In nature, you may see many insects(昆虫) and animals of different colors. Have you ever wondered why?

    Locusts are super delicious food for birds, but it is not always an easy job for birds to catch them. It is neither because locusts are good jumpers or runners nor because they are smarter than their enemies. The reason is that the colors, of locusts change with the colors of crops(庄稼). When crops are young, locusts look green. But when autumn comes, locusts change to the yellow and brown color as crops do.

    Brown bears, tigers and other animals move quietly through forests. They can't be seen easily by their enemies. This is because they have colors similar to the trees. For the same reason, polar bears that live on a land of snow and ice are white. Butterflies and bees living among the flowers are colorful like flowers. Soil insects are mostly dark colored and they live under the soil(土壤)in a dark and wet environment. However, insects with colors different from plants can easily be found and eaten by others. So in order to survive, they have to hide themselves in the daytime and appear only at night.

    Have you ever noticed some even stranger acts? The ink fish in the sea can send out some very black ink when it faces danger. As the ink spreads over, its enemies will find themselves suddenly in a dark world. At the same time the ink fish immediately swims away. That is how it keeps itself safe though it is not strong at all.

    Do you notice music playing there when you go somewhere? Today most stores, stations restaurants and other places play music. You might even hear music in an office or on a farm.

Scientists believe that music changes the way people behave. They think that Western classical music makes people feel rich. When a restaurant plays classical music, people spend more money on food and drinks. When the restaurant plays modern music, people spend less money. Without music, people spend even less.

Scientists also believe that loud, fast music makes people eat faster. In fact, people eat their food faster when the music gets faster. Some restaurants play fast music during their busy hours. This gets people to eat faster and leave more quickly. Restaurants can make more money this way.

Some scientists think that music makes people think and learn better. They say that music helps students be more active. It is true that people learn better when they are relaxed. And listening to music can help people relax.

    Next time you hear music somewhere, be careful. It might change the way you do things.

    Trees are one of the oldest " citizens (公民) " of our Earth. They keep our air clean, reduce noise pollution, improve water quality and provide food and building materials.

    Just like us, trees change a lot as they grow. At 1 to 3 years old, young trees learn how to protect themselves. For example, many trees grow thorns( 刺) to warn animals not to go near. Most young trees have large, deep green leaves so that they can catch enough sunlight and change it into their food and energy.

    When trees are 4 years old, they begin to grow very rapidly and become strong enough to face challenges later in life. At the age of 15, trees become young adults. They grow more slowly and begin to produce flowers and fruit.

    It is not until the tree is 20 to 25 years old that it becomes a real adult. The tree reaches its largest size. The adult tree gives us shade, oxygen and natural beauty; it is also a great place for a tree house, or a place for us to read a book, listen to music and so on. If we give the adult tree proper care, it will go on to live healthily for many years.

    Gradually, trees begin to grow older and older and even die. At this time, they still have their important place in nature. When a tree becomes hollow (空心的) or part of it becomes dead, it provides a home to small animals and is a source of food for many other animals.

    In many ways, the life of a tree is similar to our own life experience. When we are looking at the life of a tree, we learn about that each period of life brings its own form of joy and challenge.

    Enjoy every minute of the life of the trees and take care of the trees!

    The coffee shop Starbucks will give people a discount if they bring their own cups. It wants to cut down on the number of paper cups that are put in the rubbish bins. It is part of a two month experiment in cafes in England. Starbucks wants to reduce waste and recycle more, The president of Starbucks in the UK said, "We are very happy to increase recycling rates(比率)，and reusable cups are a key part of our waste reduction plan." Bosses will decide later if they will continue the discounts. People who bring their own cups will not get a discount on the cafe's cheaper filter coffee.

    The problem of paper cups has been in the news a lot. Around seven million cups are thrown away every day. Reporters say that some cafes lie about how many paper cups they recycle. The reporters say the cafes do not recycle as many cups as they say. Customers wrongly believe that a coffee shop is environmentally friendly. Less than one in 400 paper cups at coffee shops are recycled. A coffee drinker said she would bring her own cup. She said, "I am so sad that cafes recycle so little. I thought they were more responsible."

    We always think that it's OK for us to leave our plants home during our vacation as plants won't scream like pets, right?

    A recent study done by a group of scientists at the Tel Aviv University has discovered that some plants will scream when they are under stress.

    The research was carried out on tomato plants and tobacco plants by cutting their stems (茎) and depriving (剥夺) them of water. A microphone was placed 10cm away from them. When their stems were cut, the plants started "screaming" between 20 and 100 kilohertz, and the scientists guess that this scream is probably meant to warn other plants nearby.

    When the tomato plants' stems were cut, 25 ultrasonic (超声的) pain sounds were recorded in an hour, and at the same time, 15 ultrasonic pain sounds were recorded from the tobacco plants. When they were deprived of water, the tomato plants recorded even more pain sounds with 35 pain sounds in an hour while the tobacco plants recorded about 11 pain sounds.

    The plants also acted differently to different kinds of stresses. For example, the tobacco plants gave out a stronger "scream" when they were deprived of water than when their stems were cut. But plants that were in no immediate (立刻的) danger gave out less than one ultrasonic sound per hour.

    The group of scientists said that plants are not as quiet as we had always thought, but in fact their voices are so high-pitched that we just can't hear them.

    Last year, another study has found out that plants feel pain when they are touched or hurt and they will give off a terrible smell.