Biogeochemical Cycles - Part I

Biogeochemical Cycles - Part I

Biogeochemical Cycles

Living Organisms

Non-living

Di erent Reactions on Earth

Ar

O Oxidising

atmosphere

CH

Plants Animals

CO Ocean

N HO

Biotic components

Abiotic components

The movement of chemical substances among the living and non-living components of the Earth

Main biogeochemical cycles are Carbon cycle, Oxygen cycle, Hydrogen cycle, Nitrogen cycle, Phosphorus cycle, Sulphur cycle and Water cycle

Carbon Cycle

Carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere and the atmosphere of the Earth through a biogeochemical

cycle called Carbon Cycle.

All organic compounds have carbon

3

CO is released in atmosphere by respiration of animals, combustion of fossil fuels in industries and automobiles.

Auto & Factory emissions

CO Cycle

Animal

Plant

respiration

respiration

Ocean uptake

Root respiration

Organic waste

Photosynthesis

1

Plants remove CO from atmosphere.

2

Lithosphere has CO in the form of fossil fuels

Oxygen Cycle

This biogeochemical cycle explains the movement of oxygen gas within the atmosphere, the ecosystem, biosphere and the lithosphere.

21% O in air Used for Respiration, Combustion, Atom in molecules like H O, CO Oxidation and Decomposition

Atmospheric

oxygen

O O

1

All green plants during the process of photosynthesis, release oxygen back into the atmosphere as a by-product.

Photosynthesis

Carbon dioxide

Oxygen

2

All aerobic organisms use

free oxygen for respiration.

3

Animals exhale carbon dioxide back into the atmosphere which is again used by the plants during photosynthesis. Thus oxygen is balanced in the atmosphere.

Biogeochemical Cycles - Part II

Nitrogen (N2) Cycle

Nitrogen Cycle is a biogeochemical process which transforms the elemental nitrogen present in the atmosphere to a more usable form for living organisms.

Process of Nitrogen Cycle

Nitrogen xation Nitri cation Assimilation Ammoni cation Denitri cation

1

Atmospheric nitrogen: 78% N (elemental form)

2

But animals & plants cannot utilize gaseous form of nitrogen

3

Ammonia and other soluble forms as NO - & NO - can be used

Lightning converts nitrogen to ammonia and nitrate which return to soil & water by rain

Too much nitrogen from fertillizers returns to soil, contaminates ground water.

Forest res release N from trees which then goes back to the atmosphere.

Animals eat plants to receive N to be used to make DNA, RNA & proteins. Animals excrete wastes.

Plants and animals die, return to the soil, are decomposed

Denitrifying bacteria convert nitrogen to an unusable form, return it to atmosphere

Decomposers ( Worms, bacteria, beetles, fungi) break down waste and dead things. Bacteria x N which is released into soil & water & used by plants

ATMOSPHERIC NITROGEN 78% Nitrogen from atmosphere returns to soil and water with the help of bacteria and algae.

Algae converts unusable Nitrogen to usable

Fish dies, decompose

Phosphorus Cycle

Phosphorus cycle involves both aquatic and soil reservoirs

Rocks contain phosphate (PO 3-)

Weathering or erosion of rocks

Urine

Waste decomposition Plant Uptake

Inorganic phosphate (HPO ) Geological Upheaval

Dissolved Phosphates

Incorporation into sedimentary rocks (as phosphates of Ca, Mg and Fe)

Excretion & decomposition

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