Ecosystems

1
Ecosystems
2
Studying organisms in their environment
biosphere
ecosystem
community
population
organism
3
Essential questions

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

4
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

5
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

6
Energy flows through ecosystems
sun
secondary consumers (carnivores)
primary consumers (herbivores)
producers (plants)
7
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
8
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)
9
Ecological pyramid
sun

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

1
100
100,000
1,000,000,000
10
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?

11
Food webs

• Food chains are linked together into food webs
• Who eats whom?
• a species may weave into web at more than one
  level
• bears
• humans
• eating meat?
• eating plants?

12
Energy in an Ecosystem

• Summarize how energy is cycled through an
  ecosystem

13
Ecosystem inputs
biosphere
energy flowsthrough
nutrients cycle

• inputs
• energy
• nutrients

14
Generalized Nutrient cycling
consumers
consumers
producers
consumers
decomposers
decomposers
nutrientsENTER FOOD CHAIN made availableto
producers
nutrientsmade availableto producers
return toabioticreservoir
abioticreservoir
abioticreservoir
geologicprocesses
geologicprocesses
15
Carbon cycle

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

16
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
17
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
18

• 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
19
Transpiration
Remembertranspiration?
20
Breaking the water cycle

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

forest ? desert
desertification
21
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
80
40
loss out of ecosystem!
Concentration of nitrate (mg/l )
4
Deforestation
2
Why isnitrogen soimportant?
0
1965
1966
1967
1968
Year
22
Learning Check

• Differentiate between the nitrogen, water, carbon
  and phosphorus cycles
• Sources of each?
• Outputs of each?

23
Disoolved Oxygen and Productivity

• How do you determine how well an ecosystem is
  functioning?
• Measure the productivity of the organisms
• Lab Bench

24
Productivity

• Primary productivity
• rate at which plants and other photosynthetic
  organisms produce organic compounds in an
  ecosystem.
• Gross productivity
• the entire photosynthetic production of organic
  compounds in an ecosystem.
• Net productivity
• the organic materials that remain after
  photosynthetic organisms in the ecosystem have
  used some of these compounds for their cellular
  energy needs (cellular respiration).

25
Lab 12 Dissolved Oxygen

• primary productivity
• measured in 3 ways
• amount of CO2 used
• rate of sugar (biomass) formation
• rate of O2 production

26
Productivity

• Since oxygen is one of the most easily measured
  products of both photosynthesis and respiration,
  a good way to gauge primary productivity in an
  aquatic ecosystem is to measure dissolved oxygen.

27
Lab 12 Dissolved Oxygen

• Description
• measure primary productivity by measuring O2
  production
• factors that affect amount of dissolved O2
• temperature
• as ?water temperature, its ability to hold O2
  decreases
• photosynthetic activity
• in bright light, aquatic plants produce more O2
• decomposition activity
• as organic matter decays, microbial respiration
  consumes O2
• mixing turbulence
• wave action, waterfalls rapids aerate H2O ?O2
• salinity
• as water becomes more salty, its ability to hold
  O2 decreases

28
Lab 12 Dissolved Oxygen