Hardcover à Oxygen PDF/EPUB å

Hardcover à Oxygen PDF/EPUB å



10 thoughts on “Oxygen

  1. Andrew Davis Andrew Davis says:

    An excellent example of what a popular science book should be Some criticised it for being too technical I disagree With so much material on Internet one can easily clarify some of the difficult parts even when admittedly some of the passages could be explained a bit better The author is a prominent expert in his field and that's perhaps why I prefer this to an approach often used by journalists or the science popularisers to ensure maximal understanding whilst oversimplifying the issue The author very skilfully links the facts with references to his own scientific career personal views on yet unresolved topics and his interaction with the other luminaries in the field My notes for future references followPhotosynthesis is a process used by plants and other organisms to convert light energy normally from the Sun into chemical energy that can be later released to fuel the organisms' activities This chemical energy is stored in carbohydrate molecules such as sugars which are synthesized from carbon dioxide and water In most cases oxygen is also released as a waste product Photosynthesis maintains atmospheric oxygen levelsThe process always begins when energy from light is absorbed by proteins that contain green chlorophyll pigments In these light dependent reactions some energy is used to strip electrons from suitable substances such as water producing oxygen gas The hydrogen freed by water splitting is used in the creation of two further compounds reduced nicotinamide adenine dinucleotide phosphate NADPH and adenosine triphosphate ATP the energy currency of cellsThe overall euation for the type of photosynthesis that occurs in plants is as follows6 CO2 6 H2O C6H12O6 6 O2Carbon dioxide Water plus light photons Sugar OxygenCyanobacteria is bacteria that obtain their energy through photosynthesis By producing gaseous oxygen as a by product of photosynthesis cyanobacteria are thought to have converted the early reducing atmosphere into an oxidizing one causing the Great Oxygenation Event dramatically changing the composition of life forms on Earth by stimulating biodiversity and leading to the near extinction of anaerobic organisms that is oxygen intolerant There is an evidence that cyanobacteria were producing oxygen as far back as 267 billion years agoSynechococcus is a unicellular cyanobacterium that is very widespread in the marine environment Its size varies from 08 µm to 15 µm The photosynthetic coccoid cells are preferentially found in well–lit surface waters where it can be very abundant generally 1000 to 200000 cells per millilitre Many freshwater species of Synechococcus have also been describedProchlorococcus is a genus of very small 06 µm marine cyanobacteria with an unusual pigmentation chlorophyll b These bacteria belong to the photosynthetic picoplankton and are probably the most abundant photosynthetic organism on Earth and responsible for a large percentage of the photosynthetic production of oxygenThe amount of oxygen in the air is 21% regardless of the altitude However at higher elevation there is a less of air and therefore we pull less of oxygen At an elevation of 2100 m the atmospheric pressure is about 77% of the sea level and therefore for the same breath we pull only 77% of oxygen On the peak of Mount Everest the pressure is only 33% of the sea levelIn South Africa goldmines at depth of over 39 km an ancient river deposits are dated to some 28 to 31 billion years They contain uranium oxide UO2 which indicates that at that time there were only “trace” amount of oxygen The UO2 reacts easily with oxygen and that’s why we don’t find it rivers todayBased on analysis of rocks for the contents of uranite it has been noted that concentration of atmospheric oxygen increased substantially around 23 to 235 billion years ago It is referred to as the “great oxidation event” GOE The exact reason behind it is still being argued about One theory refers to the evolution of cyano bacteria A convincing theory and supported by the author relies on combination of Oxygen released from the organic carbon and the reducing flux of gases from the mantle through volcanos Once the flax started slowing down an excess oxygen was left in the atmosphereFollowing GOE with oxygen the oxidation of rocks has increased This in turn liberated enormous uantities of Phosphorus to the oceans and conseuently vast amount of organic matter and its burial in the rocksThe high amounts of buried organic carbon represented in turn a huge oxygen sink drawing down levels of atmospheric oxygen It’s expected they were less than 10% of the present levelsAround 580 million years ago the oldest fauna can be found on sea floor where they operated without light At that time oxygen rose to at least 15% of present levelsAround 300 million years ago the land plants become so diversified and developed a series of tough organic molecules like cellulose to grow tall and resist microbial decay The vast expanses of low laying swampland collected and buried massive amounts of organic plant debris and this is why so much coal was formed during that time During that time the gigantic insects developedThe drop in oxygen concentration that followed was probably due to changes in paleogeography A supercontinent called Pangea became fully assembled and as result far fewer low laying swampy areas were available These sandy continental sediments are virtually free of organic matter and thus provides no input of oxygen to the atmosphere This reduced the supply of oxygen to the atmosphere and drop in oxygen concentrationOver the last 350 million years a continuous record of charcoal in continental sedimentary rocks suggests that O2 has always comprised at least 15% of the atmosphere because wood cannot burn below this thresholdIn broad outline oxygen is regulated because an increase in oxygen increases the consumption of oxygen andor decreases the rate of oxygen production A decrease in oxygen has opposite effectsOxygen and the Rise of Vascular Land Plants The data of Fig 2 show a pronounced and extended rise in atmospheric O2 over the period 375–275 mega annum Ma spanning the Carboniferous and Permian periods What could have brought this rise about? The modelling shows that increased oxygen production caused by increased burial of organic carbon was the chief suspect This increased burial is attributed to the rise and spread of large woody vascular plants on the continents beginning at about 375 Ma The plants supplied a new source of organic matter to be buried on land and carried to the oceans via rivers This ‘‘new’’ carbon was added to that already being buried in the oceans thus increasing the total global burial flux This is especially true of lignin a substance that is decomposed only with difficulty by micro organisms The rise of ligniferous plants and an initial level of microbial lignin breakdown lower that that at present may have contributed to increased organic matter burial and better preservation This high burial rate is reflected by the abundance of coals during this period which is the greatest abundance in all of earth historyAnother factor favouring extensive Permo Carboniferous organic matter burial was the presence of vast swamps on the continents brought about by the presence of extensive poorly drained flatlands and large areas of coastal plains brought about by glacially induced fluctuations of sea level This situation enabled the preservation of organic debris leading ultimately to coal formation because of the relative lack of organic decay in stagnant anoxic waters Why coal formation organic burial and oxygen production dropped toward the end of the Permian period Fig 2 is not clear but it may be tied up with sea level drop and a general drying of the continentsThe level of atmospheric oxygen cannot rise indefinitely unless the freuency of forest fires becomes so excessive that plant life cannot persist Fossil charcoal as evidence of paleo fires has been found for all times that trees have populated the land and the lower limit for the production of charcoal has been estimated to be at about 13% O2


