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!

    Do you know fish come out of eggs when they are born? After the little fish comes out of the egg, it eats the food in the egg. When it is big, it leaves the egg. It swims in the water. You can see the eyes and nose. Its ears are hidden in the head.

    Spree fish eat other fish. Some fish have small mouths and teeth and they often eat plants.

    Winter is very cold in many countries. It's easy for you and me to keep warm. If we are cold, we can just buy a warm coat or use a heater and we will feel better. But what about animals? How do they keep warm in winter?

    Some animals migrate(迁移). This means they travel to places where the weather is warmer. Many birds leave before the winter starts. They fly in groups. If they fly together, the trip will be safer. They like to migrate to the same places every year. Do you know how they can find the same places? Scientists say that birds use the sun, moon and stars to help them. Other animals like moose (麋鹿) also migrate. Fish and whales swim to warmer water.

    Some animals don't have leave their homes. They hibernate in winter. They fall into a very deep sleep. The animals' temperature drops and their breathing slows down. Before the winter, these animals must eat too much food that they get very fat. If they don't eat enough, they may die when they are hibernating.

    The world is not hungry, but it is thirsty. It seems strange that nearly 3/4 of the Earth is covered with water while we say we are short of（短缺）water. Why? Because about 97% of water on the Earth is sea water which we can't drink or use for watering plants directly(直接地）. Man can only drink and use the 3%-the water that comes from rivers and lakes. And we can't even use all of that, because some of it has been polluted(污染）.

    Now more water is needed. The problem is Can we avoid（避免）a serious water shortage later on? First, we should all learn how to save water. Secondly, we should find out the ways to reuse it. Scientists have always been researching in the field. Today, in most large cities water is used only once and then runs to the seas or rivers. But it can be used again. Even if(即使）every large city reused its water, there would not be enough. What can people turn to next?

    The seas seem to have the best answer. There is a lot of water in the seas. All that needs to be done is get the salt out of the sea water. This is expensive, but it's already used in many parts of the world. Scientists are trying to find a cheaper way of doing it. So you see, if we can find a way out, we'll be in no danger of drying up.

    Autumn in Tibet is very beautiful because there are many fresh and bright colours everywhere.

    In north Tibet, one can travel several hundred kilometres by car and cannot see even a person. No one can be found in the north of Shuanghu-only treeless fields and grasslands. Warm autumn days bring life to all of nature. Wild animals become active, and Tibetan antelopes like to play near the lakes. When they run, sometimes they can reach 80 km an hour, leaving the hungry wolves far behind.

    Autumn in south Tibet is very different from that in north Tibet. Mount Qomolangma in southwest Tibet, the highest mountain on Earth, is world-famous for its beauty. It is over 8, 000metres high. There are over 2,300 kinds of plants and about 300 different kinds of wild animals on Mount Qomolangma.

    A 22-year old British student has invented a mobile fridge that could save millions of lives across the world.

    Will Broadway's "Isobar" has been designed to keep vaccines(疫苗) at the ideal temperature while they are being sent in developing countries. And Will doesn't plan to make money from his creation. His purpose is to get vaccines to people who need them, which is why he won't be trying to get a patent(专利). Will's Isobar has won him the James Dyson Award that challenges young people to "design something that solves a problem".

    Present methods of transporting vaccines can lead to the vaccines freezing(冻住) before reaching their places in developing countries, but the Isobar keeps a temperature of 2 to 8 degrees for 30 days.

    Will's invention is expected to save the lives of 1.5 million people across the world, a number he says is "amazing". Having now finished college education, he is making an effort to take the Isobar into production. "I would be hands-on, all the way through it, knowing that it works," he says. "It's amazing to just give it a go, even in my back yard, and see the potential(潜能) of the technology."

    The product has been designed to transport vaccines, but already Will sees the possibility of other medical uses in the developing world and beyond. "Blood donations, organ transplants(器官移植)- if they get trapped in traffic, you still use cold bags that really aren't good enough for a long time," he says.

    There is also a possible, non-medical use of the Isobar. "It would be a great thing to take on a five-day trip where you have no power," he says. But he insists vaccine transportation is the primary function(功能) of his invention.