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Ecosystems
Chemical Cycling
All matter cycles...it is neither created
nor destroyed...
Matter is made of atoms from different elements
Biogeochemical cycles:
describe the movement of elements
in the ecosystem
Elements are found in:
Living things  biotic reservoirs
Non-living things  abiotic reservoirs
And they can move:
Between these reservoirs
And within each reservoir
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General Scheme for Chemical Cycles
1. each chemical has main abiotic reservoir
where? air, soil/rock, water
what chemical form?
2. Movement of chemical in the abiotic reservoir
is USUALLY through geologic processes
3. producers are involved in the abiotic  biotic transition
what type of chemical form does it need to be in?
4. each chemical has a biotic reservoir
what type of chemical form?
5. Movement of chemical in the biotic reservoir
is through food chain
6. Organisms return some chemical to abiotic reservoir
through excretion (feces or urine) and cellular respiration
7. But decomposers are ultimately involved
in biotic  abiotic transition
by returning chemicals trapped in dead organic matter
8. Human activities affect cycles
Carbon cycle
Key component of organic molecules
Atmospheric CO2 regulates climate
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Carbon Cycle
Presence of Carbon Dioxide allows for life on earth
The amount of CO2 in the atmosphere determines
the temperature, by the
GREEN HOUSE EFFECT
Some of the sun energy is absorbed by Earth
some of this absorbed energy is reflected back
some of this reflected energy is reemitted back
by Carbon Dioxide and other GH gases
Without these gases the Earth would be 59oF cooler!!!
What will be the effect of
changing the amount of carbon dioxide in the atmosphere?
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Human impact on the carbon cycle
•
We have increased the amount CO 2 in the air by burning fossil fuels
•
We have decreased the removal of CO 2 in the air by deforestation
CONSEQUENCE OF TWO
 increased global temperature
Nitrogen cycle
78% of atmosphere
In proteins and DNA
In limited supply to organisms;
requires lightning or bacteria to become usable by plants
A potent fertilizer
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Nitrogen cycling depends on different bacteria
Human impact on the nitrogen cycle
We have increased the amount of phosphorous available to
producers by using synthetic fertilizers
these erode into rivers or lakes, causing:
EUTROPHICATION
excess nutrient enrichment in water,
which increases production of organic matter
by aquatic producers...
… which when decomposed by oxygen-using
bacteria can deplete water of oxygen
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Human impact on the nitrogen cycle
Increased amount of nitrates in atmosphere by combustion of fossil fuels
Nitrates react with moisture to form nitric acids: ACID RAIN
Affects development of animals
Soil quality
Vegetation
Concrete construction
Phosphorous Cycle
In DNA
In limited supply to organisms
A potent fertilizer
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Phosphorous depends on slow geologic processes
Human impact on the phosphorous cycle
We have increased the amount of phosphorous available to
producers by using fertilizers
causing EUTROPHICATION
Other activities that realease phosphorous
And lead to eutrophication:
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Deforestation affects the nitrogen and
phosphorous cycle too
Differences and Similarities
Which of the following are required so that chemicals can cycle?
producers, consumers, decomposers
Which cycle depends more on a variety of bacteria?
Which cycles have an atmospheric reservoir?
Which cycle has a soil reservoir? Implication
Which cycles are affected by fossil fuel combustion?
Which cycles are associated with acid rain?
Which cycles are associated with eutrophication?
Which cycles are associated with global warming?
Which cycles are affected by deforestation?
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