阅读部分需要提取的观点是:
- Main point: 基因改良树木优点很多
- Sub point 1: 可以抵御病虫害
- Sub point 2: 可以提高农民的收入
- Sub point 3: 可以保护天然森林
听力材料:
Sure, there is benefit to planting genetically modified trees, but are these trees really as great as they first sound? When you examine the subjects closely, there are some serious problems and causes associated with the using of genetic modified trees.
当然,种植基因改良树木是有好处的,但是真的有利到可以作为首选作物吗?当你仔细审视这些理由的时候,就会发现基因改良树木会带来一些严重的问题。
First, genetically modified trees may be resistant to one particular condition, but it doesnt necessarily ensure their survival. You see: a typical non-modified tree population is genetically diverse. That means that for most threatening conditions, for climate, insects, and pests, whatever, there will be at least some individual trees of any given species tree that are resistant. So, even if the most of one kind of tree were killed, those few resistant ones will survive and ensure the survival of that species of tree. But, genetically modified trees are genetically much more uniform, so if there is supposed to an environmental challenge they have not been designed for, they will all die. So, if the climate changes or new pest engages in, the genetically modified trees will likely be completely wagged out.
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