Biogeochemical Cycles

1. Biogeochemical
Cycles

2. Nitrogen Cycle
Nitrogen is needed by all organisms for cell-
building.
Atmospheric nitrogen (N
2
) is inert and needs
to be changed into more reactive forms.
Reactive forms of nitrogen: ammonium
(NH
4
+
), nitrates (NO
3
-
)

3. Nitrogen Cycle
Processes:
1.Nitrogen fixation
2.Nitrogen uptake or assimilation
3.Decomposition
4.Nitrification
5.Denitrification

5. Nitrogen Cycle
Human Activities
1.Using synthetic nitrogen fertilizers
Increased agricultural production
Contamination of groundwater
Algal blooms
Fish kills
2.Burning fossil fuels
Air pollution
Acid rain
Global warming

6. Let’s Review

7. Let’s Review

8. Carbon dioxide - Oxygen Cycle
CO
2
is needed by plants in photosynthesis
(making food) and is a greenhouse gas.
O
2
is needed by organisms in respiration
(getting energy from food).
Processes:
1.Photosynthesis
2.Respiration
3.Combustion

11. Carbon dioxide-Oxygen Cycle
1.Photosynthesis
the process by which plants make food
(glucose)
CO
2
+ H
2
O
sunlight
C
6
H
12
O
6
+ O
2
releases O
2
into the air

12. Carbon dioxide-Oxygen Cycle
1.Respiration
the process by which living things get energy
by “burning” food
C
6
H
12
O
6
+ O
2
CO
2
+ H
2
O + energy
releases CO
2
into the air

13. Carbon dioxide-Oxygen Cycle
1.Combustion
the process by which fuels are burned to
release energy (heat)
fuel + O
2
CO
2
+ heat
releases CO
2
into the air

14. Carbon dioxide - Oxygen Cycle
Human Activities
Deforestation
Increased CO
2 ® global warming
Decreased O
2
2.Burning fossil fuels
Increased CO
2 ® global warming
Air pollution

15. The End