presentation on biogeochemical cycles 2
TRANSCRIPT
Presented by Mina MazharRoll no : 2401Bsc 3rd yearPunjab College Chishtian
Definition of biogeochemical cyclesTypes of biogeochemical cyclesMajor biogeochemical cyclesNitrogen cycle Phosphorous cycle
The pathway in which the chemical elements circulate in the biosphere through a characteristic paths from environment to organisms and back to the environment are called biogeochemical cycles.These cycles involves the back and forth movement of materials between biotic and abiotic factors.
The term "biogeochemical" tells us that biological, geological and chemical factors are all involved. The circulation of chemical nutrients like carbon, oxygen, nitrogen, phosphorus, calcium, and water etc. through the biological and physical world are known as biogeochemical cycles. In effect, the element is recycled, although in some cycles there may be places (called reservoirs) where the element is accumulated or held for a long period of time (such as an ocean or lake for water).
GASEOUS CYCLES The cycle in which the
reservoir is in the atmosphere or hydrosphere are termed as gaseous cycles.
The main pool of nutrients possessing gaseous cycle are the atmosphere and ocean.
Gaseous cycles circulate many basic elements of life such as oxygen , carbon dioxide , nitrogen and hydrogen.
SEDIMENTARY CYCLES The cycles in which the
reservoir is in the earth’s crust are called sedimentary cycles
The main reservoirs of sedimentary cycles are the rocks of earth crust.
Sedimentary cycles circulate elements like sulphur , phosphorous and calcium.
Nitrogen cyclePhosphorous cycle
DefinitionBiological functionEcological functionProcessHuman influence
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification.
Nitrogen is necessary for all known forms of life on Earth. It is a component in all amino acids, as it is incorporated into proteins, and is present in the bases that make up nucleic acids such as RNA and DNA
Nitrogen gas (N2) is the largest constituent of the Earth's atmosphere , but this form is relatively nonreactive and unusable by plants. Chemical processing or natural fixation (through processes such as bacterial conservation) are necessary to convert gaseous nitrogen into compounds such as nitrate or ammonia which can be used by plants. The abundance or scarcity of this "fixed" nitrogen (also known as reactive nitrogen) frequently limits plant growth in both managed and wild environments. The nitrogen cycle, like the carbon cycle, is an important part of every ecosystem.
The processes of the nitrogen cycle transform nitrogen from one form to another. Many of those processes are carried out by microbes, either in their effort to harvest energy or to accumulate nitrogen in a form needed for their growth.
The connversion of gaseous nitrogen to ammonia and nitrates is called nitrogen fixation. It may biological fixation or non biological.
Non-biological fixationNitrates are the product of non biological fixation during lightning , electrical discharges in the clouds or occasionally by cosmic radiations.The atmospheric nitrogen combines with oxygen9as ozone and produces nitrogen oxides.These nitrogen oxides get dissolved in rain water and reached the earth as nitric acid(H2NO3) and react with mineral compounds to form nitrates and other nitrogenous compounds.N2 +O2 2NO2NO + 2O 2NO22NO2 + O N2O5N2O5 + H2O 2HNO32HNO3 + Ca(NO3) Ca(NO3)2+CO2+H2O
In this method gaseous nitrogen is split into two atoms . The free nitrogen then combines with hydrogen to form ammonia with release of about 13kcal of energy.N2 2N2N+3H2 2NH3It is brought about by following ways NODULATED LEGUMES AND NON LEGUMINOUS PLANTSFREE FIXERSCYAONOBACTERIA
It is the major step of nitrogen cycle.In this process proteins in dead plant and animal material are broken down by bacteria and fungi to amino acids.The amino acids are oxidized to carbon dioxide, water and ammonia with a yeild of energy.CH2NH2COOH + 1/2 O2 2CO2 + H2O + NH3 + 173Kcal
Ammonium or the ammonia ion is absorbed directly by plant roots incorporated into amino acids and passed through the food chain. Some of the ammonia is dissolved in water, part of it is trapped in the soil, and some is fixed in clay minerals
It is the process in which ammonia is oxidized into nitrate and nitrite yeilding energies.It is common in warm,moist soils with a pH of 7. The oxidation benefits the bacteria as it helps in maintaining there energies for metabolic activities. .Two groups of bacteria are involved in nitrification. One group belonging to the genus Nitrosomones use the ammonia in the soil as their sole source of energy. They oxidize it first to nitrous acid and water and then to nitrite.NH3 + H2O2 HNO2 + H2 + 165 KcalHNO2 H + NO2The other group belonging to genus nitrobacter exploits the energy left in nitrite ion and oxidizes it to nitrate. A small amount of energy is released.NO + 1/O2 NO3
The process by which the nitrates are reduced to gaseous nitrogen by certain organisms is called denitrification.The denitrifiers are fungi and bacteria PseudomonasThey are anaerobes and prefer an oxygenated environment but if oxygen is limited they can use NO3ions instead of oxygen as the hydrogen acceptor. In doing so they release N2 in the gaseous state as a byproduct.C6H12O6 + 4NO3 6CO2 + H20 + 2N2
As a result of extensive cultivation of legumes (particularly soy, alfalfa, and clover) and pollution emitted by vehicles and industrial plants, human beings have more than doubled the annual transfer of nitrogen into biologically available forms .
