When we think about endangered species, we typically think of mammals such as whales, tigers or pandas. But the over 5, 500 of mammal species on Earth is a relatively poor number—and it pales in comparison with bacteria, of which there are at least a million different species.
Despite their vast numbers, little research has been done to understand the impact that modern human practices have on these tiny organisms(生物), which have an important influence on many aspects of our lives.
There are also reasons for concern over the way humans are affecting bacterial species, and in many cases we are causing the same type of problems that affect larger organisms. Bacterial population structures are definitely changing, and bacterial species are being transported to new locations. Perhaps some bacteria are even on their way to extinction, although we don’t really have enough information to be certain yet.
Why should we care if bacteria are being spread to new places? Besides the obvious potential for spreading diseases to humans, animals and crops, there are also hidden dangers.
Microorganisms are invisible to the naked eye, so we tend to ignore them and don’t necessarily appreciate their role in how the planet operates. Bacteria are very important to biogeochemistry—the cycling of nutrition and other chemicals through ecosystems. For instance, before humans invented a way to make fertilizer industrially, every single nitrogen(氮)atom in our proteins and DNA had to be chemically caught by a bacterial cell before it could be taken in by plants and then enter the human food chain. The oxygen we breathe is largely made by microorganisms in the oceans rather than mainly by rainforests, as is opposite to common belief.
Our effects on bacteria have the potential to change these basic bacterial functions. It is vital to gain a better understanding of how humans are affecting microorganisms’ distribution, their abundance, and their life-keeping processes. Although bacteria are invisible, we overlook them at our own risk.
12. What can be learned about the bacteria according to the text?
A.Their population is becoming larger. |
B.Some of them may become endangered species. |
C.They only cause great threat to other creatures. |
D.Much attention has been drawn to their researches. |
13. What was the first step of the cycling of a nitrogen atom before entering our body?
A.Being caught by a bacterial cell. | B.Entering the human food chain. |
C.Being transported by humans. | D.Being taken in by plants. |
14. Where is the majority of oxygen produced according to the text?
A.In the human food chain. | B.In the rainforest. |
C.In the mountains. | D.In the oceans. |
15. Which part of the newspaper is the text probably taken from?
A.Science and technology. | B.Health and medicine. |
C.Agriculture and animals. | D.Environment and energy. |