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Ppt on Biogeochemical Cycle

  1. Jawahar Navodaya Vidyalaya, Balod (CG) CBSE Activity on science Made By Aayush Uike Guided By Mrs. Tandra Dhar (Pgt.Biology) Mrs. Jaimala Shrivastav (Pgt.Chemistry) Mr. Sujit Kumar Deshmukh (Pgt.Physics)
  2. Introduction • The Term Biological Cycle is derived from three basic words: Bio-Life; Geo-Earth and Chemical-elements "C,O,N,P,S". • Biogeochemical cycle refers to any of the natural pathways by which essential elements of living matter are circulated. The term biogeochemical is a contraction that refers to the consideration of the biological, geological, and chemical aspects of each cycle. • Elements within biogeochemical cycles flow in various forms from the nonliving (abiotic) components of the biosphere to the living (biotic) components and back. In order for the living components of a major ecosystem (e.g., a lake or a forest to survive, all the chemical elements that make up living cells must be recycled continuously. Each biogeochemical cycle can be considered as having a reservoir (nutrient) pool—a larger, slow-moving, usually abiotic portion—and an exchange (cycling) pool—a smaller but more-active portion concerned with the rapid exchange between the biotic and abiotic aspects of an ecosystem.
  3. Cycling Elements • Macronutrients- Nutrients required in relatively large amount are known as Macronutrients. • 6 major Macronutrients- Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorous. • Other Macronutrients-Sulfur, Potassium, Calcium, Iron and Magnesium. • Micronutrients-Nutrients required in small amount are known as Micronutrients. (they are required in small amount but are still necessary).Such as Boron, Copper, Molybdenum.
  4. Types of Biological Cycle Biological Cycle can be classified as:- (I) Gaseous Cycle -The term gaseous Cycle refers to the transformation of gases between various biogeochemical reservoirs, Lithosphere, Hydrosphere & Atmosphere. Important Gaseous Cycles are:- (i) Nitrogen Cycle (ii) Oxygen Cycle (iii) Carbon Cycle (iv) Water Cycle (II) Sedimentary Cycle - Sedimentary Cycle includes the leaching of minerals and salts from the earth's crust which then settle as sediment or rock before the cycle repeats. Sedimentary Cycle includes:- (i) Phosphorus Cycle (ii) Sulfur Cycle (iii) Iron Cycle
  5. Nitrogen Cycle Nitrogen Cycle Definition “Nitrogen Cycle is a biogeochemical process which transforms the inert nitrogen present in the atmosphere to a more usable form for living organisms.” Furthermore, nitrogen is a key nutrient element for plants. However, the abundant nitrogen in the atmosphere cannot be used directly by plants or animals. Stages of Nitrogen Cycle Process of Nitrogen Cycle consists of the following steps – Nitrogen fixation, Nitrification, Assimilation, Ammonification and Denitrification. These processes take place in several stages and are explained below: Nitrogen fixation During the process of Nitrogen fixation, the inert form of nitrogen gas is deposited into soils from the atmosphere and surface waters, mainly through precipitation. Later, the nitrogen undergoes a set of changes, in which two nitrogen atoms get separated and combine with hydrogen to form ammonia (NH4+). The entire process of Nitrogen fixation is completed by symbiotic bacteria which are known as Diazotrophs. Azotobacter and Rhizobium also have a major role in this process. These bacteria consist of a nitrogenase enzyme which has the capability to combine gaseous nitrogen with hydrogen to form ammonia. Nitrogen fixation can occur either by the atmospheric fixation- which involves lightening or industrial fixation by manufacturing ammonia under high temperature and pressure condition. This can also be fixed through man-made processes, primarily industrial processes that create ammonia and nitrogen-rich fertilizers.
