A biogeochemical cycle is a process by which a chemical element or compound moves through the biosphere, the lithosphere, the hydrosphere, and the atmosphere of a planet. Biogeochemical cycles involve the exchange of materials between living organisms and their environment.
There are several important biogeochemical cycles that play a key role in the functioning of Earth’s ecosystem, including the water cycle, the carbon cycle, the nitrogen cycle, and the phosphorus cycle.
The water cycle involves the movement of water through the environment, including evaporation from the surface of the Earth, precipitation, and infiltration into the ground. The carbon cycle involves the movement of carbon between the atmosphere, the oceans, and living organisms. The nitrogen cycle involves the movement of nitrogen between the atmosphere, soil, and living organisms. The phosphorus cycle involves the movement of phosphorus between the lithosphere, the hydrosphere, and living organisms.
Understanding the biogeochemical cycles is important for understanding the functioning of Earth’s ecosystem and for predicting the impacts of human activities on the environment. For example, human activities such as burning fossil fuels and deforestation can alter the balance of elements in the biogeochemical cycles, leading to negative impacts on the environment and on the species that depend on it.
Nitrogen cycle
The nitrogen cycle is a very complex and well-buffered gaseous type of biogeochemical cycle in which nitrogen is converted into many forms, passing from the atmosphere to the soil to the organism, and back to the atmosphere. The nitrogen cycle involves various steps like nitrogen fixation, nitrification, assimilation, ammonification, and denitrification. In the nitrogen cycle, the reservoirs are the atmosphere, sediments, dissolved nitrogen of the ocean, inorganic ocean components, soil, terrestrial biomass, and marine biomass.
Credit: EssauMejia, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
- The nitrogen in the protoplasm is broken down from organic to inorganic forms by a series of decomposer bacteria, each performing a particular part of the cycle. Some amounts of nitrogen produce end products such as ammonium and nitrate, which the green plants most readily absorb. The atmosphere is the most significant nitrogen source, constituting about 78 % of nitrogen. The continuous production of nitrogen inside the atmosphere is by denitrifying bacteria. Similarly, nitrogen continuously enters the cycle through nitrogen-fixing microorganisms (biological fixation), other physical fixation, lightning, etc.
- The nitrifying bacteria like Nitrosomonas (which converts ammonia to nitrite) and Nitrobacter (which converts nitrite to nitrate) obtain energy from the breakdown of organic matter, whereas the denitrifying and nitrogen-fixing bacteria require energy from other sources of organic matter or sunlight to complete their cycle.
- The heterotrophic organisms break down the proteins present in their protoplasm enzymatically and, through excretion, remove the excess nitrogen as urea, uric acid, or ammonium.
- The nitrifying bacteria oxidize the ammonium to nitrite and nitrite to nitrate to produce energy for livelihood. The plants use these three: ammonium, nitrite, and nitrate, as basic sources of nitrogen. Most plants prefer to use ammonium than nitrate as nitrate is a more energy-expensive source of nitrogen than ammonium. The plants which have utilized nitrate must produce enzymes to convert the nitrates back into ammonium.
- Nitrogen fixation is of three types: atmospheric fixation, industrial nitrogen fixation, and biological nitrogen fixation.
- Atmospheric nitrogen fixation involves lightning which breaks the nitrogen into nitrogen oxides to be used by the plants,
- Industrial nitrogen fixation is an artificial technique developed to help in nitrogen fixation. In this, firstly, ammonia is produced by the direct combination of nitrogen and hydrogen, and it is converted into urea, used as fertilizers. Industrial fixation of nitrogen requires a large amount of fossil fuel energy, which makes nitrogen fertilizer more expensive than other fertilizers.
- Biological nitrogen fixation is done by the Rhizobium bacteria and other cyanobacteria, which transform the unusable form of nitrogen into readily usable forms.
- Nitrogen fixation takes place by the action of cyanobacteria which may occur in free-living forms or in symbiotic association with fungi, lichens, mosses, ferns, and at least one seed plant. The efficient nitrogen fixers are purple bacterium Rhodospirillum, Pseudomonas-like soil bacteria, Rhizobium bacteria, Trichodesmium blue-green bacteria, Anabaena, etc. The enzyme nitrogenase has a major role in nitrogen fixation as it can catalyze the splitting of nitrogen and reduce acetylene to ethylene. Biological nitrogen fixation occurs both in the autotrophic and heterotrophic levels of ecosystems as in both aerobic and anaerobic zones of the soil and aquatic sediments.
