Biogeochemical Cycles Cycling of Organic Matter

Week 3 Bio 20 Cyber High

Cycling of Organic Matter  The materials used in building the bodies of living organisms are limited to the atoms and molecules that make up the planet.  There is no alternative source of matter.  Therefore, to maintain life on Earth, matter must be recycled.

Cycling of Organic Matter  Food is organic matter. Every time you eat, organic matter that was once part of other living things passes into your body.  Through the process of digestion, complex organic molecules are broken down into simpler molecules.  Cells use these simple molecules to build the complex molecules that become part of your own structure.

Cycling of Organic Matter  Decay  After death, decomposer organisms make the materials available to other living things.  Decomposers break down the organic matter in dead bodies and feces into small, inorganic molecules

Properties of Water  All living things need water  Water can be found in the biosphere in three states 1.Solid (snow or ice) 2.Liquid 3.Gas ( vapour)  Water is continuously entering and leaving living systems

Properties of Water

 Water: a Polar molecule  Water molecules have a positive pole and a negative pole causing water molecule to be a polar molecule  Polar molecule – a molecule that has a positive and a negative end

Properties of Water  The attraction between opposing charges of different molecules create a special hydrogen bond.  Hydrogen bonds pull water molecules together

Biogeochemical Cycles  Matter can neither be created or destroyed  It cycles through the biosphere.  As it cycles, it follows certain characteristic pathways  These pathways are called “Biogeochemical Pathways”  Bio = Life  Geo = Earth

Biogeochemical Cycles  A biogeochemical pathway can be defined as  the complex cyclical transfer of nutrients...  from the environment to an organism and back to the environment.  There are 3 major cycles to understand  Carbon/Oxygen Cycle  Nitrogen Cycle  Phosphorus Cycle

The Carbon Cycle

 Also called the Carbon-Oxygen Cycle.  Refers to the flow of CO 2 through the biosphere.  The main part of this cycle involves the interrelation between cellular respiration and photosynthesis.

Photosynthesis Cellular Respiration

The Carbon Cycle  Carbon dioxide is also released by the activities of :  Volcanoes  Automobiles  Combustion of any source  Uplifting and weathering

The Carbon Cycle

Reservoirs for Carbon Organic Carbon -Organic carbon is held in the bodies of all living things. -All living things die, and decomposition eventually returns the carbon to the cycle in inorganic form. -There is one important exception to this rule: Some ecosystems such as bogs, store huge quantities of carbon in organic form. -Peat

Reservoirs for Carbon Inorganic Carbon  When Carbon is not in organic form it may be found in three main reservoirs. 1.The Atmosphere 2.The Ocean 3.Earth’s Crust

Human Impact on the Carbon Cycle  Human have modified the global carbon cycle by:  Mining fossil fuels and burning them, releasing carbon from organic reservoirs faster than normal.  Humans are also increasing the amount of carbon dioxide in the inorganic reservoir by clearing away vegetation in order to build or farm.  Oceans can hold only so much carbon dioxide

The Nitrogen and Phosphorus Cycles

The Nitrogen Cycle  The complex cycling of nitrogen between organisms and the environment.  The air is 79% nitrogen.  The main component of most fertilizers is a nitrogen compound.

Nitrogen and Plants  Nitrogen is a chemical that plants need to grow well.  Nitrates are a group of nitrogen containing compounds that are readily absorbed by the roots of plants

Nitrogen and Animals  Nitrogen is also needed for the construction of proteins and nucleic acids  Muscle tissue  Hair  Bones  Cell parts  DNA  RNA

Nitrogen Usage  Nitrogen is usually utilized in life in the form of nitrates.  There are 2 main ways atmospheric nitrogen can be converted into useful forms. 1) Lightning 2) Bacteria

Method #1 -- Lightning  Lightning can force nitrogen and oxygen together to form nitrates  these will fall with precipitation and be absorbed by plant roots.  The plants will change these into their own proteins.  Animals eat the plants and reorganize those proteins into the ones they need.

Method #2 -- Bacteria  These can convert atmospheric nitrogen into nitrates.  Nitrogen-fixing bacteria can also be found in small lumps called nodules on the roots of legumes.  Legumes can utilize atmospheric nitrogen  Legumes are members of the bean family and include:  Clover and Alfalfa…

Legumes

Nitrogen and decomposers  After an organism dies, it decays.  Decaying matter which contains nitrogen produces ammonia.  Ammonia will degrade into nitrites.  Nitrites will degrade into nitrates.  The nitrates will now re-enter the cycle.

Bacteria  Some bacteria will actually convert the nitrates back into atmospheric nitrogen.  Denitrifying bacteria.  These bacteria do not need oxygen -- anaerobic respiration.

Denitrification  the process in which nitrates are converted to nitrites and then to nitrogen gas

Atmospheric pool of nitrogen Lightning Fertilizers Nitrogen-fixing bacteria in root nodules of legumes

1 Atmospheric pool of nitrogen 2 Nitrogen-fixing bacteria in root nodules of legumes 3 Fertilizers 4 Soil nitrate 5 Nitrate take up by plant roots 6 Plant and animal proteins 7 Dead organisms 8 Decomposers 9 Nitrate bacteria 10 Nitrate bacteria 11 Denitrifying bacteria 12 Lightning

a Atmospheric nitrogen b Lightning causes oxygen to react with nitrogen c Rain dissolves the oxides of nitrogen that are formed d Fertilizer e Soil f Nitrogen-fixing plants (legumes) g Plants use nitrate to make protein h Plants are eaten by animals i Excretion j Death k Bacterial decomposition of nitrates to nitrogen

Phosphorus Cycle  Phosphorus is a nutrient required by all living things.  Component of bones and teeth  DNA  ATP  Phosphorus Cycle is simpler than the carbon or nitrogen cycles because it does not involve movement through the atmosphere.

The Phosphorus Cycle  Phosphorus is used in only one important inorganic form…  Phosphate Ion (PO 4 3- )  Plants absorb this through their roots.  After plants incorporate phosphorus...  it is transferred through the food chain  it is eventually returned to the soil.  excretions of animals  actions of decomposers.

The Phosphorus Cycle  Two methods of P recycling:  geological (abiotic Long-term cycle)  living organisms (biotic short- term cycle)

Long Term Cycle  Most common form: a part of rocks  Properties:  soluble - dissolve in water  Phosphates dissolve in water—erosion (weathering) carries them from land to streams and rivers and then finally to the oceans  Oceans  sediments may be thrust upward (uplifting) and once again form land through geological activity

The Phosphorus Cycle The weathering of rocks gradually adds phosphorus to the soil and to the waterways.

Long Term Cycle

Short Term Cycle  Phosphates in water also enter the food chain through photosynthetic organisms  Decomposition of dead organisms  soluble phosphates are absorbed by plants and used during photosynthesis  Plants are eaten by animals

Short Term Cycle

Phosphorous Cycle