B sc micro, biotech, biochem i es u 4 biogeochemicalcycles

Biogeochemical Cycles

Course : B.Sc. Microbiology/ Bio-Technology/ Bio-ChemistrySem I

Sub: Environmental ScienceUnit 4

What are biogeochemical cycles?• Earth system has four parts

– Atmosphere– Hydrosphere– Lithosphere– Biosphere

• Biogeochemical cycles: The chemical interactions (cycles) that exist between the atmosphere, hydrosphere, lithosphere, and biosphere.

• Abiotic (physio-chemical) and biotic processes drive these cycles

• Focus on carbon and water cycles (but could include all necessary elements for life). N - cycle weakly touched on!

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Biogeochemical Cycle

• Bio- life

• Geo-earth

• Chemical- elements• A biogeochemical cycle or substance

turnover or cycling of substances is a pathway by which a chemical substance moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. A cycle is a series of change which comes back to the starting point and which can be repeated.

What is common amongst them?

• Each compound (water, carbon, nitrogen) typically exists in all four parts of the Earth System

• There are – ‘Pools’

– Fluxes in and out of pools– Chemical or biochemical transformations

• Transformations – are important

– can lead to positive & negative consequences

What Sustains Life on Earth?

• Solar energy, the cycling of matter, and gravity sustain the earth’s life.

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Two Secrets of Survival: Energy Flow and Matter Recycle

• An ecosystem survives by a combination of energy flow and matter recycling.

Figure 3-14Figure 3-14

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MATTER CYCLING IN ECOSYSTEMS

• Nutrient Cycles: Global Recycling– Global Cycles recycle nutrients through the

earth’s air, land, water, and living organisms.– Nutrients are the elements and compounds that

organisms need to live, grow, and reproduce.– Biogeochemical cycles move these substances

through air, water, soil, rock and living organisms.

Water’ Unique Properties• There are strong forces of attraction between

molecules of water.

• Water exists as a liquid over a wide temperature range.

• Liquid water changes temperature slowly.

• It takes a large amount of energy for water to evaporate.

• Liquid water can dissolve a variety of compounds.

• Water expands when it freezes.

PrecipitationPrecipitation

Transpiration

Condensation

Evaporation

Ocean storage

Transpiration from plants

Precipitation to land

Groundwater movement (slow)

Evaporation from land Evaporation

from ocean Precipitation to ocean

Infiltration and Percolation

Rain clouds

RunoffSurface runoff

(rapid)

Surface runoff (rapid)

Water Cycle

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• The Water Cycle (also known as the hydrologic cycle) is the journey water takes as it circulates from the land to the sky and back again. The Sun's heat provides energy to evaporate water from the Earth's surface (oceans, lakes, etc.). Plants also lose water to the air (this is called transpiration). The water vapor eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air over land, precipitation (rain, sleet, or snow) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers; this is called groundwater. But most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas as slightly salty water.

The Water Cycle (also known as the hydrologic cycle)

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Water Cycle

• involves the processes of photosynthesis, transpiration, evaporation and condensation, respiration, and excretion

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Effects of Human Activities on Water Cycle

• We alter the water cycle by:– Withdrawing large amounts of freshwater.– Clearing vegetation and eroding soils.– Polluting surface and underground water.– Contributing to climate change.

The Carbon Cycle

All living things are made of carbon. Carbon is also a part of the ocean, air, and even rocks. Because the Earth is a dynamic place, carbon does not stay still

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• In the atmosphere, carbon is attached to some oxygen in a gas called carbon dioxide.

• Plants use carbon dioxide and sunlight to make their own food and grow. The carbon becomes part of the plant. Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions of years. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon dioxide.

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Effects of Human Activities on Carbon Cycle

• We alter the carbon cycle by adding excess CO2 to the atmosphere through:– Burning fossil fuels.– Clearing vegetation

faster than it is replaced.

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Carbon-Oxygen Cycle

• Involves the processes of respiration and photosynthesis.

• In respiration, oxygen and glucose are combined releasing energy and producing water and carbon dioxide.

• In photosynthesis water and carbon dioxide along with the energy from the sun are combined to produce glucose (containing energy) and oxygen.

• Each process compliments the other and the ecosystem maintains its balanced communities.

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Nitrogen cycle

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• 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.

• The majority of Earth's atmosphere (78%) is nitrogen, making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition.

• Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen

cycle.

Nitrogen Cycle

• Nitrates (used by plants)• Build plant proteins• Eaten by animals• made into animal proteins• Plants and animals die• bacteria decay• Ammonia (NH3)• Nitrifying Bacteria• Nitrates (used by plants)

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Effects of Human Activities on the Nitrogen Cycle

• We alter the nitrogen cycle by:– Adding gases that contribute to acid rain.– Adding nitrous oxide to the atmosphere through

farming practices which can warm the atmosphere and deplete ozone.

– Contaminating ground water from nitrate ions in inorganic fertilizers.

– Releasing nitrogen into the troposphere through deforestation.

Effects of Human Activities on the Nitrogen Cycle

• Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.

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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.