  2. Sally Sally says:

    This book describes current research on the history of oxygen in earth's atmosphere It was particularly good at conveying the collegiality of science and the way that data and conflicting hypotheses are built up tested and rethought While written for the general public reading it reuires close attention I found it sobering that the tremendous uantities of cyanobacteria existing in the oceans were only discovered in 1979 since they were too small to be caught in the netting used to gather specimens Who knows what else is hiding in plain sight?


  3. Steve Steve says:

    I often complain about popular science books written by journalists and how they often elide over many of the technical details which is where the mystery and the beauty lie This book is kind of the opposite a working scientist who writes moderately well but gets a little too lost in the details Which in the end it makes me wonder who the intended audience is The subject how did the Earth's atmosphere get to have so much free oxygen is massive and inspiring and there seem to be few people that are ualified to write this book than Canfield It is uite interesting but I found myself far too often bogged down in the details losing sight of the big picture he was trying to convey As such it was of a slog than a delight I cannot help but compare with the bio chemistry books written by Nick Lane and wonder what makes the difference; one was delightful and I have eagerly sought out subseuent work the other is interesting but something I probably won't pursue any further


  4. Daniel Martins Daniel Martins says:

    When I first heard about Oxygen I immediately wanted to read it This is an amazingly important topic for understanding the history of life on Earth and it was written by a true renowned specialist Prof Donald Canfield Although the positives hugely outweigh the negatives such as the author's clear and precise use of language and the careful selection and exposure of data there were some distracting features such as the oversimplification of relatively simple geological and biological processes I also think that some topics such as the evolution of oxygenic photosynthesis could have been developed further It would have added depth and length to a rather short book that left me wanting


