Chapter 54 (pgs. 1198 1222) Ecosystems AP minknow How

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Chapter 54 (pgs. 1198 1222)Ecosystems

• AP minknow
• How energy flows through the ecosystem by
  understanding the terms in bold that relate to
  food chains and food webs.
• The difference between gross primary productivity
  and net primary productivity.
• The carbon and nitrogen biogeochemical cycles.

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• What Is the Ecosystem Approach to Ecology?
• 1.Describe the relationship between autotrophs
  and heterotrophs in an ecosystem. 
• 2.Explain how decomposition connects all trophic
  levels in an ecosystem. 
• 3.Explain how the first and second laws of
  thermodynamics apply to ecosystems.
• Primary Production in Ecosystems
•  4.Explain why the amount of energy used in
  photosynthesis is so much less than the amount of
  solar energy that reaches Earth. 
• 5.Define and compare gross primary production and
  net primary production. 6.Define and compare
  biomass and standing crop. 
• 7.Compare primary productivity in marine,
  freshwater, and terrestrial ecosystems.
• Secondary Production in Ecosystems
• 8.Explain why energy is said to flow rather than
  cycle within ecosystems. Use the example of
  insect caterpillars to illustrate energy flow.  
• 9.Define, compare, and illustrate the concepts of
  production efficiency and trophic efficiency. 
• 10.Distinguish between energy pyramids and
  biomass pyramids. Explain why both relationships
  are in the form of pyramids. Explain the special
  circumstances of inverted biomass pyramids.
• How Specific Immunity Arises
• 11.Explain why food pyramids usually have only
  four or five trophic levels 12.Define the pyramid
  of numbers. 
• 13.Explain why worldwide agriculture could feed
  more people if all humans consumed only plant
  material. 
• 14.Explain the green-world hypothesis. Describe
  six factors that keep herbivores in check.

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• The Cycling of Chemical Elements in Ecosystems
• 15.Describe the four nutrient reservoirs and the
  processes that transfer the elements between
  reservoirs. 
• 16.Explain why it is difficult to trace elements
  through biogeochemical cycles. 
• 17.Describe the hydrologic water cycle. 
• 18.Describe the nitrogen cycle and explain the
  importance of nitrogen fixation to all living
  organisms. 
• 19.Describe the phosphorus cycle and explain how
  phosphorus is recycled locally in most
  ecosystems. 
• 20.Explain how decomposition affects the rate of
  nutrient cycling in ecosystems. 
• 21.Describe the experiments at Hubbard Brook that
  revealed the key role that plants play in
  regulating nutrient cycles.
• Human Impact on the Chemical Dynamics of the
  Biosphere
• 22.Describe how agricultural practices can
  interfere with nitrogen cycling. 
• 23.Explain how "cultural eutrophication" can
  alter freshwater ecosystems. 
• 24.Describe the causes and consequences of acid
  precipitation. 
• 25.Explain why toxic compounds usually have the
  greatest effect on top-level carnivores. 
• 26.Describe how increased atmospheric
  concentrations of carbon dioxide could affect
  Earth. 
• 27.Describe how human interference might alter
  the biosphere.

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Ecosystems, Energy, and Matter

• Ecosystems, Energy, and Matter
• An ecosystem consists of all the organisms living
  in a community
• As well as all the abiotic factors with which
  they interact

• Ecosystems can range from a microcosm, such as an
  aquarium
• To a large area such as a lake or forest

• Regardless of an ecosystems size
• Its dynamics involve two main processes
• energy flow and chemical cycling
• Energy flows through ecosystems
• While matter cycles within them

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54.1 Ecosystem ecology emphasizes energy flow
and chemical cycling

• Ecosystem ecologists view ecosystems
• As transformers of energy and processors of
  matter
• Ecosystems are not supernatural so
• They abide by..
• Thermodynamics
• The Law of Conservation of Energy
• The Law of Conservation of Matter

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Trophic Relationships

• Energy and nutrients pass from primary producers
  (autotrophs)
• To primary consumers (herbivores) and then to
  secondary consumers (carnivores)

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Trophic Relationships

• Only 10-20 of energy flows from one trophic
  level to the next.

