The document discusses the carbon/oxygen cycle which involves four main processes: 1. Photosynthesis where plants take in carbon dioxide and water to release oxygen and sugar using energy from the sun. 2. Respiration where animals take in oxygen and sugars to release carbon dioxide, water, and energy. 3. Combustion which is the burning of fossil fuels like coal, gas, and oil, releasing carbon dioxide. This over-contribution of carbon dioxide is accelerating global warming. 4. Decomposition where dead plants and animals are broken down by insects, fungi and bacteria, returning carbon and other elements to the soil and air.

1. Topic 4
Cycles of Life

2. 4.1 – The Carbon/Oxygen Cycle
4.2 – The Nitrogen Cycle
4.3 – Phosphorus and ___ Cycle
Cycles of Life
All life requires nutrients and nutrients are
continually recycled … if they were not, they
would become used up and life on Earth
would cease to exist.

3. 4.1 – The Carbon/Oxygen Cycle
The Carbon/Oxygen Cycle is interconnected
and involves three major processes and one
minor process:
1. Photosynthesis
2. Respiration
3. Combustion
4. Decomposition

4. 1. Photosynthesis
Green plants/trees take in carbon dioxide
and water using the chlorophyll in their
leaves and energy from the sun they
release oxygen, sugar and water vapor.

5. 1. Photosynthesis

6. 1. Photosynthesis
Formula:

7. 2. Respiration
Animals take in
simple sugars
and oxygen
and release
carbon dioxide,
water and
energy

8. 2. Respiration
Formula:

9. 3. Combustion
This is the process of burning. When
combustion occurs CO2 is released into
the atmosphere. Natural combustion
includes volcanic eruptions, however
most pollution problems occur
because cars and factories
release CO2 by their burning
fossil fuels.

10. 3. Combustion
Fossil Fuels: Coal, Gas and Oil

11. 3. Combustion
During the Carboniferous Period (300
mya) large amounts carbon (in the tissue
of plant matter) was trapped underground.
Because of lack of oxygen and
tremendous pressure, the plant matter
was compressed into fossil fuels.

12. 3. Combustion
Combustion due to fossil fuels over
contributes to the carbon cycle, which is
accelerating the negative effects of
global warming.

13. 4. Decomposition
When an animal or plant dies all the carbon,
oxygen, nitrogen, water, calcium etc. return
to the soil and air during decomposition.
Certain insects, fungi and bacteria aid in the
decomposition process and are called
decomposers.

14. 4. Decomposition

15. Putting It All Together …

16. PHOTOSYNTHESIS

17. RESPIRATION

18. COMBUSTION

19. DECOMPOSITION

20. Topic 4.1 Assignment
1. Carbon/Oxygen Cycle Notes
2. Read page 1-4.
3. Complete Questions #