1. Biogeochemical Cycles
Chapter 3
Lesson 4

2. Introduction
Every organism needs nutrients to build tissues and carry out life functions.
Like water, nutrients pass through organisms and the environment.
3 nutrient pathways: move carbon, nitrogen, and phosphorus through the environment.
Oxygen plays an important role in all 3 Nutrient Cycles.

3. Carbon Cycle
Carbon is a major component of all organic compounds, including carbohydrates, lipids (fats), proteins, and DNA.
During Photosynthesis, plants use the carbon to build carbohydrates.
Organisms die, decomposers break down the bodies, releasing carbon to the environment.
Geologic forces can turn accumulated carbon into carbon-containing rocks or fossil fuels.
When animals break down “food”, carbon dioxide is released into the environment as a by-product.

4. The Carbon Cycle
Photosynthesis and Cellular Respiration form the basis of the carbon cycle.

5. Photosynthesis takes place in the leaf .
Performed only by plants and plant-like organisms (algae)
Process where CO2, H2O, and sunlight are converted into O2 and glucose (carbohydrate)
Chemical Formula:
CO2 + H2O → O2 + C6H12O6
Photosynthesis takes place in the leaf .

6. Cellular Respiration Opposite of photosynthesis
Defined as the breakdown of glucose by cells to create energy
Glucose & O2 are broken down into H2O, CO2, and energy
Done by ALL living things
Chemical Formula:
C6H12O6 + O2→ CO2 + H2O

7. So…What’s the Problem?
If it were just photosynthesis and cellular respiration, the cycle would be balanced.
Humans have disrupted the carbon cycle through combustion- burning of fossil fuels.
Excess CO2 has caused global climate change which has caused the melting of polar ice caps, severe storms, and floods.