The Oxygen Disaster. How Earth's biosphere was turned inside out 2.45 billion years ago
The oxygen disaster is an important event in the history of life on our planet. It led to the death of some organisms while giving life to other, more advanced multicellular organisms. Let's examine why the oxygen disaster occurred and what consequences it had.
Our planet appeared 4.54 billion years ago. The first signs of organic matter on Earth date back to about 4 billion years ago. That is, the Earth wasn't a lifeless planet for that long.
Archaea is the name given to a very long period in the history of life on Earth. The first life on Earth did not use oxygen in its chemical reactions to produce energy.
The first prokaryotes - that is, simple unicellular cells without a formalized nucleus - gradually evolved into bacteria and cyanobacteria. Cyanobacteria are rather large bacteria capable of photosynthesis and producing oxygen.
Bacteria lived benthic lifestyles - literally, life at the bottom. Bacteria covered the bottom of the ocean in a thin layer.
Most of the bacteria were anaerobic to begin with. That is, they used mechanisms to generate energy without using oxygen. Such mechanisms are still common today. For example, when you give your muscles a strength load (lifting a barbell), they get their nutrition from creatine phosphate. And you switch to oxygen supply when you do prolonged endurance exercise - such as walking or running.
At the end of the Archean, cyanobacteria developed rapidly over 300 million years. And the world began to gradually become saturated with oxygen.
At a certain concentration of oxygen, the process began to increase. Anaerobic microorganisms began to retreat, giving way to new, more efficient species. The anaerobic ones were pushed into their niches of habitat. Conversely, the aerobic (oxygen-using) ones emerged from their niches and populated the planets.
As scientists say - the biosphere was turned inside out.
What the oxygen disaster led to
The emergence of complex organisms. By modern standards, there still wasn't much oxygen in the atmosphere after the oxygen disaster. We could hardly breathe without an oxygen tank. Hydrogen sulfide and carbon dioxide dominated the atmosphere.
But even paltry amounts of oxygen were enough for the rapid development of wildlife. Mushrooms, large algae, and the first animals, sponges, appeared.
The ozone layer appeared. Ozone consists of three oxygen atoms. Its thin layer formed in the stratosphere. It is protection from the most aggressive ranges of ultraviolet light.
Without the ozone layer, the spread of life on land would be extremely unlikely. And even in the ocean, life would still live on the bottom.
The Huron glaciation. But it was not without a fly in the ointment for life on Earth.
This is what the Earth would have looked like from space during the Huron glaciation.
The proportion of greenhouse gases in the atmosphere began to decrease. The main contributor to the greenhouse effect at that time was methane. Methane was more than 20 times more effective than carbon dioxide for creating the greenhouse effect.
Methane began to actively bind with oxygen, turning into carbon dioxide and water. Heat became less trapped and the temperature began to cool dramatically.
The temperature on Earth dropped to minus 40 degrees. This was one of the largest glaciations in the history of the planet and lasted 300 million years.
When the glaciation ended, life boomed. Multicellular evolution blossomed. A fairly complex and sophisticated animal appeared: the spryggina. Spryggina was only five centimeters long. However, this animal is the most likely candidate for being the ancestor of all modern multicellular animals, including humans.