1999年考研英语作文主要考查了考生对图表信息的理解和分析能力，以及对相关话题的论述能力。以下是根据您提供的信息和我所知知识整理出的作文要点和范文结构：
作文要点
人口增长的影响 ：描述美国从1800年到1990年人口的增长情况。物种灭绝的情况：
说明同期美国野生动物物种的灭绝数量急剧上升。
原因分析：
探讨导致物种灭绝的可能原因，如生态平衡的破坏、污染和沙漠化等。
保护建议：
提出针对野生动物保护的措施或建议。
参考范文结构
引言
：简要介绍人口增长和物种灭绝的现象。
主体段落 第一段：描述人口增长的趋势。 第二段：分析物种灭绝的原因。 第三段：提出保护野生动物的建议。 结论
范文示例
```
The Impact of Population Growth on Wildlife
As is shown by the two graphs, the period between 1800 and 1990 witnessed a remarkable growth in the United States population. However, this growth was accompanied by a drastic rise in the number of wildlife species that became extinct. The comparison of the graphs clearly illustrates this point.
The reasons for this phenomenon are not hard to find. The destruction of ecological balance is a major factor. With the increase in human population, pollution and desertification have become increasingly serious, leading to the loss of habitats and food sources for wildlife. Furthermore, the conversion of land for agricultural and urban use has also played a crucial role.
To address this issue, it is imperative that we take immediate and effective measures to protect wildlife. This includes establishing more protected areas, enforcing stricter environmental regulations, and raising public awareness about the importance of biodiversity. By taking these steps, we can help ensure that future generations will be able to enjoy and benefit from the rich natural resources of our planet.
In conclusion, while population growth brings about many challenges, it is our responsibility to ensure that it does not come at the expense of our wildlife. By working together, we can help preserve the natural world for future generations.
```
以上范文仅供参考，实际写作时可以根据自己的理解和观点进行调整。希望这些信息对您有所帮助，