There is little rain in desert. Because deserts are so dry, they have no "quilt" to help stop the soil from going away. As a result, they may get very hot during the day with the sun shining, but don't hold the heat overnight. Many deserts can quickly get cold once the sun goes down. Some deserts can reach temperatures of over 100 degrees F during the day and then drop below freezing (32 degrees F) during the night.

The largest hot and dry desert in the world is the Sahara Desert in Northern Africa. The Sahara is a sandy desert with great sand hills. It covers over 3 million square miles of Africa. Other large deserts include the Arabian Desert in the Middle East, the Gobi Desert in Northern China and Mongolia, and Kalahari Desert in Africa.

Animals that live in the desert are also used to needing little water. Many get all the water they need from the food they eat. Other animals keep water that they can use later. The camel stores up fat in its hump while other animals keep something they need in their tails.

Only certain types of plants can live in the terrible environment of the desert. You won't see a lot of tall trees in the desert. Most plants have a way to keep water in their leaves, or trunks so they can live a long time without water.

Now deserts cover around 20% of the world's land, but they are growing. This is called desertification and is caused by different reasons including human activities. The Sahara Desert is growing larger and larger each year. What should we do with it ?

The Internet, mobile phones and Ipads are part of our lives now. Technology is greatly affecting all ways of our lives, from the ways we work to the ways we play. And it even causes a number of social problems such as cloning humans.

    We have had lots of technology and it has changed our lives a lot. There is no doubt that humans will continue to use more and more technology. Here are some examples of modern technology that will change our ideas and will affect our lives greatly.

    Global positioning system(GPS)(全球定位系统)

    It's a system that uses radio signals from satellites to show exact(精确的) information. It tells you where the user is on the earth in all weather conditions. It's made up of three parts: satellites, control equipments(设备) on land and receivers.

    Space Technology

Russian and American scientists have worked together for the international Space Station(ISS) for a long time. They hope the ISS will provide a long-lasting lab. Such a lab will bring humans limitless(无限的) advantages. It's even hoped that one day spare technology will take humans to their new houses in space.

    Underwater Robot

Hercules is a kind of underwater robot with some high technology equipments. It will be used to search for ancient ships which were destroyed into the deep sea during their journey long ago.

The world is changing so quickly that it's hard for us to catch up with all the new inventions because they seem to come out every month. It's important for us to learn about new technology and the role that it plays in our lives. So we should be willing to accept modern technology, or we will fall behind the times.

    Do you know why different animals or pests have their special colors? Colors in them seem to be mainly used to protect themselves.

Some birds like eating locusts (蝗虫), but birds cannot easily catch them. Why? It is because locusts change their colors with the change of the colors of crops. When crops are green, locusts look green. But as the harvest time comes, locusts change into the same brown color as crops have. Some other pests whose colors are different form plants are easily found and eaten by others. So they have to hide themselves for lives and appear only at night.

    If you study the animals' life, you'll find the main use of colors is to protect themselves. Bears, lions and other animals move quietly through forests. They cannot be easily seen by hunters because their colors are much like the trees.

    Colors are useful not only on the land, but also in the sea. A kind of fish in the sea can give out a kind of black liquid (液体) when the fish face danger. The liquid spreads over quickly, so they cannot be found by their enemies and can quickly swim away. That is why they live safely though they are not strong at all.

    These days haze(雾霾) is around us here and there. In fact, everyone has the power to change their living habits to help reduce it. Many local governments call on their people to take action to make the air cleaner.

    Transport is one of the biggest contributors(促成物) to haze. When, where, bow, why and what you drive all affect air quality. When one drives to work for one year, he uses as much energy as a bus rider uses in 10 years. So walk or ride your bicycle to work or school whenever possible. If it is necessary, you can use public transport instead of your car. Each person using public transport for a year instead of a car can save nearly a tonne of pollutants, including CO₂, from going into the atmosphere.

    Carpooling is another way to reduce carbon emissions (排放). Carpooling is the sharing of car journeys so that more than one person travels in a car. It immediately reduces your car's emissions by half.

    What you do inside your living space can have a big effect on the air quality outside it. You can do a lot of things inside and around your home that will help you pollute less and save some money.

    A large amount of our energy supply comes from burning coal, another contributor to haze. By cutting down your electricity use, you are cutting down on haze. So you may try to reduce your use of electricity by turning off lights, using your air conditioner wisely during the summer months, or updating some of your electrical appliances to low-energy models. For example, you can use energy-saving lamps that require less energy and last 10 times longer than common bulbs.

    The Legendary Berlnuda Triangle (百慕大三角): A Mystery No More

    For years, people have believed that an area of the Atlantic Ocean between Bermuda, Puerto Rico and Florida, USA was a dangerous place. They thought planes and boats passing through here were likely to disappear. By 1964, a writer had called the area the "'Bermuda Triangle". The name stuck, and so did the mystery.

    In 1945, five US Navy planes, called Flight 19 took off from Florida and never came back. After they disappeared into the Bermuda Triangle, different ideas had begun to spread that the area was a dangerous place. Even before this famous flight, several ships had disappeared in these waters. People had many different ideas about why this appended. Some people even believed that a huge octopus (章鱼) was responsible!

    However, scientists believe that weather is part of the problem. Unusually shaped clouds above the area create strong winds that go down into the water, creating huge tsunami (海啸) waves that can take down boats or low-flying planes. And many researchers believe that there's no mystery, at all Ship goes down and plane accidents happen all over the world. It just seems to happen more in the Bermuda Triangle because there's more traffic.

    The Bermuda Triangle is also one of the deepest areas of the Atlantic, with some areas being 8 km (5 mi.) deep. So, remains are hard to find which makes the disappearances seem even more mysterious. In 2011, the Flight 19 planes were found, showing that they didn't completely disappear. But no matter how much evidence（证据） there is that the Bermuda Triangle is no more dangerous than any other part of the ocean, many still believe that you mustn't go there.

    Do you often run outdoors to keep healthy? Have you ever thought about how running helps to clean up the earth? Sometimes a creative mind can bring us a win-win(双赢)situation.

    Plogging, a new way to exercise, began in Sweden(瑞典).The name "plogging" comes from two words the Swedish(瑞典的)word "plocka", which means" to pick up(捡起)", and the word" jogging", which means "to run slowly". A Swedish man called Erik started the movement. He saw rubbish here and there when riding to work each day. He became worried about the dirty environment and decided not to go to work by bike any more. Instead, he began to run to work and pick up the rubbish at the same time. To his joy, more and more people followed him and soon plogging became popular.

    Many people choose plogging instead of just jogging because they think plogging is a good way to help clean up the earth. Sometimes rubbish is difficult to collect because it may scatter all around. But if the runners pick up the rubbish on the way, it is quite different. After all, many hands make light work. Another reason is that plogging burns more calories(卡路里).According to a research, plogging for 10 minutes burns 48 calories, while usual jogging for 10 minutes burns about 39 calories.

    Everyone on the earth should play a part in cleaning it up! It's time for us to take action together. So ready? Let's plog tomorrow!