更多" Many microorganisms survive such "的相关试题:
[单项选择] Many microorganisms survive such environmental stresses as heat, cold and desiccation not by rapid rates of mitosis, but by producing specialized cells designed to persist in a dormant state in hostile environments. Most fungi, for Line example, yield single-celled spores, which, through wind distribution, can survive for long periods of time before germinating and sprouting fungal filaments of their own. Other types of bacteria produce a special type of spore called an endospore, capable of withstanding such extremes as boiling and freezing temperatures, and even ultraviolet radiation.
Though research results remain tentative, several factors may protect endospores from environmental stress: they have a low water content, unusual proteins and a tough spore coat absent in mature bacterial cells. When garden fruits and vegetables, which may contain botulism endospores, are preserved by canning at boiling temperatures, we know that these spores survive the heat and sprout in the foo
A. Low temperatures
B. Ultraviolet radiation
C. Acidic environments
D. High temperatures
E. Drying processes
[多项选择]Many governments realized that environmental issues should and could only be resolved through international cooperation. But there are different opinions from developed and underdeveloped countries on ratifying the Kyoto Protocol. What is your suggestion to reaching an agreement
[填空题]Animals can not survive some catastrophic events such as starvation, disease, or competition from other species.
[单项选择]Once environmental damage ______, it takes many years for the system to recover.
A. had done
B. is to do
C. does
D. is done
[填空题]Since the early 1990s environmental trends have started to affect our economic trends, with the effects of losing large amounts of topsoil being felt.
[填空题]In Schwartz’s opinion, it is environmental forces that are the main threes to change the future of the world.
[单项选择]The Spread of Microorganisms
There is scarcely a place on earth which is naturally free of microorganisms
(46). But on external body surfaces, on lining membranes and inside tubes and organs that are connected with the outside---such as the mouth, throat, nose and large intestine ---- both harmless and pathogenic microbes live in large numbers. (47). If these natural defenses are sound, a person may conceal many microbes without ill effect. However, if his resistance becomes lowered, an infection can result.
Microbes are spread about through an almost infinite variety of means. (48). The more crowded the conditions, the greater the chances of epidemics breaking out.
(49).
Although microbes cannot fly, the dust of the air is alive with them. In close quarters the atmosphere is further polluted by bacteria-loaded tiny drops discharged by coughing and even normal conversation. Pathogenic microbes are also spread by rats, mice, flies and mosquitoes. (50). In slum areas there