  5. Anett Kovacs Anett Kovacs says:

    In Oxygen A Four Billion Year History ecology professor Donald E Canfield recounts the history of Earth's atmosphere focusing on one of the most important elements of life oxygen The author describes scientific theories around the oxygenation of our planet and their evolution precisely and in a very detailed manner This book is a bit technical than your typical popular science book which I enjoy but it might not be everyone's cup of tea Nevertheless it is a very informative book about a fascinating subject


  6. Leo W. Leo W. says:

    Solid interesting science The writing however falls far below the admittedly high standard set by Andrew Knoll in Life on a Young Planet The First Three Billion Years of Evolution on Earth


  7. Steven Steven says:

    Although this is a popular science book written for a general audience there are a few technical spots Canfield does a superb job describing the great oxygen event and the subseuent reducing atmosphere that caused the great rusting or oxidizing event Banded iron formations are evidence of this The rise in oxygen brought an increase in biodiversity Canfield does an excellent job of detailing the history of oxygen on Earth


  8. Megan Megan says:

    This might be better if you have a thorough chemistry background The topic was interesting but the book was weighed down by chemical diagrams and reaction euations


  9. Peter Tillman Peter Tillman says:

    Good book by a student of Bob Garrels See notesSadly it's due I'll have to get it back to finish it Too many booksSet back to want to read for now


  10. Steve Jones Steve Jones says:

    This is a uite readable and interesting book by one of the world's leading authorities on geochemistry earth history and the early oceans It covers the evidence gathered over the last several decades and before concerning the evolution of Oxygen in Earth's atmosphere Other popular science accounts on this and related topics have given a detailed and maybe misleading? account of the changes in the Oxygen content of the atmosphere but Canfield is much conservative in his account of what happened and when Up until about 24 billion years ago there was virtually no Oxygen in the Earth's atmosphere At this point the Great Oxygenation Event occured and free Oxygen first appeared in the Earth's atmosphere Between this point and the start of the Phanerozoic Eon 540 million years ago it is extremely difficult to put numbers on the evolution of Oxygen in the atmosphere based on the geochemical evidence we have to date The most that Canfield will admit to is that Oxygen levels in the atmosphere during the early stages of the Phanerozoic Eon were in the range 10% to 20% of present atmospheric levels and only displayed a significant increase during the Late Silurian and Early Devonian Periods some 420 million years ago There is considerable evidence of very high rates of oxygen liberation during the Carboniferous and early Permian Periods when atmospheric oxygen concentrations may have significantly exceeded modern levels What is particularly interesting in Canfield's account is how the evolution of the Oxygen content of the atmosphere and oceans interacted with other geophysical cycles including the carbon silicate weathering phosphorus and nitrogen cycles If you have an interest in the modern understanding of Earth systems science this book is well recommended


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Oxygen ❮Reading❯ ➸ Oxygen Author Donald E. Canfield – Larringtonlifecoaching.co.uk The air we breathe is twenty one percent oxygen an amount higher than on any other known world While we may take our air for granted Earth was not always an oxygenated planet How did it become this wa The air we breathe is twenty one percent Oxygen an amount higher than on any other known world While we may take our air for granted Earth was not always an Oxygenated planet How did it become this way Oxygen is the most current account of the history of atmospheric Oxygen on Earth Donald Canfield one of the world's leading authorities on geochemistry earth history and the early oceans covers this vast history emphasizing its relationship to the evolution of life and the evolving chemistry of the Earth With an accessible and colorful first person narrative he draws from a variety of fields including geology paleontology geochemistry biochemistry animal physiology and microbiology to explain why our Oxygenated Earth became the ideal place for lifeDescribing which processes both biological and geological act to control Oxygen levels in the atmosphere Canfield traces the records of Oxygen concentrations through time Readers learn about the great oxidation event the tipping point billion years ago when the Oxygen content of the Earth increased dramatically and Canfield examines how Oxygenation created a favorable environment for the evolution of large animals He guides readers through the various lines of scientific evidence considers some of the wrong turns and dead ends along the way and highlights the scientists and researchers who have made key discoveries in the fieldShowing how Earth's atmosphere developed over time Oxygen takes readers on a remarkable journey through the history of the Oxygenation of our planet.