1. Unit A: Energy and Matter Exchange in the Biosphere
Chapter 3
Section 3.2
The Carbon and Oxygen Cycle

2. Unit A: Energy and Matter Exchange in the Biosphere
The Carbon Cycle
Carbon is the key element for living things.
Carbon can be found in the atmosphere and dissolved in the oceans as part of the inorganic carbon dioxide (CO2) molecule.
Each year 50 to 70 million tonnes of carbon dioxide are cycled into more complex organic substances.
This is done through photosynthesis.
Some of the organic carbon is released back to the atmosphere through cellular respiration.

3. Carbon dioxide  Glucose  Carbon dioxide
Because photosynthesis and cellular respiration are complementary processes, and because the carbon that they use is repeatedly cycled through both processes, this is known as the carbon cycle.
The carbon cycle – is the cycle of matter in which carbon atoms move from an inorganic form to organic and then back to inorganic.
Carbon dioxide  Glucose  Carbon dioxide
Carbon is released from living beings through body waste and decomposition.
Carbon is released from fossil fuels through combustion, the chemical reaction of carbon molecules with water to form carbon dioxide and water.

4. Reservoirs for Inorganic Carbon
Inorganic carbon can be found in 3 main reservoirs or storages areas:
Atmosphere
Oceans
Earth’s crust

5. Reservoirs for Organic Carbon
Unit A: Energy and Matter Exchange in the Biosphere
Reservoirs for Organic Carbon
Organic carbon is stored in 2 main sources:
Living things
2. Bogs
- bogs contain very little oxygen, so decomposition is very slow
- therefore carbon can remain in dead plant matter for many years
- occasionally these deposits are overlaid with sediment and eventually the carbon will be trapped in-between layers of rock
- the result is the carbon containing fossil fuel coal
- the same process happens at the bottom of the ocean to form oil

6. Unit A: Energy and Matter Exchange in the Biosphere
The Carbon Cycle

7. Unit A: Energy and Matter Exchange in the Biosphere
The Oxygen Cycle
The oxygen cycle consists of the movement of oxygen gas (O2), from living things into the atmosphere through photosynthesis, and then back into living things through cellular respiration.
Oxygen atoms are also present in carbon dioxide, water, glucose, and other substances which contribute to the cycle as well.

8. Unit A: Energy and Matter Exchange in the Biosphere
The Oxygen Cycle

9. Human Impact on the Carbon Cycle
Unit A: Energy and Matter Exchange in the Biosphere
Human Impact on the Carbon Cycle
Our major impact on the carbon cycle is through the burning of fossil fuels.
The excess carbon dioxide contributes to the greenhouse effect and therefore to global warming.

10. Unit A: Energy and Matter Exchange in the Biosphere

11. Unit A: Energy and Matter Exchange in the Biosphere
The Albedo Effect
If global warming continues to increase, much of our permanent ice and snow cover will melt.
As radiation from the Sun reaches Earth, it is reflected back by Earth’s surface.
Some surfaces reflect radiation better than others.
The term albedo is used to describe the extent to which a surface can reflect radiation.
The higher the albedo, the greater the ability to reflect.
The lower the albedo, the greater the ability to absorb.

12. Unit A: Energy and Matter Exchange in the Biosphere
Surfaces like snow and ice have very a high albedo.
In the winter the Sun’s energy reflects off the snow and ice keeping temperatures low.
Global warming affects the amount of snow and ice Earth has.
If the climate warms, there will be less snow and more energy will be absorbed instead of reflected, further increasing global warming.
This is called the snow-temperature feedback cycle.

13. Snow – Temperature Feedback Cycle
Unit A: Energy and Matter Exchange in the Biosphere
Snow – Temperature Feedback Cycle
Climate Warms
Earth’s surface has lower albedo, more energy is absorbed
Less snow, shorter winters