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Phosphorus cycle• 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, aluminium 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 cannot be found in the air as a gas; it only occurs under highly reducing conditions as the gas phosphine PH3.

Dissolvedin Ocean

Water

Marine Sediments Rocks

uplifting overgeologic time

settling out weatheringsedimentation

LandFoodWebs

Dissolvedin Soil Water,Lakes, Rivers

death,decomposition

uptake byautotrophs

agriculture

leaching, runoff

uptake byautotrophs

excretion

death,decomposition

mining Fertilizer

weathering

Guano

MarineFoodWebs

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1. When rocks high in phosphorus are exposed to water, the rock weathers out and goes into solution

2. autotrophs absorb this phosphorus and use it in many different ways, 

3. then the plant is eaten by a heterotroph and obtains phosphorus from the plant

4. then the phosphate leaves the body, and decomposers move the phosphorus into the soil or water then another plant will absorb this phosphorus.

Effects of Human Activities on the Phosphorous Cycle

• We remove large amounts of phosphate from the earth to make fertilizer.

• We reduce phosphorous in tropical soils by clearing forests.

• We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

What Sustains Life on Earth?

• Solar energy, the cycling of matter, and gravity sustain the earth’s life.

Oxygen cycle

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Oxygen cycle• All organisms living an animals

breathe in oxygen. Oxygen constitutes about 20% of the atmosphere. It is essential for respiration. It produces energy in living beings by the oxidation of foods. During this process, CO2 is released which is used by the plants in making food during photosynthesis. During the process of photosynthesis, oxygen gas is released back into the atmosphere. Thus, this cycle is completed.20

Oxygen cycle

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Oxygen cycle• Oxygen cycle, circulation of oxygen in various forms

through nature. Free in the air and dissolved in water, oxygen is second only to nitrogen in abundance among uncombined elements in the atmosphere. Plants and animals use oxygen to respire and return it to the air and water as carbon dioxide (CO2). CO2 is then taken up by algae and terrestrial green plants and converted into carbohydrates during the process of photosynthesis, oxygen being a by-product. The waters of the world are the main oxygen generators of the biosphere; their algae are estimated to replace about 90 percent of all oxygen used. Oxygen is involved to some degree in all the other biogeochemical cycles. For example, over time, detritus from living organisms transfers oxygen-containing compounds such as calcium carbonates into the lithosphere.

Sulphur Cycle

Hydrogen sulfide

Sulfur

Sulfate salts

Decaying matter

Animals

Plants

Ocean

IndustriesVolcano

Hydrogen sulfideOxygen

Dimethyl sulfide

Ammoniumsulfate

Ammonia

Acidic fog and precipitationSulfuric acid

WaterSulfurtrioxide

Sulfur dioxide

Metallicsulfidedeposits

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Effects of Human Activities on the Sulfur Cycle

• We add sulfur dioxide to the atmosphere by:– Burning coal and oil– Refining sulfur containing petroleum.– Convert sulfur-containing metallic ores into free

metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.

What do you think?

• Does life on earth control earth’s life-sustaining processes or does life merely influence these life-sustaining process?

Images:1.http://www.centerforecopsychology.org/images/image2.jpg 2.http://image.slidesharecdn.com/biogeochemicalcycles-130609103318-phpapp02/95/biogeochemical-cycles-4-638.jpg?cb=1370792062 3.http://en.harunyahya.net/resimleri/sites/4/62/the-food-cycle.jpg 4.https://lh4.ggpht.com/dA7aCeK4Br2RGMjqXu9HZILHd_q9twMzmEelevDnHZpiVVGUMsHvzaZQjyb5yIun8qYMTg=s151 5.http://www.mrnorton.com/Podcasts/Digital%20Posters%202009-2010/4th%20Period/Water/WaterCycleKS.JPG 6.https://lh4.ggpht.com/FplaEfmu-0A-YXbsAaD9rpGOSlNaOEP-F34VVXcCtu8Ltue6oJEZdjeZCHfaZAC4BEMw=s132 7.https://s-media-cache-ak0.pinimg.com/236x/00/a9/44/00a94471151401ace96c0168ca2e3798.jpg 8.http://www.quia.com/files/quia/users/repasy_p/nutrientcycles/carboncycle3 9.https://lh5.ggpht.com/vZipErPS3JNmvN22fRti9pMhh8vEBJ-O4ALE3Ve5_fIZ63s1H1koVzp-26FSag-if0Bf=s85 10.https://lh6.ggpht.com/AgnYsZWsI7fVbul3Qs7GlllRviZzoYdKKsKmqNc9UwJ6Q3r6UkTKQD_Byb1_LsoT7ENl1tI=s115

References

Images:11.https://lh5.ggpht.com/yySasAxNRgtCSUaGuHkCktWqCMVmvTpLf080fKAToyoTE-

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wtI1YsXAA25BMgUgA=s136 19.http://www.keepbanderabeautiful.org/oxygen-cycle-i.jpg 20.https://lh6.ggpht.com/6CHiLGb9q0vmq8c-

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References

Books:

1.Environmental studies by R.Rajagopalan

2.Environmental Science by Richard T Wright & Bernard J Nebel

References