Find Which Direction Is South

    Do you have a good sense of direction? If not, please take with you a compass. But if you forget to take a compass, you can still find your way.

    It's never a good idea to imagine that the family member who was entrusted (委托) with the job of map-reading actually knows where the family is. You can tell by the slightly confused load on their faces that nothing on the ground seems to match the map. Never mind. The sun is shining and it's still morning.If you don't know the exact time, you can still find out where south is, but you'll need to be patient.

    ①Find a straight stick and put it in the ground in a place where you can mark its shadow.

    ②Try to position the stick as vertically(垂直)as you can. You can check this by making a simple plumb line (铅锤线) with a piece of string and weight. You haven't got any string? OK, use a thread from your clothes with a button tied at the end to act as a weight.

    ③Mark the end of the shadow cast by the stick.

    ④Wait approximately half an hour and mark the end of the shadow again.

    ⑤Keep doing this until you have made several marks.

    ⑥The mark nearest the stick will represent the shortest shadow, which is cast at midday, when the sun is highest in the sky and pointing to the exact south.

    ⑦Pick a point in the distance along the line between the shortest shadow and the stick.

    ⑧That point is south of where you are.

    ⑨Now you can turn the map, like you did before, and find which way you should be travelling.

    Do you know why different animals or pests(害虫) have their special colors? Colors in them seem to be mainly used to 1 themselves.

    Some birds like eating locusts(蝗虫), but birds cannot 2 catch them. Why? It is because locusts change their 3 with the change of the colors of crops. When crops are green, locusts look 4 But as the harvest time comes, locusts change into the same brown colo 5 crops have. Some other pests whose colors are 6 plants are easily found and eaten by 7 So they have to hide themselves for lives and appear only 8 

    If you 9 animals' life, you'll find the main use of colors is to protect 10 Bears, lions and other animals 11 quietly through forests. They cannot be easily seen by hunters 12 their colors are much like the trees.

    Colors are useful not only on the land, but also in the 13 A kind of fish can 14 （液体) when they face danger. The liquid spreads over quickly, so they cannot be found by their enemies and can quickly swim away. That is 15 they can live safely though they are not strong at all. So colors are really useful to animals.

    In most parts of the world, many students help their schools make less pollution. They join environment clubs. In an environment club, people work together to make our environment clean.

    Here are some things students often do.

    No-rubbish lunches. How many lunch bags do you throw away after lunch? Environment clubs ask students to bring their lunches in bags that can be used again. Every week they will choose which classes make the least rubbish and report them to the whole school.

    No-car day. On a no-car day, nobody comes to school in a car including the students and the teachers. Cars give pollution to us, so remember:

    Walk, jump, bike, or run!

    Use your legs! It's lots of fun!

    Turn off the water! Do you know that some toilets can waste twenty to forty cubic (立方) meters of water an hour? In a year, that would fill in a small river. In the environment clubs, students repair those broken toilets.

    We love our environment. Let's work together to make it better.

    Mike Myers is a teacher at Chauncey Rose High School in Terre Haute, Indiana. Last year, he taught his students about the world's rain forests. They learned that rain forests are important because the plants and animals of the rain forests give us food, wood and medicine.

    Destruction of the world's rain forests is a severe problem. As part of a class project, Myers' students bought three acres (英亩) of rain forest in Central America. They paid $25 for each acre. The students hope that the land they bought will be protected and not destroyed.

    Last June, Myers and four of his students took a boat ride down a river. They saw alligators and crocodiles. In the middle of the week, a guide took Myers and his students into the rain forest. "The monkeys were not happy that we were in their forest. They broke small branches off the trees and threw them at us," one of the students said. "It was a great journey of exploring nature for all of us," said Myers.

    Each student close something special about Costa Rica to study involving the plants animals, food, and culture. During the last few days the group had time to do fun activation. They went whitewater rafting and horseback riding, and visited Costa Rica's active volcano.

    Myers hopes to make the trip every year with a different group of kids.

    Everyone knows the strange feeling of your fingers wrinkling up (起皱) when they're wet. Sometimes when in water, it seems as if your hands have aged 30 years in a second. But is this an accident? Or is it something that nature has built into our bodies?

    Scientists at the University of Newcastle in the UK recently did a test. They asked people to pick up things (some wet and some dry). And take them from one place to another. Some people did this with dry hands, while others had to leave their hands in water for 30 minutes first so that their skin was wrinkled. The study found the second group with wet hands had an advantage when carrying things that were also wet.

    The scientist Tom Smulders said that "this wrinkling of our fingers in wet conditions could have helped with gathering food from wet vegetation or streams". Wrinkling happens when blood vessels contract (血管收缩) and pull the skin back.

    A long time ago, humans lived a very difficult life in a brutal world, where the smallest advantage could make a huge difference. Having wrinkled skin might have helped people catch fish. This would help them get through the winter. These humans would then have had an advantage. Their genes would be accepted by natural selection.