Oxygen

The discovery of oxygen is often split between English chemist Joseph Priestly and Swedish apothecary Carl Schelle, and the French tax-collector and father of modern chemistry Antoine Lavoisier. Oxygen was said to be a dangerous poison that will kill us. It's hailed as the "Elixir of Life".

Oxygen was originally called "dephlogisticated air" by Joseph Priestley.

At the height of the French Revolution, he was accused of tax fraud and selling adulterated tobacco, then guillotined despite appeals to spare his life in recognition of his contributions to science.

Today Earth's oxygen rate is 21% and 79% rate of nitrogen, along with carbon dioxide, neon as the 1%.

But Lavoisier's story of oxygen might be false. In 1604, 170 years before Lavoisier and company, the Polish alchemist Michael Sendivogius wrote that "Man was created of the Earth, and lives by virtue of the air; for there is in the iar a secret food of life... whose invisible congealed spirit is better than the whole Earth.

The word "oxygen" is derived from the Greek word for "acid-former", for the mistaken belief that oxygen is crucial for all acid formations. 

Though, it's needed for some (like sulphuric and nitric acids), but not those like hydrochloric acid.

Oxygen therapies picked up after a number of reports that indicated that higher oxygen pessures did affect health.

Scottish physiologist John Scott Haldane, used oxygen to treat injuries caused by chlorine gas in WW1. He stated in his book "Respiration" in 1922, that some patients with respiratory ciculatoty and infectious conditions could be cured by continuous oxygen inhalation. But even today, it's unclear how his beneficials his therapries are. A New England journal in 20000 showed that inhalation of 80% oxygen for 2 hours caused the risk of wound infection after colorectlca surgery, compared with routine practice (30% oxygen for 2 hours).

Astronauts often breath pure oxygen for weeks, though the capsule in space is pressurized to only 1/3 of atmospheric pressure, making it like breathing 33% oxygen. The contrast that pressure makes to the oxygen concentration in the atmosphere shows why 3 astronauts died when Apollo 1 caught fire in 1967, on testing ground. The capsule in space is always pressurized to a higher pressure than the surrounding vacuum, meaning that spacecraft are built to wiststand greatetr pressure inside than outside. To keep the pressure difference, Apollo 1 is pressurized to above atmospheric pressure while on gruond. But, the spacecraft was still ventilated with pure oxygen, meaning that instead of atmospher equal to 33% oxygen, the crew were actuallly breathing the equivalent of 130% oxygen. In the oxygen-rich atmosphere, a spark fromthe electrical wiring led to an uncontrollable fire, reaching a tempearture of 2500°C in minutes.

Oxygen is more than just fire risk: It's toxic to breath, depending on the concentration and duration of exposure.

The realization that oxygen is toxic came from earliest scuba diving experiences in the 19th century. The word “Scuba” was later coinage and stands for self-contained underwater apparatus. Divers were vulnerable as they carried their apparatus with them and usually breathed pure oxygen. The apparatus’ oxygen at depth below 8 meters causes seizures similar to an epileptic grand-mal, a disaster if the diver loses consciousness underwater. French physiologist Paul Bert first described oxygen convulsions. He discussed the effect of oxygen on animals subjected to different pressures in a hyperbaric chamber. Very high oxygen concentrations caused convulsions and death in minutes. A decade later, Scottish James Smith showed that lower oxygen levels are as deadly, but delayed. Animals exposed to 75%+ oxygen (at normal air pressure) had such serious inflammation of the lungs after a few days that they died. For this, oxygen dosages in hospitals are always strictly controlled. Paul Bert and James Smith are still commemorated in diving terminology. Oxygen is roughly ⅕ of atmosphere pressure, so pure oxygen at 2-atmosphere pressure is 10x normal exposure. 

