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Green algae grow at the edges of a glacial lake in Wales. Hundreds of millions of years ago, similar algae adapted to survive temporarily outside of the water may have kicked off the evolution of green land plants.
Algae didn't always hang out in the seas, but one fateful day, about a billion years ago, a simple bacterial cell swallowed a cyanobacteria cell, writes Ed Yong at The Atlantic. This chance occurrence allowed the bacteria to produce energy from the sun, a process known as photosynthesis.
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