3. Ecosystem defined: a community
of organisms and it’s corresponding abiotic
environment through which matter cycles
and energy flows
• Wide variation in ecosystems
• Boarders can be well defined or vague
• Can be natural or artificial, managed or
• Wide range in scale
• Common to all ecosystems: energy flow
and cycling of matter
5. Exchange Pools
chemicals are held for only short periods
of time and are generally biotic
Example: plants and animals (which
temporarily use carbon in their systems
and then release back into the air)
7. Biogeochemical Cycle
circuit or pathway by which a
chemical element or molecule
moves through both biotic ("bio-")
and abiotic ("geo-") compartments
of an ecosystem.
In effect, the element is recycled
Biology. Life. Living things. These cycles
all play a role in the lives of living things.
The cycles might limit the organisms of
Earth or they might happen along side,
changing the environment
Earth. Rocks. Land. This refers to the
non-living processes at work. Oxygen
cycles through many systems. It's in you
and plants for the 'bio' part of the cycle.
Oxygen might also wind up in rocks. The
'geo' part of its cycle.
• Molecules. Reactions. Atoms. All cycles
include these small pathways. Complete
molecules are not always passed from
one point to the next. Sometimes
chemical reactions take place that
changes the molecules and locations of
the atoms. Think about oxidation as an
example of the
'chemical' part of these pathways.
11. What are the main cycles?
In a gas cycle elements move through
the atmosphere. Main reservoirs are the
atmosphere and the ocean.
In a sedimentary cycle elements move
from land to water to sediment. Main
reservoirs are the soil and sedimentary
12. What are the Biogeochemical
Cycles of interest to Ecology?
• Carbon Cycle (gas)
• Nitrogen Cycle (gas)
• Oxygen Cycle (gas)
• Phosphorous Cycle (sedimentary)
• Sulfur Cycle (sedimentary)
• Hydrogen Cycle (gas)
• Water Cycle
• Mercury Cycle (new one)
• human caused cycle of atrazine (new one)
13. What does it need?
It always involves equilibrium states:
a balance in the cycling of the element
However, overall balance may involve
compartments distributed on a global
16. Matter cycling in ecosystems
Nutrient Cycles: Global Recycling
Global Cycles recycle nutrients through the
earth’s air, land, water, and living
Nutrients are the elements and compounds
that organisms need to live, grow, and
Biogeochemical cycles move these
substances through air, water, soil, rock and
20. What Is Carbon?
The basis of life of earth
Found in rocks, oceans, atmosphere
21. Carbon Cycle
The same carbon atoms are used
repeatedly on earth. They cycle between
the earth and the atmosphere.
22. Plants Use Carbon Dioxide
Plants pull carbon dioxide from the
atmosphere and use it to make food –—
The carbon becomes part of the plant
23. Animals Eat Plants
When organisms eat plants, they take in
the carbon and some of it becomes part
of their own bodies.
24. Plants and Animal Die
When plants and animals die, most of
their bodies are decomposed and carbon
atoms are returned to the atmosphere.
Some are not decomposed fully and end
up in deposits underground (oil, coal,
25. Carbon Slowly Returns to Atmosphere
Carbon in rocks and underground
deposits is released very slowly into the
This process takes many years.
26. Cycle – Repeats Over and
Over and Over and Over …
42% CO2 returned by plants,
46% by decomposers, animals by12%
27. Carbon Cycle Diagram
Carbon in Atmosphere
carbon to make
take in carbon
break down dead
part of oil or coal
Fossil fuels are
is returned to
28. Carbon in Oceans
Additional carbon is stored in the ocean.
Many animals pull carbon from water to use in
Animals die and carbon substances are
deposited at the bottom of the ocean.
Oceans contain earth’s largest store of carbon.
31. Human Impact
Fossil fuels release carbon stores very
Burning anything releases more carbon
into atmosphere — especially fossil fuels
Increased carbon dioxide in atmosphere
increases global warming
Fewer plants mean less CO2 removed
32. What We Need to Do
Burn less, especially fossil fuels
Promote plant life, especially trees
36. Effects of Increased Nitrogen
1. Loss of soil nutrients (calcium, potassium)
2. Acidification of rivers and lakes (fertilizers and
combustion of coal).
3. Increases nitrogen oxides in the atmosphere
(greenhouse gas—global warming).
(reduce ozone—increasing UV penetration).
37. Effects of Increased Nitrogen
4. Aids in spreading weeds into nitrogen poor
areas (+Eutrophication of lakes, ponds,
5. Increasing nitrogen increases carbon fixation
(linked to carbon cycle).
6. Increasing acidification increases weathering
(increases rate of phosphorous cycle).
46. Biogeochemical Cycle =
All the chemicals, nutrients, or elements
— such as carbon, nitrogen, oxygen,
phosphorus — used in ecosystems by
living organisms operate on a closed
47. Gaia Hypothosis
Some have proposed that the earth’s
various forms of life control or at least
influence its chemical cycles and other
The strong Gaia hypothesis: life controls the
earth’s life-sustaining processes.
The weak Gaia hypothesis: life influences
the earth’s life-sustaining processes.
In contrast to energy, which moves in
one direction through the ecosystem,
materials are continually recycled
from the abiotic environment to
organisms, and back to the abiotic
Changes in one of the biogeochemical
cycles usually influences the other