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

    Some birds like eating locusts (蝗虫), but birds cannot easily catch them. Why? It is because locusts change their colors together with the change of the colors of crops(庄稼). When crops are green, locusts look green. But as the harvest time comes, locusts change to the same brown color as crops have. Some other pests with different colors from 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 animal life, you'll find the main use of coloring is to protect themselves. Bears, lions and other animals move quietly through forests. They cannot be easily seen by hunters (猎人). This is because they have the colors much like the trees.

    Have you ever noticed an even stranger act? A kind of fish in the sea can send out a kind of very black liquid (液体)when it faces danger. While the liquid spreads over (散开), its enemies (敌人)cannot find it. And it immediately swims away. So it has lived up to now though it is 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.

    Bioplastic(生物塑料) is a kind of plastic, but it is not the same as normal plastic. Normal plastic is made from chemical materials and takes a very long time to degrade(降解). But bioplastic is good for the environment. It is made by using bacteria(细菌) to process(加工) natural sources like vegetable oils, corn or sugar. It can degrade more easily.

    But there is a problem with bioplastic. The "food" that bacteria eat is what we eat. This means that bacteria are competing against humans for the same resources.

    Now scientists have found a new way to make bioplastic——using two kinds of bacteria and sunlight, according to Newsweek.

    One of the bacteria can use sunlight to produce sugar. The other kind lives in the salty waters of Bolivia. It eats the sugar that the first bacteria produce and then it can produce polymers(聚合物). Polymers are used to create bioplastics. The way the bacteria store polymers is similar as humans store fats.

    The new way to produce bioplastic has many advantages. It is 20 times faster than the normal way we produce bioplastic. Moreover, using these two bacteria saves resources.

    Firstly, producing a lot of bioplastic requires corn and sugar, which are used to feed normal bacteria. And growing corn and sugar needs farmland. But these two bacteria can just use sunlight. The land that is saved can be used to grow food for humans. Besides, this system doesn't need rich land or clean water at all, scientists said to Newsweek.

    The next problem scientists face is that they want to put their lab research into real-world practice. By doing this, bioplastic made with these two bacteria can be widely produced in the future.

    In many places the weather changes during the year. These changes are called seasons. In the north and south there are four seasons in a year. At the North and South Pole, there are only two seasons. In tropical (热带) places near the Earth's equator (赤道), there are two seasons: a 'wet' season and a 'dry' season. Each season brings changes. They are important for plants and animals that live in different parts of the world.

    Spring starts when the day and night are the same length. The weather gets warmer and sunnier. Trees and plants start to grow. Many animals have their babies in spring.

    Summer begins on the longest day of the year. In the north this is on June 21 or 22. Summer is usually the warmest and sunniest time of the year. Fruit grows faster on trees and plants. Young animals grow bigger and stronger.

    Autumn starts when the day and night are the same length again.

During autumn, the leaves change color and fall down from the trees. Some animals collect food before winter comes.

    Winter begins on the shortest day of the year. In the north this is on December 21 or 22. The weather is colder and in some places there is lots of snow. Plants and trees stop growing. Some animals, like bats and bears, find places to hide and sleep. This is called hibernation.