  6. Nitrification In this process, the ammonia is converted into nitrate by the presence of bacteria in the soil. Nitrites are formed by the oxidation of Ammonia with the help of Nitrosomonas bacterium species. Later, the produced nitrites are converted into nitrates by Nitrobacter. This conversion is very important as ammonia gas is toxic for plants. The reaction involved in the process of Nitrification is as follows: 2NH4+ + 3O2 → 2NO2– + 4H+ + 2H2O 2NO2– + O2 → 2NO3– Assimilation Primary producers – plants take in the nitrogen compounds from the soil with the help of their roots, which are available in the form of ammonia, nitrite ions, nitrate ions or ammonium ions and are used in the formation of the plant and animal proteins. Ammonification When plants or animals die, the nitrogen present in the organic matter is released back into the soil. The decomposers, namely bacteria or fungi present in the soil, convert the organic matter back into ammonium. This process of decomposition produces ammonia, which is further used for other biological processes. Denitrification Denitrification is the process in which the nitrogen compounds makes its way back into the atmosphere by converting nitrate (NO3-) into gaseous nitrogen (N). This process of the nitrogen cycle is the final stage and occurs in the absence of oxygen. Denitrification is carried out by the denitrifying bacterial species- Clostridium and Pseudomonas, which will process nitrate to gain oxygen and gives out free nitrogen gas as a byproduct. Importance of Nitrogen Cycle Importance of the nitrogen cycle are as follows: •Helps plants to synthesis chlorophyll from the nitrogen compounds. •Helps in converting inert nitrogen gas into a usable form for the plants through the biochemical process. •In the process of ammonification, the bacteria help in decomposing the animal and plant matter, which indirectly helps to clean up the environment. •Nitrates and nitrites are released into the soil, which helps in enriching the soil with necessary nutrients required for cultivation. • Nitrogen is also cycled by human activities such as combustion of fuels and the use of nitrogen fertilizers. These processes, increase the levels of nitrogen-containing compounds in the atmosphere. The fertilizers containing nitrogen are washed away in lakes and rivers and results in eutrophication.
  7. Oxygen Cycle What is Oxygen Cycle? Oxygen cycle, along with the carbon cycle and nitrogen cycle plays an essential role in the existence of life on the earth. The oxygen cycle is a biological process which helps in maintaining the oxygen level by moving through three main spheres of the earth which are: • Atmosphere • Lithosphere • Biosphere This biogeochemical cycle explains the movement of oxygen gas within the atmosphere, the ecosystem, biosphere and the lithosphere. The oxygen cycle is interconnected with the carbon cycle. The atmosphere is the layer of gases presents above the earth’s surface. The sum of Earth’s ecosystems makes a biosphere. Lithosphere is the solid outer section along with the earth’s crust and it is the largest reservoir of oxygen. Stages of the Oxygen Cycle The steps involved in the oxygen cycle are: Stage-1: All green plants during the process of photosynthesis, release oxygen back into the atmosphere as a by-product. Stage-2: All aerobic organisms use free oxygen for respiration. Stage-3: Animals exhale Carbon dioxide back into the atmosphere which is again used by the plants during photosynthesis. Now oxygen is balanced within the atmosphere.
  8. Importance of Oxygen Cycle As we all know, oxygen is one of the most essential components of the earth’s atmosphere. It is mainly required for: • Breathing • Combustion • Supporting aquatic life • Decomposition of organic waste. Oxygen is an important element required for life, however, it can be toxic to some anaerobic bacteria (especially obligate anaerobes). The oxygen cycle is mainly involved in maintaining the level of oxygen in the atmosphere. The entire cycle can be summarized as, the oxygen cycle begins with the process of photosynthesis in the presence of sunlight, releases oxygen back into the atmosphere, which humans and animals breathe in oxygen and breathe out carbon dioxide, and again linking back to the plants. This also proves that both the oxygen and carbon cycle occur independently and are interconnected to each other. Uses of oxygen cycle The four main processes that use atmospheric oxygen are: Breathing – It is the physical process, through which all living organisms, including plants, animals and humans inhale oxygen from the outside environment into the cells of an organism and exhale carbon dioxide back into the atmosphere. Decomposition: It is one of the natural and most important processes in the oxygen cycle and occurs when an organism dies. The dead animal or plants decay into the ground, and the organic matter along with the carbon, oxygen, water and other components are returned into the soil and air. This process is carried out by the invertebrates, including fungi, bacteria and some insects which are collectively called as the decomposers. The entire process requires oxygen and releases carbon dioxide. Combustion: It is also one of the most important processes which occur when any of the organic materials, including fossil fuels, plastics and wood, are burned in the presence of oxygen and releases carbon dioxide into the atmosphere. Rusting: This process also requires oxygen. It is the formation of oxides which is also called oxidation. In this process, metals like iron or alloy rust when they are exposed to moisture and oxygen for an extended period of time and new compounds of oxides are formed by the combination of oxygen with the metal.