Most free radicals of biological importance are simply reactive of forms of molecular oxygen, which can damage biological molecules. Oxygen always acts in exactly the same way: All oxygen toxicity are caused by formation of free radicals from oxygen. The idea that breathing oxygen causes aging is very simple. We produce free radicals continuously inside all of our body cells as they respire. Most are most “mopped up” by antioxid and defence, which neutralize their effects. The issue is that our defense aren’t perfect. A portion of radicals of free radicals slip through the net and these can damage vital components of cells and tissues, like DNA and proteins. The damage will gradually accumulate until it finally overwhelms the ability of the body maintains its integrity. The gradual deterioration is known as ageing.

Chpt 1

In the start, there was no oxygen. 4 billion years ago, the air probably contained about a partin amillion of oxygen. The atmosphere today is less than 21% oxygen.

Many oxygen-hating organisms still exist. They die at an oxygen level above 0.1%. They're said to be anaerobic - they don't use oxygen and often have to live in its absence. Many evolved to evolve their antioxidant protection, after the rise in atmospheric oxygen. If this assumption is true, then the big rise in atmospheric oxygen must serious challenge to early life.

• antioxidant: 

According to the free-radical theory of ageing said earlier, oxygen toxicity sets limits on lives. 

• radical: 

The following sections will explore facts about ageing and death.

Stanley Miller and Harold Urey in the US, in the 1950s passed electric sparks (simulating lightning) through a gaseous atmosphere comprising the 3 Jupiter gases and collected the end-product).

The last common ancestor of all known life, LUCA (Last Universal Common Ancestor), is thought to have used traced oxygen to respire, even prior her descendants learning to photosynthesize (at least to create oxygen). Instead of with fermentation, the first cells are thought to have extracted energy from many inorganic elements,and compounds like nitrate, nitrite, sulphate, sulphite, and oxygen. If this is true, LUCA may have been resistant to oxygen toxicity prior to there was any free oxygen in the air.

The more antioxidants consumed, the more we can protect ourselves against free radicals, which is why fruit and vegetables are healthy; they have many antioxidants. Many today supplement their diet with potent antioxidants thinking that their diet can't give a needed supply. The implication is that if enough of the right antioxidants are consumed, ageing can be delayed forever, which has been touted as "the antioxidant miracle". The truth is more complicated.

Where did Earth's modern atmosphere come from? The answer may be volcanoes. Along with emitting sulphurous fumes (precipitated in rains), volcanic gases have nitrogen, carbon dioxide (in about the right balances), a bit of neon, and no methane, ammonia, or oxygen. Where did its oxygen come from? 

Only 2 sources are in the air. The most important is photosynthesis, process in which plants and cyanobacteria use sunlight energy captured by green pigment chlorophyll to 'split' water. The splitting of water releases oxygen, that's discharged into the atmosphere as a waste product, while the chemical energy derived from the split is used to bind carbon dioxide from the air and package it into sugars, fats, proteins, and nucleic acids making up organic matter. Photosyntsis thus uses sunlight,water, and carbon dioxide to produce organic matter. It It gives off oxygen as waste product. If photosynthesis is the only living process, oxygen wold proceed to build up in the air until the plants used up all the available carbon dioxide. Then everything would grind to a halt. Clearly this has not been the case. 

Most oxygen today produced by plants is used by animal, fungi, and bacteria respirations, using oxygen to burn up or oxidize the organic material taken in as a food, extracting energy for the organism's use and releasing carbon dioxide back into the air. As organisms consume organic matter coming from another one,they can be classed together as consumers, which gain their energy through the respiration (controlled burning) of sugars, fats, made by main photosynthetic producers. THe overall reaction of respiration,win which oxygen and sugars are consumed and the waste products carbon dioxide and water are produced, is almost exactly the opposite of photosynthesis. Oxygen from photosynthesizers are almost utterly used by animals.

Solar energy, mainly ultraviolet rays can split water to form hydrogen and oxygen without biological catalyst. Hydrogen gas is light enough to escape Earth's gravity. Oxygen, a heavier gas, is retained in the atmosphere by gravity.  

