How Cyanobacteria Created (and Nearly Destroyed) Life on Earth

For life to have occurred on Earth, an infinite number of factors had to play out just right. Among those factors: cyanobacteria. These organisms are the reason we have oxygen in the air to breathe. But the little life-givers also caused the first mass extinction on the planet. Bacteria giveth and bacteria taketh away.

The TED-Ed video lesson below was written by biologist and cyanobacteria expert Anusuya Willis, narrated by Julianna Zarzycki, and animated by Augenblick Studios. It offers a brief history of the little single-celled organisms that could—from their first days as anaerobic microbes some 3.5 billion years ago through developing the ability to photosynthesize, and on to their oxygen-pumping, life-demolishing days as the instigators of the The Great Oxygenation Event (or the Oxygen Catastrophe), in which nearly all life on Earth was annihilated about 2.5 billion years ago.

It’s not all bad news, though. Later on, the oxygen levels in the atmosphere stabilized to the roughly 21 percent we enjoy today. That led to a mess of microbes that could photosynthesize, which eventually became plant cells. Cyanobacteria are still found everywhere today—and thanks to them, so are we.

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