  9. Carbon Cycle Carbon cycle shows the movement of carbon in elemental and combined states on earth. Diamond and graphite are the elemental forms of carbon and in combined state, it is found as carbonates in minerals and as carbon dioxide gas in the atmosphere. Carbon Cycle Definition Carbon cycle is the process where carbon compounds are interchanged among the biosphere, geosphere, pedosphere, hydrosphere, and atmosphere of the earth. Carbon Cycle Steps Following are the major steps involved in the process of the carbon cycle: • Carbon present in the atmosphere is absorbed by plants for photosynthesis. These plants are then consumed by animals and carbon gets bioaccumulated into their bodies. • These animals and plants eventually die, and upon decomposing, carbon is released back into the atmosphere. • Some of the carbon that is not released back into the atmosphere eventually become fossil fuels. • These fossil fuels are then used for man-made activities, which pumps more carbon back into the atmosphere. Importance of Carbon Cycle Even though carbon dioxide is found in small traces in the atmosphere, it plays a vital role in balancing the energy and traps the long-wave radiations from the sun. Therefore, it acts like a blanket over the planet. If the carbon cycle is disturbed it will result in serious consequences such as climatic changes and Global Warming. Carbon is an integral component of every life form on earth. From proteins and lipids to even our DNA. Furthermore, all known life on earth is based on carbon. Hence, the carbon cycle, along with the nitrogen cycle and oxygen cycle, plays a vital role in the existence of life on earth.
  10. Water Cycle What is the Water Cycle? During this process, water changes its state from one phase to another, but the total number of water particles remains the same. In other words, if it were possible to collect and boil 100 gms of water, it will still retain a mass of 100 gms as steam. Likewise, if 100 gms of steam is collected and condensed, the resultant water would still weight 100 gms. Water changes its state through a variety of processes from evaporation, melting and freezing, to sublimation, condensation, and deposition. All these changes require the application of energy. Implications of Water Cycle • The water cycle has a tremendous impact on the climate. For instance, the greenhouse effect will cause a rise in temperature. Without the evaporative cooling effect of the water cycle, the temperature on earth would rise drastically. • The water cycle is also an integral part of other biogeochemical cycles. • Water cycle affects all life processes on earth. • The water cycle is also known the clean the air. For instance, during the process of precipitation, water vapour have to attach themselves on to particles of dust. In polluted cities, the raindrops, apart from picking up dust, also pick up water- soluble gas and pollutants as they fall from the clouds. Raindrops are also known to pick up biological agents such as bacteria and industrial soot particles and smoke.
  11. Stages of Water Cycle There are many processes involved in the movement of water. Listed below are different stages of the water cycle. 1. Evaporation The sun is the ultimate source of energy, and it powers most of the evaporation that occurs on earth. Evaporation generally happens when water molecules at the surface of water bodies become excited and rise into the air. These molecules with the highest kinetic energy accumulate into water vapour clouds. Evaporation usually takes place below the boiling point of water. Another process called evapotranspiration occurs when evaporation occurs through the leaves of plants. This process contributes to a large percentage of water in the atmosphere. 2. Sublimation Sublimation occurs when snow or ice changes directly into water vapour without becoming water. It usually occurs as a result of dry winds and low humidity. Sublimation can be observed on mountain peaks, where the air pressure is quite low. The low air pressure helps to sublimate the snow into water vapour as less energy is utilised in the process. Another example of sublimation is the phase where fog bellows from dry ice. On earth, the primary source of sublimation is from the ice sheets covering the poles of the earth. 3. Condensation The water vapour that accumulated in the atmosphere eventually cools down due to the low temperatures found at high altitudes. These vapours become tiny droplets of water and ice, eventually coming together to form clouds. 4. Precipitation Above 0 degrees centigrade, the vapours will condense into water droplets. However, it cannot condense without dust or other impurities. Hence, water vapours attach itself on to the particle’s surface. When enough droplets merge, it falls out of the clouds and on to the ground below. This process is called precipitation (or rainfall). In particularly cold weather or extremely low air pressure, the water droplets freeze and fall as snow or hail. 5. Infiltration Rainwater gets absorbed into the ground through the process of infiltration. The level of absorption varies based on the material the water has seeped into. For instance, rocks will retain comparatively less water than soil. Groundwater can either follows streams or rivers. But sometimes, it might just sink deeper, forming aquifers. 6. Runoff If the water from rainfall does not form aquifers, it follows gravity, often flowing down the sides of mountains and hills; eventually forming rivers. This process is called runoff. In colder regions, icecaps form when the amount of snowfall is faster than the rate of evaporation or sublimation. The biggest icecaps on earth are found at the poles.
