A chance encounter about 1.9 billion years ago, led to life on Earth, say scientists.

New research finds that an amoeba-like organism engulfed a bacterium that had developed the power to use sunlight to break down water to make oxygen.

The bacterium could have been intended as prey, but instead became incorporated into its attacker's body, transforming it into the ancestor of every tree, flowering plant and seaweed on Earth today.

Paul Falkowski, professor of biochemistry and biophysics at Rutgers University in New Jersey  says that this single event transformed evolution of life on Earth.

"The descendants of that tiny organism transformed our atmosphere, filling it with the oxygen needed for animals and, eventually humans to evolve."

Amoeba-like organism: Preyed on the bacteria that would become the ancestor of every tree on Earth