John Mitchinson and John Lloyd, The book of general ignorance, 2006
p.156
What produces most of the earth's oxygen?
Algae.
They release oxygen as a waste product of photosynthesis. Their net oxygen output is higher than that produced by all the trees and other land-based put together.
Ancient algae are also the main constituent of oil and gas.
... [...] ...
One form of cyanobacteria, spirulina, yields 20 times more protein per acre than soya beans. It consists of 70 percent protein (compared with beef's 22 percent), 5 percent fat, no cholesterol, and an impressive array of vitamins and minerals. Hence the increasing popularity of the spirulina smoothie.
It also boosts the immune system, particularly the production of protein interferons, the body's front-line defense against viruses and tumour cells. [ what other plant foods, spices, ..., food combination (synthesis) boost the production of the body natural interferons; under what condition were these food grown, how long does these factors remain with the food after harvesting, what type of cooking, preparation, ... destroy and or preserve the boosting factors ]
... [...] ...
Its significance for the future may be that algae can be grown on land that isn't fertile, using (and recycling) brackish water. It's a crop that doesn't cause soil erosion, requires no fertilizers or pesticides, and refreshes the atmosphere more than anything else that grows.
(Mitchinson, John, 1963-, The book of general ignorance / John Mitchinson and John Lloyd., 1. Questions and answers, 2006, )
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oxygen
cyano bacteria
spirulina: 70 percent protein, 5 percent fat, no cholesterol, vitamins, minerals
boosts the immune system
boosts the production of protein interferons
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Ben Bova, New Earth, 2013
pp.211-212
p.211
Longyear's lean face was entirely serious. “I've been thinking about this planet's ozone
Jordan felt surprised.
“It's much thicker than Earth's”, Longyear said.
“Well, it has to be, doesn't it? Sirius emits much more ultraviolet radiation than our Sun does. The ozone layer screens out the UV, protects life on the planet's surface.”
“Exactly right”, said Meek.
Longyear leaned closer and asked, “But how did the ozone get there, in the first place?”
Jordan blinked at him. “As I understand it, the ultraviolet light coming in creates a reaction that turns some of the oxygen molecules high in atmosphere into ozone: oxygen-three, isn't it, where regular oxygen is a two-atom molecule.”
“Right”, said Longyear. “But how did the oxygen get into the atmosphere?”
Feeling as if he were taking a high school science exam, Jordan answered, “From living plants that give off oxygen as a result of photosynthesis.”
“Aha!” Meek pounced. “And how could plant life arise in the face of heavy ultraviolet radiation reaching the planet's surface?”
Jordan was puzzled by that. “Why ... how did photosynthetic plants arise on Earth? In the oceans, wasn't it? Single-celled bacteria in the water.”
“That's what happened on Earth, true enough”, said Longyear. “The so-called blue-green algae──”
“Cyanobacteria, actually”, Meek interrupted.
A frown flashed across Longyear's face as he continued, “Those single-celled creatures lived deep enough in the water so that the Sun's UV didn't reach them.”
“The water protected them”, Jordan said.
“Right. And over many eons, they pumped enough oxygen into Earth's atmosphere to allow an ozone layer to build up. The ozone layer protected the planet's surface from killing levels of ultraviolet and life could eventually evolve on land.”
p.212
Jordan spread his hands. “So the same thing has happened here, obviously.”
“Not so obvious, Jordan”, Longyear contradicted. Ticking off points on his stubby fingers, biologist said, “One, Sirius puts out so much UV that it's tough to see how life could have arisen n the first place.”
“Really? Even in the oceans?”
Raising a second finger, Longyear went on, “Which brings us to point number two : time. It took billions of years for life to evolve in the oceans of Earth. Billions of years for those cyanobacteria to generate enough oxygen to change the atmosphere and form an ozone layer.”
“This planet can't be that old”, Meek said. “Sirius itself can't be more than half a billion years old, from what Elyse Rudaki's told me.”
“That's not enough time for a thick ozone layer to be built up”, Longyear resumed.
“So how did it get there?” Meek demanded.
“How did life evolve on the ground without an ozone layer to protect it from lethal levels of US?” Longyear added.
Jordan looked at them: Longyear earnest, serious, troubled; Meek burning with righteous indignation.
“Life couldn't get started on the ground without a strong UV shield, a thick ozone layer high in the atmosphere”, Longyear repeated. “But the ozone layer couldn't get created until life spent billions of years producing oxygen.”
p.212
“I've run the numbers through the computer. Considering the level of ultraviolet that Sirius emits, and the time scale involved, there's no way that such a thick ozone layer could have been built up.”
p.213 geomagnetic field
“That's because there's no planetary magnetic field, as on Earth”, said Jordan.
“Uh-huh. And how did Adri's people evolve to the level of high technology without a geomagnetic field to protect them?”
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