Part 4: BiogeochemicalCycles

•All the matter that Earth has ever had and ever will have has been present since its formation over 4 billion years ago. Except for the occasional meteorite impact, no new matter is ever added to the planet and no matter ever disappears. Instead, the same matter is used and reused in an ever-repeating pattern of cycles.

The Water Cycle

transpiration

Biogeochemical Cycles

• This means that the same nutrients have been recycled over and over again through organisms and the environment since the beginning of the Earth!

• This means all living things are deeply interconnected with each other and their environment!

• These cycles are called biogeochemical cycles.

(bio = living, geo = Earth)

• Nutrients that are used by organisms in large quantities are hydrogen, oxygen, (water), carbon, nitrogen and phosphorous.

Carbon Cycle

•Carbon (C) is the basis of life on Earth. While the most abundant substance in organisms is water, carbon is the second most abundant. 18% of the human body is made of carbon. All organisms need carbon to survive. Whether the carbon is in the form of a sugar or carbon dioxide gas, we all need it. The Earth only has a fixed amount of carbon. The carbon cycle is the ultimate form of recycling.

The Carbon Cycle – part 1

When organisms die, some of the carbon gets buried in the earth

Step 1: Photosynthesis

• Producers use the sun’s energy to take carbon dioxide from the air and convert it to sugar (photosynthesis).

(Sugar)

Step 2: Cellular Respiration

• Carbon moves through the food chain when consumers eat plants and animals.

• The carbon is released when plants and animals use the food to produce energy (respiration)

Consumer

Step 3: Decomposition

• When plants and animals die, decomposers break down their bodies and also produce carbon dioxide through respiration.

•Sometimes, the dead organisms get buried under soil or sand before decomposition can happen. Over millions of years, pressure and heat builds up and turns the organisms into fossil fuels (oil, coal, natural gas.)

•Instead of returning to the atmosphere, the carbon from these lifeforms is trapped within the Earth. Over millions of years, more and more of the carbon on Earth has been trapped in this manner. Today, almost 99% of all the carbon on Earth has been locked up deep within the Earth.

•As rocks weather, this carbon is slowly released back into the atmosphere, creating a balance. For the past several hundred million years, the amount of carbon being locked up in the Earth and the amount being released by weathering rocks was almost perfectly balanced.

The Carbon Cycle – part 2

Combustion:

Step 4: Disturbing the Carbon Cycle

• This important balance has been altered significantly in the past century as humans have begun using fossil fuels to produce energy. By burning the Earth’s store of carbon, humankind is able to create the energy needed to heat our homes and run our cars and factories. However, we must be careful as we do so. By releasing more carbon into the atmosphere than is being locked up, we risk causing damage to the delicate carbon cycle.

What Does Carbon Have to do With Climate Change?• Climate change occurs when carbon dioxide and other air pollutants

and greenhouse gasses collect in the atmosphere and absorb sunlight and solar heat that have bounced off the earth’s surface.

• Normally, this heat would escape into space—but these pollutants, which can last for years to centuries in the atmosphere, trap the heat and cause the planet to get hotter.

• That's what is known as the Greenhouse Effect.

• Carbon sinks are good; they absorb the carbon from the atmosphere

• Carbon sources are bad; they release the carbon into the atmosphere

Volcanoes and forest

fires are natural ways

that carbon is released

into the atmosphere.

• Carbon cycle game:

• http://oceanservice.noaa.gov/education/pd/climate/teachingclimate/carbon_cycle_game.pdf

• Deforestation destroys plants that would normally have helped to remove carbon from the atmosphere

• Burning fossil fuels releases more carbon into the atmosphere.

• Carbon dioxide is a greenhouse gas. This means it absorbs and reemits heat energy.

• More CO2 in the atmosphere has caused the global temperature to change.