Genetic modification, a process used tochange an organism’s genes and hence its characteristics, is not being used toimprove trees. Through genetic modification, it is possible to create treesthat produce more fruit, grow faster, or withstand adverse conditions. Plantinggenetically modified trees on a large scale promises to bring a number ofbenefits.
First, genetically modified trees aredesigned to be harder than nature trees; that it, they are more likely tosurvive than their unmodified counterparts. In Hawaii, for example, a newpest-resistant species of papaya tree has been developed in response toring-spot virus infections that have repeatedly damaged the native papaya-treepopulation. Planting the genetically modified papayas has largely put an end tothe ring-spot problem.
Moreover, genetically modified treespromise to bring a number of economic benefits to those who grow them.Genetically modified trees tend to grow faster, give greater yields – of food,fruit, or other products – and be hardier. This allows tree farmers to getfaster and greater returns on their farming investment and save on pesticidesas well.
Finally, the use of genetically modifiedtrees can prevent overexploitation of wild trees. Because of the growing demandfor firewood or building timber, many forests around the world are being cutdown faster than they can be replaced. Introducing genetically modified trees –designed for fast growth and high yield in given geographic conditions – wouldsatisfy the demand for wood in many of those areas and save the endangerednative trees, which often include unique or rare species.
- 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#p#副标题#e#
Sure, there is benefit to plantinggenetically modified trees, but are these trees really as great as they firstsound? When you examine the subjects closely, there are some serious problemsand causes associated with the using of genetic modified trees.
First, genetically modified trees may beresistant to one particular condition, but it doesn’t necessarily ensure theirsurvival. You see: a typical non-modified tree population is genetically diverse.That means that for most threatening conditions, for climate, insects, andpests, whatever, there will be at least some individual trees of any givenspecies tree that are resistant. So, even if the most of one kind of tree werekilled, those few resistant ones will survive and ensure the survival of thatspecies of tree. But, genetically modified trees are genetically much moreuniform, so if there is supposed to an environmental challenge they have notbeen designed for, they will all die. So, if the climate changes or new pestengages in, the genetically modified trees will likely be completely waggedout.
That is the second point. There are hiddencauses associated with the growing genetically modified trees. You see, thecompany that genetically modified tree can charge tree farmers much more forits seeds than unmodified tree seeds would cost. Also, after you’ve grown thetree, you cannot just collect the seeds and plant the new tree for free. Bylaw, you have to pay the company every time you plant.
现在说第二点。在基因改良树木的生长过程中伴随着一些隐含问题。你看，公司都是以高于天然种子很多的价格向农民出售基因改良树木种子的。同时，你现在不能再每年收获之后收集种子，然后来年免费再种了。因为根据法律规定，你每年都必须向种子公司支付费用。And finally, genetically modified trees might actually cause evenmore damage to the local wild trees. You see, genetically modified trees oftengrow more aggressively than natural trees do. And genetically modified treesare typically planted among natural trees. As a result, the genetically modifiedtrees out compete the native trees for resources: sunlight, soil nutrition andwater. Eventually, crowd out the nature trees.
Main point: 优点之中都存在问题
Sub point one: 如果遇到不能抵御的病虫害，可能会全部死亡
Sub point two: 会增加农民的成本，因为种子公司有权每年收费
Sub point three: 会损害天然森林，因为会争夺自然资源
In the lecture, the professor claims thatalthough they may be some benefit, planting genetic modified trees will bringpotential problems and costs. She totally opposes the three statements made inthe reading passage.
Firstly, the professor indicates thatgenetic modified trees may resistant, but this cannot guarantee their survival.She points out that in fact the unity of genes within genetic modified plant willincrease their likelihood to wipe out when there is some threatening situation.The professor counters the claim made by the reading passage.
Secondly, the professor opposes the readingpassage by pointing out there is hidden cost behind modification trees. Thoughgenetic modification trees may provide more products or can save pesticide,their seeds are usually charged at a higher price. In addition, according tothe law, a farmer has to pay for the seed each time they plant the trees. Thiswill not bring any economic benefit mentioned in the reading passage.
Last but not least, the professor opposesthe statement that genetic modification trees will prevent overexploit of wildtrees. In fact, genetic modification trees tend to grow aggressively and can easilyexhaust the resource of normal trees. This will bring disastrous result for thelocal vegetation.