Fig. 55-1

1
Fig. 55-1
ECOSYSTEMS AP CHAP 55
An ecosystem consists of all the organisms living
in a community, as well as the abiotic factors
with which they interact
2
Fig. 55-2
Regardless of an ecosystems size, its dynamics
involve two main processes energy flow and
chemical cycling Energy flows through (one way)
ecosystems while matter cycles within them
3
Physical laws govern energy flow and chemical
cycling in ecosystems

• The first law of thermodynamics states that
  energy cannot be created or destroyed, only
  transformed
• Energy enters an ecosystem as solar radiation, is
  conserved, and is lost from organisms as HEAT!
• The second law of thermodynamics states that
  every exchange of energy increases the entropy of
  the universe
• In an ecosystem, energy conversions are not
  completely efficient, and some energy is always
  lost as HEAT!

4
Conservation of Mass

• The law of conservation of mass states that
  matter cannot be created or destroyed
• Chemical elements are continually recycled within
  ecosystems
• Ecosystems are open systems, absorbing energy and
  mass and releasing heat and waste products.

5
Energy, Mass, and Trophic Levels

• Autotrophs build molecules themselves using
  photosynthesis or chemosynthesis as an energy
  source heterotrophs depend on the biosynthetic
  output of other organisms
• Energy and nutrients pass from primary producers
  (autotrophs) to primary consumers (herbivores) to
  secondary consumers (carnivores) to tertiary
  consumers (carnivores that feed on other
  carnivores)

6

• Detritivores, or decomposers, are consumers that
  derive their energy from detritus, nonliving
  organic matter
• Prokaryotes and fungi are important detritivores
• Decomposition connects all trophic levels

7
Fig. 55-3
8
Fig. 55-4
Tertiary consumers
Microorganisms and other detritivores
Secondary consumers
Primary consumers
Detritus
Decomposition connects all trophic levels
Primary producers
Heat
Key
Chemical cycling
Sun
Energy flow
9
Energy and other limiting factors control primary
production in ecosystems

• Primary production in an ecosystem is the amount
  of light energy converted to chemical energy by
  autotrophs during a given time period.ie.amount
  of PHOTOSYNTHESIS

10
In primary producers the main energy input is
from the solar energy. In a plant, not all of the
solar energy available actually makes it into the
leaf.
Only about 1 of visible light that strikes
photosynthetic organisms is converted to chemical
energy in photosynthesis.
11

• It is the energy that is incorporated into the
  biomass that is available for the next trophic
  level.

12
In the consumer a further series of energy losses
occur. The consumer will take in a certain amount
of energy from the trophic level beneath it.
13

• It is generally accepted that only around 10 of
  the energy gained from the previous trophic level
  is passed on to the next level. All other energy
  is lost as described above. This limits the
  number of trophic levels in any food chain.

14
Gross and Net Primary Production

• Total primary production is known as the
  ecosystems gross primary production (GPP)
• Since autotrophs also have to respire to obtain
  energy, their GPP is reduced by the amount of
  energy used for fuel in cell respiration.

15

• Net primary production (NPP) is GPP minus energy
  used by primary producers for cell respiration
• Only NPP is available to consumers

16
SO
Only NPP is available to consumers

• NPP GPP - R

17

• Its like Gross Pay what you make
• Net Pay what you bring home
• NPP GPP from photosynthesis R from cellular
  respiration
• Or GPP NPP R

18

• In many ecosystems, NPP is about ½ of GPP.
• NPP represents the storage of chemical energy
  that will be available to consumers.
• NPP can be expressed as energy per unit area per
  unit time (J/m2 yr) or as biomass added per unit
  area per unit time (g/m2 yr) added in that unit
  of time.

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Energy lost
Reflected
Tree Layer
Shrub layer
Solar Radiation
Absorbed
Energy accumulated as biomass
Herb Layer
Transmitted
Energy cannot be created or destroyed so all of
this has to add up.
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Our LabWe are calculating the NPP for our Fast
Plants by measuring their biomassaccumulated.
Remember some energy is lost as heat and used in
respiration.
21

• Then we are measuring the transfer of energy
  from plants to butterfly larvae in Secondary
  Production.

22

• Primary productivity can also be determined by
  measuring oxygen being produced
• Or the amount of carbon compounds being produced
• Think photosynthesis.

23

• This can be done by measuring the amount of
  oxygen in samples of water in bottles in light
  and dark.