The Mars Global Surveyor has been observing Mars since 1999 and has detailed images of sedimentary rocks that NASA says probably formed in lakes and shallow seas. Erosional channels show that flowing water have once existed on Mars. Whether these oceans drained away under Mars' surface or evaporated into space is unknown.

Unlike Earth, Mars and Venus have oxidized slowly and never accumulated oxygen in their atmospheres. The critical contrast between Earth and other planets may be the oxygen rate formation. If oxygen is formed slowly, not faster than rate at which new minerals and gases are exposed by weathering and volcanic activities, then all this oxygen will be consumed by the crust instead of increasing in the air.

Life saved the Earth from the same fate of Mars and Venus. The oxygen injection of photosynthesis overwhelmed the available exposed reactants in Earth's crust and oceans, letting free oxygen accumulate in the atmosphere and then stop water loss. 

Creator of the Gaia hypothesis James Lovelock estimates that today's oxygen rate is 300k tons or 3 million tons of water a year, which would take 4.5 billion years to lose just 1% of the Earth's ocean. Life on Earth is thanks to photosynthesis. 

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Rock can dissolve carbon dioxide, which is weakly acidic, causing carbon dioxide to be lost from the air and petrified in carbonates. But when glaciers form over land, the underlying rock becomes insulated from the air by ice layers, meaning that rock erosion rates by carbon dioxide is cut to a fraction and the carbon dioxide stays in the air, in which carbon dioxide builds up in the air, as it's also emitted more or less continuously from active volcanoes. 

As carbon dioxide is a greenhouse gas, the effect it produced increased greenhouse effect. Earth's surface gets warmer. Global warming halts the spread of glaciers from the poles. Today, anywhere there are large land masses around the poles any spread of the polar glaciers to the Equator is offset by the greenhouse effect getting stronger whenever the glaciers advance and weaken whenever retreating. 

• to halt: to stop ("halte" in French)

In the Precambrian snowball Earth, as continents clustered together in tropics, glaciers formed by poles over sea only, which couldn't affect the rate of rock weathering on the continents. The rocks kept on drawing down carbon dioxide from the air. Atmospheric carbon dioxide levels began to fall. The gradual draw-down of carbon dioxide had an anti-greenhouse effect, encouraging the spread of glaciers. There was nothing to stop the advance: the equatorial continents kept sucking up more and more carbon dioxide. Worse still as the glaciers marched on to the Equator, they reflected the Sun's light and heat, cooling the planet further, sending the Earth to cool and covered in ice, reflecting back the Sun's heat, causing Earth to risk to stay as an eternal snowball. Yet today, Earth is fine.

Why? When the equatorial continents were finally sealed under the ice, the continuous draw-down of carbon dioxide by rock weathering ceased. Without liquid water exposed to the atmosphere; no evaporation, no rain. Any carbon dioxide stayed in the air. All climatic traffic between the air and the frozen seas and buried rocks stopped. Deep under Earth's surface, vulcanic forces were oblivious to the icy crust. Active volcanoes burst through the ice, spewing volcanic gases into the air with carbon dioxide. Over million of years, carbon dioxide accumulated in the air again, re-warming Earth and melting ices. But the continents' juxtaposition of around the Equator proceeded to set the same snare: the whole crazy snowballing and melting repeated itself as many as four times before they were finally dispersed to the four corners of Earth by forces of plate tectonics. This story is hypothetical, but Joseph Kirschvink and others dispelled that glaciers have enchouched the Equator at that time.

• juxtaposition: 

Another way that life may have survived a snowball Earth is methane production, another greenhouse gas, melting the ice or maybe Earth was a slushball, not a snowball, where the sea never fully froze. 

The accumulation of oxygen at that time shows that erosion rate risen back then, which may have been where the evolution of the first animals took place, the Vendobionts.

