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Ecosystems
Chapter 54
I. Energy Flow
A.
B.
Trophic Structures
Energy Budget
Global EB
GPP & NPP
Biomass
Limits of PP- aquatic, terrestrial
C.
Secondary Productivity
Energy Efficiency
Pyramids-production, #s, biomass
D.
Biological Magnification
II. Biogeochemical Cycles
A.
B.
C.
D.
Water
Carbon
Nitrogen
Phosphorous
III. Human Impact
A.
B.
C.
D.
Chemical Cycles
Acid precipitation
Toxins & biological
Magnification
Climate change-CO2 & O3
A. Trophic Structures- Energy
Flow

Energy flow one way- sun is inflow
 Food
chains & webs are short b/c trophic
energy level loses 90%
Energy Transfer

Energy in
 from
the Sun
 captured by autotrophs =
producers

Energy moves through
 food
chain
transfer of energy
from autotrophs to
heterotrophs
(herbivores to carnivores)
 heterotrophs = consumers

Energy Transfer
 Primary
producers primary
consumers secondary consumers
tertiary consumers
 Detrivores/Decomposers get
energy from detritus most
important part in an ecosystem
connects all levels
B. Energy Budget Primary
Production
 Producers
determine the energy
budget for an ecosystem
GPP
amount of solar energy
converted into chemical energy all
photsynthesis
NPP = GPP- Respiration (cost of staying
alive)
PP  J/m2/y or biomass
Primary Production
 Aquatic
Systems light &
nutrients are limiting factors
for PP
 Terrestrial Systems 
temperature, moisture,
nutrients
C. Secondary Production

The mount of chemical energy in
consumers’ food that is converted into
their
Energy Inefficiency
incomplete
digestion
metabolism
Pyramids of Production

represent the loss of energy from a food
chain
 how
much energy is turned into biomass
Pyramid of Numbers

levels in pyramids of production are
proportional to number of individuals
present in each trophic level
Implications

Dynamics of energy through ecosystems
have important implications for human
populations
 what
food would be more ecologically
sound?
D. Biological Magnification




Toxins can become concentrated in successive
trophic levels of food webs
Humans produce many toxic chemicals that are
dumped into ecosystems.
These substances are ingested and
metabolized by the organisms in the
ecosystems and can accumulate in the fatty
tissues of animals.
These toxins become more concentrated in
successive trophic levels of a food web, a
process called biological magnification.
Fig. 54.24

The pesticide DDT, before it was banned,
showed this affect.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 54.25
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Biogeochemical Cycles
 Nutrient
cycles
 Gases cycle on a global level
 Solids cycle slowly and locally
Fig. 54.15
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The water cycle is more of a physical
process than a chemical one.
Fig. 54.16
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The carbon cycle fits the generalized scheme
of biogeochemical cycles better than water.
Fig. 54.17
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The Nitrogen Cycle
 Nitrogen
enters ecosystems through
two natural pathways.
Atmospheric
deposition, where usable
nitrogen is added to the soil by rain or
dust.
Nitrogen fixation, where certain
prokaryotes convert N2 to minerals
that can be used to synthesize
nitrogenous organic compounds like
amino acids.
Fig. 54.18
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 54.19
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
III. Human Impact

Rising atmospheric CO2.
Since the Industrial Revolution, the
concentration of CO2 in the
atmosphere has increased greatly as a
result of burning fossil fuels.

Measurements in 1958 read 316 ppm and
increased to 370 ppm today
Fig. 54.26
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The Greenhouse Effect

Rising levels of atmospheric CO2 may have an
impact on Earth’s heat budget.
 When
light energy hits the Earth, much of it is
reflected off the surface.
 CO2 causes the Earth to retain some of the
energy that would ordinarily escape the
atmosphere.
 This phenomenon is called the greenhouse effect.
 The Earth needs this heat, but too much could be
disastrous.
Global Warming

Scientists continue to construct models
to predict how increasing levels of CO2 in
the atmosphere will affect Earth.
 Several
studies predict a doubling of CO2 in
the atmosphere will cause a 2º C increase in
the average temperature of Earth.
 Rising temperatures could cause polar ice cap
melting, which could flood coastal areas.
 It is important that humans attempt to
stabilize their use of fossil fuels.
Ozone Depletion


Life on earth is
protected from the
damaging affects of
ultraviolet radiation
(UV) by a layer of O3,
or ozone.
Studies suggest that
the ozone layer has
been gradually
“thinning” since 1975.
Fig. 54.27b
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Ozone Depletion
Probably results from the accumulation of
chlorofluorocarbons, chemicals used in
refrigeration and aerosol cans, and in certain
manufacturing processes.
 The result of a reduction in the ozone layer
may be increased levels of UV radiation that
reach the surface of the Earth.
 This radiation has been linked to skin cancer
and cataracts.

The impact of human activity
on the ozone layer is one
more example of how much
we are able to disrupt
ecosystems and the entire
biosphere.