How long to breathe (the equivalent of) all of the atmosphere?

How long to breathe (the equivalent of) all of the atmosphere?

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I have done some rough calculations of how long it might take humanity: approx 80,000 years (that's taking Earth's population as 7.5 billion, 11,000 litres a day of breathing, the weight of 1 litre of air at sea level at 1.225 grams, and the total weight of the atmosphere at 5140 trillion tonnes)

Please let me know if my calculations are massively out!

My question for you is admittedly much more complicated to answer - how long would it take all animal species combined to breathe the equivalent sum total weight of the atmosphere? and how long would it take all life combined (also including the weight of air of respiration in plants, fungi, algae, etc)?

Volume is probably not the best way to think about respiration for most of life on Earth, as it only really applies to animals with lungs (a small proportion of earth's biomass). Instead, it would make more sense to think about rates of respiration in terms of oxygen demands. With that in mind, an average human needs around 0.85 kg of oxygen per day (according to NASA). So, the annual oxygen needs of the human population would found by multiplying 0.85 kg/person/day by 365.25 days/year and 7.5 billion people to get ~2.3e+12 kg of oxygen per year.

For a crude estimate of how long it would take to use up our atmosphere's oxygen at that rate, we could simply divide the total capacity of oxygen in the atmosphere (~1.4e+18 kg) by the annual oxygen demand of the current human population (2.3e+12 kg), to get a rough estimate of 600,000 years for Earth's current population to use up all of Earth's current atmospheric oxygen (note that both calculations require some pretty dubious assumptions, but the problem already seems to start that way if I'm reading it right).

For an even cruder estimate of all life on earth, we can again take the Atmospheric Oxygen capacity (~1.4e+18 kg) and divide by the annual oxygen flux from atmosphere to biosphere (~3.0e+14 kg) to get around ~4700 years. (note that this assumes no flux from the biosphere back into the atmosphere, and also assumes that lithospheric flux is negligible.)

If you want to go further and calculate how long it would take for just animals to use up an atmosphere worth of oxygen, you could start by looking at how Earth's biomass is distributed, and make some more assumptions about the oxygen demand of other animals compared to humans following this same idea that I've used above.

Capacity and Flux estimates came (via wikipedia) from (Walker JC (1980) "The Oxygen Cycle". The Natural Environment and the Biogeochemical Cycles), but there are probably more up-to-date estimates available somewhere. The general idea would be the same.

Origin Of 'Breathable' Atmosphere Half A Billion Years Ago Discovered

Ohio State University geologists and their colleagues have uncovered evidence of when Earth may have first supported an oxygen-rich atmosphere similar to the one we breathe today.

The study suggests that upheavals in the earth's crust initiated a kind of reverse-greenhouse effect 500 million years ago that cooled the world's oceans, spawned giant plankton blooms, and sent a burst of oxygen into the atmosphere.

That oxygen may have helped trigger one of the largest growths of biodiversity in Earth's history.

Matthew Saltzman, associate professor of earth sciences at Ohio State, reported the findings October 28 at the meeting of the Geological Society of America in Denver.

For a decade, he and his team have been assembling evidence of climate change that occurred 500 million years ago, during the late Cambrian period. They measured the amounts of different chemicals in rock cores taken from around the world, to piece together a complex chain of events from the period.

Their latest measurements, taken in cores from the central United States and the Australian outback, revealed new evidence of a geologic event called the Steptoean Positive Carbon Isotope Excursion (SPICE).

Amounts of carbon and sulfur in the rocks suggest that the event dramatically cooled Earth's climate over two million years -- a very short time by geologic standards. Before the event, the Earth was a hothouse, with up to 20 times more carbon dioxide in the atmosphere compared to the present day. Afterward, the planet had cooled and the carbon dioxide had been replaced with oxygen. The climate and atmospheric composition would have been similar to today.

&ldquoIf we could go back in time and walk around in the late Cambrian, this seems to be the first time we would have felt at home,&rdquo Saltzman said. &ldquoOf course, there was no life on land at the time, so it wouldn't have been all that comfortable.&rdquo

The land was devoid of plants and animals, but there was life in the ocean, mainly in the form of plankton, sea sponges, and trilobites. Most of the early ancestors of the plants and animals we know today existed during the Cambrian, but life wasn't very diverse.

Then, during the Ordovician period, which began around 490 million years ago, many new species sprang into being. The first coral reefs formed during that time, and the first true fish swam among them. New plants evolved and began colonizing land.

&ldquoIf you picture the evolutionary &lsquotree of life,' most of the main branches existed during the Cambrian, but most of the smaller branches didn't get filled in until the Ordovician,&rdquo Saltzman said. &ldquoThat's when animal life really began to develop at the family and genus level.&rdquo Researchers call this diversification the &ldquoOrdovician radiation.&rdquo

The composition of the atmosphere has changed many times since, but the pace of change during the Cambrian is remarkable. That's why Saltzman and his colleagues refer to this sudden influx of oxygen during the SPICE event as a &ldquopulse&rdquo or &ldquoburst.&rdquo

&ldquoAfter this pulse of oxygen, the world remained in an essentially stable, warm climate, until late in the Ordovician,&rdquo Saltzman said.

He stopped short of saying that the oxygen-rich atmosphere caused the Ordovician radiation.

&ldquoWe know that oxygen was released during the SPICE event, and we know that it persisted in the atmosphere for millions of years -- during the time of the Ordovician radiation -- so the timelines appear to match up. But to say that the SPICE event triggered the diversification is tricky, because it's hard to tell exactly when the diversification started,&rdquo he said.

&ldquoWe would need to work with paleobiologists who understand how increased oxygen levels could have led to a diversification. Linking the two events precisely in time is always going to be difficult, but if we could link them conceptually, then it would become a more convincing story.&rdquo

Researchers have been trying to understand the sudden climate change during the Cambrian period ever since Saltzman found the first evidence of the SPICE event in rock in the American west in 1998. Later, rock from a site in Europe bolstered his hypothesis, but these latest finds in central Iowa and Queensland, Australia, prove that the SPICE event occurred worldwide.

During the Cambrian period, most of the continents as we know them today were either underwater or part of the Gondwana supercontinent, Saltzman explained. Tectonic activity was pushing new rock to the surface, where it was immediately eaten away by acid rain. Such chemical weathering pulls carbon dioxide from the air, traps the carbon in sediments, and releases oxygen -- a kind of greenhouse effect in reverse.

&ldquoFrom our previous work, we knew that carbon was captured and oxygen was released during the SPICE event, but we didn't know for sure that the oxygen stayed in the atmosphere,&rdquo Saltzman said.

