By Moira Whitehouse PhD.

• Carbon is an element found on Earth in both living and nonliving things.

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• The characteristics of the remarkable carbon atom make possible compounds necessary for life on Earth.

• Carbon along with hydrogen, oxygen, nitrogen, phosphorous, calcium and sulfur form most of the compounds that make up living things.

• Carbon is an element found throughout the universe.

• Carbon is an element found in all living things and without it there would be no life on Earth.

Free clip art for educational use http://www.dorlingkindersley-uk.co.uk/nf/ClipArt/Image/0,,239037_1584216_,00.html

• Carbon is also part of nonliving things such the oceans, rocks ,animal shells, and the atmosphere.

• Carbon atoms continually move through living things, the oceans, the atmosphere and the crust of the Earth.

• However, carbon doesn’t stay in one place. It’s always on the move.

• This movement is known as the carbon cycle

The global carbon cycle can be divided into two categories:

geological which operates over large time scales (millions of years),

and biological/physical,which operatesshorter time scales(days to thousands of years).

The geological carbon cycle

In the geological carbon cycle, with time frames in the hundreds of millions of years, carbon within rocks is dissolved and then carried by run-off water to the ocean.

http://www.esi.utexas.edu

Carbon dioxide in the atmosphere combines with water to form a weak acid. This acid dissolves a mineral called calcium carbonate found in limestone rock.

This mineral is carried to the oceans where it is deposited forming limestone on the sea floor.

http://oceanexplorer.noaa.gov

http://earthobservatory.nasa.gov

As the Earth’s plates move, layers of limestone subduct under the continental plate. The great heat and pressure far below the Earth’s surface cause the limestone to melt releasing carbon dioxide. The carbon dioxide then moves into the atmosphere through volcanic eruptions.

As previously noted, the global carbon cycle can be divided into two categories:

geological which operates over large time scales (millions of years),

and biological/physical,which operatesshorter time scales(days to thousands of years).

Remembering that this is a cycle, we can start about anywhere in the cycle and will end up at that point when we finish.

Starting here

Photosynthesis

Carbon moves from the atmosphere to producers. In the atmosphere, carbon exists as a gas called carbon dioxide (CO2). Plants use light energy from the Sun and CO2 from the air for the process of photosynthesis,

CO2 from the air

Producers absorb carbon dioxide from the air to make molecules of glucose (food) which includes carbon atoms.

photosynthesis

6CO2 + 6HO2 = C6O12O6 + 6O2

After plants make glucose molecules, they change these molecules into molecules of starches, proteins, and fats, all which also contain carbon atoms—carbon atoms that were once part of the CO2 in the air.

http://www.epa.gov/

By photosynthesis, tiny producers in the ocean called phytoplankton, absorb a massive amount of dissolved carbon dioxide from the water and release oxygen into the atmosphere.

These organisms use carbon to make their shells of calcium carbonate (CaCO3 ). When they die, the shells settle to the bottom of the ocean and are buried by sediment. Eventually theseshells change into limestone on the sea floor,and can become part of the geological carbon cycle.

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Carbon removed from the ocean by marine creatures can also end up as rock on the ocean floor.

to consumers

Carbon moves from producers to consumers via food chains.

The carbon that is in plants is transferred to the animals that eat them.

Carnivores in turn get carbon from the animals they eat.

http://www.ncat.org/

At the most basic level, we should understand that the photosynthesizers are feeding us all.

http://alaska.fws.gov/

This represents a big part of the carbon cycle, but certainly not all of it. Now we have to get the carbon back into the air to keep the cycle going.

Back to theair throughRespiration

Carbon gets back into the air is through respiration.

Carbon moves from living things to the atmosphere or water as a result of respiration (“burning” of food for energy).

When animals or any other nonproducers metabolize glucose, they expel carbon dioxide gas (CO2) into the atmosphere or water.

Plants cells also under respiration and get rid of carbon dioxide gas through the stomata in their leaves.

http://extension.oregonstate.edu

Both plants and animals release carbon dioxide when they “burn” glucose for energy to carry out their life processes. Plants, however, store some carbon in starches, fats and proteins.

