Welcome, everybody, to this week's post! Today, I talk about a massive explosion of life...
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| A map of Earth displaying the predicted locations of the continents at 541 million years ago, the beginning of the Cambrian. Source: Wikipedia |
So, we left off at the beginning of the Cambrian period, 541,000,000 years ago. (That's a LOT of zeroes...)
Cambrian Period (541 million years ago - 485.4 million years ago)
At the beginning of this period, life was simple. Most organisms were single-celled, and those that weren't were still tiny. But something happened. We don't actually know what that something was, but we know it happened. And life exploded! Suddenly, evolution sped up. All kinds of lifeforms appeared - some big, some small. Most animals appeared then!
It seems everything happened there and then... but some things still didn't. The seas were indeed warm and rich, and were the stage for everything I mentioned previously. However, the land was still dry and almost devoid of life. There was some oxygen in the atmosphere, and so some molluscs emerged from the sea to graze on the biological soil crust (a thin film of microbes living on the surface of the soil.)
Now, the presence of a microbial soil crust tells us that the Cambrian Earth's land was quite arid - it'd probably have been almost impossible to find a place that wasn't a desert. Also pertaining to the land, pay attention to the position of the continents. You can see that most of Earths land at that time was concentrated around the South Pole.
Earth's mean temperature over the 55.6 million years was about 21 °C, 7 °C above today's mean temperature of 15 °C. The level of oxygen was around 12.5% of the atmosphere, below today's average of around 21% and the level of carbon dioxide was around 4,500 parts per million - sixteen times higher that before the Industrial Revolution, and still around 10.5 times higher than today's levels of around 400 parts per million.
As I have mentioned, it was my birthday on Tuesday. I made a post on Instagram to celebrate it and I thought that it'd be nice to show it here. So here it is:
So then, I'll be seeing everybody next week - bye for now!