We talk every day. When we have good news, we like to share it with our good friends and when something terrible happens, we will make it known to others soon. But can you imagine that a tree can talk and share news , too? Of course, no tree moveslipsand says words just as people do. However, some trees do manage to communicate with each other.

Willow (柳树) trees are the best-known of these trees. When insects (昆虫) begin nibbling (叮咬) a willow tree, the tree sends out a special smell at once. This smell tells the other willows that harmful insects are coming near. All of them quickly make a chemical (化学物质) in their leaves. This chemical is bad to the insects. The insects do not like it and they fly away soon. In this way, the willow trees protect themselves from the insects.

The next time when you take a walk in the woods, maybe the trees are “talking” to each other quietly. And when someone says that trees cannot “talk”, please tell them that even trees give messages to each other, too.

A crow(乌鸦) is about twenty inches(英寸) long and black all over. Crows are dirty birds because they live on bad food. Crows eat a lot of waste food. In this way they are more useful to us than any birds. They clean up the dirty things in our streets. Crows are always hungry. They look for food all day, and in the evening you can see them in large numbers flying back to their nests(巢) in the trees. They sleep there at night.

Crows are much noisier than other birds. Very often a large number of crows will get together on one house and talk. Sometimes they talk together, and sometimes they do it by turns(轮流) like human beings(人类). It is easy to tell(判断) from crow’s sound if they are pleased or angry. Perhaps crows talk a lot because they are friendly birds. A pair of crows will live together all their lives, and if one of them dies, the other one becomes very sad and quiet for the rest of its life and some time later it dies too.

Do you want to know how and why a fall leaf changes color? We first have to understand what leaves are and what they do.

Leaves are the world’s food factories. Plants take water from the ground through their roots and take CO2 from the air. Plants use sunlight to turn water and CO₂ into glucose(葡萄糖), a kind of sugar. Plants use it as food for energy and growing.

   A chemical called “chlorophyll” in the leaves gives plants their green colour. As summer ends and autumn comes, the days get shorter and shorter, and trees “know” to begin getting ready for winter.

   During winter, there is not enough sunlight or water. Trees rest during this time and live on the food they store during the summer. They begin to shut down their food-making factories. As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves.

   The bright reds and purples we see in leaves are made mostly in autumn. In some trees, like maples(枫树), sunlight and the cool nights of autumn turn the glucose in the leaves into a red colour. And we can enjoy the beautiful red leaves during autumn.

Why do we like drinking water from plastic bottles? Some people think it is healthy and clean. Others drink bottled water because it’s easy— you can carry it around with you. In hot countries, like Greece, we often buy bottles of cold water in the summer.

However, making lots of plastic is not a good idea for many reasons. First of all, we need a lot of oil for plastic products. We usually use oil as a source(资源) of energy. If we reduced the number of bottles we made, we wouldn’t need so much oil. Plastic bottles also pollute the environment. If we recycled all our plastic bottles, we wouldn’t need so much space for rubbish dumps. But in Greece, we don’t recycle much of the plastic we use. In 2006, Greeks recycled only about 10% of plastic waste. The rest became rubbish on land and in rivers and sees.So next time you want to throw away a plastic bottle in the litter bin, stop and think. If you recycled it, you would help the environment. But what can you do when there isn’t a recycling bin near you? Well, there are lots of useful ways that you can use your bottles again. For example, an empty bottle makes a great piggy bank for your pocket money, and if you cut a bottle in half, you will have a plant pot.Go green! You can make a difference.

Animals do many different, amazing things to get through the winter. Some of them migrate. They travel to other places where the weather is warmer or where they can find food.

Many birds migrate in autumn. Because the trip can be dangerous, some travel in large groups. For example, geese(鹅) fly in noisy, “V”-shaped groups. Other kinds of birds fly alone.

Some animals stay active in winter. They must change themselves as the weather changes. Many change their doing or their bodies. For example, snowshoe rabbits grow white fur to help them hide in the snow.

Food is hard to find in winter. Some animals, like mice, collect lots of food in autumn and store it to eat later. Some animals eat different kinds of food as the seasons change.

Some animals hibernate for part or all of the winter. This is a special, very deep sleep. The animal’s body temperature drops, and its heartbeat and breathing slow down. It uses very little energy. In autumn, these animals get ready for winter by eating much more food than in summer and storing it as body fat. They use this fat to keep them alive while hibernating.

Water makes good protection for many animals. When the weather gets cold, they move to the bottom of lakes and rivers. There, frogs and many fish hide under rocks or fallen leaves. Cold water holds more oxygen than warm water, and frogs can breathe through their skin.

