【版本2】还真碰到了那个Caterpillar的题， 这篇阅读比较长而且逻辑关系很强， 没把眼镜差点看破了. 关键词：caterpillar, wasp, attractive chemicals. 主要讲plants have developed their own defensive system by attracting wasps, the predator of caterpillar host. caterpillar咬完树叶后， 树叶会自己分泌chemical attracion 引来wasps, 科学家开始怀疑是caterpillar自己在吃剩下的树叶上留下的chemical attraction 后来发现不是. 第一个题问文章concern什么， 我选E, 关于defensive system 第二个是inferred from the passage, wasp would be attracted by which of following , 忘选什么了
Parasitic and predatory arthropods often prevent plants from being severely damaged by killing herbivores as they feed on the plants.
Recent studies show that a variety of plants, when injured by herbivores, emit chemical signals that guide natural enemies to the herbivores. It is unlikely that herbivore-damaged plants initiate the production of chemicals solely to attract parasitoids and predators. The signaling role probably evolved secondarily from plant responses that produce toxins and deterrents against herbivores and antibiotics against pathogens. To effectively function as signals for natural enemies, the emitted volatiles should be clearly distinguishable from background odors, specific for prey or host species that feed on the plant, and emitted at times when the natural enemies forage. Our studies on the phenomena of herbivore-induced emissions of volatiles in corn and cotton plants and studies conducted by others indicate that (i) the clarity of the volatile signals is high, as they are unique for herbivore damage, produced in relatively large amounts, and easily distinguishable from background odors; (ii) specificity is limited when different herbivores feed on the same plant species but high as far as odors emitted by different plant species and genotypes are concerned; (iii) the signals are timed so that they are mainly released during the daytime, when natural enemies tend to forage, and they wane slowly after herbivore stops.
拼图：本文应为结论（假设）or现象解释型文章。（待验证，目前偏向前者）
第一段：提出植物、caterpillar、wasp/parasitic wasp之间关系的假设or现象：caterpillar是herbivore，caterpillar feed on plants. 这样plants就有可能被过度破坏，为了防止这种过度破坏，植物会释放一种chemical/odor，借以吸引wasp----毛毛虫的天敌(natural enemies)，这样wasp就会干掉(kill) caterpillar。植物得以免于被过度破坏。
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发表于 2009-7-26 22:46:00