They compared measurements of inorganic carbon -- captured during weathering -- with organic carbon -- produced by plankton during photosynthesis. And because plankton contain different ratios of the isotopes of carbon depending on the amount of oxygen in the air, the geologists were able to double-check their estimates of how much oxygen was released during the period, and how long it stayed in the atmosphere.

They also studied isotopes of sulfur, to determine whether much of the oxygen being produced was re-captured by sediments.

Saltzman explained the chain of events this way: Tectonic activity led to increased weathering, which pulled carbon dioxide from the air and cooled the climate. Then, as the oceans cooled to more hospitable temperatures, the plankton prospered -- and in turn created more oxygen through photosynthesis.

&ldquoIt was a double whammy,&rdquo he said. &ldquoThere's really no way around it when we combine the carbon and sulfur isotope data -- oxygen levels dramatically rose during that time.&rdquo

What can this event tell us about climate change today? &ldquoOxygen levels have been stable for the last 50 million years, but they have fluctuated over the last 500 million,&rdquo Saltzman said. &ldquoWe showed that the oxygen burst in the late Cambrian happened over only two million years, so that is an indication of the sensitivity of the carbon cycle and how fast things can change.&rdquo

Global cooling may have boosted life early in the Ordovician period, but around 450 million years ago, more tectonic activity -- most likely, the rise of the Appalachian Mountains -- brought on a deadly ice age. So while most of the world's plant and animal species were born during the Ordovician period, by the end of it, more than half of them had gone extinct.

Coauthors on this study included Seth Young, a graduate student in earth sciences at Ohio State Ben Gill, a graduate student, and Tim Lyons, professor of earth sciences, both at the University of California, Riverside Lee Kump, professor of geosciences at Penn State University and Bruce Runnegar, professor of paleontology at the University of California, Los Angeles.

Story Source:

Materials provided by Ohio State University. Note: Content may be edited for style and length.

How long to breathe (the equivalent of) all of the atmosphere? - Biology

Earth's atmosphere contains the air we breathe, the weather we experience and is our natural shield against the harsh conditions of space.

Earth's atmosphere is our natural shield against the harsh conditions of space— including everything from meteors and falling satellites to deadly ultraviolet radiation from the sun. It also contains the air we breathe, the weather we experience and helps to regulate planetary temperatures.

The atmosphere consists of layers of gases, called "air", that surround the planet and are retained by Earth's gravity.

"Air" is the common name given to the combination of gases used by organisms for breathing and photosynthesis. By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide and smaller amounts of various other gases as well as varying amounts of water vapor. Air composition and atmospheric pressure is not consistent throughout the atmosphere, however, and varies at different altitudes, giving the atmosphere 5 distinct principle layers.

The Layers of the Atmosphere:

The Troposphere:
Beginning at the surface of Earth, the troposphere extends to around seven miles up. This is the layer we live in and contains most of what we consider to be "the atmosphere", including the air we breathe and nearly all of the weather and clouds we see. In the troposphere, the temperature of the air decreases the higher you go.

The Stratosphere:
This layer exists between seven to 31 miles above the surface of Earth. Unlike the troposphere below, the air temperature actually increases with altitude making the air stratified. When possible, commercial jet aircraft fly in the lower stratosphere to avoid the turbulence which is common in the troposphere, due to convection.

The Mesosphere:
The third layer of Earth's atmosphere, the mesosphere extends from around 31 to 50 miles high (the height at which you are considered an astronaut by U.S. standards). Considered one of the coldest places on Earth, the average temperature is around -120°F. This layer is where most meteors burn up upon entering Earth's atmosphere and is the highest elevation at which a cloud can form.

The Thermosphere:
Home to the Kármán Line and spanning the area 50 to 440 miles above Earth's surface, the thermosphere is the atmospheres second to last layer. The thermosphere is where high energy ultraviolet and x-ray radiation begin to be absorbed causing massive temperature variations. Highly dependent on solar activity, temperatures here can range from as low as -184°F to as high as 3,630°F. However, despite the high temperatures, this layer of the atmosphere would still feel very cold to our skin due to the very thin atmosphere.
In the thermosphere, Earth's curvature becomes distinctly clear and space travelers begin to experience "weightlessness". Because of the heavily ionized atmosphere present in the thermosphere, it is also home to the phenomenon known as auroras.

The Exosphere:
The final layer of Earth's atmosphere, where it gradually gives way to outer space, is the exosphere. This layer extends from around 440 miles above Earth to nearly 6,200 miles. The atmosphere in the exosphere is incredibly thin and no longer behaves like normal gas. The atoms and molecules are so far apart that they can travel hundreds of miles without colliding with one and another. This layer contains a large portion of low-Earth orbiting satellites.

Factors contributing to a challenging interaction

To prevent and resolve challenging interactions, one needs to consider factors that might contribute to these situations. Two important factors are the local healthcare setting in which the interactions take place, and the variation in clinical practice between regions and countries. In particular, the majority of healthcare settings are overworked and overstretched to meet demand, and this continuously affects interactions. Insufficient time for consultation or interaction with patients plays an important role, as healthcare system pressures are increasing patient numbers and expectations, against a background of cost-cutting. Foremost, it is important to bear in mind that both patients and healthcare practitioners want a positive interaction to ensure the best possible health outcome, as time spent in consultations is valuable for both parties. Figure 1 summarises several other important contributing factors.

Factors contributing to a challenging interaction.

The patient

Each patient has their own medical and psychosocial history that understandably will affect their behaviour. Patients will walk into your clinic with a set of beliefs and expectations affected by their personality and the severity of their symptoms, and the implications of this for their quality of life. They may also have had negative experiences and previous disappointments within the healthcare system that may be challenging to overcome and may generate some mistrust. They may feel that their illness is beyond their personal control, which can make them dependent on others’ help, particularly their healthcare professional. Such circumstances can, understandably, make a patient feel anxious, worried, hopeless and uncertain about their health, which can be displayed as tension and negative reactions towards the healthcare professional.

With increasing advances in medical research, expectations of the healthcare system and in healthcare practitioners have also increased. Patients can have very high expectations and trust in the system, and when it appears that their condition is a medical � end” or that their prognosis cannot be determined with precision due to the nature of the disease, it can be very upsetting. Language barriers, cultural diversity and their previous interactions with professionals or authority figures can also contribute to and affect interactions, and lead to misunderstandings. Moreover, patients may also have other considerations to make, for example, if their diagnosis may impact on other commitments (professional, caring responsibilities, etc.). Patients often work, may care for children or parents, or have other commitments that may be impacted by the diagnosis or may have impacted on the timeframe in which they seek help, all of which will be going through their mind. Being defined by their diagnosis and labelled as 𠇊 patient” is not, and should not be, the only thing in their lives.