Decaying matter(still respiration)

Another way that the carbon gets back into the air:

When living things die, the carbon from which they are made can move back to the air.

By “eating” this decaying matter they return carbon dioxide to the air or soil through respiration. This isn’t some special creation of CO2, the gas is released as the result of their normal bodily functions, eating carbon burping carbon dioxide, it is still respiration.

Decomposers are organisms that eat the dead or decaying organisms, and in doing so carry out the natural process of decomposition.

The primary decomposers are bacteria and fungi.

In the process of carrying out their unsavory but very necessary duties, they do a great service to us all by continually chipping a way at the planets unending supply of smelly carrion and releasing carbon dioxide back into the air.

Continuing around the carbon cycle....

Burning fossil fuels

Back to theair through

Plants and animals that do not decompose for various reasons, may be buried deep in the earth (with their carbon intact) and over millions of years change into into coal, crude oil or natural gas.

We know that there is a great reservoir of energy in the form of carbon stored deep underground in the form of coal, oil and gas.We should also recognize that trees store great amounts of carbon.Carbon moves from the atmosphere to bodies of water when carbon dioxide is dissolved and stored in oceans, lakes and rivers.

Storage of carbon:

Most of the Earth’s carbon dioxide is found in the ocean where wave action is important in taking CO2 from the air.

Free photo courtesy of http://www.pdphoto.org/

That’s the ol’ Carbon cycle for you.It has been a sweet system for millions of years.But recently, there has been problem.

And it is right here.

Man has been busy releasing as much of that stored up carbon as he can, while at the same time ridding the planet of much of its plant life.

This is the problem:

Life as we know it is possible on Earth because of a natural greenhouse effect keeps our planet about 60o F warmer than it otherwise would be.

natural greenhouse effect

http://clinton5.nara.gov/Initiatives/Climate/greenhouse.html

When we burn fossil fuels to power our factories, power plants and vehicles, carbon in the form of CO2 moves from the fossil fuels into the atmosphere.

The burning and logging of forests (add) carbon to the air by reducing the amount of carbon stored in trees.

The result is that the atmospheric levels of CO2 have increased 30 percent since 1860. Most scientists believe that these steady additions have begun to tip a delicate balance of greenhouse gases in the atmosphere causing the earth’s temperature to rise.

This model of earth’s natural greenhouse protection shows what is happening over time. Notice that the red area is getting thicker indicating a hotter world for us all.

http://www.nps.gov/goga/naturescience/climate-change-causes.htm

For review, we can take a look at this model of the carbon cycle.

Nitrogen Cycle

Important facts about nitrogen

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• Nitrogen is a gaseous element found on Earth in both living and nonliving things.

• Nitrogen is a gaseous element found on Earth in both living and nonliving things.

• 79% of the atmosphere on Earth is nitrogen gas.

Wikipedia commons

• Nitrogen is an element found on Earth in both living and nonliving things.

• All living things need nitrogen to live, grow and reproduce.

• 79% of the atmosphere on Earth is nitrogengas.

• Nitrogen is an element found on Earth in both living and nonliving things.

• All living things need nitrogen to live, grow and reproduce.• Nitrogen is necessary for cells to carry out the life processes.

• 79% of the atmosphere on Earth is nitrogengas.

• Nitrogen is an essential component of both proteins and DNA.

Graphic image of a molecules of proteinGraphic image of DNAimages from Wikipedia Commons

Nitrogen, DNA and Proteins

• All cells have a genome, information inherited from “parents”. The genome is the blueprint on how to “build” a cell like a construction design is blueprint for how to build house.

• So how is nitrogen important to the “building” of a cell?

First, nitrogen is an essential component of DNA, the molecule in the cell that contains all the instructions of how the cell is to be made and what it is to do.

Second, the actual house, “the cell,” is build out of protein molecules which all contain the element nitrogen. .

Think of any process that may be happening in the cells of a living organism.

