[不定项选择题]共用题干 Ecosystem
1. The word “ecosystem” is short for ecological（生态的）system. An ecosystem is where living creatures expand within a given area. You can say that an ecosystem is the natural environment where biological organisms（生物）such as plants,animals and humans co-exist in this world. So naturally that includes you and me. Yes,we are all members of an ecosystem!
2 .There are different kinds of ecosystems depending on the type of surface or environ-ment. Most are naturally made such as the ocean or lake and the desert or rainforest.Some are man-made or artificial to encourage co-habitation（同居）between living and non-living things in a monitored environment,such as a zoo or garden.
3 .Plants make up the biggest group of biological creatures within an ecosystem,and that's because they are the natural food producers for everyone. Plants raised in the earth need air and collect sunlight to help them grow. When they grow,the plants and its fruits or flowers eventually become a source of food to animals,microorganisms（微生物）and even hu- mans,of course. Food is then converted to energy for the rest of us to function,and this hap-pens in a never-ending cycle until the living creatures die and break up back in the earth.
4 .Ecosystems are the basis of survival for all living things.We depend on plants and ani-mals for food. In order for us to exist,we need to grow and care about other organisms. We also need to care for the non-living things within our environment like our air and water so we can continue living as a population. Since plants,animals and humans are all of various species（物种）,we all play a role in maintaining the ecosystem.
5 .To preserve our ecosystems,we should stop using too much energy,which happens when we consume more than our share of resources. Humans should not disturb the natural habitat（栖息地）of plants and animals,and allow them to grow healthily for the cycle to con-tinue. Too many people in a habitat can mean displacement（搬迁）: imagine being thrown out of your home because there is no more space for everyone. Worse,overpopulation can also ru- in the environment and cause destruction of existing plants and animals. Plants,animals and humans are all effective in______.
A.our share of resources
B.a biological creature
C.a given area
D.the maintenance of the ecosystem
E.the source of food
F.various species