- The nitrification process involves the conversion of ammonia into nitrate in the presence of bacteria in the soil. Nitrification is very important as ammonia gas is toxic to plants. Firstly, nitrites are formed by the oxidation of ammonia with the help of species of Nitrosomonas bacteria. Then, the nitrites are converted into nitrates with the help of Nitrobacter bacteria.
- Assimilation involves the absorption of nitrogen compounds (nitrite ions, nitrate ions, or ammonium ions) by the plants from the soil with the help of their roots. The absorbed nitrogen compounds are used in the formation of plant and animal proteins. Thus, the plant protein is consumed by the primary consumers, and in this way, the food web starts.
- Ammonification involves the conversion of organic matter back into ammonium compounds by the action of the decomposers (bacteria or fungi). In this way, the nitrogen present in the organic matter is released back into the soil when the plants or animals die.
- Denitrification involves the conversion of nitrate into gaseous nitrogen. In this way, the nitrogen compounds return back to the atmosphere as the final stage. This process occurs in the absence of oxygen by the action of species of denitrifying bacteria Clostridium and Pseudomonas. This bacteria process the nitrate to gain oxygen and release nitrogen gas as a byproduct.
Phosphorous cycle
Phosphorous is a necessary constituent of protoplasm. The phosphorous circulates with organic compounds in the form of phosphates, which becomes available to the plants. The phosphorous cycle is a simple, less well-buffered, regulated sedimentary-type cycle. In the phosphorous cycle, the reservoirs are sediments, land, deep oceans, terrestrial biota, surface oceans, and the atmosphere.
- Due to the rainfall and weathering, the rocks release phosphate ions and other minerals which are transported in the soil and water.
- Plants absorb the inorganic phosphate from the soil. The animals consume the plants. In this way, the phosphate enters organic molecules like DNA. The phosphate returns back to the soil when the plants and animals die and decay in the soil.
- The mineralization process occurs when the bacteria break down the organic matter of the soil into inorganic phosphate which can be later taken up by the plants.
- The phosphorous present in the soil reaches the water resources through surface runoff.
Sulphur cycle
The sulphur is an essential constituent of specific amino acids. It is reduced by autotrophs and consolidated into proteins. The sulphur cycle illustrates the active process between the air, water, and the earth’s crust, the key role the microorganisms play, and the complications caused by industrial air pollution. In sulphur cycle, the reservoirs are the lithosphere, ocean, sediments, soils, lakes, marine biota, and atmosphere.
Hydrogen sulphide is produced from the decomposition of proteins. The gaseous form of sulphur is converted to other forms like sulphur dioxide, sulphate and sulphur aerosols. The sulphur aerosols reflect the sunlight into the sky, which leads to global cooling and to acid rain.
- The weathering of rocks releases the sulfur.
- The sulphur when comes in contact with air convert into sulphates.
- The plants and microbes absorb the sulphates and convert them into organic forms of sulphur.
- The animals consume the organic forms of sulphur, as a result, sulphur cycles in the food chain.
- The decomposition of dead animals release some sulphur which enters the tissue of microbes.
- The sulphur is directly released into the atmosphere by different natural sources like volcanic eruptions, evaporation of water and breakdown of organic matter. The sulphur from the atmosphere gets released into the earth through rainfall.
Carbon cycle
The carbon cycle is crucial to all life on the earth as it is a vital component of the body, from proteins and lipids to even our DNA. In the carbon cycle, the reservoirs are sediments, rocks, deep oceans, soils, surface oceans, atmosphere, deep ocean, terrestrial biomass, surface sediments, and marine biomass. The carbon cycle represents carbon cycling in elemental forms (E.g., diamond, and graphite) and combined state (E.g., carbonates in minerals and carbon dioxide gas in the atmosphere).
In the carbon cycle, carbon compounds are interchanged among the earth’s biosphere, geosphere, hydrosphere, and atmosphere.
- Autotrophs, i.e., plants, absorb carbon in the atmosphere in the form of carbon dioxide, which they utilize for photosynthesis.
- The animals consume the plants, and the carbon gets into the animal’s bodies.
