Download Primary productivity

Chapter 54
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Ecosystems
Ecosystem
• Community of organisms plus the abiotic
factors that exist
in a certain area
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Relationships, I
• Trophic structure / levels~ feeding
relationships in an ecosystem
• Primary producers~ the trophic level
that supports all others; autotrophs
• Primary consumers~ herbivores
• Secondary and tertiary
consumers~ carnivores
• Detrivores/detritus~ special consumers
that derive nutrition from non-living organic
matter
• Food chain~ trophic level food pathway
Energy Flow, I
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•
•
•
Primary productivity (amount of light energy converted to chemical energy by autotrophs)
•Gross (GPP): total energy
•Net
(NPP): represents the storage of energy available to consumers
•Rs:
respiration
NPP = GPP - Rs
Biomass: primary productivity reflected as dry weight of organic material
Secondary productivity: the rate at which an ecosystem's consumers convert chemical
energy of the food they eat into their own new biomass
Energy Flow, II
• Ecological efficiency: % of E
transferred from one trophic level to
the next (5-20%)
• Pyramid of productivity:
multiplicative loss of energy in trophic
levels
• Biomass pyramid: trophic
representation of biomass in
ecosystems
• Pyramid of numbers: trophic
representation of the number of
organisms in an ecosystem
Energy inefficiency
incomplete
digestion
metabolism
Chemical Cycling
•
•
•
•
•
Biogeochemical cycles: the various nutrient circuits, which involve both abiotic and biotic
components of an ecosystem
Water
Carbon
Nitrogen
Phosphorus
Carbon cycle
CO2 in
atmosphere
Combustion of fuels
Industry and home
Diffusion
Respiration
Photosynthesis
Plants
Animals
Dissolved CO2
Bicarbonates
Photosynthesis
Deposition
of dead
material
Animals
Plants and algae
Carbonates in sediment
Deposition of
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dead material
Fossil fuels
(oil, gas, coal)
Nitrogen cycle
Atmospheric
nitrogen
Carnivores
Herbivores
Plankton
with
nitrogenfixing
bacteria
Birds
Plants
Death, excretion, feces
Fish
Decomposing bacteria
Excretion
Amino acids
Ammonifying bacteria
Loss to deep sediments
Nitrifying bacteria
Soil nitrates
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Nitrogenfixing
bacteria
(plant roots)
Nitrogenfixing
bacteria
(soil)
Denitrifying
bacteria
Phosphorus cycle
Plants
Land
animals
Animal tissue
Urine and feces
Soluble soil
phosphate
Decomposers
(bacteria and
fungi)
Loss in
drainage
Decomposers
(bacteria and
fungi)
Animal tissue
and feces
Rocks and
minerals
Phosphates
in solution
Aquatic
animals
Plants and
algae
Precipitates
Loss to deep sediment
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Nutrient
cycling
Decomposition
connects all
trophic levels
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What have we done!
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Human Impact
• Biological magnification: trophic process
in which retained substances become more
concentrated at higher levels
• Greenhouse effect: warming of planet due
to atmospheric accumulation of carbon dioxide
• Ozone depletion: effect of
chlorofluorocarbons (CFC’s) released into the
atmosphere
• Acid Precipitation
• Cause: Overpopulation?
Impact of ecology as a science
• Ecology provides a scientific context for
evaluating
environmental issues
– Rachel Carson, in 1962,
in her book, Silent Spring,
warned that use of
pesticides such as DDT
was causing population
declines in many
non-target organisms
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Barry Commoner’s Laws of Ecology
• Everything is connected to everything else
• Everything must go somewhere
 there is no such place as “away”
• Nature knows best
• There is no such thing as a free lunch
Laws of Unintended Consequences
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 nitrogen oxides
 sulfur dioxide
Acid Precipitation
• power plants
• industry
• transportation
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Acid rain
BioMagnification
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BioMagnification
• PCBs
– General Electric
manufacturing plant
on Hudson River
– PCBs in sediment
– striped bass nesting
areas
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Carbon Dioxide
Global Warming
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CO2
NOx
methane
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Ozone Depletion
protects from
UV rays
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Ozone Depletion
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Bad ozone vs. good ozone
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Ozone Depletion
• Loss of ozone above Antarctica
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