2005-2006 Ecosystems

Chapter 54

2005-2006

Ecosystem • Community of organisms plus the abiotic

factors that exist in a certain area

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• 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

incompletedigestion

metabolism

Chemical Cycling• Biogeochemical cycles: the various nutrient circuits, which involve both abiotic and biotic

components of an ecosystem• Water• Carbon• Nitrogen• Phosphorus

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Carbon cycleCO2 inatmosphere

Diffusion RespirationPhotosynthesis

Photosynthesis

Plants and algae

PlantsAnimals

Industry and home

Combustion of fuels

Animals

Carbonates in sediment

Bicarbonates

Deposition ofdead material

Depositionof deadmaterial

Fossil fuels(oil, gas, coal)

Dissolved CO2

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Birds

Herbivores

Plants

Amino acids

CarnivoresAtmosphericnitrogen

Loss to deep sediments

Fish

Plankton withnitrogen-fixingbacteria

Nitrogen-fixingbacteria(plant roots)

Nitrogen-fixingbacteria (soil)

Denitrifyingbacteria

Death, excretion, feces

Nitrifying bacteria

Soil nitrates

Excretion

Decomposing bacteria

Ammonifying bacteria

Nitrogen cycle

2005-2006Loss to deep sediment

Rocks andminerals

Soluble soilphosphate

Plants andalgae

Plants Urine

Land animals

Precipitates

Aquaticanimals

Animal tissueand feces

Animal tissueand feces

Decomposers(bacteria andfungi)

Decomposers(bacteria andfungi)

Phosphatesin solution

Loss indrainage

Phosphorus cycle

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Nutrient cycling

Decompositionconnects all trophic levels

2005-2006

What have we done!

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?

2005-2006

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 ofpesticides such as DDTwas causing populationdeclines in manynon-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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Acid Precipitation nitrogen oxides sulfur dioxide

• power plants• industry• transportation

2005-2006 Acid rain

2005-2006

BioMagnification

2005-2006

BioMagnification• PCBs– General Electric

manufacturing plant on Hudson River

– PCBs in sediment– striped bass nesting

areas

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Carbon DioxideGlobal Warming

2005-2006

CO2

NOx

methane

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Ozone Depletion

protects from UV rays

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Ozone Depletion

2005-2006

Bad ozone vs. good ozone

2005-2006

Ozone Depletion• Loss of ozone above Antarctica