The healthcare practitioner

There is a wide variability in the development of appropriate communication skills among European healthcare practitioners and this has been a challenge. Communication skills courses or training are not included in the specialist curriculum in all European Union (EU) countries, nor are they included in the essential qualifications for specialist post applications.

A lack of communication skills training can result in:

inappropriate choice of words and phrases, perhaps due to assumptions being made about the patient’s level of health literacy or understanding of human biology

lack of planned structure in delivering difficult news (e.g. scattered information confusing patients or no clear plan at all)

inappropriate choice of setting to deliver difficult news

lack of options offered to the patient

not involving the patient in the decision-making process (e.g. treatment decisions taken without involving them and without addressing their needs and wishes)

rushing the patient to agree to a proposed treatment plan

rushing the consultation due to other pressures or

not referring the patient to appropriate support services/resources (e.g. counselling, palliative care, support groups and quality trusted information).

Bad news may be broken in a nonempathetic way, messages may be given to the nurses over the patient’s head while interrupting the consultation, difficult words may be used that the patient does not understand, and the patient may feel excluded from conversations with almost no concern showed for their feelings and emotions. Often, what is everyday routine clinical data to the healthcare practitioner may be completely unfamiliar to the patient, giving the impression that the clinician is cold and unsympathetic to the individual’s emotions as they try to come to terms with the diagnosis and its implications.

Overstretched clinic time may result in doctors not having time to actually listen to the patient’s concerns. What is the patient actually afraid of? What do they want to know? What are their experiences? These are questions that will be overlooked due to lack of time. Insufficient time further impacts the consultation as there is not time for the patient to verbalise, and for the doctor to appreciate, the valuable contribution that the patient brings in having the lived experience of the condition, especially if this is a rare disease.

In a complex clinical case, doctors may seem so preoccupied with finding the solution to the clinical problem that it is sometimes easy to forget that the patient might be overwhelmed by anxiety, frustration and negative emotions, and require re-assurance to feel safe, at ease and trust in the doctor.

Healthcare setting (either outpatient clinic or wards) is a familiar setting for doctors to have difficult conversations, whereas for patients, it can be uncomfortable and sometimes awkward, especially if they are at the point of receiving their diagnosis.

In addition, a doctor’s emotions may get the better of them or their behaviour might be affected by a lack of sleep, hunger, their own health status, lack of job satisfaction or other concerns. Finally, the doctor’s approach and communication style will influence their interactions and could have serious adverse effects on the patient (e.g. if the healthcare practitioner is arrogant or impatient and believes they don’t have a responsibility to discuss the situation with the patient or explain the condition in terms the patient could understand).

It’s important for doctors to recognise that some patients may be intimidated and perceive inequality in the doctor–patient relationship, which can be exacerbated by doctors acting in a way that is perceived by the patient as condescending or patronising. All this can be remedied with appropriate training and relevant professional development.

The system

Dysfunctional healthcare systems can only add to the tension between patients and doctors. Simple things like long waiting times in the clinic, consecutive unjustified cancellations, or delays to previous appointments or investigations essentially, anything that may have gone wrong in the patient pathway can potentially lead to a challenging interaction between patients and doctors. Doctors are probably the first person patients will spend some time with after something has gone wrong and therefore they will hear the patient’s immediate frustrations first hand.

Lack of resources in terms of staffing levels or of maintaining patient privacy and dignity during consultation is another contributing factor for example, during a consultation there may be several doctors or nurses moving in and out of the room that distract attention and may affect dignity and privacy.

A lack of centralised documentation systems can sometimes lead to asking the patient to repeat the same information over and over again, and consequently dedicating less time to actually managing the clinical case and addressing the patient’s needs. Constant repetition for every new doctor may cause the patient frustration, while it is difficult for the doctor to know what the patient already understands.

There is one animal that seems to survive without oxygen

In 2010, it seemed that biology textbooks would have to be rewritten. At the bottom of the Mediterranean Sea, in one of the most extreme environments on Earth, one research team found evidence of an animal able to live its entire life without oxygen.

Not one of the other million or so known animal species can do that. Oxygen, in some form, is often assumed to be vital for animal life. Yet the existence of these creatures seemed to blow a hole in this theory, with far-reaching implications for our understanding of life on Earth.

The tiny Mediterranean animals belong to a group called the loriciferans &ndash an animal group so unusual that it was not discovered until the 1980s.

Because the mud at the bottom of the L'Atalante basin is completely devoid of oxygen, the team did not expect to find "higher lifeforms"

Loriciferans are about the size of a large amoeba. They live in muddy sediments at the bottom of the seas. But supposedly, that mud should contain some oxygen to allow the animals to breathe. The mud in the L'Atalante basin at the bottom of the Mediterranean does not.

Over a period of a decade, Roberto Danovaro at the Polytechnic University of Marche, Italy, and his colleagues trawled the depths of the L'Atalante basin. It lies 3.5km beneath the surface, about 200km (124 miles) off the western coast of Crete. The inner part of the basin is completely devoid of oxygen, because ancient salt deposits buried beneath the seafloor have dissolved into the ocean, causing the water to become extra salty and dense.

The dense water does not mix with the normal oxygen-rich seawater above, and becomes trapped in seafloor valleys. The oxygen-free water has been in place for over 50,000 years.

Because the mud at the bottom of the L'Atalante basin is completely devoid of oxygen, the team did not expect to find "higher lifeforms" &ndash which basically means animals &ndash living there. But in fact they found three new species of loriciferans, apparently thriving in the mud.

It is not just zero oxygen levels that the critters must contend with. Loriciferans are surrounded by poisonous sulphides, and live in such extreme salty water that normal cells would turn into dried out husks.

We took 10 years to confirm through experiments that the animals were really actually living without oxygen

"When we first saw them we couldn't believe it," says Danovaro. "Before this study only two [loriciferan] specimens had ever been found in the deep Mediterranean. There were more organisms in 10 square centimetres of anoxic basin than in the rest of the Mediterranean Sea put together!"

But the biggest surprise of all was the fact that the tiny animals seemed to survive without any oxygen at all.

"We knew that some animals, such as parasitic flatworm nematodes, can spend part of their lives without oxygen, living in the intestine," says Danovaro. "However, they don't spend their whole life cycle this way. Our discovery challenged all previous thoughts and assumptions about the metabolism of animals."

He says this made their discovery difficult for other scientists to believe. "Indeed we didn't believe it ourselves at first. We took 10 years to confirm through experiments that the animals were really actually living without oxygen."

Those experiments were difficult to perform. The scientists could not bring the living animals up to the surface, because the journey would instantly kill them. What they could do was test the tiny animals for signs of life in the seafloor.

