这些用英文怎么表达？?

　　These statistics are important from an ecological point of view.

　　就生态学而言，这些统计数字很重要。

　　The last of these reasons is by far the most important.

　　这些理由中最后一条比其他的重要得多。

　　Teachers are up against some major problems these days.

　　老师们最近面临着一些重大问题。

　　Everyone experiences these problems at some time in their lives.

　　每个人在人生的某个阶段都会经历这些问题。

　　These changes have occurred over a long time span.

　　这些变化经过了很长一段时间才形成。