24
Experiment we used to do
25
Rememberthe difference between gross and net
primary productivity.

• Gross productivity is the total amount of
  productivity in the environment. Net
  productivity is the average productivity produced
  at a certain period of time.
• Gross primary productivity is the total amount of
  something made in an area. Net primary
  productivity is the amount of that energy that
  can actually be used.
• Gross primary production is the overall total of
  production.

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• Primary productivity is the amount of light
  energy converted to chemical energy during a
  period of time. It is the photosynthetic output
  of an ecosystems autotrophs.
• The NPP is an ecosystems GPP minus the energy
  used by producers in their own cellular
  respiration (R).
• So NPP GPP R
• GPP NPP R

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• Tropical rain forests, estuaries, and coral reefs
  are among the most productive ecosystems per unit
  area
• Marine ecosystems are relatively unproductive per
  unit area, but contribute much to global net
  primary production because of their volume

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Fig. 55-6
Net primary production (kg carbon/m2yr)

0
1
2
3
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Primary Production in Aquatic Ecosystems

• In marine and freshwater ecosystems, both
  light and nutrients control primary production

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Nutrient Limitation

• More than light, nutrients limit primary
  production in the ocean and in lakes
• A limiting nutrient is the element that must be
  added for production to increase in an area
• Nitrogen and phosphorous are typically the
  nutrients that most often limit marine production

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Fig. 55-7
EXPERIMENT
Long Island
Shinnecock Bay
G
F
E
C
D
Moriches Bay
B
Nutrient enrichment experiments confirmed that
nitrogen was limiting phytoplankton growth off
the shore of Long Island, New York
Great South Bay
Atlantic Ocean
A
Ammonium NH3
RESULTS
30
Ammonium enriched
Phosphate enriched
24
Unenriched control
18
Phytoplankton density (millions of cells per mL)
12
6
0
A
B
C
D
E
F
G
Collection site
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Table 55-1
What is the limiting factor in this area?
IRON
33

• Upwelling of nutrient-rich waters in parts of the
  oceans contributes to regions of high primary
  production
• The addition of large amounts of nutrients to
  lakes has a wide range of ecological impacts
• In some areas, sewage runoff has caused
  eutrophication of lakes, which can lead to loss
  of most fish species

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Primary Production in Terrestrial Ecosystems

• In terrestrial ecosystems, temperature and
  moisture affect primary production on a large
  scale
• Evapotranspiration is related to net primary
  production

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Fig. 55-8
3,000
Tropical forest

2,000
Net primary production (g/m2yr)
Temperate forest
1,000
Mountain coniferous forest
Desert shrubland
Temperate grassland
Arctic tundra
0
1,500
1,000
500
0
Actual evapotranspiration (mm H2O/yr)
37

• On a more local scale, a soil nutrient is
  often the limiting factor in primary production

What is the limiting factor in this soil example?
38
Energy transfer between trophic levels is
typically only 10 efficient

• Secondary production of an ecosystem is the
  amount of chemical energy in food converted to
  new biomass during a given period of time

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Production Efficiency

• When a caterpillar feeds on a leaf, only about
  one-sixth of the leafs energy is used for
  secondary production
• An organisms production efficiency is the
  fraction of energy stored in food that is not
  used for respiration

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Fig. 55-9
200 6
Plant material eaten by caterpillar
200 J
67 J
Cellular respiration
100 J
Feces
33 J
Growth (new biomass)
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Trophic Efficiency and Ecological Pyramids

• Trophic efficiency is the percentage of
  production transferred from one trophic level to
  the next
• It usually ranges from 5 to 20
• Trophic efficiency is multiplied over the length
  of a food chain
• Approximately 0.1 of chemical energy fixed by
  photosynthesis reaches a tertiary consumer
• A pyramid of net production represents the loss
  of energy with each transfer in a food chain

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Fig. 55-10
Energy transfer between trophic levels is
typically only 10 efficient
Tertiary consumers
10 J
Secondary consumers
100 J
Primary consumers
1,000 J
Primary producers
10,000 J
1,000,000 J of sunlight
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• In a biomass pyramid, each tier represents the
  dry weight of all organisms in one trophic level
• Most biomass pyramids show a sharp decrease at
  successively higher trophic levels
• Certain aquatic ecosystems have inverted biomass
  pyramids producers (phytoplankton) are consumed
  so quickly that they are outweighed by primary
  consumers