They showed that fluorescent molecules that are only taken up by living cells were incorporated into the loriciferans' bodies. They also used a stain that reacts only to the presence of active enzymes. The stain reacted with loriciferans from the basin, but not from the obviously dead remains of other microscopic animals found in l'Atalante.

The closer the researchers' samples came to the anoxic basin of water, the fewer living loriciferans they found

What's more, some of the loriciferans appeared to have eggs in their bodies, suggesting that they were reproducing. Others loriciferans were found in the process of shedding their shell and moulting, a further indication that they were alive.

Finally, the loriciferans in l'Atalante were completely intact and not at all decomposed &ndash unlike other microscopic animals the researchers found in the salty, oxygen-absent environment.

After this careful work Danovaro and his colleagues made their findings public: the loriciferans were, indeed, living in an environment completely devoid of oxygen. Their 2010 paper, published in the journal BMC Biology, was a scientific sensation.

Even so, some other researchers are not convinced. A second team visited the Mediterranean in 2011 to examine for themselves the loriciferans and their unusual environment. Their findings, which were published late in 2015, challenge the idea that the loriciferans really do live without oxygen.

Joan Bernhard at the Woods Hole Oceanographic Institution in Massachusetts led this second team. She and her colleagues collected mud and water samples from just above the anoxic pools of L'Atalante. Due to technical difficulties, the pools themselves were too dense for their remotely operated vehicle to penetrate.

If the tiny animals really were dead and inhabited by bacteria, this would have been obvious

The team found the same species of loriciferans discovered by Danovaro. But these loriciferans were living in environments with normal levels of oxygen, and in the upper layers of the sediment above the anoxic pools, which had low levels of oxygen.

The closer the researchers' samples came to the anoxic basin of water, the fewer living loriciferans they found.

Bernhard argues that it is extremely unlikely that loriciferans would be adapted to live both in areas totally without oxygen and high in salt, and also in environments with plentiful oxygen and normal levels of salt.

Instead, her team argues that cadavers of dead loriciferans could have floated down into the muddy sediments of the L'Atalante basin, where they were inhabited by "body-snatching" bacteria. Many species of bacteria are known to be able to live without oxygen, and they could have incorporated the biomarkers into the loriciferans' bodies, potentially fooling Danovaro and his colleagues into believing that the loriciferans were alive.

However, in June 2016 Danovaro and his team came back fighting against this alternative scenario. They say that, because Bernhard's team did not collect mud samples from the areas of the basin that are permanently without oxygen, they cannot be sure that loriciferans do not live there.

All lifeforms on Earth must generate energy if they are to eat, reproduce, grow and move around

Danovaro's team also points out that, if the tiny animals really were dead and inhabited by bacteria, this would have been obvious when the loriciferans were examined under a microscope. But, in fact, the loriciferans showed no sign of being decayed and decomposed by microbes. Additionally, no bacteria were seen living inside the loriciferans, and a dye used to stain living tissue stained all parts of the loriciferans' bodies, not just the parts where bacteria would likely colonise a dead animal.

Finally, they say that the thick layers of ancient mud deposits further support their argument.

"We were able to prove that these animals were present in different layers within the mud," says Danovaro. "Some of the layers are several thousand years old and so, if these animals were just dead and preserved, it's a bit unbelievable that the animals in 3,000-year-old mud are just as maintained as those found at the surface. The most likely explanation is that the animals can penetrate sediments, and swim and push to go down."

But why is there such a controversy over whether animals can survive without oxygen anyway? No one doubts that bacteria can survive without oxygen, for instance. Why does it seem so unlikely that animals can?

Answering this question requires an explanation for why animals like us breathe oxygen in the first place. All lifeforms on Earth must generate energy if they are to eat, reproduce, grow and move around. That energy comes in the form of electrons, the same negatively-charged particles that flow through electrical wires and power your laptop.

On primordial Earth the atmosphere was heavy with a smog of carbon dioxide, methane and ammonia

The challenge for all life on Earth is the same, whether it is a virus, bacterium or elephant: you have to find both a source of electrons and a place to dump them to complete the circuit.

Animals get their electrons from the sugar in the food they eat. In a series of chemical reactions that happen inside animal cells, these electrons are released and bind to oxygen. That flow of electrons is what powers animal bodies.

Earth's atmosphere and oceans are full of oxygen, and the reactive nature of the element means that it is "eager" to steal electrons. For animals, oxygen is a natural choice for an electron dump.

However, oxygen was not always as plentiful as it is now. On primordial Earth the atmosphere was heavy with a smog of carbon dioxide, methane and ammonia. When the spark of life first ignited, there was little oxygen around. In fact, oxygen levels in the oceans were probably extremely low up until about 600 million years ago &ndash about the same time that animals first appeared.

This means that older, more primitive lifeforms evolved to use other elements as their electron dumps.

Many of these lifeforms &ndash such as bacteria and archaea &ndash are still living happily without oxygen today. They thrive in places on Earth that have little oxygen, for example in mud banks and near geothermal vents. Instead of passing electrons to oxygen, some of these creatures can pass on their electrons to metals like iron, meaning that they effectively conduct electricity. Others can "breathe" sulphur or even hydrogen.

The theory is that the evolution of life exploded when oxygen became available in the atmosphere and ocean

The one thing that unites these oxygen-free lifeforms is their simplicity. They all consist of just one cell. Until the 2010 discovery of the loriciferans, no complex multicellular lifeforms had been found that can live entirely without oxygen. But why is that?

According to Danovaro, this stems from two fundamental points. First, breathing oxygen is far and away a better approach to generating energy. "Complexity and organisation requires oxygen, because this is more efficient for the production of energy," he says.

When oxygen levels rose, hundreds of millions of years ago, it was as if a brake had been taken off evolution's ambitions. A group of lifeforms called the eukaryotes &ndash which includes animals &ndash took advantage, adapting to harness the new substance in their metabolism and becoming far more complex as a consequence.

"The theory is that the evolution of life exploded when oxygen became available in the atmosphere and ocean," says Danovaro.

But this is only part of the story. Some species of microbe also began to breathe oxygen but, unlike animals and some other eukaryotes, they did not become complex. Why not?

Danovaro says the key to understanding the mystery comes from looking at mitochondria, the tiny structures inside eukaryotic cells that act as the lifeform's powerhouse. Inside these mitochondria, nutrients and oxygen are combined to generate a substance called ATP, the body's universal energy currency.

It wouldn't work if they were the size of an elephant

Mitochondria are found in almost all eukaryotes. But bacteria and archaea do not carry mitochondria, and this is a key difference.

"When mitochondria evolved, they made the process of making energy and ATP much more efficient, but they needed oxygen to do this," says Danovaro.

