英语听力：探索发现 科学新发现：我们的大气层-10（在线收听） |
Evidence of the first oxygen in the atmosphere. The gas was released by a humble microscopic living organism called cyanobacteria. Well it turns out cyanobacteria are the only things that can actually produce oxygen, so we know that at some point cyanobacteria colonized enough of the planet in order to produce enough oxygen that it became resident in the atmosphere. As the microbes multiplied and spread, the gas built up in the air, transforming the planet in a process known as the Great Oxidation Event.
Oxygen is very powerful. The world got turned upside-down. Everything has to begin to adapt to now a completely new atmosphere where oxygen is dominating.
First the oxygen reacted with the oceans, causing iron within them to form rusty deposits on the seafloor. Then its effects reached dry land. It reacted with soil and rock, giving them a reddish, rusty tinge. And once these minerals had absorbed their fill of oxygen, the gas began to gather in the atmosphere with dramatic consequences for life.
Complex animals could have much higher metabolisms because of the sheer potential that oxygen provided for them, a whole different kind of evolution was able to take place. Powered by oxygen, life evolved from single-celled organisms to complex animals. |
| 原文地址：http://www.tingroom.com/lesson/yytltsfx/2014/284450.html |