Table of contentsStages of the carbon cycleExamples of the carbon cycleAtmosphereLithosphereBiosphereOceansNitrogen cycleAll living things are made of carbon. Carbon is also part of the ocean, air and even rocks. Because Earth is a dynamic place, carbon does not stay still. It's on the move! In the atmosphere, carbon is bound to a certain amount of oxygen in a gas called carbon dioxide. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay Plants use carbon dioxide and sunlight to make their own food and grow. The carbon becomes an integral part of the plant. Plants that die and are buried can turn into carbon-based fossil fuels like coal and oil over millions of years. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon dioxide. Carbon dioxide is a greenhouse gas that traps heat in the atmosphere. Without this gas and other greenhouse gases, Earth would be a frozen world. But humans have burned so much fuel that there is about 30 percent more carbon dioxide in the air today than there was about 150 years ago, and the Earth is becoming a warmer place. In fact, ice cores show us that there is now more carbon dioxide in the atmosphere than there has been in the last 420,000 years. Carbon dioxide in the atmosphere blocks the sun's rays from escaping into space, much like the glass walls of a greenhouse. . This isn't always a bad thing: a certain amount of carbon dioxide in the atmosphere is good for keeping the Earth warm and stabilizing its temperature. But Earth has experienced catastrophic warming cycles in the past, such as the Permian extinction, which is believed to have been caused by a drastic increase in the level of greenhouse gases in the atmosphere. No one knows exactly what caused the change that caused the Permian extinction. Greenhouse gases may have been added to the atmosphere by an asteroid impact, volcanic activity or even massive wildfires. Whatever the cause, during this warming episode, temperatures increased drastically. Much of the Earth became desert and more than 90% of all species living at that time became extinct. This is a good example of what can happen if the essential cycles of our planet undergo a major change. Another important variable affected by the carbon cycle is ocean acidity. Carbon dioxide can react with ocean water to form carbonic acid. This has been an important stabilizing force in the carbon cycle over the years, since the chemical balance between carbon dioxide and carbonic acid means that the ocean can absorb or release carbon dioxide as atmospheric levels rise. go up and down. However, as you might guess, increasing ocean acidity can cause problems for marine life – and it could eventually pose a problem for other parts of the carbon system. Many forms of marine life that have shells, for example, can extract carbon from water to create the calcium carbonate from which they make their shells. If these species suffer, the ocean could lose some of its ability to remove carbon from the atmosphere. Finally, there is of course the role of life in the carbon cycle. The activity of plants and animals has been one of the major forces affectingchanges in the carbon cycle over the last billion years. Photosynthesizers have radically changed Earth's atmosphere and climate by removing enormous amounts of carbon from the atmosphere and transforming that carbon into cellular materials. These activities created free oxygen and the ozone layer, and generally paved the way for the evolution of animals that obtain their energy by breaking down organic matter created by photosynthesizers and extracting the energy that photosynthesizers used to make these molecules. With one particular animal species – humans – making big changes, the future of Earth's carbon cycle is uncertain. All of these cycles in closed systems eventually correct themselves – but sometimes this happens because of drastic population.reduction of offending species through starvation.Stages of the carbon cycleAtmospheric carbon To be part of the carbon cycle carbon, carbon atoms start out as a gas. Carbon dioxide – CO2 – can be produced by inorganic processes or by the metabolism of living things. Before Earth was inhabited, carbon dioxide likely came from volcanic activity and asteroid impacts. Today, carbon is also released into the atmosphere by the activities of living things, such as the exhalations of animals, the actions of decomposer organisms, and the burning of wood and fossil fuels by humans. Regardless of how carbon dioxide enters the atmosphere, CO2 gas is the starting point of the carbon cycle. Carbon Absorbed by Producers “Producers” – organisms that produce food from sunlight, such as plants – absorb carbon dioxide from the atmosphere and use it to build sugars, lipids, proteins and other building blocks essential to life. For plants, CO2 is absorbed through pores in their leaves called “stomata”. Carbon dioxide enters the plant through the stomata and is incorporated into carbon containing compounds with the help of solar energy. Plants and other producing organisms such as cyanobacteria are essential to life on Earth because they can transform atmospheric carbon into living matter. Carbon transfer via producers that are consumed “Consumers” are organisms that eat other living things. Animals are the most visible type of consumer in our ecosystems, although many types of microbes also fall into this category. Consumers incorporate carbon compounds from plants and other food sources when they consume them. They use some of these carbon compounds in food to build their own bodies – but much of the food they eat is broken down to release energy, in a process almost the opposite of what the producers do. While producers use the sun's energy to make bonds between carbon atoms, animals break these bonds to release the energy they contain, ultimately transforming sugars, lipids and other carbon compounds into units of a only carbon. These are ultimately released into the atmosphere in the form of CO2. This process of “cellular respiration” – during which oxygen gas is inhaled and carbon dioxide is exhaled – is a major source of carbon release into the atmosphere. But it's not always the last step in the carbon cycle. What about carbon compounds that are not eaten or broken down by animals? Carbon released by decomposers Plants and animals that die without being eaten by other animals are broken down by othersorganisms, called “decomposers”. Decomposers include many bacteria and some fungi. They