1 . City trees grow faster and die younger than trees in rural forests, a new study finds.

Studies had shown forests take in greenhouse gas. But there hadn’t been much data on whether city trees grow, die and take in CO₂ at the same rate as forest trees do. So Lucy Hytyra and her workmates at Boston University in Massachusetts decided to find out.

To figure out how quickly trees were growing, the researchers tracked their diameters (直径) between 2005 and 2014. The team focused on red oaks and red maples growing on Boston streets. These trees grew four times faster than the same species did in a nearby forests. Faster-growing trees take in more CO₂. Over the nine years, the researchers tracked these trees, and they found city ones took in four times as much CO₂ from the air as the forest trees did. The city trees also, however, were twice as likely to die. So over the lifetime of each type of tree, forest trees actually take in more CO₂.

“City trees grow faster mainly because they have less competition for light from their neighbors,” Hutyra says. In a forests, trees tend to grow close together, shading their neighbors. Street trees also benefit from higher levels of nitrogen (氮) in rainwater. Nitrogen is an element that helps plants grow. Still, she says that her team’s findings may not apply to arid cities. “In locations short of water like Phoenix or Los Angeles, city trees might respond differently because it’s very hot in the city and they have so little water.” At such sites, she says, “Trees might grow slower.”

So why were Boston’s streets trees twice as likely as their country cousins to die young? City roads can leave big-tree roots less room to grow. Plus, people often decide to cut down trees that are sick, or in the way of some desired building or view.

2 . It’s a popular belief that a fish's memory lasts for only seven seconds. It may seem sad to think that they don’t remember what they’ve eaten or where they’ve been, and they don't identify you or any of their friends- every moment in their life would be like seeing the world for the first time.

But don’t be so quick to feel sorry for them. A new study has found that fish have a much better memory than we used to think. In fact, certain species of fish can even remember events from as long as 12 days ago. In the study, researchers from Mac Ewan University in Canada trained a kind of fish called African cichlids to go to a certain area of their tank to get food. They then waited for 12 days before putting them back in the tank again. Researchers used computer software to monitor the fish’s movements. They found that after such a long break the fish still went to the same place where they first got food. This suggested that they could remember their past experiences.

In fact, scientists had been thinking for a long time that African cichlids might have a good memory. An earlier study showed that they behaved aggressively (挑衅地) in front of certain fish, perhaps because they remembered their past “fights”. But until the latest findings, there was no clear evidence.

Just as a good memory can make our lives easier, it also plays an important part when a fish is trying to survive in the wild. “If fish are able to remember that a certain area contains safe food, they will be able to go back to that area without putting their lives at risks,” lead researcher Trevor Hamiton told Live Science.

For a long time, fish were placed far below chimpanzees, dolphins and mice on the list of smart animals. But this study has given scientists a new understanding of their intelligence.

4 . Most animals have little connection with animals of a different kind, unless they hunt them for food. Sometimes, however, two kinds of animals come together in a partnership which does good to both of them. You may have noticed some birds sitting on the backs of sheep. This is not because they want a ride, but because they find easy food in the parasites (寄生虫) on sheep. The sheep allow the birds to do so because they remove the cause of discomfort. So although they can manage without each other, they do better together.

Sometimes an animal has a plant partner. The relationship develops until the two partners cannot manage without each other. This is so in the corals of the sea. In their skins they have tiny plants which act as "dustmen", taking some of the waste products from the coral and giving in return oxygen (氧气) which the animal needs to breathe.

If the plants are killed, or are even prevented from light so that they cannot live normally, the corals will die.

5 . The World Health Organization warns that millions of people are dying every year from indoor air pollution. The WHO finds that poor cooking, heating and lighting technologies are killing millions of people each year. Indoor air pollution results from the use of dangerous fuels and cook-stoves in the home. To help fight the problem, the WHO announced, new guidelines aimed at reducing household pollutants.

WHO officials say nearly three billion people are unable to use clean fuels and technologies for cooking, heating and lighting. And they say more than seven million people die from exposure to indoor or outdoor air pollution each year. Of that number, the WHO says about 4. 3 million people die from household air pollution given off by simple coal cook-stoves. WHO officials say indoor pollution leads to early deaths from stroke(中风), heart and lung disease. The main victims are women and girls in developing countries, where they usually stay at home and do the household work.

Carlos Dora is Coordinator in the WHO’s Department of Public Health, Environmental and Social Determinants of Health. He says people should not use unprocessed coal and kerosene (煤油) fuel indoors. He says opening a window or door to let out the harmful air will not improve the situation. It will only pollute the outdoors.

Nigel Bruce is a professor of Public Health at the University of Liverpool. He says researchers are developing good cook-stoves and other equipment to burn fuels in a more efficient way.

WHO experts note some new, safe and low-cost technologies that could help are already available. In India, you can buy an induction (电磁) stove for about $ 8.00. And in Africa you can buy a solar lamp for less than $ 1. 00. But, this, the agency says, is just a start. It is urging developing countries to use cleaner fuels and increase access to cleaner and more modern cooking and heating items.

Last weekend, my classmates and me paid a visit to a fruit-picking garden, where is not far from our school.

Early in the morning, we set off from the school and arrived the garden after a thirty-minute ride. The garden looked very beautiful but we saw varieties of fruits. All of us got exciting and hurried into the fields. We pick oranges, peaches and other fruits for several hours until we were worn out. It’s really good for us to get close to the nature. Most important, we acquired some knowledges about fruits at the same time.

How a meaningful experience we had!

9 . The climate we live in affects many areas of our lives.     1    A warmer world would be a sicker world.

Climate researchers predict that the world climate will become warmer. High temperatures in summer is becoming more frequent and very cold winters more rare. With winters becoming warmer, there are likely to be up to 20, 000 fewer cold-related deaths. However, there is a danger that bacteria would no longer die off seasonally during the cold period.     2    

More heat waves may increase the number of hot-weather related deaths by up to 2, 800. They could cause an extra 5,000 deaths a year from skin cancer and may cause an increase of up to 2,000 cases of eye diseases.     3    

Higher average global temperatures mean that diseases, or their carriers, may be able to move to areas that were too cold for them to survive at an earlier time. It's possible that a warm type of malaria (疟疾) will appear in some parts of the world and be a seasonal danger for up to four months each year.     4     They will cause damage to our homes, food, and water supplies and then affect our health.

    5    Those living in poor and developing countries are going to be less able to adapt to changes. Health effects are not likely to be limited to the human population, and wildlife would also be seriously affected.

Hurricane Katrina has been one of the strongest storms that affect the coast of the United States during the last 100 years. Once a hurricane starts it can     1     (move) around by powerful winds. They vary from class 1 to class 5. Hurricane Katrina has been the     2     (bad) storm in the past decade in the US, having reached class 5,    3     has caused lots of damage.

Some scientists claimed that global warming was     4     (blame) for the power of Hurricane Katrina due to the fact that it is warming the oceans. Hurricane Katrina had a strong effect on the US coast. The area     5     (affect) is almost the size of the UK. New Orleans suffered     6     (severe) from damage after the hurricane. Most of the city was     7     water from flooding, including expressways and bridges. Almost 2 million people lost their power and had to wait several weeks for it to be restored. It was     8     disaster for the city. Help came from all over the United States. Many people went down to New Orleans to volunteer. Others started charity events to fund the     9     (reconstruct) of the city. It was because of all people’s efforts     10     the city began to breathe again.