1. 18.2 The Carbon and nitrogen cycle
What are ecosystems made of?
Our Biosphere

2. Learning Targets
Describe the short term cycling of carbon through the processes of photosynthesis and respiration
Identify carbon sinks and carbon sources
Describe short term and long term storage of carbon
Describe how human actions interfere with the natural carbon cycle
Describe the nitrogen cycle

3. Carbon Cycle All life on earth is built around carbon atoms
Carbon is found in many forms:
Atmosphere (Carbon Dioxide)
Biosphere (Carbohydrates)
Hydrosphere (Calcium carbonate)
Geosphere (Carbon arrangement)
Carbon is provided by the environment, moves through organisms and then returns to the environment again.

4. Short term cycle Atmospheric Carbon Dioxide
Photosynthesis
Cellular Carbon Dioxide
Respiration, decay, or consumption
Short term cycling of carbon begins with carbon dioxide and the process of photosynthesis.
Plants and algae have the ability to take the inorganic carbon in carbon dioxide and transformed into organic carbon, which is food.
Plants and animals engage in reverse of photosynthesis, which is respiration

5. Photosynthesis

7. Long term cycles Organic materials are buried
AKA – Fossil Fuels
Peat, coal, tar, oil, soil
Carbon stored in the ocean
Many ocean creatures use calcium carbonate (CaCO3) to make their shells or to make the reef material where coral animals live.
Carbon might also be stored as chemical energy in the cells of the plant or the animal. If this happens, the carbon will stay stored as part of the organic material that makes up the plant or animal until it dies.
it decomposes and the carbon is released back into the environment. Other times, the organic material of the organism is buried and transformed over millions of years into coal, oil, or natural gas. When this happens, it can take millions of years before the carbon becomes available again.
When algae die, their organic material becomes part of the ocean sediments, which may stay at the bottom of the ocean for many, many years. Over millions of years, those same ocean sediments can be forced down into the mantle when oceanic crust is consumed in deep ocean trenches. As the ocean sediments melt and form magma, carbon dioxide is eventually released when volcanoes erupt.

9. Carbon Sinks and Carbon Sources
Carbon sources (add carbon)
Fossil fuel use, deforestation, animals, decaying plant remains
Carbon sinks (store carbon)
Healthy living forests and our oceans act as carbon sinks.
Reservoirs can change from a sink to source and vice-versa
Carbon sources are places where carbon enters into the environment and is available to be used by organisms.
Carbon sinks are places where carbon is stored because more carbon dioxide is absorbed than is emitted.
Places in ecosystem that store carbon are reservoirs.
Average time that carbon stays in a reservoir is residence time.
Amount of CO2 in the atmosphere is very low – 0.03%, therefore some increase or decrease have large effect.

10. Scientists can use data from air bubbles trapped in the ice of glaciers to determine what the natural level of carbon dioxide was before the Industrial Revolution, when humans began to use lots of fossil fuels.
Measurements of the different gases in the air bubbles tell us that the natural level of carbon dioxide was about 280 parts per million. Today the amount of carbon dioxide in our atmosphere is 388 parts per million and that amount continues to rise every year.

11. Human Actions Impact Carbon Cycle
Largest source of atmospheric CO2 is burning fossil fuels
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.

12. Human Actions Impact Carbon Cycle
Second largest source of atmospheric CO2 is deforestation
Carbon sink – Trees absorb CO2
When trees are cut, lose ability to absorb CO2
Carbon source- If tree is burned or decomposes
When we cut down trees, we lose their ability to absorb carbon dioxide and we also add the carbon that was stored in the tree into the environment. Healthy living forests act as a carbon sink, but when we cut them down, they are a carbon source

13. Why Carbon Cycle is Important
Why small amounts of CO2 important?
CO2 absorbs infrared energy from Sun
Greenhouse gases trap heat that should radiate out into space
Greenhouse gas levels increase, global temperatures increase = Global Warming

14. The Nitrogen Cycle Most abundant gas in atmosphere
Essential component of organic materials
Amino Acids
Proteins
DNA and RNA
Chlorophyll molecules used for photosynthesis

15. The Nitrogen Cycle Must be “fixed” or converted to a usable form
“Fixed” in 3 ways
Lightning
Blue-green algae
Mainly “fixed” by bacteria in soil
Nitrogen fixing bacteria combine nitrogen with oxygen = nitrates or ammonia
Just like how photosynthesis converts sunlight to a useable energy

16. Symbiotic relationship with legumes (peas, beans, peanuts)
Symbiotic relationship with legumes (peas, beans, peanuts). Use carbohydrates from plant to produce ammonia. When plant dies, the fixed nitrogen fertilizes the soil
Animals eat plant tissue and create animal tissue.

17. Excess fertilizers run off the land, and causing nitrification in ponds and rivers, ending up in the ocean causing a “Dead Zone”. Nitrogen “fertilizes” ponds causing bacteria to grow. When bacteria die, their decomposition uses up all the available oxygen killing everything else.
Dead Zone