- The carbon releases back into the atmosphere when the plants and animals die and decompose in the soil.
- Fossil fuels are formed when the carbon produced from the decomposition of dead plants and animals is not released into the atmosphere.
- Thus, formed fossil fuels release carbon back into the atmosphere in the form of carbon dioxide through human activities like the burning of fossil fuels.
Hydrologic cycle
The hydrologic cycle is a vital biogeochemical cycle. In the hydrologic cycle, the largest reservoir is the ocean, whereas the little reservoir is the atmosphere. The main steps involved in the hydrologic cycle or water cycle are:
- The sunlight aids in evaporating water from the oceans into the atmosphere.
- The transpiration by the plants and vegetation also increases the amount of water vapor in the atmosphere.
- The condensation process occurs in the clouds and the atmosphere.
- Then, through the precipitation (rainfall), the water falls back down on the earth. Due to the surface runoff, the water return back to the ocean.
- During this whole process, the water is utilized as well as reused.
- The global amount of water on the earth is the same as that of the prehistoric ages. The amount of water frozen has highly differed over geological time.
- The movement or flux of water is different from place to place.
- The water cycle has been observed to be highly affected by human activities in the present era.
The biogeochemical cycles are very much important as they regulate the elements vital for the existence of life on the earth by the natural cycling of nutrients through the physical and biological aspects. This has made possible the continuous survival and effective functioning of the ecosystems.
What are the 4 biogeochemical cycles?
The four main biogeochemical cycles are nitrogen cycle, hydrologic cycle, sulphur cycle and carbon cycle.
What is the best definition for biogeochemical cycles?
‘Bio’ refers to the living organisms and ‘geo’ refers to the earth. ‘Geochemistry’ refers to the phenomenon related with the chemical composition of the earth and the exchange of elements between different parts of the earth’s crust, atmosphere, ocean, rivers and other water bodies’. ‘Biogeochemistry’ refers to the phenomenon related with the exchange of materials between living and non-living components of the ecosphere. Thus, biogeochemical cycles can be best defined as the cycling of materials or nutrients between the living and non-living components of the environment.
What is biogeochemical cycle and its types?
Biogeochemical cycle is the natural pathway through which the important nutrients or components of living matter are circulated throughout the biological, geological and chemical aspects of the environment. The biogeochemical cycle is mainly of two types: Gaseous cycle and Sedimentary cycle. Gaseous cycles include the cycles of carbon, nitrogen, oxygen and water whereas Sedimentary cycles include the cycles of sulphur, phosphorous and rock.
What are the 5 biogeochemical cycles?
The five biogeochemical cycles are nitrogen cycle, phosphorous cycle, sulphur cycle, carbon cycle and hydrologic cycle.
What is a biogeochemical cycle example?
All the cycles occurring among the organisms and the environment come under biogeochemical cycle. Examples are nitrogen cycle, hydrologic cycle, sulphur cycle, carbon cycle, etc.
Why are they called biogeochemical cycles?
The term ‘biogeochemical cycles’ incudes all the biological, geological and chemical aspects of each cycle.
Why are biogeochemical cycles important?
The biogeochemical cycles are important because they are processes of natural cycling and help in the proper functioning of ecosystem by playing the following roles:
– It will transform the matter from one form to another which helps in the optimization of matter in a form specific to particular organism. For example- water in liquid form utilized by the human.
– It facilitates the storage of the elements. For Example- the Nitrogen cycle help in the nitrogen fixation.
– It connects different variants of the ecosystem such as one living organism to another, living organism to non-living organism.
– It regulates the flow of substances through the cycles like sedimentary cycles and gaseous cycles.
What is the best definition for biogeochemical cycles 3 points?
– A biogeochemical cycle or substance turnover or cycling of substances is a pathway by which a chemical substance moves through biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth.
– A biogeochemical cycle is a natural cycle in which the finite amount of matter, in the form of atoms present within the earth cycles throughout the biotic and abiotic components of the ecosystem.
– Biogeochemical cycles are those cycles in which the organic and inorganic matter is transferred within the living organisms and the environment.
How does human interfere the biogeochemical cycle?
