独立写作:Do you agree or disagree with the following statement? Movies and television programs should present stories in which good people are rewarded and bad people are punished.
综合写作Reading: large animals’ extinction 如mammoth human's overkill lead to extinction:
1. North American 到达这个地方与大型哺乳动物的灭绝是at the same time.2. 大动物以前没有遇到过predator,他们vulnerable更有利于移民来的人去kill.3. 只发现有大动物的死的痕迹,没有发现小动物死的痕迹。
Listening: the speaker totally refused the passage she believe that there is no relationship between the extinction of large mammals in the north America and human hunting, instead she thinks that the extinction was caused by other factors such as climate change
Plant communities assemble themselves flexibly, and their particular structure depends on the specific history of the area. Ecologists use the term “succession” to refer to the changes that happen in plant communities and ecosystems over time. The first community in a succession is called a pioneer community, while the long-lived community at the end of succession is called a climax community. Pioneer and successional plant communities are said to change over periods from 1 to 500 years. These changes—in plant numbers and the mix of species—are cumulative. Climax communities themselves change but over periods of time greater than about 500 years.
An ecologist who studies a pond today may well find it relatively unchanged in a year’s time. Individual fish may be replaced, but the number of fish will tend to be the same from one year to the next. We can say that the properties of an ecosystem are more stable than the individual organisms that compose the ecosystem.
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