Biogeochemical cycles describe the cycling of essential nutrients like carbon, oxygen, nitrogen, phosphorus, and sulfur between the biotic (living) and abiotic (non-living) components of ecosystems. Energy from the sun drives these cycles as nutrients are exchanged between organisms, water, air, soil, and rock. Humans have disrupted natural biogeochemical cycles through activities like burning fossil fuels, clearing vegetation, using fertilizers, and pollution, which has contributed to issues like climate change and algal blooms.

1. Biogeochemical Cycles

2. What IS a “biogeochemical cycle”?
 BIO = “life”
 GEO = “earth”
 CHEMICAL = “elements – C, O, N, P, S
• a cycling of nutrients (water, carbon, oxygen,
nitrogen, phosphorus, sulphur) from the abiotic
components of the ecosystem (water, air, soil,
rock) through the biotic components (plants,
animals, fungi, bacteria)

3. Two Secrets of Survival: Energy
Flows and Matter Cycles
 An ecosystem
survives by a
combination of
energy flow (from
Sun to Earth) and
matter cycling.
 Remember: the
Earth is a
CLOSED system
Figure 3-14

4. THE HYDROLOGIC (WATER) CYCLE
Rain clouds
Condensation
Transpiration Evaporation
Precipitation Transpiration
to land from plants
Precipitation Precipitation
Evaporation
Surface runoff from land Evaporation
Runoff from ocean Precipitation
(rapid)
to ocean
Infiltration and Surface
Percolation runoff
(rapid)
Groundwater movement (slow)
Ocean storage
Fig. 3-26, p. 72

5. Effects of Human Activities
on Water Cycle
 We alter the water cycle by:

Withdrawing large amounts of freshwater.

Clearing vegetation and eroding soils.
 Polluting surface and underground water.
 Contributing to climate change.

6. The Carbon Cycle
Fig. 3-27, pp. 72-7

7. Effects of Human Activities
on Carbon Cycle
 We alter the carbon
cycle by adding
excess CO2 to the
atmosphere through:
 Burning fossil fuels.
 Clearing vegetation
faster than it is
replaced

 photosynthesis =
 CO2
Figure 3-28

8. THE NITROGEN CYCLE

9. Effects of Human Activities
on the Nitrogen Cycle
 We alter the nitrogen cycle by:
 Adding nitrous oxide to the atmosphere from
vehicles and factories which contributes to acid
rain.
 Contaminating ground water from nitrate ions in
inorganic fertilizers.
 Releasing nitrogen into the troposphere through
deforestation (less N assimilated by trees).

10. THE Human Influenced NITROGEN CYCLE

11. THE PHOSPHORUS CYCLE
mining Fertilizer
excretion Guano
agriculture
uptake by weathering uptake by
autotrophs autotrophs
Marine Dissolved leaching, runoff Dissolved Land
Food in Ocean in Soil Water, Food
Webs Water Lakes, Rivers Webs
death, death,
decomposition decomposition
sedimentation settling out weathering
uplifting over
geologic time
Marine Sediments Rocks
Fig. 3-31, p. 77

12. Effects of Human Activities
on the Phosphorous Cycle
 We remove large amounts of phosphate from
the earth to make fertilizer.
 We reduce phosphorous in tropical soils by
clearing forests.
 We add excess phosphates to aquatic
systems from runoff of animal wastes and
fertilizers – excess phosphorus causes algal
blooms

13. Algal blooms

14. Assignment: Put the 4 cycles
together on one poster!
 Draw the hydrologic, carbon, nitrogen,
phosporus and cycles onto one piece of
poster paper.
 Include the required terminology
 Follow the criteria on the rubric provided
 Assessment will be done by performance
(explanation of the cycles by the group)