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| (i) Life emerges; epoch of geochemistry begins. (ii) Anoxygenic photosynthesis: start of energy epoch 2, sunlight. (iii) Emergence of cyanobacteria. (iv) Great Oxidation Event: energy epoch 3, oxygen. (v) Probable eukaryotic fossils appear. (vi) Fossils of red algae appear. (vii) Start of energy epoch 4, flesh. (viii) Vascular plants colonize land; fire appears on Earth. Finally, the burning logs indicate the start of energy epoch 5, fire. The dates of (i)–(iii) are highly uncertain. For (i) I have taken the earliest date for which there is evidence consistent with life20. For (ii) I have taken the earliest date for which there is evidence consistent with photosynthesis18,19,21. For (iii), I have marked the date currently supported by fossil evidence for the presence of cyanobacteria (see main text, ‘Cyanobacteria and the oxygenation of the air’). Tick marks represent intervals of 25 million years. Figure drawn by F. Zsolnai. |
Monday, 15 May 2017
Key events during the energy expansions of evolution
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  The Shroud of TurinThe subject of intense study, the Shroud of Turin is a linen cloth bearing the image of a man who appears to have been crucified. Though carbon dating places the shroud's origin in the Middle Ages, some believe the image on the cloth is that of Jesus of Nazareth, recorded on the shroud at the time of his proclaimed resurrection. Skeptics, however, have dismissed the shroud as a medieval forgery created using paint or even crude photography. How recently did the shroud undergo carbon dating? More... Discuss |
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This Day in History
 Volvo Car Company Founded (1927)In 1924, Assar Gabrielsson, sales manager at the Swedish ball-bearing manufacturer SKF, and engineer Gustaf Larson decided to build an automobile that could withstand Sweden's rough roads and harsh climate. Their first car—nicknamed "Jakob"—rolled off the line on April 14, 1927, which Volvo considers its founding date. The following year, they created a truck that was immediately popular and contributed to the company's early success. The name Volvo is Latin, not Swedish, and means what? More... Discuss |
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Today's Birthday
 Julie Frances Christie (1941)Christie is a British actress who became an icon of the 1960s "Swinging London" era. Just four years after she made her film debut, she won an Academy Award for her performance in Darling (1965). Throughout the course of her long career, she has been notoriously selective about the roles she accepts and has appeared in such notable films as Dr. Zhivago and Hamlet. After resisting the idea of marriage for many years, Christie finally married for the first time at what age? More... Discuss |
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In the News
unornamented discuss | |
| Definition: | (adjective) Lacking embellishment or ornamentation. |
| Synonyms: | unembellished, plain, spare, bare |
| Usage: | Strangers, who saw her for the first time, saw a lady in the prime of her life—a lady plainly dressed in unornamented white. |
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 A man can never quite understand a boy, even when he has been the boy.Gilbert Chesterton (1874-1936) Discuss |
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