In other words, animal life arose as a consequence of two points. First, the eukaryotes had gained mitochondria inside their cells. Then, when oxygen levels rose, these mitochondria allowed some of those eukaryotes to gain complexity and become animals.

So how come loriciferans can get by without oxygen when other animals cannot?

"They are very tiny, about the size of a large amoeba," says Danovaro. "The small size helps. It wouldn't work if they were the size of an elephant. As they are small their energy requirement is less."

The loriciferans might differ from other animals in another important respect. They seem to lack the oxygen-using mitochondria found in all other animals. Instead, they may carry structures related to mitochondria called hydrogenosomes.

Some animals &ndash like the loriciferans &ndash may have stuck it out and lived without oxygen, remaining small as a consequence

These use protons instead of oxygen as their electron dump. Hydrogenosomes may even be one of many primitive types of mitochondria, which evolved in early eukaryotes to produce energy before atmospheric oxygen levels arose.

"I think the eukaryote common ancestor was a facultative anaerobe that could live with or without oxygen, much like E. coli, a well-known bacterium," says William Martin, a professor of molecular evolution at the University of Dusseldorf, Germany.

This has important ramifications for understanding how and in what conditions complex life first appeared. The first eukaryotes probably evolved before oxygen was routinely freely available in the ocean, so the mitochondria-like structures inside their cells might have been adapted to both oxygen-present and oxygen-absent conditions. Then, as oxygen became more abundant, first in the atmosphere and then in the ocean, some eukaryotes adapted to their new oxygen-rich environments and became large and complex. They became animals.

But some animals &ndash like the loriciferans &ndash may have stuck it out and lived without oxygen, remaining small as a consequence.

For this scenario to work, the loriciferans must have retained their ability to live without oxygen from their ancient ancestors. But there is an alternative: the loriciferans might have gained their ability to do without oxygen very recently, perhaps by stealing genes from other species in a process known as horizontal gene transfer.

As soon as you put it under the microscope you kill it

"This could be evolution in action, as all previously-known species of loriciferans respire oxygen," says Danovaro. "It is possible that this is an extreme adaptation to allow the loriciferans to live in an environment without competitors or predators."

For now the scientific community waits with bated breath for more evidence confirming or disproving the original finding. "I think it is a stalemate at present," says Martin. "What is needed are more samples for closer study."

Final proof would be seeing the animals swimming around in the mud, but according to Danovaro, the small size of loriciferans and their difficult-to-reach environment makes it hard to make those sorts of observations.

"The animal is one-tenth of a millimetre so it requires a special system, because as soon as you put it under the microscope you kill it," he says. "In principle you can extract its DNA, which is the next thing we are working on, but someone could still say, 'well, that animal is dead'. It's a very long track to get final confirmation but we are very optimistic."

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The Surprising Ways Your Breath Connects You to the Entire Planet

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Exhale Richard Legner/Getty Images

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Breathing is so universal and continuous that it can be easy to forget about—until we can’t do it anymore. Then it becomes symbolic of life itself. We take special note of words that are carried on final breaths, and sometimes we even cherish the physical substance of the breaths themselves. Henry Ford kept a glass test tube of air in his home for many years, and inside the tube was said to be a sample from the last breath of his late friend and fellow inventor Thomas Edison. According to sources at the Henry Ford Museum in Dearborn, Michigan, several such tubes are believed to have been left open to the air of the room near Edison’s deathbed. “Though he is mainly remembered for his work in electrical fields,” Edison’s son Charles reportedly said, “his real love was chemistry. It is not strange, but symbolic, that those test tubes were close to him at the end.” After Edison’s death, Charles had the tubes sealed and later passed one of them on to Ford as a memento.

Keep this in mind as you take your next breath. Notice how you tighten your diaphragm and relax the muscles in the walls of your chest. This effort alone consumes roughly 3 percent of your metabolic energy at rest, all in order to pull the equivalent volume of a grapefruit into your lungs. Trillions of air molecules are now trapped within your chest like fish in a net. Only a few of them, the oxygens, are what you’re after. An average adult uses nearly two pounds of them every day, and this particular breath full will help to keep you alive for the next few minutes. It will also connect you to the rest of life on Earth and to the planet itself in surprising ways that we will soon explore.

Depending on the time of day and the season of the year, the air you walk through and pull into your lungs changes more than you might expect. This is just one of many discoveries by Ralph Keeling, a scientist at the Scripps Institution of Oceanography who tests the atmosphere the way a police officer might test your breath with a Breathalyzer.

Your Atomic Self: The Invisible Elements That Connect You to Everything Else in the Universe

For more than two decades Keeling has been measuring the oxygen content of air samples that are collected daily in Hawaii, Antarctica, and elsewhere, sealed into small containers, and shipped to his lab in La Jolla, California. Like traces of alcohol in someone’s breath, slight changes in the composition of the atmosphere can tell a lot about what the world’s combined masses of people, vegetation, and plankton are doing.

It is often said that forests are the “lungs of the planet” because they produce oxygen that we breathe, but the metaphor falls short in some respects. Lungs don’t produce oxygen but instead consume it, and Keeling’s work has shown that only about half of your oxygen comes from terrestrial plants. The rest is made by algae and cyanobacteria in lakes and oceans, with a small additional measure produced by the splitting of water vapor in the upper atmosphere by radiation from the sun and distant stars.

However, when combined with the carbon dioxide analyses that his late father, Charles David Keeling, launched at Mauna Loa Observatory in Hawaii in 1958, the long-term oxygen records do show an almost eerie resemblance to the readouts of a medical breath-monitoring device. Annual pulses of oxygen are mirrored by cyclic drops in CO2, and together these data open a unique window on the atomic connections between plants and the earth.

When the elder Keeling first began to study the air, he expected it to vary a great deal from place to place. To his surprise, however, much of the variability vanished when samples were collected with consistent methods at remote locations where the air is free of local influences from respiring forests and cities. The atmosphere mixes more thoroughly and rapidly than scientists had hitherto realized, and average CO2 concentrations in Hawaii are remarkably similar to those at the Scripps pier in La Jolla.

Equally noteworthy, however, were various kinds of rhythmic oscillations that appeared in the gas records. Every day the carbon dioxide concentrations dropped slightly, only to recover at night, and larger seasonal pulses occurred with dips in summer and peaks in winter. When Ralph Keeling began to measure oxygen to complement his father’s work, his results showed similar patterns but in reverse. With these data you can watch the atmosphere respond to the breathing of countless plants and microbes as the earth spins on its axis and circles the sun.