Erosion rate can be estimated with the measure of the 2 strontium ratio in marine carbonates: strontium-86 and strontium-87. Earth's crust is rich in strontium-87 and its mantle is rich in strontium-86. 

For 2 billion years before sulphate-reducing bacteria, sulphide creation processes of reducing bacteria caused the sedimentary iron sulphide to become enriched in sulphur 32 by roughly 3% compared with background ratios, then 590 million years ago, sulphides in sediments became enriched by roughly 5% ever since, which is nearly diagnostic of today's ecosystem. 

The figure of 3% is simple. Sulphate-reducing bacteria rely on a one-step conversion of sulphate into hydrogen sulphide, a process that enriches the sulfur-32 in hydrogen sylphide by about 3%. Enriched hydrogen sulfide is then free to react with iron to make pyrites. The issue is that 5% enrichment cannot be achieved by a one-step process bacterial process, but canonly happen in an ecosystem recycling its raw material the same way that we concentrate carbon dioxide form our breath by repeadtely breathing in and out of a plastic bag. In hydrogen sulfide's case, the recycling needs oxygen.

Canfield and Teske proposed that "modern" ecosystems need modern level of oxygen, started to develop soon after the last snowball Earth. They back their conclusion by molecular clock calculations, which confirm an increase in the number of sulfur-metabolizing bacteria species. Thus they project a rise in atmospheric oxygen to nearly modern levels in the Precambrian'sfinals years.

The second way that points to a rise in free oxygen is the pattern of so called rare earth elements. The relative amounts of these trace elements like cerium, in marine carbonates depends on their abundance in sea water at the time, and this depends on their solubility. The solubility of many elements differs according to oxygen level. It's seen that iron is less soluble in presence of oxygen whereas uranium becomes more soluble. If a shift in the relative concentrations of many elements in rocks, it indicates of the oxygenation degree of the seas at the time of their formation.

We emerge blinking, then from the Varanger ice age (last snowball Earth) which ended some 590 milion years ago when it had seas and air well enough for us to breath. Admist a few millions years of the dawn of a new and better world, the first big animals known as Vendobionts floated in shallow wters and worms wending their way through the muddy bottoms of the continental shelves worldwide. 

In Nature in 1995m Graham Logan and others argued with Nietzsche that we owe our most god-like traits to the primal need for defecation. Fecal pellets from the first big animals spotted cleansed the oseasm paving the way for the Cambrian explosion.

The fall lof Vendobionts to predaitrs are bog, but its certain that the rising atmosphere oxygen did correlate with radiartyopns in biological  diversity in the Precambrian era

insert a geologicaltimline of the late precambrian period and cambrian explosion

The amountof energy determines the length of all food chain lost fromone level of the chain to the next. This in turn depends on the efficiency of energy metablosim, whic is mostly less than 10% efficient in without oxygen (less than 10% ofthe total energy available in the food is extracted). If this organism is eaten in turn,the energy available to the predator is less than 1 % of the originally synthesized bythe main producer. THis is the end of the food chain: beow a 1% threshold there's simply not enough energy available to eke out a living, resulting food chains to be very short without oxygen. Bacteria are often are specialized or compete for scarce resource, rather than eating each other. In contrast oxygen powered respiration is about 40% efficient in energy extraction, meaning that th 1% energy threshold is crossed only at the food chain's 6th lvl. Abruptly carnivorous food chains pay and the predator is born. The dominant position of predatorrs in modern ecosystems isn't possible without oxygen. It's no fluke that the Cambrian animals were the Earth's first predators. Predation is a powerful stimulus to weight gaining both predators and prey, either to eat larger prey or to survive. Big size needs structural support, lignin, and collage, and oxygen for their synthesis. Lignin is best known as the cement binding cellulose into a strong and flexible matrix in forests. As the paper necessitates the expensive and time-consuming chore of removing most of the lignin, commercial interest has been in genetically modifying plantation trees to produce less lignin. Collagen is the animal world's answer to lignin. It's a protein and essential part of the supporting connective tissues in flesh, skin, around organs, and the tendons at joints. Before constructing, bonus oxygen atoms must be used into the protein collagen-chains, cross-linking them together to form triple-chain molecules like a rope. Growing older, more of a body's collagen cross-links form, so meat from older animals is tougher than younger ones.