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Fig. 55-11
Trophic level
Dry mass (g/m2)
Tertiary consumers
1.5
Secondary consumers
11
Primary consumers
37
Primary producers
809
(a) Most ecosystems (data from a Florida bog)
Trophic level
Dry mass (g/m2)
Primary consumers (zooplankton)
21
Primary producers (phytoplankton)
4
(b) Some aquatic ecosystems (data from the
English Channel)
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Biological and geochemical processes cycle
nutrients between organic and inorganic parts of
an ecosystem

• Life depends on recycling chemical elements
• Nutrient circuits in ecosystems involve biotic
  and abiotic components and are often called
  biogeochemical cycles

46
Biogeochemical Cycles

• Gaseous carbon, oxygen, sulfur, and nitrogen
  occur in the atmosphere and cycle globally
• Less mobile elements such as phosphorus,
  potassium, and calcium cycle on a more local level

47
Fig. 55-13
Reservoir A
Reservoir B
All elements cycle between organic and inorganic
reservoirs
Organic materials available as nutrients
Organic materials unavailable as nutrients
Fossilization
Living organisms, detritus
Coal, oil, peat
Respiration, decomposition, excretion
Assimilation, photosynthesis
Burning of fossil fuels
Reservoir D
Reservoir C
Inorganic materials available as nutrients
Inorganic materials unavailable as nutrients
Weathering, erosion
Minerals in rocks
Atmosphere,soil, water
Formation of sedimentary rock
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• In studying cycling of water, carbon,
  nitrogen, and phosphorus, ecologists focus on
  four factors
• Each chemicals biological importance
• Forms in which each chemical is available or used
  by organisms
• Major reservoirs for each chemical
• Key processes driving movement of each chemical
  through its cycle

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• The Water Cycle
• Water is essential to all organisms
• 97 of the biospheres water is contained in the
  oceans, 2 is in glaciers and polar ice caps, and
  1 is in lakes, rivers, and groundwater
• Water moves by the processes of evaporation,
  transpiration, condensation, precipitation, and
  movement through surface and groundwater

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Fig. 55-14a
Transport over land
Solar energy
Net movement of water vapor by wind
Precipitation over land
Evaporation from ocean
Precipitation over ocean
Evapotranspiration from land
Percolation through soil
Runoff and groundwater
51

• The Carbon Cycle
• Carbon-based organic molecules are essential to
  all organisms
• Carbon reservoirs include fossil fuels, soils and
  sediments, solutes in oceans, plant and animal
  biomass, and the atmosphere
• CO2 is taken up and released through
  photosynthesis and respiration additionally,
  volcanoes and the burning of fossil fuels
  contribute CO2 to the atmosphere

52
Fig. 55-14b
CO2 in atmosphere
Photosynthesis
Cellular respiration
Photo- synthesis
Burning of fossil fuels and wood
Phyto- plankton
Higher-level consumers
Primary consumers
Carbon compounds in water
Detritus
Decomposition
53

• The Terrestrial Nitrogen Cycle
• Nitrogen is a component of amino acids, proteins,
  and nucleic acids
• The main reservoir of nitrogen is the atmosphere
  (N2), though this nitrogen must be converted to
  ammonia or nitrate for uptake by plants, via
  nitrogen fixation by bacteria
• Organic nitrogen is decomposed to ammonia by
  ammonification, and ammonia is decomposed to
  nitrate in soil by nitrification
• Denitrification converts nitrates back to N2
• in the atmosphere.

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NITROGEN
Nitrogen Fixation
BACTERIA
ammonia, nitrates
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Organic nitrogen from metabolism
ammonification

BACTERIA
BACTERIA
ammonia nitrification
DECOMPOSITION
nitrates
denitrification N2
BACTERIA
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Fig. 55-14c
N2 in atmosphere
BACTERIA are super important here!
Assimilation
Denitrifying bacteria
NO3

Nitrogen-fixing bacteria
Decomposers
Nitrifying bacteria
Ammonification
Nitrification
NH3
NH4
NO2


Nitrogen-fixing soil bacteria
Nitrifying bacteria
57

• The Phosphorus Cycle
• Phosphorus is a major constituent of nucleic
  acids, phospholipids, and ATP
• Phosphate (PO43) is the most important inorganic
  form of phosphorus
• The largest reservoirs are sedimentary rocks of
  marine origin, the oceans, and organisms
• Phosphate binds with soil particles, and movement
  is often localized
• DOES NOT CYCLE IN THE ATMOSPHERE