The pacemaker of these pulses is sunlight. When dawn awakens California, the lawns and palm trees of La Jolla begin to pump oxygen into the air and pull carbon dioxide out of it, as does the Pacific plankton drifting offshore. When that portion of the world spins onward into the shadow of night again, the oxygen production shuts down, but the cellular CO2 factories keep running and quickly drive local carbon dioxide levels back up again while oxygen levels drop.

A similar pattern emerges in alternating hemispheres through the seasons, as well. When plants sprout and leaf out in spring, O2 rises rapidly and CO2 declines. Later in the year when photosynthesis slows and dead leaves begin to decay and release carbon dioxide, the opposite trends prevail.

The Keeling records clearly show that we affect the atmosphere, too, but in more disturbing ways. In early 2013 average concentrations of heat-trapping carbon dioxide reached 400 parts per million (ppm, or a ten-thousandth of a percent), having risen from an average closer to 312 ppm during the 1950s. Most of that change represents the burning of fossil fuels along with the decay and fires associated with deforestation. Unlike the photosynthesizers, these artificial “lungs” of the modern world consume O2 and release CO2 like our own, and they do it continuously on a massive scale.

While the long-term carbon dioxide record tilts upward along with global average temperatures, the oxygen trend points downward. According to the Scripps O2 Program site, oxygen concentrations at La Jolla dropped by 0.03 percent between 1992 and 2009. This, as Ralph Keeling said in an interview with the San Diego Union-Tribune, is the global “signature of combustion.”

Should we now worry about running out of oxygen in addition to global warming? Not according to Keeling. In another Union-Tribune interview he explained that there is plenty of oxygen in the air, and the tiny percentage of loss of oxygen in itself isn’t an issue. Rather, “the trend in oxygen helps us to understand . what’s controlling the rise in CO2.” In other words, declining oxygen shows how closely tied we are to this planet, and how much we now affect the atomic world around us.

From space, Earth resembles a floating blue bead, and if you keep that image in mind it will help to drive home an important lesson. As abundant as atoms are on this planet, their numbers are finite. Watch a satellite video of the clouds that sweep across the face of the world, and you will see in an instant that the winds that carry them over one curved horizon may reappear on the opposite horizon. When viewed from a great distance the sky resembles a shockingly thin film, and most of its molecules are packed into a mere 10-mile slice of a total planetary diameter of nearly 8,000 miles. At sea level you might find more than 10 trillion trillion atoms in a cubic yard of air, but just outside that vaporous skin is the relative vacuum of the solar system. The next time you see a photo of the earth taken from space, try to convince yourself that a pollutant-spewing smokestack anywhere in the world doesn’t unleash potentially harmful substances into the same precious air supply that keeps you and your loved ones alive.

Keeling showed that oxygen gas emitted by plants and plankton mixes throughout each respective hemisphere within two months and spreads worldwide in a little more than a year. The sensitivity of the oxygen and carbon dioxide balance of the atmosphere to the activities of living things shows that recycling is not just a passing fad but a tradition that has always been practiced on the atomic level by all life on Earth. To live, rather than to merely exist like inanimate rock, is to borrow and repurpose the elements of the world around you, and then release them again.

As brilliant as he was, Henry Ford apparently failed to realize that he needed no test tube to capture the atomic essence of Edison’s last breath. You can collect a sample of it anytime—along with samples from the last breaths of Jesus, Shakespeare, and Leonardo—and even with a few bits of air that carried your own first cries as a newborn. It’s easy to do, here on this sky-blue sphere of atoms. Just take a breath.

Excerpted and adapted from Your Atomic Self* by Curt Stager. Copyright © 2014 by the author and reprinted by permission of Thomas Dunne Books, an imprint of St. Martin’s Press, LLC.*
Editor: Samantha Oltman (@samoltman)

Photosynthetic Floatation

Photosynthetic organisms capture energy from the sun and matter from the air to make the food we eat, while also producing the oxygen we breathe. In this Snack, oxygen produced during photosynthesis makes leaf bits float like bubbles in water.

Video Demonstration

Tools and Materials

  • Baking soda (sodium bicarbonate)
  • Gram scale
  • Water
  • Liquid dish soap
  • Spoon or other implement (for mixing solution)
  • Soda straw or hole punch
  • Spinach leaves or ivy leaves
  • 10-mL syringe (without a needle)
  • Clear plastic cup (1-cup size) or 250-mL beaker
  • Incandescent or 100-watt equivalent lightbulb in fixture (preferably with a clamp)
  • Timer
  • Notepaper and pencil (or similar) to record results
  • Optional: ring stand, foil, thermometer, ice, hot water, colored gel filters


  1. Make a 0.1% bicarbonate solution by mixing 0.5 grams baking soda with 2 cups (500 mL) water. Add a few drops of liquid dish soap to this solution and mix gently, trying to avoid making suds in the solution.
  2. Using the straw or hole punch, cut out 10 circles from your leaves (see photos below). (Straws work best with spinach hole punches work best with ivy.)

To Do and Notice

Turn on the light, start a timer, and watch the leaf disks at the bottom of the cup. Notice any tiny bubbles forming around the edges and bottoms of the disks. After several minutes, the disks should begin floating to the top of the solution. Record the number of floating disks every minute, until all the disks are floating.

How long does it take for the first disk to float? How long does it take for half the disks to float? All the disks?

When all the disks have floated, try putting the cup in a dark cabinet or room, or cover the cup with aluminum foil. Check the cup after about fifteen minutes. What happens to the disks?

What’s Going On?

Plants occupy a fundamental part of the food chain and the carbon cycle due to their ability to carry out photosynthesis, the biochemical process of capturing and storing energy from the sun and matter from the air. At any given point in this experiment, the number of floating leaf disks is an indirect measurement of the net rate of photosynthesis.

In photosynthesis, plants use energy from the sun, water, and carbon dioxide (CO2) from the air to store carbon and energy in the form of glucose molecules. Oxygen gas (O2) is a byproduct of this reaction. Oxygen production by photosynthetic organisms explains why earth has an oxygen-rich atmosphere.

The equation for photosynthesis can be written as follows:

In the leaf-disk assay, all of the components necessary for photosynthesis are present. The light source provides light energy, the solution provides water, and sodium bicarbonate provides dissolved CO2.

Plant material will generally float in water. This is because leaves have air in the spaces between cells, which helps them collect CO2 gas from their environment to use in photosynthesis. When you apply a gentle vacuum to the leaf disks in solution, this air is forced out and replaced with solution, causing the leaves to sink.

When you see tiny bubbles forming on the leaf disks during this experiment, you’re actually observing the net production of O2 gas as a byproduct of photosynthesis. Accumulation of O2 on the disks causes them to float. The rate of production of O2 can be affected by the intensity of the light source, but there is a maximum rate after which more light energy will not increase photosynthesis.