Ozone is good at absorbing ultraviolet rays so once a thick ozone layer is built, the penetration of damaging ultraviolet rays into the lower atmosphere is cut by a factor of 30+. 

It's said that oxygen can be the cornerstone of Precambrian evolution and it's very possible that rising-oxygen level was the key for the Precambrian period to evolve. The deadlock of was broken by a second snowball Earth that catapulted oxygen to modern levels. To look for extraterrestrial life, we must look for volcanoes, plate tectonics.

No clear proof shows that free oxygen caused a global holocaust inte Precambrian,but there's a big contrast between modern oxygen level of 21% to Carboniferous of 35%.

Insect flight mechanics is complex. A nameless Swiss aerodynamicist proved that bumblebee can fly nor glide.

J. M. Wkeling and C. P. Ellington said that our grasp of dragonfly earodynamics is limited by a poor understanding of the interactions between the wingsand that we are unable to model their aerial performance for sure.

Because fires consume oxygen they’re assumed to limit the atmosphere’s oxygen accumulation. Without human meddling, fires are often ignited by lightning strikes. Now most lightnings don’t start fires as forest vegetation is damp, mainly when electical storms are accompanied by 

• damp: slightly wet

• torrential: falling/flowing rapidly

torrential rain. But if we organic matter burns freely in air with 25%+ oxygen given an atmosphere with such levels, lightnings could trigger conflagration even in rain forests. 

• conflagration: big fire destroying a big area/property

The higher the oxygen level, the greater chance of fire and as the fires rage they use up excess oxygen. If oxygen levels rise too high fire would restore the balance. Charcoal is nearly indestructible by organisms, including bacteria. No form of of organic carbon is likely to be buried intact. As oxygen only accumulate in the air if there’s a n imbalance between how much oxygen is produced by photosynthesis and the amount consumed by respiration, rocks, and volcanic gases. Non-buried organic remains aren’t oxidized of oxidized to carbon dioxide, so the oxygen is left over inthe air. A scharcoal is more likely to be buried intact than usual decaying plant matter, a forest fire’s net result is to increase carbon burial and thus to raise the atmospheric oxygen, which in turn make fire more likely and pushes up oxygne until there’s no life on land. Only then, when all organic production and photosynthesis on land has ceased,can oxygen levels dwindle slowly as the gas is removedby reaction with eroded minerals and volcanic gases. Id maybe a spore remains, life can come back, but if it does, the ecycle of flames and destruciton iterate nonstop. Fire is a very poor control of atmosphreic oxygen. This is familiar with environmental scientists who try to model changes in atmospheric composition but there

Methane-producing bacteria thrive in stagnant swamps where oxygen levels are very low and cannot tolerate higher levels. They gain energy by breaking down organic remains there to release methane gas, which is no trivial process. Lovelock guess roughly 400 million tons of methane are emitted intot the atmosphere annually. 

Sometimes, plant growth can be halted utterly, called photorespiration and unlike the plant'snormal mitochondrial respiration, taking place only in sunlight.Itspurposeis a mystery the net effect si that the plant takesup oxygen and and releases carbon ioxide, which parallels normal respiration (as it implies) but fails to create energy. Unlikenormal respiration, photorespiration competes with photosynthesis for the enzyme uses known by the sonorous acronymn of Rubisco (stands for ribulose-1, 5-bisophate carboxylase/oxygenase). This underminesthe efficiency of photosynthesis and reduce plant growth.

