Coral reefs are one of the most fragile, biologically complex, and diverse marine ecosystem on Earth. This ecosystem is one of the fascinating paradoxes of the biosphere: how do clear and thus nutrient-poor waters support such prolific and productive communities? Part of the answer lies within the tissues of the corals themselves. Symbiotic cells of algae known as zoozanthellae carry out photosynthesis using the metabolic wastes of the coral thereby producing food for themselves, for their corals, hosts, and even for other members of the reef community. This symbiotic process allows organisms in the reef community to use sparse nutrient resource efficiently.
Unfortunately for coral reefs, however, a variety of human activities are causing worldwide degradation of shallow marine habitats by adding nutrients to the water. Agriculture, slash---and ---bum land clearing, sewage disposal and manufacturing that creates waste by-products all increase nutrient loads in these waters. Typical symptoms of reef decline are destabilized herbivore populations and an increasing abundance of algae and filter-feeding animals. Declines in reef communities are consistent with observations that nutrient input is increasing in direct proportion to growing human populations, thereby threatening reef communities sensitive to subtle changes in nutrient input to their waters.
1.The passage is primarily concerned with（ ） .
2.The passage suggests which of the following about coral reef communities?
3.The author refers to “filter-feeding animals” (line 17) in order to （ ）.
4.According to the passage, which of the following is a factor that is threatening the survival of coral reef communities?
5.It can be inferred from the passage that the author describes coral reef communities as paradoxical most likely for which of the following reasons?
问题1选项
A.describing the effects of human activities on algae in coral reefs
B.explaining how human activities are posing a threat to coral reef communities
C.discussing the process by which coral reefs deteriorate in nutrient-poor waters
D.explaining how coral reefs produce food for themselves
问题2选项
A.Coral reef communities may actually be more likely to thrive in waters that are relatively low in nutrients.
B.The nutrients on which coral communities thrive are only found in shallow waters.
C.Human population growth has led to changing ocean temperatures, which threatens coral reef communities.
D.The growth of coral reef communities tends to destabilize underwater herbivore populations.
问题3选项
A.provide an example of a characteristic sign of reef deterioration
B.explain how reef communities acquire sustenance for survival
C.identify a factor that helps herbivore populations thrive
D.indicate a cause of decreasing nutrient input in waters that reefs inhabit
问题4选项
A.The waters they inhabit contain few nutrient resources.
B.A decline in nutrient input is disrupting their symbiotic relationship with zooxanthellae.
C.The degraded waters of their marine habitats have reduced their ability to carry out photosynthesis.
D.Waste by-products result in an increase in nutrient input to reef communities.
问题5选项
A.They are thriving even though human activities have depleted the nutrients in their environment.
B.They are able to survive in spite of an over-abundance of algae inhabiting their waters.
C.They are able to survive in an environment with limited food resources.
D.They are declining even when the water surrounding them remains clear.
第1题:B
第2题:A
第3题:A
第4题:D
第5题:C
1.主旨大意题。本文第一段讲了珊瑚礁是如何在清澈且无养料的海水中繁衍的。第二段开头开始转折，作者指出人类活动是怎样对珊瑚礁的栖息地造成破坏的， 所以B选项‘解释人类活动如何对珊瑚礁群落构成威胁’为正确答案。
2.细节判断题。根据文章第一段“how do clear, and thus nutrient-poor waters support such prolific and productive communities? ” 用一个反问句表明珊瑚礁适合在低养料的清澈海水中生长。确定A选项符合题意。珊瑚礁很难在浅水滩边繁殖，所以B选项错误，排除。人类活动导致海水中的养料增加，而并非增加了海水的温度，从而破坏了珊瑚礁的 栖息地，C选项错误，排除。食草动物数量的不稳定并不是珊瑚礁生长造成的，而是珊瑚礁遭到破坏的一种表现，D选项错误，排除。
3.细节判断题。根据文章第二段“Typical symptoms of reef decline are destabilized herbivore populations and an increasing abundance of algae and filter-feeding animals. 珊瑚礁衰退的典型症状是食草动物种群的不稳定，以及藻类和滤食性动物数量的增加。”确定作者提到filter-feeding animals是为了说明珊瑚礁减少的特征。A选项正确。
4.细节判断题。根据文章最后一段“Agriculture, slash-and-bum land clearing, sewage disposal and manufacturing that creates waste by-products all increase nutrient loads in these waters. 农业、刀耕火种、污水处理以及制造业向海水中排放了 大量的垃圾，从而增加了海水的营含量。”和“Declines in reef communities are consistent with observations that nutrient input is increasing in direct proportion to growing human populations, thereby threatening reef communities sensitive to subtle changes in nutrient input to their waters. 珊瑚礁对养料排入海水中发生的微妙变化很敏感，随着人口的增加，排放到海水的养料也随之増加，珊瑚礁的数量也就减少了。”可知人类排放的垃圾增加了海水的营养含量，从而威胁着珊瑚礁的生长。D选项符合题意。
5.推理判断题。作者在第一段提到珊瑚礁之所以能在清澈并且少养料的海水中生长，是因为有一种叫虫黄藻的水藻与它共生。虫黄藻能够与珊瑚礁的粪便进行光合作用，从而又为珊瑚礁提供食物。因此，尽管在食物资源极度缺乏的环境下，珊瑚礁也能够生长。所以C选项‘它们能够在食物资源有限的环境中生存’符合题意。
