1. Ecology Part 6 Carbon & Nitrogen Cycles
R. Martinez, 2012

2. Biochemical Cycles
1. Materials (e.g. elements) cycle within an ecosystem.
2. They cycle among organisms the physical environment.
3. Types of Cycles:
A. Carbon Cycle
B. Nitrogen Cycle
C. Water Cycle
D. Phosphorous Cycle

3. What is Carbon? An element The basis of life on earth
Found in all living organisms
Also found in rocks, oceans, atmosphere
Two main types:
Carbon sources
Carbon sinks

4. The Carbon Cycle
A. Carbon sources: Release carbon into the atmosphere.
i. Types include:
Cellular Respiration:
Burning of fossil fuels (combustion)
Decomposers:
Decomposers like bacteria and fungi, use the energy trapped in dead plants and animals and release CO2
Plants absorb CO2 (photosynthesis) and release CO2 (respiration).
Plants use sugar to make their cell walls so they absorb far more carbon dioxide than they produce.
Most animals cannot digest cellulose which is what plants cell walls are made of, so when plants are eaten or die, the carbon that was absorbed by the plant is trapped. This is where decomposers come in...

5. The Carbon Cycle
Plants absorb CO2 (photosynthesis) and release CO2 (respiration).
Plants use sugar to make their cell walls so they absorb far more carbon dioxide than they produce.
Most animals cannot digest cellulose which is what plants cell walls are made of, so when plants are eaten or die, the carbon that was absorbed by the plant is trapped. This is where decomposers come in...
B. Carbon sinks: Remove carbon from the atmosphere.
i. Type includes:
1. Photosynthesis:
a. Photosynthesis conducted by:
i. Terrestrial – Plants/Trees
ii. Aquatic - Phytoplankton

6. What is Nitrogen? 79% of the atmosphere is nitrogen gas
Atmospheric N2 is in a form most living things cannot use. N2
free
nitrogen

7. The Nitrogen Cycle
Nitrogen Cycle: The nitrogen cycle is complex and has several stages:
Organisms need nitrogen and phosphorus to build proteins and nucleic acids.

8. How do we get Nitrogen?
A. Nitrogen is processed into a useable form by the following (known as nitrogen fixation):
Nitrogen fixation is N2  NH3 (ammonia)
Nitrogen-fixing bacteria convert nitrogen into ammonia/nitrates.
Plants absorb nitrates.
Animals eat plants. N2
in air
nitrogen-fixing
bacteria
NITRATES

9. How do we get Nitrogen?
normal conditions.
5. Nitrogen fixation can also be caused by lightning!

10. How does Nitrogen return to the atmosphere?
B. Denitrifying bacteria convert the nitrates back into nitrogen.

11. The Role of the Decomposer
When plants and animals die, the nitrogen contained in these organisms is digested by decomposers and released into the soil as ammonia. Without these decomposers, the nitrogen would remain trapped in the dead animals. These decomposers recycle the nitrogen and are a key component of the cycle.