Rik-rrork. That's the sound made by frogs singing at night. You might have thought the noises were just the musical sounds of ure. You probably didn't realize that you were listening to frogs' communicating with one another. These familiar sounds are not random(随意的) but are actually meaningful to frogs.

Being Heard but Not Seen

    Frogs are good at being heard but not seen. These animals have several characters that protect them n predators (捕食者 ). One is their size. Most frogs are small, which helps them hide easily. Many frogs have coloring that allows them to hide in their environment, making it difficult for predators to find them. In addition, most frogs are active at night. So it is difficult for most animals to see them in the dark.

Small but Loud

    Frogs call to tell other frogs where they are. Their voices can be very loud. But when frogs feel the footsteps of a larger animal, they become silent.

    Many of the world's frogs live in rain forests, where there are many different animals calling to their own species (物种 ) in their own ways. Frogs need to call loudly enough to be heard through the noise in order to find other frogs.

Singing with Purpose

      Peter Narins is a scientist who studies how frogs call to one another. He has learned that frogs use their calls to help them tell friend from enemy. They sing the same notes at the same volume (音量 ) each time they call. In addition, Narins has found that frogs of the same species always sing the same patterns (模式 ). These patterns are like a code that is different from other animals' calls and difficult for others to copy. Narins also observed that timing plays a role in frog calls. Many frogs call only at a certain time of night.

More Work to Do

    Scientists want to better understand the purpose of frog calls. Studies continue to explore the details of frogs' unique communication. Being heard but not seen is one way frogs stay safe. The idea that they have found a way to survive in a dangerous world is simply amazing.

    Technology is everywhere. We see it any place we go and, in fact, almost all of us carry some piece of technology with us every time we leave the house. What I always forget, though, is just how useful and powerful technology can be when we want to help others.

    There is not a single room in my house that does not have some electronic devices （设备）lying around in it. Whenever I am at home, I am almost always using at least one electronic device. If you walked into my living room on any given day, you would find that, first, I have the television on. At the same time, I usually have my laptop resting on my knee, or I will be using my mobile phone. Even when I'm not at home I am always using my phone, and at work or in cafés, I sit down and connect to the local wireless network on my laptop.

    I must say that I waste a lot of time on the computer and the time I spend on it could be much better spent if I were to take up a little online volunteering.

    The technology we carry about everywhere can have a great power to do good for the world and to help others and recently I discovered just how much online volunteering there is to do in the world. From using your language skills to do translations, to developing and managing projects and helping with IT work, there is so much that so many people can do to help people in their own countries and across the world. The United Nations, in fact, has a huge page with "Volunteers Recruited" on its website.

    This work can support the poor and help charities who cannot pay for staff members. Many organizations only require you to work an hour a week﹣some even less. And the support provided by online volunteers can really help make a difference to those in need.

    A zero-waste life is a lifestyle that hardly creates any rubbish. So, a zero-waste store is about providing a kind of everyday and pleasant-looking zero-waste products to help people start on a zero-waste life journey.

    "Zero waste" or "danshari" was first suggested by a French woman called Bea Johnson. Her idea is: live a life and try not to create any rubbish; use different kinds of ways to save the environment such as stopping the use of one-off objects; giving unwanted things to others or giving them away to organizations like the Red Cross.

    Yu Yuan, 27, is deeply interested in this idea. She and her boyfriend have lived in Beijing for many years. And earlier she used to buy things without thinking about them carefully until she saw a video about "zero waste", in which a family of four placed the rubbish they produced every year in a jar (罐). After watching the video, Yu wanted to experience this zero-waste lifestyle with her boyfriend.

    A zero-waste life follows the 6R rule-Refuse Reduce, Reuse, Repair, Recycle and Rot. Over August-October when Yu followed the rule of zero waste 6R, she and her boyfriend Joe Harvey both produced only two cans of rubbish.

    Now, the couple have opened a small shop in Beijing, where they use wood products to take the place of plastic ones and cloth bags printed with environmentally friendly logos. Most products sold in the store can be reused. The store also has second-hand books and CDs/DVDs with, ideas to make the best of the used things.

    "Those who once experienced the non-waste lifestyle have slowly changed their ideas," says Ya, "The zero-waste lifestyle is not for ascetics (苦行僧). It is just around us at our finger-tips." Yu expects some of her friends to join her on the road to zero waste.

    Humans can go to the hospital when they're ill. But as for animals, what should they do？To stay healthy, animals have their own ways to heal(治愈)themselves. Now let's get to know their special skills.

    Skill One

    Have you ever seen your dog or cat lick(舔)its wounds？Why do they do it？It probably feels good, but it's good medicine. Licking cleans a wound, and saliva(唾液)has chemicals that kill germs(细菌).

    Skill Two

    To avoid diseases, many animals have good living habits. They hate to be dirty. Most animals separate their pooping(排便)areas from their eating areas. Horses poop far away from the grass they eat. Rabbits put their poop in special pooping areas.

    Skill Three

    Have you ever heard of the expression "starve a fever(发烧时宜饿)"？Many animals stop eating when they're ill. When a sick animal stops eating, it can stop germs from getting necessary things.

    Skill Four

    Another way that animals heal themselves is to raise their body temperature. High temperature can kill germs. Warm—blooded animals(like us)get fevers to fight with germs.

    Cold—blooded animals(like snakes)look for pieces of wood or rocks heated by the sun.

    Fish move to warmer waters.

    When you carry your heavy schoolbag on the way to school or home, do you know the fact that the heavy schoolbag influences your interest in learning knowledge? Don't worry. You may be able to say goodbye to your heavy schoolbag in the near future.

    Instead of burying(埋葬) your face in an ocean of textbooks, newspapers, magazines and novels, you will soon find that an E-book reader can take the place of them all.

    An E-book reader is a new kind of mini machine designed to hold thousands of text files and display them on the screen as real text printed(印刷) on a paper page.

    In the same way in which the iPod(a kind of MP3) has changed the way people enjoy music, E-book readers could change the way that books are read. Some scientists have predicted that E-books will be used widely in our daily life, especially in schools.

    The size of an E-book reader is the same as that of real books. Its screen is different from that of a computer. It is as thin as a piece of paper. The words on an E-book reader's screen look exactly the same as those on real pages. However, you can do more with an E-book reader than you can with a real book. The reader can change the size of the words and connect to the Internet to download new books.