評論
打印
Many millions of years later, the first extremely small plants began to appear on the surface of the water.
好幾百萬年以后，水的表面開始出現了極小的植物。
They multiplied and filled the oceans and seas with oxygen, which encouraged the later development of early shellfish and all sorts of fish.
它們繁殖起來就使得早期的海洋充滿了氧氣，這為早期的貝類及其他各種魚類的發育進一步創造了條件。
Next, green plants began to grow on land.
接著，綠色是植物開始出現在陸地上。
They were followed in time by land animals.
隨后，陸地上出現了動物。
Some were insects.
其中有一些是昆蟲。
Others, called amphibians, were able to live on land as well as in the water.
另外一些叫兩棲動物，既能生活在陸地上水里，也能生活在水里。
Later when the plants grew into forests, reptiles appeared for the first time.
后來，當這些植物成長為森林，爬行動物首次亮相。
They produced young generally by laying eggs.
它們一般是通過孵蛋而繁衍后代的。
After that, some huge animals, called dinosaurs, developed.
再后來一些叫做恐龍的巨型動物出現了。
They laid eggs too and existed on the earth for more than 140 million years.
它們也生蛋，在地球上生存了一億四千多年。
However, 65 million years ago the age of the dinosaurs ended.
然而，六千五百萬年前，恐龍時代結束了。
Why they suddenly disappeared still remains a mystery.
它們為什么會突然滅絕至今仍是個謎。
This disappearance made possible the rise of mammals on the earth.
恐龍的滅絕使地球上哺乳動物的產生有了可能。
These animals were different from all life forms in the past, because they gave birth to young baby animals and produced milk to feed them.
哺乳動物不同于以往所有的生物形式，因為它們能從體內生產出幼仔并給幼仔哺乳。
Finally about 2.6 million years ago some small clever animals, now with hands and feet, appeared and spread all over the earth.
最后，大約260萬年前，一些小巧聰明、長著手腳的動物出現了，它們散布在地球的各個地方。
Thus they have, in their turn, become the most important animals on the planet.
于是，他們接著成為了這個行星上最重要的動物。
But they are not looking after the earth very well.
然而，他們對地球卻并不怎么在意。
They are putting too much carbon dioxide into the atmosphere, which prevents heat from escaping from the earth into space.
它們把過多的二氧化碳釋放到大氣層中，這使得地球上的熱不能釋放到太空中去。
As a result of this, many scientists believe the earth may become too hot to live on.
因此很多可科學家相信地球可能會因此變得太熱而不適合生物的生存。
So whether life will continue on the earth for millions of years to come will depend on whether this problem can be solved.
所以，在未來的數百萬年中，生命能否在地球上延續取決于這個問題能否得到解決。
