We sometimes call the lion “the king of the jungle”, because it is stronger and more dangerous than other animals. It can 36 faster than many animals and it can hunt other beasts. It is one of the highest animals in the 37 food chain（食物链）.
In the sea, the shark is one of the animals at the top of the food chain. It can swim faster than 38 other sea animals, and it can use its big teeth to eat them.
What is at the top of the world’s food chain? People are! We are not the biggest or fastest, but we are the 39 . We could not run faster than cheetahs(猎狗)，so we 40 cars and now we can move the fastest. We could not fight better than lions, so we invented guns. Now we can hunt the beast
People’s inventions（发明）are clever, but they can be 41 ,too. For example, people built 42 , and now they make the air and rivers dirty. This can make terrible changes. Dirty rivers kill fish. 43 bears cannot eat the fish. If we kill one part of the food chain, other parts also will die. Remember that we are a part of the food chain, 44 we are in danger, too. If we protect animals, we are protecting 45 ! We should and we could do something for the world!