People in southern China like famous and expensive dish—shark fin soup, but no scientific studies have shown that shark fins are good for health. So why do they eat them? Do they realize that they're killing a whole shark each time they enjoy a bowl of shark fin soup?

When people catch sharks, they cut off their fins and throw the shark back into the ocean. This is not only cruel, but also harmful to the environment. Without a fin, a shark can no longer swim and slowly dies. Sharks are at the top of the food chain in the ocean's ecosystem. If their numbers drop too low, it will bring danger to all ocean life. In fact, around 70 million sharks are caught and traded in this industry every year. The numbers of some kinds of sharks have fallen by over 90 percent in the last 20 to 30 years. Help save the sharks!

    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.

    Like humans, dogs donate blood too, and not every dog can donate blood. The dogs are screened(检查) for health first. Dogs must have the correct blood type, weigh at least 55 pounds and be younger than 8 years old. They may donate three or four pints(品脱) a year, which can help animals that are suffering from illnesses like cancer or an accident like being hit by a car. One pint can save up to three dogs.

    Owners volunteer their pets for the short procedure (程序), which requires no sedative, a kind of medicine given to calm him or her down. It's the dog that finally chooses to lie still and give. If the dogs want to get up and leave, they can.

    Sandy Lucas brought her 7-year-old black German shepherd, Rains, to the bloodmobile(流动血站) when it was parked at her small village. Sandy said she wouldn't have troubled herself with highway traffic and city parking problems to take the dog to Penn Vet's animal hospital in downtown Philadelphia, which is twice as far as her home. But the bloodmobile made it easy to find out if Rains could donate. "I was very, very excited that she had the right blood that was needed to help another dog out," said Sandy. "We'll surely do it again."

    Is there intelligent（有智力的）life on other planets? For years, scientists said "no." or "we don't know." But today this is changing. Seth Shostak and Alexandra Barnett are astronomers（天文学家）. They believe intelligent life exists（存在）somewhere in the universe. They also think we will soon contact them.

    Why do Shostak and Barnett think intelligent life exists on other planets? The first reason is time. Scientists believe the universe is about 12 billion years old. "This is long enough for other planets to have intelligent life, "say Shostak and Barnett. The second reason is size the universe is huge. "Tools like the Hubble Telescope（哈勃望远镜）have shown that there are at least 100 billion galaxies, "says Shostak. "And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be similar to the earth. "

    In the past, it was hard to look for signs of intelligent life in the universe. But now, powerful telescopes（高倍望远镜）allow scientists to discover smaller planets-the size of Mars or the earth-in other solar systems, these planets might have intelligent life.

    Have beings from space already visited the earth? "Probably not, "says Shostak. "It's a long way away. However, intelligent beings may contact us in other way, such as radio signals（信号）. In fact, they may be trying to communicate with us now, but we don't have the right tools to receive their messages. However, this is changing. By 2025, we could make contact with other life forms in our universe and we might help each other. "

    What will man be like in the future-in 5. 000 or even 50, 000 years from now？We can only make a guess, of course, but we can be sure that he will be different from what he is today. For man is slowly changing all the time. Now look at the chart below, and you'll find some differences.

    Perhaps all this gives the impression that future man will not be a very attractive creature(生物) to look at！This may well be true. All the same, in spite of all these changes, future man will still have a lot in common with us. He will still be a human being, with thoughts and emotions(情感) similar to our owns.