The population of the Earth is growing faster. It is important that we look after the Earth. We need it! The Earth gives us a lot of things. We also give the Earth a lot, but some of the things are not good.

   In nature, when something dies, other animals and plants get food from it. Every animal or plant gives food for other animals or plants. However, animals can't get food from many of the things that we "give" the Earth. Animals and plants can't eat metal, plastic and glass. These things will stay in the ground for many, many years.

   Some rubbish is very dangerous for plants and animals. In some places, many animals live together. One animal makes food for many more animals. If we put rubbish and chemicals in the water, the plankton(浮游生物) can die. If there isn't any plankton, many animals have nothing to eat.
   So what can we do? Don't leave any rubbish in the countryside! Don't make so much rubbish!

    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.

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    Jupiter(土星) is the fifth planet from the sun and it is the largest one in the solar system. It is about 11 times bigger than the earth. Jupiter's strangest thing is its huge red spot. Pictures taken from space tell us that the red spot is probably a hurricane(飓风). It is so big that the earth would fit right in the middle of it. Sometimes the hurricane looks like a huge oven with orange-red waves (波浪). Some other time the color almost disappears.

    On the earth, hurricanes move. We can watch them travel across water to land. Jupiter's red spot also moves. Scientists say it “walks”. It is carried along by air in Jupiter's atmosphere(大气层).

    So far, Jupiter has been visited by four spacecrafts. All of them flew by Jupiter very quickly. On the next trip to Jupiter, a spacecraft will stay near the planet much longer. New information will be sent back to the earth. Soon scientists will know much more about this strange red spot in the atmosphere.

    Sometimes people cry when they are sad. Other times people cry tears of joy. But your eyes make tears all the time, whether you are crying or not. Do you know the tears help keep your eyes healthy? They keep your eyes from drying out. A special area of the eye drips (滴) all the time. It keeps the eye humid.

    If you look in a mirror, you can see tiny holes in the comers of your eyes. Each hole leads to a small tube that runs to your nose. Tears run slowly into this tube drip by drip. Day and night the holes drain (流走) the tears away. If they didn't, you would always look as if you were crying.

    If you begin to cry, there are many more tears. The holes can't drain all of them. Then extra tears run out onto your face.    

    Tears help keep eyes safe. If there is something harmful in the air, the eyes fill with tears. These tears coat your eyes. They keep the harmful air out.

    Contact lenses(隐形眼镜) can make the eyes too dry. Some people have to add tears to their eyes. They buy bottles of eye drops to keep their eyes wet.

    As everyone knows, animals are our friends. Of all the animals, dogs are friendly to 1.

    Dogs are always staying 2 human beings. They are in different colours. There are many different 3 of dogs. Hunting dogs can 4people get more prey(猎物). The seeing-eye dogs can help 5people a lot. The police dogs can help the police.

    Today it is 6 to imagine the life without dogs. Maybe everyone is happy to see dog. Dogs are good at7 and smelling. Some dogs can find the people who are trapped(困) 8 the broken house. Some dogs can help take care of the houses. 9someone strange comes close to the house, they will bark to frighten him. Even some dogs can help look after kids when their 10 are not at home.

    In a word, dogs are our best friends among all animals.