Nitrous oxide (N2O) has risen in the atmosphere as a result of agricultural fertilization, biomass burning, cattle and feedlots, and industrial sources. N2O has deleterious effects in the stratosphere, where it breaks down and acts as a catalyst in the destruction of atmospheric ozone. Nitrous oxide is also a greenhouse gas and is currently the third largest contributor to global warming, after carbon dioxide and methane. While not as abundant in the atmosphere as carbon dioxide, it is, for an equivalent mass, nearly 300 times more potent in its ability to warm the planet.
Ammonia (NH3) in the atmosphere has tripled as the result of human activities. It is a reactant in the atmosphere, decreasing air quality and clinging to water droplets, eventually resulting in nitric acid (HNO3) that produces acid rain. Atmospheric ammonia and nitric acid also damage respiratory systems..Ammonia and nitrous compounds contributes to smog and acid rain, damages plants and increases nitrogen inputs to ecosystems..Decreases in biodiversity can also result if higher nitrogen availability increases nitrogen-demanding grasses, causing a degradation of nitrogen-poor, species diverse heathlands.
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DefinitionEcological functionBiological function Process of the cycleHuman influences
The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth.
Phosphorus is an essential nutrient for plants and animals. Phosphorus is a limiting nutrient for aquatic organisms. Phosphorus forms parts of important life-sustaining molecules that are very common in the biosphere. Phosphorus does not enter the atmosphere, remaining mostly on land and in rock and soil minerals. Eighty percent of the mined phosphorus is used to make fertilizers.
The primary biological importance of phosphates is as a component of nucleotides, which serve as energy storage within cells (ATP) or when linked together, form the nucleic acids DNA and RNA. The double helix of our DNA is only possible because of the phosphate ester bridge that binds the helix. Besides making biomolecules, phosphorus is also found in bone and the enamel of mammalian teeth, whose strength is derived from calcium phosphate. It is also found in the exoskeleton of insects, and phospholipids (found in all biological membranes).It also functions as a buffering agent in maintaining acid base homeostasis in the human body.
Phosphates move quickly through plants and animals; however, the processes that move them through the soil or ocean are very slow, making the phosphorus cycle overall one of the slowest biogeochemical cycles.Initially, phosphate weathers from rocks and minerals, the most common mineral being apatite. Overall small losses occur in terrestrial environments by leaching and erosion, through the action of rain. In soil, phosphate is absorbed on iron oxides, aluminum hydroxides, clay surfaces, and organic matter particles, and becomes incorporated (immobilized or fixed). Plants and fungi can also be active in making P soluble.Unlike other cycles, P is not normally found in the air as a gas; it only occurs under highly reducing conditions as the gas phosphine PH3
Human interference in the phosphorus cycle occurs by overuse or careless use of phosphorus fertilizers. This results in increased amounts of phosphorus as pollutants in bodies of water resulting in eutrophication. Eutrophication devastates water ecosystems.