Download Energy Flow and Cycles of Matter

Ecosystem Ecology
Chapter 3
Terms to remember…
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Ecosystem
Biotic/abiotic
Producer/autotroph
Consumer/heterotroph
Photosynthesis/cellular respiration
Trophic levels
Primary consumer/secondary consumer/tertiary consumer
Food chain/food web
Herbivore/carnivore/omnivore
Scavenger/detritivore/decomposer
Energy flow in ecosystems
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ONE WAY!
Laws of thermodynamics always apply:
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Energy cannot be created or destroyed, only
converted from 1 form to another
Whenever energy is converted from 1 form to
another, some of the energy is lost as heat
Simplified version: food chain
Detailed version: food web
Energy input  autotroph  heterotroph
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Note that the  shows the direction of energy flow
Ecological pyramids
Used to compare trophic levels
 Types:
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 Pyramid
of numbers
 Pyramid of biomass
 Pyramid of energy
Ecosystem productivity
GPP = gross (total) energy captured
during photosynthesis
 Plants use some of this energy during
cellular respiration
 NPP = net (remaining) energy
 NPP = GPP – plant respiration
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Productivity…
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Influenced by lots of factors:
 Type
of plants
 Available solar radiation, nutrients, water
 Maturity of the community
 Human impacts
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See table 3.8 p. 64
Bioaccumulation
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As substances move through a food chain, some
are not passed on
These substances can be stored in the bodies of
organisms in the food chain – bioaccumulation
Fat-soluble toxins tend to build up in higher
levels of a food chain – biological
magnification
Example – DDT pesticide and Bald Eagle
Biogeochemical cycles
Not one way!
 Earth is a closed system – matter cannot
escape
 Law of conservation of matter:
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 Matter
cannot be created or destroyed, it can
only be changed from one form to another.
Water (hydrologic) cycle
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Necessary for life:
 Provides
a medium for chemical reactions,
transports material throughout bodies, and
moderates temperatures
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Important processes:
 Precipitation
 Evaporation,
 Runoff
transpiration
Carbon cycle
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C is in organic compounds: proteins, nucleic
acids, lipids, carbohydrates
CO2 is stored in the atmosphere (and in some
rocks)
Important processes:
 Photosynthesis
 Respiration,
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decomposition, combustion
Human impact on carbon cycle – increased
combustion has increased amount of CO2 in
atmosphere
Nitrogen cycle
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N is found in proteins, nucleic acids, and chlorophyll
78% of atmosphere is N, but this is not in a form that can
be absorbed by living things
Nitrogen fixation – converts atmospheric N into nitrates
and nitrites - forms that can be used by plants:
combustion, volcanic action, lightning, and nitrogenfixing bacteria
Nitrogen-fixing bacteria – live in nodules on the roots
of plants called legumes
Nitrogen is returned to the atmosphere during
decomposition
Phosphorus cycle
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P is found in nucleic acids, ATP and phospholipids found
in cell membranes
P is not found as a gas in the atmosphere
It cycles from the soil, into the food chain and back
Phosphorus is a limiting factor in many aquatic
ecosystems
Sudden input into an ecosystem can cause rapid growth
of algae – algal bloom
When algae begins to die and decompose, the oxygen in
the system is consumed, resulting in hypoxic conditions