First Life

Unicellular cyanobacteria. Copyright Microbial Diversity, Rolf Schauder and David Graham, 1997.

First Life

3.9 to 1

Billion Years Ago

Cyanobacteria. Copyright Microbial Diversity, Rolf Schauder and David Graham, 1997.

Life on Earth

3.9 billion years ago

The arrival of life on earth happened almost 4 billion years ago. It started as a simple microbe and for 3 billion years - almost three-fourths of all the time Earth has been in existence - living organisms never grew larger than a single cell. Yet small as they were, some of these tiny microbes slowly transformed Earth's environment.

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The Age of Microbes

Solar-Powered Bacteria

3.8 billion years ago

Shortly after life appeared here a group of blue-green bacteria, or 'cyanos,' developed Earth's first solar powered energy system, breaking down carbon dioxide through photosynthesis and creating oxygen. The photographs above are pictures of such unicellular cyanobacteria taken in laboratory conditions.

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Photosynthesis

First Super-continent

2.5 billion years ago

Over time, Earth's relatively brittle crust has been broken by heat from below and meteors from above into 8 large and 7 smaller pieces called tectonic plates. 2,500 million years ago, the plates were huddled together as Earth's first super-continent. Since then, the continents have bunched together and split apart again 3 or 4 times.

The Grand Canyon. Copyright P.L. Sissons, for conditions of use see Copyright and Acknowledgments link on the Home page.

This constant rearranging of Earth's basic floor plan is quite unsettling and has created some pretty drastic upheavals. The rocks which form the base of the Grand Canyon (photograph above) are attributable to continental drift 1.7 billion years ago.

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Continental Drift

The Great Oxygen Poisoning

1.8 billion years ago

Oxygen released through photosynthesis inexorably accumulated. Over 2 billion years, this oxygen eventually created pollution on such a scale that it became lethal for almost all early bacteria. They were anaerobic, which means they were poisoned by the oxygen they produced, just as we would be poisoned by the carbon dioxide we exhale. It led to one of the greatest mass extinctions Earth has ever witnessed.

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Pollution

Tiny Plants and Pre-animals

1.7 billion years ago

What happened after the great oxygen poisoning is one of the turning points in Earth history. Single-celled bacteria began to incorporate other bacteria. Instead of being digested, the captured bacteria were kept intact to contribute their special capacities to the larger cell. The first plants evolved by incorporating blue-green bacteria which gave them photosynthesizing capacity. Tiny pre-animals evolved by incorporating aerobic bacteria, giving them the mechanism for respiration which is used by all animals.

Fungi - the world's first recyclers

Fungus in the Catskills. Copyright P.L. Sissons. For conditions of use see Copyright and Acknowledgements link on the Home page.

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The Ecosystem

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© Copyright T. H. Sissons "All of Time Online" 2004-2006 all rights reserved , except for The cyanobacteria photographs at the top of this page which are © Copyright Microbial Diversity, Rolf Schauder and David Graham 1997