Ø Human interfere with the biogeochemical cycle through their rapid and unsustainable developmental activities carried out for urbanization, modernization and industrialization. People burn forests and clear the land for cultivation of agricultural crops and for pasture. In addition, the people use large amount of chemical fertilizers and pesticides in agricultural land, which disrupts the balance between the nitrogen fixation and denitrification. As a result, the nitrogen fertilizers are lost as nitrates to groundwater and run off which finally gets mixes into the aquatic system and causes water pollution. The high-temperature combustion and release of smoke from automobiles, industries and burning of fossil fuels increase the amount of nitrous oxide, nitric oxide and nitrogen oxide in the atmosphere. The increased amount of nitric acid in the air combines with other elements to form smog and acid rain.
The water cycle has been affected through different human activities like construction of river dams for hydroelectricity, irrigating water for farming purposes, deforestation and burning of fossil fuels. Due to the increased temperature, the annual precipitation has been badly affected and has become irregular causing extreme droughts or heavy rainfall. Due to the pollution and sedimentation, the quality of water has been highly degraded.
The increased amount of carbon dioxide in the atmosphere due to human activities like fossil fuel burning, overpopulation, deforestation, etc. is leading to overgreen house effect and the increase of earth’s global temperature, thus, affecting the carbon cycle too.
Due to the altered biogeochemical cycles and climate change, the issues like food security, health problems, vulnerability of biodiversity, etc. have been arising.
The balance of the global sulphur cycle has been affected by the human activities through activities like burning of fossil fuels (especially coal), releasing high amount of hydrogen sulphide gas in the atmosphere. The mixing of this gas with the rainfall results in acid rain, which is detrimental to the living beings.
What are the characteristics of biogeochemical cycle?
The characteristics of biogeochemical cycle can be discussed as follows:
– They are more or less circular pathways.
– The essential elements like carbon, nitrogen, hydrogen, oxygen and phosphorous are needed in large quantities which exhibit definite biogeochemical cycles.
– There are two basic types of biogeochemical cycles: gaseous and sedimentary.
– The chemical elements move through the abiotic and biotic components of the ecosystem.
What is a sedimentary biogeochemical cycle?
In a sedimentary biogeochemical cycle, the soil, rocks and minerals are the main pool and the crust of the earth is the reservoir. The sedimentary biogeochemical cycles are slow and less perfect systems as their elements may get stored in the reservoir pool and may go out of circulation for long periods. The elements like phosphorous and sulphur have sedimentary cycles as they are abundant in the earth’s crust. The living organisms acquire the mineral elements from the inorganic sources. The mineral elements are available as dissolved salts in soil water or in lakes, streams and seas. The soluble salts enter the water cycle being transported through the soil to streams and lakes and eventually reaching the seas. Other salts come back to the earth’s crust through sedimentation being incorporated into salt beds, silts and limestone. After weathering, they enter the cycle again
What are biogeochemical cycles Class 9?
Biogeochemical cycles are natural cycles by which essential elements of living matter are circulated. Examples: carbon cycle, water cycle, nitrogen cycle, sulphur cycle and phosphorous cycle.
What is the difference between a pool and a flux in a biogeochemical cycle?
The main difference between a pool and a flux in a biogeochemical cycle is that the pool means the stock of the elements or matter whereas flux means the flow of elements or matter from one being to other or between the organism and the environment. The unit of measurement of pool is mass whereas the unit of flux is mass per time.
Which is not a major biogeochemical cycle?
Phosphorous cycle is not a major biogeochemical cycle.
What do geochemical and biogeochemical cycles do?
Geochemical cycles involves the chemical interactions in crustal and sub crustal reservoirs of the earth and lithosphere whereas biogeochemical cycles involve the chemical interactions in the surface reservoirs like the atmosphere, hydrosphere, lithosphere and biosphere.
Why are geochemical and biogeochemical cycles so important?
Geochemical and biogeochemical cycles are important because they maintain the balance between all the materials as well as the natural processes essential for the life functioning of the living organisms on the earth. Due to these cycles, the energy and resources do not run out, they become recycled and can be used back in many forms. They process the hazardous materials of our planet, recycle and convert them into harmless substances in the nature. For example, unwanted chemicals from industries and plastics being recycles into harmless useful materials.
What is not a gaseous biogeochemical cycle?
Phosphorous cycle is not a gaseous biogeochemical cycle.
What are the three geochemical cycles?
