Ecosystems

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Ecosystems
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Studying organisms in their environment
biosphere
ecosystem
community
population
organism
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Essential Questions

• What limits the production in ecosystems?
• How do nutrients move in the ecosystem?
• How does energy move through the ecosystem?

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Ecosystem

• All the organisms in a community plus abiotic
  factors
• ecosystems are transformers of energy
  processors of matter
• Ecosystems are self-sustaining
• what is needed?

• capture energy
• transfer energy
• cycle nutrients

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Ecosystem inputs
biosphere
constant inputof energy
energy flowsthrough
nutrients cycle
Dont forgetthe laws of Physics!
Matter cannot be created ordestroyed
nutrients can only cycle

• inputs
• energy
• nutrients

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Generalized Nutrient cycling
consumers
consumers
producers
consumers
decomposers
decomposers
nutrientsENTER FOOD CHAIN made availableto
producers
nutrientsmade availableto producers
return toabioticreservoir
abioticreservoir
abioticreservoir
geologicprocesses
geologicprocesses
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Carbon cycle

• abiotic reservoir
• CO2 in atmosphere
• enter food chain
• photosynthesis carbon fixation in Calvin cycle
• recycle
• return to abiotic
• respiration
• combustion

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Nitrogen cycle

• abiotic reservoir
• N in atmosphere
• enter food chain
• nitrogen fixation by soil aquatic bacteria
• recycle
• decomposing nitrifying bacteria
• return to abiotic
• denitrifying bacteria

Atmospheric nitrogen
Carnivores
Herbivores
Birds
Plants
Plankton with nitrogen-fixing bacteria
Death, excretion, feces
Nitrogen-fixing bacteria (plant roots)
Fish
Decomposing bacteria
amino acids
excretion
Nitrogen-fixing bacteria (soil)
Ammonifying bacteria
loss to deep sediments
Nitrifying bacteria
Denitrifying bacteria
soil nitrates
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Phosphorus cycle

• abiotic reservoir
• rocks, minerals, soil
• enter food chain
• erosion releases soluble phosphate
• uptake by plants
• recycle
• decomposing bacteria fungi
• return to abiotic
• loss to ocean sediment

Land animals
Plants
Animal tissue and feces
Urine
Soluble soil phosphate
Decomposers (bacteria and fungi)
Loss in drainage
Rocks and minerals
Phosphates in solution
Decomposers (bacteria fungi)
Animal tissue and feces
Plants and algae
Aquatic animals
Precipitates
Loss to deep sediment
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• abiotic reservoir
• surface atmospheric water
• enter food chain
• precipitation plant uptake
• recycle
• transpiration
• return to abiotic
• evaporation runoff

Water cycle
Solar energy
Transpiration
Water vapor
Evaporation
Precipitation
Oceans
Runoff
Lakes
Percolation in soil
Aquifer
Groundwater
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Transpiration
Why does water flow into, up and out of a plant?
We will discuss process in detail soon!
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Breaking the water cycle

• Deforestation breaks the water cycle
• groundwater is not transpired to the atmosphere,
  so precipitation is not created

forest ? desert
desertification
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Effects of deforestation

• 40 increase in runoff
• loss of water

• 60x loss in nitrogen
• 10x loss in calcium

loss into surface water
nitrate levels in runoff
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40
loss out of ecosystem!
Concentration of nitrate (mg/l )
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Deforestation
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Why isnitrogen soimportant?
0
1965
1966
1967
1968
Year
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Energy flows through ecosystems
sun
secondary consumers (carnivores)
primary consumers (herbivores)
Energy is incorporated into a community by what
group?
producers (plants)
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Productivity

• Primary productivity Term for the rate which
  producers photosynthesize organic compounds in an
  ecosystem.
• Gross primary productivity total amount of
  photosynthetic biomass production in an ecosystem
• Net Primary Productivity GPP respiration cost

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• Ecosystems with greater productivity are more
  stable and diverse than ecosystems with less
  productivity.
• Which ecosystems are most productive?

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Inefficiency of energy transfer
sun

• Loss of energy between levels of food chain
• To where is the energy lost? The cost of living!

17 growth
only this energymoves on to the next level in
the food chain
33 cellular respiration
50 waste (feces)
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Food chains
sun
Level 4
Tertiary consumer

• Trophic levels
• feeding relationships
• start with energy from the sun
• captured by plants
• 1st level of all food chains
• food chains usually go up only 4 or 5 levels
• inefficiency of energy transfer
• all levels connect to decomposers

top carnivore
Level 3
Secondary consumer
carnivore
Level 2
Primary consumer
heterotrophs
herbivore
Level 1
Producer
autotrophs
Fungi
Decomposers
Bacteria
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Producers Decomposers

• Producers move matter from abiotic sources
  (air/soil) to biotic sources (food web)
• Decomposers move matter
• from biotic sources to abiotic
• sources

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Ecological pyramid
sun

• Loss of energy between levels of food chain
• can feed fewer animals in each level

10 energy available for next level
Notice only 1 of sunlight energy converted by
plants
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Humans in food chains

• Dynamics of energy through ecosystems have
  important implications for human populations
• how much energy does it take to feed a human?
• if we are meat eaters?
• if we are vegetarian?

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What you need to be able to do

• Using the laws of conservation of matter and
  energy to do some basic accounting and determine
  different aspects of energy and matter usage in a
  community.
• Remember Inputs have to equal outputs

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Sample problem

• A caterpillar consumes 100 kcal of energy. It
  uses 35 kcal for cell respiration, and loses 50
  kcal as waste. Determine the trophic efficiency
  for its creation of new biomass.
• Total energy 100 kcal
• Lost and Respired 35 50 85 kcal
• Total energy for growth 15 kcal
• Efficiency part/total 15/100 .15 (or 15 or
  3/20 as fraction)

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