Populations change over time — they grow or shrink.

种群会随着时间的推移而变化——它们会增长或减少。

The chart illustrate how a nation's population changed over time.

这张图表说明了一个国家的人口是如何随时间变化的。

He is an expert in human population changes at the Brookings Institution.

他是布鲁金斯学会研究人口变化的专家。

The arabica plant's population changed over thousands of years before humans began growing it.

在人类开始种植阿拉比卡咖啡树之前的数千年里，阿拉比卡咖啡的种群发生了变化。

And by studying these types of population changes, population ecologists can learn things that go beyond a single species.

通过研究这些类型的种群变化，种群生态学家可以了解到超越单一物种的东西。

Medical experts believe rising obesity and population changes are two of the reasons growing numbers of people are having diabetes.

医学专家认为，肥胖率上升和人口变化是糖尿病患者人数增加的两个原因。

It depends on how the population changes within the country.

这取决于该国人口的变化情况。

Even though the population changes over time, the number of representatives is always kept the same.

即使人口随着时间的推移而变化，代表的数量始终保持不变。

Joshua Apte explains that the main reason for this increase is population changes in these countries over time.

Joshua Apte 解释说， 这种增长的主要原因是这些国家的人口随时间发生变化。

Another population change after World War Two was in life expectancy. An American born in the early nineteen hundreds could only expect to live about forty-seven years.

二战后的另一个人口变化是预期寿命。一个出生于19世纪初的美国人，只能活47年。

By studying the Y chromosome, which is passed on from fathers only to their biologically male children, geneticists can predict how male populations changed and spread out over time.

通过研究仅从父亲传给生理上为男性的孩子的 Y 染色体，遗传学家可以预测男性人口如何随时间变化和分布。