatest single number is in Brazil, where 1,788 species are at risk. The other five countries are Indonesia, Malaysia, China, Colombia and Venezuela.
The top three threats facing tree species are crop production, logging and farming. Most worryingly, climate change and extreme weather are also growing threats. The report adds at least 180 tree species are directly threatened by rising seas and severe weather. It notes that island tree species are more at risk than other trees because many islands have species of trees that can be found nowhere else.
1. What can we know about the world’s tree species?| A．They are in urgent need of protection. |
| B．There are 50 types of them unknown. |
| C．Most of them are in danger of dying out. |
| D．The number of them is higher than wild animals. |
| A．To attract readers to explore there. |
| B．To emphasize their special location. |
| C．To present wild animals’ important habitats. |
| D．To show the most threatened tree species there. |
| A．Their environmental benefits. | B．Their economic value. |
| C．Their characteristics. | D．Their evolution. |
| A．Confused. | B．Concerned. |
| C．Grateful. | D．Humorous. |
