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1、TPO21The lecturer points out three different shortcomings of genetically modified trees. In the aspects of adaptation, economic lucrativeness, and environmental value, they never have overwhelming advantage over natural trees. That means the points made in the reading are partial and biased.First, g
2、enetic modification doesnt necessarily make a natural tree more resistant to environmental adversities. Although genetic reconstructing may make a species stronger in a specific condition as the reading indicates, the new strain lakes the genetic diversity of a natural species. Thanks to the margina
3、l differences between individuals, there can always be some survivors among natural species following a large interruption like climate change or pest invasion. But similar changes may cause the distinction of a genetically modified species for their unification in characteristics.Second, tree farme
4、rs dont get guaranteed economic benefits if they plant genetically new strains. Companies that develop the new plants always charge farmers higher prices for artificially improved seeds, and receive money from farmers each time they grow the same plant. Such company policies and law will deprive far
5、mers of the gaining mentioned in the reading.Third, genetically modified trees dont promise to protect wild trees. Actually, since they can grow faster with fewer resources, they are more ecologically invasive. Normally they outcompete natural trees by grasping natural resources like sunshine, water
6、 and soil. Its far from the idealistic situation described in the reading.TPO22The lecturer refutes all the seemingly existing shortages of ethanol listed in the reading and holds that ethanol is quite likely a good replacement of gasoline as the future fuel.First, the application of ethanol will no
7、t create as much heat as that of gasoline does. Although the burning of ethanol will also generate carbon dioxide, it will not add to the severity of global warming. Since the production of ethanol requires the planting of corns, whose growth in turn requires carbon dioxide as nutrition, the raised
8、amount of the unwanted gas will be offset therewith. This is the situation the reading doesnt account for.Second, the production of ethanol doesnt surely reduce the food supply for farm animals. Because ethanol can be made out of any part of the plant whose cell walls contain cellulose, the cost of
9、the pants useful parts can be avoided. This advantage renders the worry of the reading totally unnecessary.Finally, the price of ethanol will be largely reduced if the scale of manufacture increases. According to statistics, if the manufacture scale, following heavier demand of consumers, can be enl
10、arged by three times, its cost will be reduced by forty percents. Under such circumstance, the government subsidies mentioned in the reading shall no longer be needed.TPO23The lecturer holds that the main reason causing the overall decline in yellow cedar population is not yet decided. The proposed
11、reasons in the reading, though responsible for the poor health of some individual plants, may not account for the decline of the whole species throughout the North American Continent.First, healthy yellow cedar trees can secret a chemical that is poisonous to insects feeding on its barks. Hence, it
12、is unlikely that the cedar bark beetle can ever attack a plant before it gets ill or dead. The reading thus finds a misleading causal relationship between the insect and the tree.Second, bears cannot be blamed for large-scaled dying of yellow cedars across North America, although they might be respo
13、nsible for the accidental dying for some individual plants. Another condition that can set bears free from this accusation is that yellow cedars growing on bear-free islands are also dying in large numbers. Hereby the reading material fails to spot the primary reason again.Third, cold climate can ne
14、ither be blamed for the general failure of cedar population. The proof can be found in the trees wider recession in areas of lower elevation, where its warmer than on higher elevations. Though cold weather may have made cedars more sensitive, it cannot be the primary killer as the reading indicates.
15、TPO24The lecturer extends possible explanations besides the conclusions made on the newly discovered T. Rex fossil and suggests that the existing evidences can lead to something other than remaining animal tissues as suggested in the reading.First, the branching channels in that leg bone can quite l
16、ikely be the colonies of bacteria, since bacteria always take the hollows in a bone structure and develop themselves following the organic material. And the soft substance inside the channels can also be the residues of these bacteria colonies, rather than once blood vessels suggested by the reading material.Second, the reading assumes the reddish spheres found in the bone to be red blood cells, finding credence from their color and size. But fossils of primitive organisms in the same a