usually only decompose already dead matter, rather than catching and eating a living animal or plant. Just like animals, decomposers break the chemical bonds in their food molecules. They create many chemicals, including in some cases CO2. Carbon that is not released into the atmosphere in this way may also be released by… Human-caused combustion Humans are the only animals we know of that can voluntarily create fire. And we often set things on fire. Our cars run by burning fossil fuels – oil and gasoline, which are made from dead plant and animal matter that has spent millions of years buried deep in the Earth. Many of our power plants are also powered by burning fossil fuels, including coal, which is another form of dead plant matter buried underground and transformed by geologic heat. Finally, humans also burn a lot of wood. We no longer burn wood to power our machines like we did in the 19th century, but now we often burn forests in order to clear land for agriculture, mining, and other purposes. To date, about half of the planet's forests have been burned or destroyed by human activity. The scientific community has been sounding the alarm: by making significant changes to Earth's carbon cycle, we could end up altering our climate or other important aspects of the planet's ecosystem that we rely on to survive. As a result, many scientists advocate decreasing the amount of carbon burned by humans by reducing car travel and electricity consumption, and investing in non-burning energy sources such as solar power and electricity. wind energy. Examples of the Carbon Cycle The carbon cycle includes many parallel systems that can either absorb or release carbon. Together, these systems help keep Earth's carbon cycle – and therefore its climate and biosphere – relatively stable. Atmosphere One of the main reservoirs of carbon is carbon dioxide present in the Earth's atmosphere. Carbon forms a stable gas molecule in combination with two oxygen atoms. In nature, this gas is released by volcanic activity and by the respiration of animals which attach carbon molecules from the food they consume to oxygen molecules before exhaling them. Humans also release carbon dioxide into the atmosphere by burning organic materials such as wood and fossil fuels. Carbon dioxide can be removed from the atmosphere by plants, which capture atmospheric carbon and transform it into sugars, proteins, lipids and other molecules essential for life.LithosphereThe Earth's crust – called "lithosphere" from the Greek word "litho ” for “stone” and “sphere” for globe – can also release carbon dioxide into the Earth’s atmosphere. This gas can be created by chemical reactions in the Earth's crust and mantle. Volcanic activity can lead to natural releases of carbon dioxide. Some scientists believe widespread volcanic activity may be behind the warming of the Earth that caused the Permian extinction. While the Earth's crust can add carbon to the atmosphere, it can also remove carbon. Movements in the Earth's crust can bury carbon-containing chemicals, such as dead plants and animals, deep down, where their carbon cannotescape into the atmosphere. Biosphere Among living things, some extract carbon from the atmosphere, while others release it. The most visible participants in this system are plants and animals. Plants remove carbon from the atmosphere. They are not doing this as a charitable act; Atmospheric carbon is actually the “food” that plants use to make sugars, proteins, lipids and other molecules essential to life. Plants use energy from the sun, harvested through photosynthesis, to make these organic compounds from carbon dioxide and other trace elements. Indeed, the term “photosynthesis” comes from the Greek words “photo” for “light” and “synthesis” for “to assemble”. OceansEarth's oceans have the capacity to both absorb and release carbon dioxide. When carbon dioxide from the atmosphere comes into contact with ocean water, it can react with water molecules to form carbonic acid – a dissolved liquid form of carbon. Like most chemical reactions, the rate of this reaction is determined by the balance between the products and reactants. When there is more carbonic acid in the ocean than carbon dioxide in the atmosphere, some carbonic acid may be released into the atmosphere as carbon dioxide. Nitrogen Cycle All life requires nitrogen compounds, for example proteins and nucleic acids. Air, which contains 79% nitrogen gas (N2), is the main reservoir of nitrogen. But most organisms cannot use nitrogen in this form. Plants must secure their nitrogen in “fixed” form, that is to say incorporated in compounds such as: nitrate ions (NO3−) ammonium ions (NH4+) urea (NH2)2CO Animals secure their nitrogen (and all other) compounds in plants (or animals). which fed on plants).Steps: Four processes participate or stages are involved in the nitrogen cycle through the biosphere:Nitrogen fixationDecompositionNitrificationDentrificationMicroorganisms play a major role in each of them.Nitrogen fixation nitrogen The nitrogen molecule (N2) is quite inert. Breaking it down so that its atoms can combine with other atoms requires a significant input of energy. Three processes are responsible for most of the nitrogen fixation in the biosphere: atmospheric fixation by lightning industrial fixation biological fixation by certain microbes — alone or in symbiotic relationships with certain plants and animals Atmospheric fixation The enormous energy of lightning breaks apart nitrogen molecules and allows their atoms to combine with oxygen in the air to form nitrogen oxides. These dissolve in rain, forming nitrates which are transported to the earth. Atmospheric nitrogen fixation probably contributes 5 to 8% of total nitrogen fixed. Industrial attachmentUnder high pressure, at a temperature of 600°C and with the help of a catalyst, atmospheric nitrogen and hydrogen (usually derived from natural gas or petroleum) can be combined to form ammonia ( NH3). Ammonia can be used directly as fertilizer, but most of it is then converted to urea and ammonium nitrate (NH4NO3). Biological fixation The ability to fix nitrogen is only found in certain bacteria and archaea. Some live in a symbiotic relationship with plants in the legume family (e.g. soya, alfalfa). Some establish symbiotic relationships with plants other than legumes (e.g. alders). Some establish symbiotic relationships with animals, for example termites and "shipworms" (wood-eating bivalves). Certain fixing bacteria2−).