18.2 THE CARBON AND NITROGEN CYCLE

Our Biosphere

Learning Targets

1. Describe the short term cycling of carbon through the processes of photosynthesis and respiration

2. Identify carbon sinks and carbon sources

3. Describe short term and long term storage of carbon

4. Describe how human actions interfere with the natural carbon cycle

5. Describe the nitrogen cycle

Carbon Cycle

1. All life on earth is built around carbon atoms

2. Carbon is found in many forms:a) Atmosphere (Carbon Dioxide) b) Biosphere (Carbohydrates) c) Hydrosphere (Calcium carbonate)d) Geosphere (Carbon

arrangement)

Short term cycle

Atmospheric Carbon Dioxide

Photosynthesis

Cellular Carbon Dioxide

Respiration, decay, or

consumption

Long term cycles

1. Organic materials are burieda) AKA – Fossil Fuelsb) Peat, coal, tar, oil, soil

2. Carbon stored in the oceana) Many ocean creatures use

calcium carbonate (CaCO3) to make their shells or to make the reef material where coral animals live.

Carbon Sinks and Carbon Sources

1. Carbon sources (add carbon)a) Fossil fuel use, deforestation, animals,

decaying plant remains

2. Carbon sinks (store carbon)a)Healthy living forests and our

oceans act as carbon sinks. 3. Reservoirs can change from a sink

to source and vice-versa

Human Actions Impact Carbon Cycle

1. Largest source of atmospheric CO2 is burning fossil fuels

2. When we burn coal, oil, or natural gas, we release the stored carbon in the process of combustion. That means that combustion of fossil fuels is also a carbon source.

Human Actions Impact Carbon Cycle

1. Second largest source of atmospheric CO2 is deforestation

2. Carbon sink – Trees absorb CO23. When trees are cut, lose ability

to absorb CO24. Carbon source- If tree is burned

or decomposes

Why Carbon Cycle is Important

1. Why small amounts of CO2 important?

2. CO2 absorbs infrared energy from Sun

3. Greenhouse gases trap heat that should radiate out into space

4. Greenhouse gas levels increase, global temperatures increase = Global Warming

The Nitrogen Cycle

1. Most abundant gas in atmosphere2. Essential component of organic

materialsa) Amino Acidsb) Proteinsc) DNA and RNAd) Chlorophyll molecules used for

photosynthesis

The Nitrogen Cycle

1. Must be “fixed” or converted to a usable form

2. “Fixed” in 3 waysa) Lightningb) Blue-green algaec) Mainly “fixed” by bacteria in soil

3. Nitrogen fixing bacteria combine nitrogen with oxygen = nitrates or ammonia

Dead Zone