Snow leopards (雪豹) are big cats. But now they are in danger. We should try to save them. Let’s learn more about snow leopards.

Snow leopards are usually from some countries such as Mongolia, China and India. They live in the mountains and their mountain homes are very cold.

People can hardly see them in the wild (野外), but we can know about 600 snow leopards live in zoos around the world. It is said that there are about 6,000 snow leopards living in the wild.

The snow leopard is a large animal. Adult snow leopards are between 60 and 120 pounds. They are about two feet tall at the shoulder. From head to tail (尾巴), they are six to seven and a half feet long.

The snow leopard has a long tail and its tail is useful. It can help the snow leopard keep balance. In winter, the snow leopard wraps (用……围住) its tail around its body to keep warm. Its long tail is like a scarf.

It’s hard to believe that a beautiful silk dress comes from thousands of very little worms (蠕虫) called silkworms! It takes about 5,500 silkworms to make 2.2 pounds of silk. The process was invented by the Chinese about 5,000 years ago.

How is silk made? The process starts with silkworm eggs. The eggs are collected and kept warm. After a few days, silkworms come out of the eggs. They are fed leaves from mulberry trees (桑树) every 30 minutes, all night and all day. The room must be kept warm, without loud noises or bad smells. After a month, they start to make cocoons (茧). After four days, the cocoons are over.

The cocoons are heated (加热), and the silkworms are killed inside them. Then the cocoons are put into water to make the silk loose (松散的). The silk from three or four cocoons is put together and made into a thread (线). One cocoon can make a thread 1 kilometer long! Finally, the silk threads are made into cloth, and the cloth is used for things like dresses, scarves and neckties (领带).

Today, silk is produced in many countries, including India and Thailand, but more than 80 percent of the world’s silk comes from China. Every year, enough silk thread is produced to go from the earth to the sun 300 times. People love silk clothes because they are beautiful and comfortable—silk feels cool in warm weather and warm in cool weather. Now you know why silk is so expensive!

We sometimes say the lion is “the king of the jungle” because it is stronger and more dangerous than the other animals. Most other animals in the jungle run more slowly than the lion, so it can hunt better. The lion is the top animal in the land food chain.

In the sea, the shark is at the top of the food chain. Most other sea animals swim much more slowly than it. It can also use its big teeth to catch other sea animals and eat them.

What is at the top of the world's food chain? Humans are! We are not the biggest or fastest, but we are the cleverest! We could not catch up with most animals, so we invented cars and now we can move the fastest. We could not fight better than a lion, so we invented guns. Now we can hunt the best.

People’s inventions help a lot, but they can be dangerous, too. For example, many years ago in Inner Mongolia, people used guns to kill a lot of wild wolves.

The wild wolves usually eat wild rabbits. But in recent years, the number of wild rabbits is becoming bigger and bigger because the number of wild wolves is getting smaller and smaller.

The wild rabbits competed for the grass with the sheep and cows. Much of the grassland became desert because the rabbits destroyed (毁坏) it seriously.

Remember that we are a part of the food chain, we are in danger, too! If we protect animals, we are protecting ourselves. Luckily, people have paid much attention to such problems. We will do more things to keep the balance of ecosystem in the future.