  12. Phosphorous Cycle What is Phosphorus Cycle? Phosphorus is an important element for all living organisms. It forms a significant part of the structural framework of DNA and RNA. They are also an important component of ATP. Humans contain 80% of phosphorus in teeth and bones. Phosphorus cycle is a very slow process. Various weather processes help to wash the phosphorus present in the rocks into the soil. Phosphorus is absorbed by the organic matter in the soil which is used for various biological processes. Since phosphorus and phosphorus-containing compounds are present only on land, atmosphere plays no significant role in the phosphorus cycle. Steps of Phosphorus Cycle Following are the important steps of phosphorus cycle: • Weathering • Absorption by Plants • Absorption by Animals • Return to the Environment through Decomposition Weathering Phosphorus is found in the rocks in abundance. That is why the phosphorus cycle starts in the earth’s crust. The phosphate salts are broken down from the rocks. These salts are washed away into the ground where they mix in the soil. Absorption by Plants The phosphate salts dissolved in water are absorbed by the plants. However, the amount of phosphorus present in the soil is very less. That is why the farmers apply phosphate fertilizers on agricultural land. The aquatic plants absorb inorganic phosphorus from lower layers of water bodies. Since phosphate salts do not dissolve in water properly, they affect plant growth in aquatic organism. Absorption by Animals The animals absorb phosphorus from the plants or by consuming plant-eating animals. The rate of the phosphorus cycle is faster in plants and animals when compared to rocks.
  13. Sulfur Cycle Sulphur is one of the most abundant elements on the earth. It is a yellow, brittle, tasteless, odourless non-metal. Sulfur is present in all kinds of proteins. Plants directly absorb sulfur-containing amino acids such as methionine, cystine, and cysteine. Sulphur is released into the atmosphere by the burning of fossil fuel, volcanic activities, and decomposition of organic molecules. On land, sulfur is stored in underground rocks and minerals. It is released by precipitation, weathering of rocks and geothermal vents. Process The process of sulfur cycle is explained below: • The sulfur is released by the weathering of rocks. • Sulphur comes in contact with air and is converted into sulphates. • Sulphates are taken up by plants and microbes and are converted into organic forms. • The organic form of sulfur is then consumed by the animals through their food and thus sulfur moves in the food chain. • When the animals die, some of the sulfur is released by decomposition while some enter the tissues of microbes. Steps of Sulphur Cycle Following are the important steps of the sulfur cycle: Decomposition of Organic Compounds Protein degradation releases amino acids that contain sulfur. Sulphates are reduced to H2S by the action of Desulfotomaculum bacteria. Oxidation of Hydrogen Sulphide to Elemental Sulphur Hydrogen sulphide oxidises to produce elemental sulfur. Certain photosynthetic bacteria from the families Chlorobiaceae and Chromatiaceae initiate the oxidation process. Oxidation of Elemental Sulphur Elemental sulfur present in the soil cannot be utilized directly by the plants. Therefore, it is converted into sulphates by chemolithotrophic bacteria.
  14. Iron Cycle Rusting of iron refers to the formation of rust, a mixture of iron oxides, on the surface of iron objects or structures. This rust is formed from a redox reaction between oxygen and iron in an environment containing water (such as air containing high levels of moisture). The rusting o iron is characterized by the formation of a layer of a red, flaky substance that easily crumbles into a powder. This phenomenon is a great example of the corrosion of metals, where the surfaces of metals are degraded into more chemically stable oxides. However, the term ‘rusting’ is generally used to refer to the corrosion of objects made of iron or iron-alloys. Factors that Affect the Rusting of Iron Many factors speed up the rusting of iron, such as the moisture content in the environment and the pH of the surrounding area. Some of these factors are listed below. • Moisture: The corrosion of iron is limited to the availability of water in the environment. Exposure to rains is the most common reason for rusting. • Acid: if the pH of the environment surrounding the metal is low, the rusting process is quickened. The rusting of iron speeds up when it is exposed to acids. Higher pH inhibits the corrosion of iron. • Salt: Iron tends to rust faster in the sea, due to the presence of various salts. Saltwater contains many ions that speed up the rusting process via electrochemical reactions. • Impurity: Pure iron tends to rust more slowly when compared to iron containing a mixture of metals.
  15. Diagram of various Cycles Oxygen Cycle Carbon Cycle Water Cycle Nitrogen Cycle Sulphur Cycle Phosphorus Cycle