To use the energy stored by photosynthesis, plants (like all other organisms with mitochondria) use the process of respiration, which is basically the reverse of photosynthesis. In respiration, glucose is broken down to produce energy that can be used by the cell, a reaction that uses O2 and produces CO2 as a byproduct. Because the leaf disks are living plant material that still require energy, they are simultaneously using O2 gas during respiration and producing O2 gas during photosynthesis. Therefore, the bubbles of O2 that you see represent the net products of photosynthesis, minus the O2 used by respiration.

When you put floating leaf disks in the dark, they will eventually sink. Without light energy, no photosynthesis will occur, so no more O2 gas will be produced. However, respiration continues in the dark, so the disks will use the accumulated O2 gas. They will also produce CO2 gas during respiration, but CO2 dissolves into the surrounding water much more easily than O2 gas does and isn’t trapped in the interstitial spaces.

Going Further

Try changing other factors that might affect photosynthesis and see what happens. How long does it take for the disks to float under different conditions? For example, you can compare the effects of different types of light sources—lower- or higher-wattage incandescent, fluorescent, or LED bulbs. You can change the temperature of the solution by placing the beaker in an ice bath or a larger container of hot water. You can increase or decrease the concentration of sodium bicarbonate in the solution, or eliminate it entirely. You can try to identify the range of wavelengths of light used in photosynthesis by wrapping and covering the beaker with colored gel filters that remove certain wavelengths.

Teaching Tips

This experiment is extremely amenable to manipulations, making it possible for students to design investigations that will quantify the effects of different variables on the rate of photosynthesis. It is helpful to have students familiar with the basic protocol prior to changing the experimental conditions.

Ask your students to think carefully about how to isolate one variable at a time. It is important to hold certain parts of the experimental setup constant—for example, the distance from the light source to the beaker, the type of light bulb used, the temperature of the solution, the height of the solution, and so on. Certain treatments may eliminate photosynthesis altogether—water with no bicarbonate, very low temperature, and total darkness.

A typical way to collect data in this assay is to record the number of disks floating at regular one-minute time intervals. This is easily graphed, with time on the x-axis and number of floaters on the y-axis.

To make comparisons between treatments, the number traditionally used is the time point at which half of the disks in the sample were floating, also known as the E50.


This experiment was originally described in Steucek, Guy L., Robert J. Hill, and Class/Summer 1982. 1985. “Photosynthesis I: An Assay Utilizing Leaf Disks.” The American Biology Teacher, 47(2): 96–99.

Related Snacks

Leaf Filter

Even plants have their favorite colors.

Oil Spot Photometer

Compare the brightness of two light sources with an oil spot on a white card.

Emergency oxygen enemas could help us "breathe" through our intestines

Scientists have made the surprising discovery that some mammals can absorb oxygen through their intestines. The team experimented by administering oxygen enemas in a gas or liquid form to mice, rats and pigs, and found that they could survive much longer in a low-oxygen environment. The find could eventually open up an alternative treatment for patients suffering respiratory failure.

Certain aquatic species, such as sea cucumbers, loaches and catfish, are known to be able to survive longer in low-oxygen waters by turning to an unorthodox alternative – effectively breathing through their butts. Specifically, the distal gut allows for gas exchange, which can provide additional oxygen to the bloodstream in a pinch.

But could that also work for other animals? Whether or not oxygen could reach the bloodstream from the intestines in mammals was the question at the heart of the new study conducted by researchers at the Tokyo Medical and Dental University and the Cincinnati Children’s Hospital Medical Center.

“The rectum has a mesh of fine blood vessels just beneath the surface of its lining, which means that drugs administered through the anus are readily absorbed into the bloodstream,” says Ryo Okabe, first author of the study. “This made us wonder whether oxygen could also be delivered into the bloodstream in the same way. We used experimental models of respiratory failure in mice, pigs and rats to try out two methods: delivering oxygen into the rectum in gas form, and infusing an oxygen-rich liquid via the same route.”

In the first tests, the team delivered pure oxygen gas to the rectums of mice, then exposed the animals to a low oxygen environment. And sure enough, three out of four test mice survived the 50-minute test, in contrast to the control group, of which no members survived the test, with the median survival time being 11 minutes.

But there’s a catch – this result requires some abrasion of the surface of the intestine, in order to help the oxygen gas pass through. Without this step, mice receiving rectal oxygen treatment only had a median survival time of around 18 minutes in a low-oxygen environment, not much longer than those without.

That caveat alone could be enough to prevent the technique from ever finding clinical relevance, so the researchers also investigated giving the animals enemas of perfluorodecalin (PFD), a liquid rich in oxygen. Importantly, this doesn’t require intestinal abrasion, and is already used to help speed up wound healing or preserve tissues and organs longer.

The animals were then tested in a chamber with oxygen levels only 10 percent of the usual atmosphere – not a lethal environment, but one that can induce hypoxia. The test mice were able to walk four times further in the chamber than the control group, and monitoring showed that more oxygen was reaching their hearts and circulating through their bodies. Mice given the PFD enemas were able to stave off hypoxia symptoms for the duration of the hour-long experiment.

In the next test, the team moved up to pigs, and found similar results. The rectal oxygen infusion improved their oxygen levels, as well as the color and coldness of their skin associated with hypoxia.

There are, however, a few key questions raised by the study. The main one, of course, is why such a roundabout route would ever be required when respirators are much more direct? But the team says that it could be delivered in an emergency, when respirators aren’t available or a patient has suffered respiratory failure and can’t get enough oxygen through their airways. A rectal liquid oxygen infusion could stave off hypoxia long enough for other treatments to be administered.

Other concerns that need to be investigated include what effects the treatment may have on the gut microbiome – after all, many of the important bugs there are used to a very low oxygen environment. The team says that no side effects were reported in the test animals, but further study will need to be conducted.

"The level of arterial oxygenation provided by our ventilation system, if scaled for human application, is likely sufficient to treat patients with severe respiratory failure, potentially providing life-saving oxygenation,” says Takanori Takebe, senior author of the study. "Although the side effects and safety need to be thoroughly evaluated in humans, our approach may offer a new paradigm to support critically ill patients with respiratory failure.”

30% Oxygen levels are not a huge deal as far as respiration goes. You would perform better in endurance events as it is easier to get more oxygen into your system but your body would adapt.

100% Oxygen can be dangerous or even toxic but a relatively modest increase to 30% is unlikely to have many side effects on humans.

There is going to be one large side effects though - fire.

At 30% oxygen levels fires burn faster, hotter and more easily. Even wet vegetation will burn and wildfires could easily sweep through any areas with available fuel.