The three geochemical cycles are rock cycle, carbon cycle and phosphorous cycle.
What is carbon 9th cycle?
In the carbon cycle, carbon is involved in the fixation of energy by the photosynthesis. The carbon dioxide of the atmosphere and water of the earth surface is the source of carbon both in all living organisms and fossil deposits. By respiration, the primary producers and consumers release the carbon back in the atmosphere in the form of carbon dioxide. Net primary productivity is the difference between the rate of carbon uptake by plants in photosynthesis and carbon release during respiration. While, Net ecosystem productivity is the difference between the rate of carbon uptake in photosynthesis and the rate of carbon loss as a result of autotrophic and heterotrophic respiration
What is 9th water cycle?
Water cycle or hydrologic cycle is a series of processes occurring in the earth involving water. Firstly, the water evaporates from the water resources like seas, oceans, etc., then they condense to form clouds, after being heavier they ultimately precipitate as rainfall back into the water resources.
What is biogeochemical cycle describe nitrogen cycle?
Nitrogen enters into the ecosystem through two pathways, first is atmospheric deposition and other is nitrogen fixation. Nitrogen is available to plants in the form of ammonium and nitrate ions. The high energy is produced by the cosmic radiation and lightning which helps in combining the nitrogen with the oxygen and hydrogen of water which produces ammonia and nitrates. The products are carried to the earth’s surface in rainwater. Biological nitrogen fixation is done by the symbiotic bacteria living in mutualistic association with plants by free living aerobic bacteria and by cyanobacteria. They split the molecular nitrogen into two atoms of free nitrogen. The free nitrogen atoms combine with hydrogen to form ammonia which is released as a waste product of microbial activity. The ammonium is present in the soil as a product of microbial decomposition of organic matter, which is taken up directly by the plants and the process is called ammonification. The plants roots compete for ammonium with two groups of aerobic bacteria (Nitrosomonas and Nitrobacter), which use it as a part of their metabolism. Nitrosomonas oxidize ammonium to nitrite ions whereas Nitrobacter oxidizes nitrite to nitrate ions, this process is called nitrification. Under anaerobic conditions, another group of bacteria (Pseudomonas) chemically reduce nitrate to nitrous oxide to nitrogen, this process is called denitrification.
What is the meaning of biogeochemical?
‘Biogeochemical’ refers to the phenomenon related with the exchange of chemical materials or matters between living and non-living components of the ecosystem. ‘Biogeochemical’ includes the biological, chemical and geological factors.
How do biogeochemical cycles affect ecosystems?
Biogeochemical cycles affect ecosystems by the conservation, recycling and circulation of essential elements which make up the organisms within the ecosystem. In this way, the biogeochemical cycles maintain balance in the biosphere.
How does mining alter the biogeochemical cycles?
Effect on Oxygen and Carbon Cycle: Bad mining practices can ignite coal fires, which can burn for decades, release fly ash and smoke consisting of huge amount of greenhouse gases and toxic chemicals. Mining releases coal mine methane, a greenhouse gas 20 times more powerful than carbon dioxide. Coal mining displaces whole communities by forcing off their land, expanding mines, coal fires and contaminated water supplies.
Effect on Sulphur Cycle: Acid mine drainage is another severe environmental problem that is associated with coal and metal mining, and sometimes with construction activities such as road building. The large quantities of mineral sulphides are exposed to atmospheric oxygen. This oxidizes the sulphides to sulphate, a process accompanied by the generation of large amounts acidity. The surface waters exposed to acid mine drainage can become severely acidified to a pH less than 3 resulting in severe biological damage and environmental degradation.
Effect on Phosphorous Cycle: Eutrophication is a large increase in the primary productivity of a lake. A human cause of artificial eutrophication is run off from mines. Mining in areas where rock is rich in phosphorus minerals can create dust that is blown by wind into nearby water systems. Similarly, rain-water can wash from mining areas to water bodies.
Effect on Nitrogen Cycle: Mining also influences the nitrogen cycle by dumping mining components and other types of substances like dirt from coal and other minerals into water-bodies. There is a great deal of environmental damage associated with these practices, including lowered dissolved oxygen levels associated with chemical contamination of the water bodies, and the presence of fecal pathogens and dirty components. The accidental contamination of water bodies with large amounts of nitrogen contributes greatly to eutrophication.