Đề khảo sát đội tuyển khối 11 môn Tiếng Anh năm học 2013 - 2014 - THPT Nguyễn Trãi, Thái Bình

HOW WE READ

I just want to introduce the next area we’ll cover: the food chain. Food chains are divided into three types. The first one is the predator( [‘predato(r)]: dong vat an thit) chain, in which larger animals feed on smaller ones, such as when a bird eats a fish. The second is the parasite chain, in which smaller animals live off larger ones, such as a tapeworm living in a eat’s intestines. And the third type is the saprophytic chain in which a micro-organism feeds off dead matter.

In each type of chain, potential energy is lost at each level. Let’s take the example of a green plant. It gets energy from the sun by photosynthesis, but can use only about 2 or 3 percent of the energy that falls on it. The plant is then eaten by a rabbit, but the rabbit can use only about 10 percent of the potential energy of the plant. The rabbit is then eaten by a fox, which can use about 12 - 15 percent of the energy from the rabbit. And finally, the fox is eaten by a mountain lion. As you can see, at each step the percentage of energy obtained increases, but all in all, a great deal of energy is lost at each step.

That’s all for today. Read the next chapter in your books. We’ll go on with more about the food chain next time.