00:01
Let's talk about the nitrogen cycle, but take out the plants because we want to explore how soil bacteria could sustain the nitrogen cycle before land plants evolved.
00:16
So nitrogen enters the world by way of bacteria and other single -celled prokaryotes.
00:22
They convert atmospheric nitrogen into biologically usable forms in the process of nitrogen fixation.
00:34
And so these nitrogen -fixing bacteria are free -living in the soil.
00:38
Others are beneficial sibeats that live inside plants, but we're going to focus on the free -living ones in the soil because this is before land plants have arrived.
00:50
So these nitrogen -fixing microorganisms capture that atmospheric nitrogen, this end to, and convert it into ammonia.
01:01
Which is nh.
01:06
And this ammonia can be taken up by plants and used to make organic molecules.
01:12
However, if the plants aren't there, it's just going to remain in the soil.
01:17
Or it is going to be taken up by nitrifying prokaryotes...