In short: No benefits, no short-term damages. But quite possibly adverse long-term effects.

A normal person breathes about 7 1/2 to 8 liters per minute in rest and under normal conditions, containing 1.6 to 1,7 liters of oxygen. Only about 0.3 liters make it into the blood.

Patients with hypoxia are often supplied with oxygen. The "standard" amount is 2 liters per minute, which effectively means doubling the normal amount of oxygen. In Emergency care, 5-6 liters per minute are not uncommon, albeit only for a short time.
None of these doses are usually sustained for months or years, so it is hard to tell what long-term effects they may have (well, 5-6 liters will certainly lead to lung damage over a longer period of time, but you might quite possibly support 2 liters for years).

Saturation in healthy people in normal atmosphere under normal pressure is slightly below 100% (around 95-98%) unless you have a really bad hangover or a condition like COPD (then you may have around 91-92% or so).

Doubling, tripling, or quadrupling the amount of oxygen (without elevated pressure so oxygen goes into watery solution) thus cannot have any measurable positive effect, since saturation cannot possibly go above 100%, and it is already there anyway.

On the other hand, oxygen is a radical and apart from being directly neurotoxic at very high doses and directly damaging lung tissue at very high doses, moderately elevated oxygen exposure will eventually increase cell aging and the risk of cancer (especially in "exposed" tissue such as the lungs).

Higher not-immediately-toxic levels of oxygen may also have effects on equipment and environment that may not be neglegible and that may affect humans indirectly:

  • higher levels of ozone
  • increased tendency for metals to rust
  • increased tendency for some organic materials to age and decay, and bleach out
  • fire accelerant, flashing sparks
  • accelerated growth of aerob or opportunistically aerob microorganisms (some fungi, most yeasts, and some bacteria)

Arthropodes would evolve to become larger. In the paleozoic era, when the oxygen levels were higher than today, giant insects roamed the Earth surface.

Most of the other animals and plants would evolve in response of this. Some of these evolutions would be problematic, others won't. The humans are no exception, and a race of giants may evolve. In some areas it will be normal to find a lot of people with more than 2 meters of height.

Fires will burn much more. As explained by @TimB.

People will be stronger and more suitable for hard work. As explained by @ArtOfCode.

Current atmospheric O2 levels are about 21%, though the Oxygen compensation point dictated by C3 plants who produce our O2 limits it to about 23% at current CO2 levels. Higher CO2 levels permits increased photosynthesis rates and a correspondingly higher atmospheric O2% level.

220 ppm CO2 has a upper O2 limit of 23%O2. 350 ppm CO2 has a upper O2 limit of 27%O2. 700 ppm CO2 has a upper O2 limit of 35%O2.

These limits are "theoretical max" which you'll never reach due to O2 consumption from both organic metabolism, and from inorganic O2 fixation (I.e. rust and other metal oxidation). Once you hit the O2 compensation point, plants stop growing. they reach a point where the O2 levels provide a compensating force on enzymes that halt production of Rubisco.

Whats this mean in modern terms? well. we have increased volcanic activity, massive forest burning in Thialand and Brazil which has driven up CO2 levels since 1800. The increase CO2 raises the maximum O2 concentration and hense the plant-based biolevels possible (ie. more crops, faster growth of plants/food).

global O2 levels move VERY slowly, though its worth noting that past CO2 levels around 1500 ppm correlated to about 35%O2, so even at high compensation points (max levels) they never reached very high.

Humans can supposedly breath 50%O2 all day long without issues, and Scuba Divers like myself can get Nitrox-certifications to use 40% Nitrox (40% O2 with 60% N2) for shallow dives (the higher O2%, reduces the %N2 in the mix to slow nitrogen gas uptake in the blood. basically we use it to do longer dives without having to decompress).

Your question about 30% is interesting. 1) it would give endurance athletes a higher "effective" VO2 Max and would theoretically allow marathon runners to run at slightly higher speeds/effort while staying in the aerobic-exercise zone. This doesn't mean they could go farther, total energy is based on calories available. only that they could burn the same energy faster. )

2) Sprinters and other anaerobic activities would be unaffected. except for recovery rates! Hockey players, basketball, soccer, etc where stop and go windsprints are common could see reduced recovery times (i.e. hockey players could go back on the ice after shorter breaks without lactic acid building up). Even in todays pro sports you see this on football sidelines and hockey benches where winded all-stars will dawn a O2 mask to reduce lactic acid. So you could sprint more often, but not necessarily any faster.

3) Insects wouldn't be bigger. The giant insects in eras past were originally thought to be from O2 absorption, but studies in hyperbaric chambers have shown that O2 absorption rates are not limiting factors. Most scientists attribute ancient giant inserts to a lack of predators in that era, and an abundance of food. They simply lived long and ate well (in addition to theories about indeterminate growth and genetic differences in ancestors).

4) Fire hazards may be an issue, though an increased oxygenation rate of metals and spoiling of foods would be the most common issue for sure.

5) Lastly, its worth noting that CO2 levels in your blood are what trigger your brain to breath. The peripheral chemoreceptors in you carotid arteries will trigger breaths when CO2 concentration rises to 40mmHg. The CO2 levels in your blood vary between breaths from 35 to about 45mmHg are generated by metabolic means. So will increasing atmospheric CO2 levels affect your ability to breath? Nope. 40mmHg which is found in your blood and lungs alveolar space is 53000 ppm. which is why it diffuses out of your blood and into the lung space (since air is only

400ppm). Increased CO2 and O2 levels shouldn't affect your ability to trigger breathing unconsciously. )

How Your Lungs Work

Your lungs are located within your chest cavity inside the rib cage (see illustration below). They are made of spongy, elastic tissue that stretches and constricts as you breathe. The airways that bring air into the lungs (the trachea and bronchi) are made of smooth muscle and cartilage, allowing the airways to constrict and expand. The lungs and airways bring in fresh, oxygen-enriched air and get rid of waste carbon dioxide made by your cells. They also help in regulating the concentration of hydrogen ion (pH) in your blood.

When you inhale, the diaphragm and intercostal muscles (those are the muscles between your ribs) contract and expand the chest cavity. This expansion lowers the pressure in the chest cavity below the outside air pressure. Air then flows in through the airways (from high pressure to low pressure) and inflates the lungs. When you exhale, the diaphragm and intercostal muscles relax and the chest cavity gets smaller. The decrease in volume of the cavity increases the pressure in the chest cavity above the outside air pressure. Air from the lungs (high pressure) then flows out of the airways to the outside air (low pressure). The cycle then repeats with each breath.

Watch the video: Proč se objekty zahřívají při vstupu do atmosféry? - Vědecké kladivo (July 2022).


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