Ecological cycles

1. Fig. 3-7, p. 55
Nitrogen
cycle
Biosphere
Heat in the environment
Phosphorus
cycle
Carbon
cycle
Oxygen
cycle
Water
cycle
Ecological
Cycles

2. MATTER CYCLING IN
ECOSYSTEMS
•Nutrient Cycles: Global Recycling
–Global Cycles recycle nutrients through the
earth’s air, land, water, and living organisms.
–Nutrients are the elements and compounds
that organisms need to live, grow, and
reproduce.
–Biogeochemical cycles move these
substances through air, water, soil, rock and
living organisms.

3. The Water Cycle
Figure 3-26Figure 3-26

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

5. Water’s Unique Properties
•There are strong forces of attraction between
molecules of water.
•Water exists as a liquid over a wide
temperature range.
•Liquid water changes temperature slowly.
•It takes a large amount of energy for water to
evaporate.
•Liquid water can dissolve a variety of
compounds.
•Water expands when it freezes.

6. 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.

7. The Carbon Cycle:
Part of Nature’s Thermostat
Figure 3-27Figure 3-27

8. CARBON CYCLE

9. Effects of Human Activities
on Carbon Cycle
•We alter the
carbon cycle by
adding excess CO
2

to the atmosphere
through:
–Burning fossil fuels.
–Clearing vegetation
faster than it is
replaced.
Figure 3-28Figure 3-28

10. The Nitrogen Cycle:
Bacteria in Action
Figure 3-29Figure 3-29

11. Nitrogen Cycle

12. Effects of Human Activities
on the Nitrogen Cycle
•We alter the nitrogen cycle by:
–Adding gases that contribute to acid rain.
–Adding nitrous oxide to the atmosphere
through farming practices which can warm the
atmosphere and deplete ozone.
–Contaminating ground water from nitrate ions
in inorganic fertilizers.
–Releasing nitrogen into the troposphere
through deforestation.

13. Effects of Human Activities
on the Nitrogen Cycle
•Human
activities such
as production of
fertilizers now
fix more
nitrogen than all
natural sources
combined.
Figure 3-30Figure 3-30

14. The Phosphorous Cycle
Figure 3-31Figure 3-31

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

16. 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.

17. The Sulfur Cycle
Figure 3-32Figure 3-32

18. Fig. 3-32, p. 78
Hydrogen sulfide
Sulfur
Sulfate salts
Decaying matter
Animals
Plants
Ocean
Industries
Volcano
Hydrogen sulfide
Oxygen
Dimethyl
sulfide
Ammonium
sulfate
Ammonia
Acidic fog and
precipitation
Sulfuric acid
Water
Sulfur
trioxide
Sulfur dioxide
Metallic
sulfide
deposits

19. Effects of Human Activities
on the Sulfur Cycle
•We add sulfur dioxide to the atmosphere
by:
–Burning coal and oil
–Refining sulfur containing petroleum.
–Convert sulfur-containing metallic ores into
free metals such as copper, lead, and zinc
releasing sulfur dioxide into the environment.

20. The Gaia Hypothesis:
Is the Earth Alive?
•Some have proposed that the earth’s
various forms of life control or at least
influence its chemical cycles and other
earth-sustaining processes.
–The strong Gaia hypothesis: life controls the
earth’s life-sustaining processes.
–The weak Gaia hypothesis: life influences the
earth’s life-sustaining processes.