Nitrogen based proteins are not only the building blocks of all living things. They are also the chemicals that control all the things that go on in a cell.

Proteins are most likely either making it happen or regulating it. Photosynthesis, digestion, respiration, movement, growth, getting rid of waste products are examples.

What then is the Nitrogen Cycle?

• Like carbon atoms, nitrogen atoms do not stay in one place.• Nitrogen atoms move in a continuous pattern through soil, air, water and all living things. • Nitrogen’s journey through the biosphere and all living things is called the nitrogen cycle.

Nitrogen travels through the five processes in the Nitrogen Cycle!

(1) Nitrogen Fixation

(4) Ammonification (2)Nitrification

(5) Denitrification

Nitrogen Cycle

(3) AssimilationAnimated graphics at http://office.microsoft.com/clipart

Although the earth's atmosphere is 79% nitrogen, plants or animals cannot use nitrogen in its gaseous form. It must be changed to a useable form for both plants and animals.

Nitrogen Fixation

In order for plants or animals to absorb nitrogen, it must be "fixed”.

How does atmospheric

nitrogen get “fixed” (changed into a

form that can be used by plants)?

N

N

Atmospheric nitrogen is converted to ammonia or nitrates.

Ammonia (NH3)Nitrogen combines with

hydrogen to make ammonia

Nitrates (NO3)

Nitrogen combines with oxygen to make nitrates

Atmospheric Nitrogen (N2)

N

N

N

N

Wikipedia Commons

And what things in the biosphere change nitrogen gas from the air into ammonia (a nitrogen compound)?

http://www.lightningsafety.noaa.gov/

Wikipedia commons

1. Nitrogen fixing bacteria in the soil

2. Nitrogen fixing bacteria found in the roots of plants such as peas, beans, peanuts and soybeans.

3. Lightning

Wikipedia Commons

Can plants use ammonia?

Most atmospheric nitrogen (N2) is “fixed” and changed to ammonia (NH3). Ammonia is highly toxic to many organisms.

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)…

…but, most can’t. Fortunately the

second processNitrification can help!

A few plants can use ammonia (NH3)

…but, most can’t. Fortunately the second process Nitrification can help!

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Nitrifying bacteria change ammonia in the soil to nitrites and then into nitrates that are dissolved in water and absorbed through the roots of most plants .

Nitrification

For acid loving plants ammonia can be the source of nitrogen. However, most plants extract their nitrogen from nitrates not ammonia.

Wikipedia Commons

Assimilation is the process by which plants absorb the nitrates andand/or the ammonia from the soil and use them to make proteins. Nitrogen isparticularly important to the production of chlorophyll.

Assimilation

More Assimilation…Animals and other living things that do not make food get the nitrogen they need by eating plants or by eating other animals that eat plants.

Wikipedia Commons

How does nitrogen

reenter the atmosphere

in the nitrogen

cycle?Animated graphics at http://office.microsoft.com/clipart

Through the fourth and fifth processes called

ammonification and denitrification!

(1) Nitrogen Fixation

(2) Nitrification(3) Ammonification

(4) Denitrification

(3) AssimilationAnimated graphics at http://office.microsoft.com/clipart

So what is ammonification?

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Ammonification is what happens when a plant or animal dies. Fungi and bacteria change the remains of the dead plants and animals into ammonia plus other substances.

Nitrificaton occurs again. Nitrifying bacteria in the soil change ammoniainto nitrites and thennitrates.

http://www.freenaturepictures.com/pictures/mushrooms-on-log.php

Now is where denitrification plays its role.

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Denitrifying bacteria in the soil change nitrates into nitrogen gas which is released into the air. And so the cycle continues.

Denitrification

Wikipedia Commons

• At the same time, nitrogen is returned to the soil through decay (ammonification) and to the air through and denitrification.

Thus, through the nitrogen cycle:

• Plants obtain nitrogen through nitrogen fixation and nitrification.

• Animals get their nitrogen from eating plants or animals that have eaten plants or other animals.

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