真题回顾：
| 【讲课要点】：生物学理论: plant invasion. 一种新树到新的ecosystem中会destroy the ecosystem |
| 【举例说明】： 1．一种树，本来是来解决问题的，问题是解决了，但是造成了新问题：来了后，长得太高了，导致其他树晒不到阳光了 2．一种树，非常attractive，但是use lots of water, other trees can not survive。. |
参考范例：
The lecture tells us that plants can be totally harmless most of the time. But when inappropriately brought into an environment, plants can also cause disasters by breaking ecological balance in local areas, which is biologically identified as plant invasion. Then the professor goes on to explain that by giving two examples. One is that a tree was introduced into South Africafor the purpose of stabilizing the local sand dunes. The tree fulfilled its task very successfully, but the bad news is that the tree grew so tall that they left very little sunlight for their neighboring plants. Threatened by this intruder, many plants started to lose their former territory. Another example is about a tree which was brought intoWestern United Statesfor its good appearance. It seems not so large, but it has very developed root system, so it absorbed twice the water as other plants of similar size. Also, it reproduced very fast. With its rapid growing, many other local plants gradually died out because of lack of essential water resource.
在这场关于生物学的讲座中，professor通过以两种不同特点的树为例，解释了生物学理论: plant invasion。
