The Power of Sunlight


Photosynthesis
3.4 billion years ago

All life needs energy to survive, and the biggest source of energy for life on Earth is the Sun. Some of the early micro-organisms evolved a way to use the energy from sunlight to make sugars out of simpler molecules. This process is called photosynthesis. But unlike green plants today, the first photosynthesising organisms did not release oxygen as a waste product, so there was no oxygen in the air.

See other: History of Life

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4 thoughts on “The Power of Sunlight

  1. Actually, Cyanobacteria or blue-green algae became the first microbes to produce oxygen by photosynthesis, perhaps as long ago as 3.5 billion years ago and certainly by 2.7 billion years ago.

    This, from Scientific American:

    For some untold eons prior to the evolution of these cyanobacteria, during the Archean eon, more primitive microbes lived the real old-fashioned way: anaerobically. These ancient organisms—and their “extremophile” descendants today—thrived in the absence of oxygen, relying on sulfate for their energy needs.

    But roughly 2.45 billion years ago, the isotopic ratio of sulfur transformed, indicating that for the first time oxygen was becoming a significant component of Earth’s atmosphere, according to a 2000 paper in Science. At roughly the same time (and for eons thereafter), oxidized iron began to appear in ancient soils and bands of iron were deposited on the seafloor, a product of reactions with oxygen in the seawater.

    “What it looks like is that oxygen was first produced somewhere around 2.7 billion to 2.8 billon years ago. It took up residence in atmosphere around 2.45 billion years ago,” says geochemist Dick Holland, a visiting scholar at the University of Pennsylvania. “It looks as if there’s a significant time interval between the appearance of oxygen-producing organisms and the actual oxygenation of the atmosphere.”

    Also, as single-celled organisms died, their decomposition process released minuscule amounts of oxygen. Over billions of years, the earth’s atmosphere ultimately arrived at the 21% oxygen level that it has continued to maintain to this day.

  2. Sadly for them but fortunately for us, during this time nearly 90% of all life on earth died as some organisms were able to evolve to thrive on oxygen, while most were not and went extinct.

    The early atmosphere of the earth was comprised almost entirely of methane, carbon monoxide, hydrogen sulfide, and ammonia. Visitors who savored the odor of rotten eggs and bleach would have felt right at home.

  3. Exactly.

    Hard to realize that the death of a tiny organism, or at least many such organisms, could change the atmosphere of an entire planet. And ironic that the deaths of those that couldn’t adapt to the strange new gas, actually hastened the process.

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