Biogeochemical Cycles

Nitrogen Cycle

Nitrogen is needed by all organisms for cell-building.

Atmospheric nitrogen (N2) is inert and needs to be changed into more reactive forms.

Reactive forms of nitrogen: ammonium (NH4

+), nitrates (NO3-)

Nitrogen Cycle

Processes:1. Nitrogen fixation

2. Nitrogen uptake or assimilation

3. Decomposition

4. Nitrification

5. Denitrification

Nitrogen Cycle

Human Activities1. Using synthetic nitrogen fertilizers

Increased agricultural production Contamination of groundwater Algal blooms Fish kills

2. Burning fossil fuels Air pollution Acid rain Global warming

Let’s Review

Let’s Review

Carbon dioxide - Oxygen Cycle

CO2 is needed by plants in photosynthesis (making food) and is a greenhouse gas.

O2 is needed by organisms in respiration (getting energy from food).

Processes:1. Photosynthesis

2. Respiration

3. Combustion

Carbon dioxide-Oxygen Cycle

1. Photosynthesis the process by which plants make food

(glucose) CO2 + H2O sunlight C6H12O6 + O2

releases O2 into the air

Carbon dioxide-Oxygen Cycle

2. Respiration the process by which living things get energy

by “burning” food C6H12O6 + O2 CO2 + H2O + energy

releases CO2 into the air

Carbon dioxide-Oxygen Cycle

3. Combustion the process by which fuels are burned to

release energy (heat) fuel + O2 CO2 + heat

releases CO2 into the air

Carbon dioxide - Oxygen Cycle

Human Activities1. Deforestation

Increased CO2 global warming

Decreased O2

2. Burning fossil fuels Increased CO2 global warming Air pollution

The End