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Fig. 55-14d
Precipitation
Geologic uplift
Weathering of rocks
Runoff
Consumption
Decomposition
Plant uptake of PO43
Plankton
Dissolved PO43
Soil
Uptake
Leaching
Sedimentation
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Decomposition and Nutrient Cycling Rates

• Decomposers (detritivores) play a key role in the
  general pattern of chemical cycling
• Rates at which nutrients cycle in different
  ecosystems vary greatly, mostly as a result of
  differing rates of decomposition
• The rate of decomposition is controlled by
  temperature, moisture, and nutrient availability
• Rapid decomposition results in relatively low
  levels of nutrients in the soil

60
Human activities now dominate most chemical
cycles on Earth

• As the human population has grown, our activities
  have disrupted the trophic structure, energy
  flow, and chemical cycling of many ecosystems

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How have humans impacted our ecosystems?

• 1) Agriculture and N cycling
• In agriculture, we have depleted our N resources
  and added back with fertilizers which have harmed
  our ecosystems.

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• 2) Contamination of Aquatic Ecosystems
• When excess nutrients are added to an ecosystem,
  the critical load (minimal amt plants can absorb)
  is exceeded
• Remaining nutrients can contaminate groundwater
  as well as freshwater and marine ecosystems and
  cause eutrophication

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3) Acid Precipitation

• Combustion of fossil fuels is the main cause of
  acid precipitation
• North American and European ecosystems downwind
  from industrial regions have been damaged by rain
  and snow containing nitric and sulfuric acid
• Acid precipitation changes soil pH and causes
  leaching of calcium and other nutrients

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Fig. 55-19
4.5
4.4
4.3
pH
4.2
4.1
4.0
2000
1995
1990
1985
1980
1975
1970
1965
1960
Year
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4) Toxins in the Environment

• Humans release many toxic chemicals, including
  synthetics previously unknown to nature
• One reason toxins are harmful is that they become
  more concentrated in successive trophic levels
• Biological magnification concentrates toxins at
  higher trophic levels, where biomass is lower

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Fig. 55-20
Herring gull eggs 124 ppm
Lake trout 4.83 ppm
Concentration of PCBs
Smelt 1.04 ppm
Zooplankton 0.123 ppm
Phytoplankton 0.025 ppm
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Brier Creek fish kill report looks at material
used in mining, wastewater treatment

• In a status report on the incident, Savannah
  Riverkeeper said the characteristics of the fish
  kill are indicative of poisoning by aluminum
  sulfate used as a coagulant in kaolin mining
  and sewage treatment.

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5) Greenhouse Gases and Global Warming

• One pressing problem caused by human activities
  is the rising level of atmospheric carbon dioxide
• Due to the burning of fossil fuels and other
  human activities, the concentration of
  atmospheric CO2 has been steadily increasing

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Fig. 55-21
What we know for sure The concentration of
atmospheric CO2 has been steadily increasing.
14.9
390
14.8
380
14.7
14.6
370
Temperature
14.5
360
14.4
14.3
350
CO2 concentration (ppm)
Average global temperature (ºC)
14.2
340
14.1
CO2
330
14.0
13.9
320
13.8
310
13.7
13.6
300
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Year
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The Greenhouse Effect and Climate

• CO2, water vapor, and other greenhouse gases
  reflect infrared radiation back toward Earth
  this is the greenhouse effect
• could cause global warming and climatic change
• Northern coniferous forests and tundra show the
  strongest effects of global warming

71
Depletion of Atmospheric Ozone

• Life on Earth is protected from damaging effects
  of UV radiation by a protective layer of ozone
  molecules
• Destruction of atmospheric ozone probably results
  from chlorine-releasing pollutants such as CFCs
  produced by human activity
• Ozone depletion causes DNA damage in plants and
  poorer phytoplankton growth

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Fig. 55-23
350
300
250
Ozone layer thickness (Dobsons)
200
Satellite studies suggest that the ozone layer
has been gradually thinning since 1975
100
0
80
60
05
2000
95
90
85
75
70
65
1955
Year
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Fig. 55-24
ozone
Chlorine atom
O2
Chlorine
O3
ClO
O2
ClO
Cl2O2
Sunlight
How free chlorine in the atmosphere destroys
ozone.
75

• Ozone depletion causes DNA damage in plants and
  poorer phytoplankton growth

76
Scientists first described an ozone hole over
Antarctica in 1985 it has increased in size as
ozone depletion has increased
Fig. 55-25
(a) September 1979
(b) September 2006

• An international agreement signed in 1987 has
  resulted in a decrease in ozone depletion

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DO YOUR PART!