Rubisco is the enzyme binding carbon dioxide and incorporates it into carbohydrate in photosynthesis. It's the most abundant enzyme and often justifiably said to be the most crucial enzyme worldwide. 

Despite being futility, photorespiration is almost universal for plants, though many have evolved ways of reducing its detrimental effects.

Photorespiration is a particular problem for C3 plants (like trees and shrubs). Grasses are often C4 plants and esfapethe worst excesses of photorespiration by compartmentalizing their photsynthesic machinery. They pcature carbon dioxide and then release it in large amounts into the cellular compartment containing Rubisco.

This shows why photores photorespiation is less needed at low oxygen levels and more needed at normal or higher levels. 

Plants that evolved in the Carboniferous (ferns, gingko, and cycads) were less sensitive to increase oxygen that plants that evolved more recently, like the angiosperm, the largest plant groups today. The older plants were also more likely to adapt to the new conditions by changing their leaf structures. These plants increased the numbers of stomata (pores through which gases enter and exit leaves) allowing more carbon dioxide to accumulate in the leaf. Though carbon dioxide levels often fall as oxygen rises, many agree that they fell from high point of roughly 3000 per million in the Devonian (385 million years ago) to as low as 300 parts by the Permian (245 million years ago). 90% of the world's coal reserves date to a a period accounting for less than 2% of the Earth's history, thus coal burial rate was 600 times faster than the average for the rest of geological time. Most organic matter isn't buried as coal. 

The event of the continent together, the Pangaea is one of the explanations for the high carbon burial rate in the Carboniferous and early Permian invokes an accidental alliance of geology, climate and biology.

Continents converged to form a supercontinent called Pangaea. The unparalleled between Carboniferous and early Permian is by a very high rate of lignin production, a very low rate of lignin breakdown and nigh-perfect conditions preserving organic matter on an unprecedented scale. Overall, to determine how much oxygen levels, it's done by knowing how much organic matter was buried before. It's said that older rocks are more likely to been utterly lost by erosion or metamorphism, while younger ones, buried closer to surface are more exposed and eroded. 

Oxygen level is said to have rose to 35% in the late Carboniferous and early Permian, then fell to 15% in late Permian, causing the worst mass extinction ever. Then in the Cretaceous (final age of dinosaurs), oxygen levels crept up again, to around 25-35%.

The only great way to confirm/reject the hypothesis that oxygen levels once reached 35% is is to find a pocket of ancient air, somehow undisturbed for millions of years, which is believed by scientists who have been drilling cores of ice from deep into the Artic and Antarctic ice caps for many years to find preserved environmental change, which is just 0.0007% of length. This seem hopeless til the mid-1980s, when geochemist Gary Landis had an idea: tiny bubbles trapped in amber can contain ancient air, which had once dissolved in the resin of trees and later formed pressured bubbles,as the resin hardened to form amber with the right tool recently made: a quadrupole mass spectrometer from the US Geological Survey sensitive enough to analyse the amount of chemical identities of gases in tiny samples and detect gas of 8 parts in a billion.

Amber jewellery with insects and spores are highly prized since Neolithic times. Trading them amber dates back roughly 5000 years. The ambers may be time capsules as dinosaur genes may be intact in the abdomens of blood-sucking insects that were engulfed in resin soon after their meal, an idea from the novelist Michael Crichton in Jurassic Park, attracting serious attention.

Curt Beck of the Amber Research Lab in New Yor, drew attention to the way how Romans restored translucence to milky (or bone) amber, which is rendered opaque by the presense of microscopic air bubbles but can be made transparent and dyed by heating in oil, the same refraction index as amber, showing that the oil can penetrate the amber matrix fully. That is, the bubbles aren't in fact fully isolated from the environment and so the air in them can exchange with air from outside; and thus wouldn't accurately reflect air composition at the time they were formed. The overall consensus which has now persisted for more than a decade was that the air trapped in amber couldn't havebeen ancient.