Every type of insect has its own life cycle and that is the way it grows and changes. Different insects spend the winter in different forms of their lives. Some insects also spend the winter without moving. Some insects spend the winter as pupae（蛹）. Other insects die after laying eggs in autumn. The eggs change into new insects in spring and everything begins all over again.

Mars is the fourth planet from the sun. It is 141 million miles away

from the sun. It has two moons. A year on Mars is 687 Earth-days long.

Mars is about half the size of Earth. If you weighed 100 pounds on

Earth, you’d weigh about 38 pounds on Mars.

   Mars’ surface looks like a red desert. There are mountains, canyons (峡谷), and craters (火山坑). There are no rivers or oceans. It is a dry planet without any liquid water. It was named by the ancient Romans for their God of War. It is very cold on Mars. Mars is much colder than our planet. The temperature on Mars is 80 degrees below zero! That is a lot colder than the North Pole!

Scientists suggest that Mars once had rivers, streams, lakes, and maybe even an ocean. Mars has mountains that are much higher than those on Earth. Mars also has bigger, deeper canyons than Earth’s. Some of these are sixty miles long and five or six miles deep. No people could live there. But it’s fun to learn about this red planet. Don’t you think so?

As space science develops, man has learned more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

  Scientists have found out that radiation(辐射) is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of the radiation from the sun and other stars, which is bad for their health. The harm of the radiation wonˈt be found until their children even grandchildren are born. Some special medicine may work a little, but no really useful medicine has been found so far.

  Space rubbish is also thought to be a great danger to spacemen. Itˈs reported that there were 9,000 man-made things flying in space. About 30% of these are satellites(卫星) (IBM), 10% are spaceships, and the rest are space rubbish. An explosion (爆炸) in space in 1999 made a cloud of 300,000 fragments (碎片), each at least 4mm in size. A small piece of these even knocked a spaceship window and caused somedamage.

  Although space is really dangerous, it interests many people on the Earth. In the near future, it may become possible for people to spend a few days in a space hotel. So we should do something to help improve the space environment.

2015—Earth Day’s 45^th anniversary(周年纪念)—may be the most exciting year in environmental history. This year, we start to face and try to work out many environment problems.

  For many people, climate(气候) change is a problem that seems far away. But the truth is that it causes many environment problems. We have to do something right now because the environment problems have an influence on the future of our planet and people’s lives on Earth.

  On Earth Day, 22 April, we need you to take part in the activity. We can show the world a new direction(方向). It’s our turn to take action!

Energy is everywhere and we use it every day.

Electricity is a form of energy and this is what powers the TV, mobile phone, fridge and more. Our growing need for energy is one of the problems facing the world today, because producing electricity also produces pollution. Here are some simple ways to make a big difference when using electricity.

On or off? Leaving televisions and computers on with the little red light showing still uses electricity, even though they might look like they’re turned off. To stop this you can turn them off.

Lights out. Turning lights off when you’re not in the room can save a lot of energy.

Fridge door closed. The fridge is an important part of the kitchen, because it keeps food fresh, cool and healthy. But it takes a lot of energy to keep cool, so try not to leave the fridge door open or put hot things inside.

Use the sun’s energy. An increasing number of people are fitting solar panels(镶板) to their houses. They create electricity from sunlight, which can then be used to power our homes. Solar heating panels make water hot, reducing the need for electricity or gas.

  Laughter is good for your health. When you laugh, several changes happen to your body. Your heart beats more slowly, and your blood pressure(血压) goes down. You breathe more deeply, and so more oxygen(氧气) is carried round your body. Chemical changes happen too. Happy-feeling chemicals go to your head and make you feel that all is good in the world. The next time you laugh, notice that you are feeling relaxed afterwards.

  Doctors have studied the results of laughing with very sick(生病的) patients. First, if a patient(病人) has a lot of pain(病痛), it is a good idea to watch funny films. One person with cancer(癌症) described his stay in hospital. "After I laughed hard for ten minutes, the pain would go and I would have about two hours of pain-free sleep." Laughing can help you get better, especially if you have a very bad illness. Again, chemical changes happen in the body. As a result, the body fights the disease and may help the patient get better.

  Laughing is good for the mind of healthy people, too. Laughing helps people relax. If there is a problem and you are able to laugh about it, you may feel more relaxed.

  Meet friends and laugh together! When they laugh very strongly, this exercises the whole body. This is part of the Indian study of human health. So, next time, explain to your friends why you are laughing. "Itˈs keeping me healthy. Laughing is the best medicine, and there are no side-effects. ”