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• Energy flows through an ecosystem
• Entering as light and exiting as heat
• Nutrients cycle within an ecosystem

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Decomposition

• Decomposition
• Connects all trophic levels

• Detritivores, mainly bacteria and fungi, recycle
  essential chemical elements
• By decomposing organic material and returning
  elements to inorganic reservoirs

Detritivores obtain energy from nonliving organic
matter called Detritus.
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54.2 Physical and chemical factors limit 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

• Earth is bombarded with 1022 joules of solar
  energy every day.
• This is enough energy to meet human demands for
  24years at our 2004 consumption level.

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Gross and Net Primary Production

• Total primary production in an ecosystem
• Is known as that ecosystems gross primary
  production (GPP)
• Not all of this production
• Is stored as organic material in the growing
  plants

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Gross and Net Primary Production

• Net primary production (NPP)
• Is equal to GPP minus the energy used by the
  primary producers for respiration
• Only NPP
• Is available to consumers
• NPP GPP R (respiration)

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Different ecosystems vary considerably in their
net primary production

• And in their contribution to the total NPP on
  Earth

(c)
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Average net primary production (g/m2/yr
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Overall, terrestrial ecosystems

• Contribute about two-thirds of global NPP and
  marine ecosystems about one-third

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Primary Production in Marine and Freshwater
Ecosystems

• In marine and freshwater ecosystems
• Both light and nutrients are important in
  controlling primary production

• The depth of light penetration
• Affects primary production throughout the photic
  zone of an ocean or lake

• More than light, nutrients limit primary
  production
• Both in different geographic regions of the ocean
  and in lakes

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Limiting Nutrients

• A limiting nutrient is the element that must be
  added
• In order for production to increase in a
  particular area
• Nitrogen and phosphorous
• Are typically the nutrients that most often limit
  marine production

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Nutrient enrichment experiments

• Confirmed that nitrogen was limiting
  phytoplankton growth in an area of the ocean

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Nutrient Enrichment Experiments
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Experiments in another ocean region

• Showed that iron limited primary production

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Limiting Nutrients

• The addition of large amounts of nutrients to
  lakes
• Has a wide range of ecological impacts

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Limiting Nutrient

• In some areas, sewage runoff
• Has caused eutrophication of lakes, which can
  lead to the eventual loss of most fish species
  from the lakes

Eutrophication Video 1 Eutrophication Video
2 Eutrophication Video 3
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Primary Production in Terrestrial and Wetland
Ecosystems

• In terrestrial and wetland ecosystems climatic
  factors
• Such as temperature and moisture, affect primary
  production on a large geographic scale
• The contrast between wet and dry climates
• Can be represented by a measure called actual
  evapotranspiration

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Actual evapotranspiration

• Is the amount of water annually transpired by
  plants and evaporated from a landscape
• Is related to net primary production

• Figure 54.8 shows
• Tropical Forest has the greatest NPP
• Desert Shrubland has the least NPP

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Soil Productivity On a more local scale

• A soil nutrient is often the limiting factor in
  primary production

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54.3 Energy transfer between trophic levels is
usually less than 20 efficient

• The secondary production of an ecosystem
• Is the amount of chemical energy in consumers
  food that is converted to their own new biomass
  during a given period of time

• When a caterpillar feeds on a plant leaf
• Only about one-sixth of the energy in the leaf is
  used for secondary production

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The production efficiency of an organism

• Is the fraction of energy stored in food that is
  not used for respiration

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Trophic Efficiency and Ecological Pyramids

• Trophic efficiency
• Is the percentage of production transferred from
  one trophic level to the next
• Usually ranges from 5 to 20

• This loss of energy with each transfer in a food
  chain
• Can be represented by a pyramid of net production

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Pyramids of Biomass

• Most biomass pyramids
• Show a sharp decrease at successively higher
  trophic levels

• One important ecological consequence of low
  trophic efficiencies
• Can be represented in a biomass pyramid

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Exceptions to the Biomass Pyramid

• Certain aquatic ecosystems
• Have inverted biomass pyramids

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Pyramids of Numbers

• A pyramid of numbers
• Represents the number of individual organisms in
  each trophic level

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Humans and Energy Efficiency

• The dynamics of energy flow through ecosystems
• Have important implications for the human
  population
• Eating meat
• Is a relatively inefficient way of tapping
  photosynthetic production

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Worldwide agriculture could successfully feed
many more people

• If humans all fed more efficiently, eating only
  plant material

Figure 54.14
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The Green World Hypothesis

• According to the green world hypothesis
• Terrestrial herbivores consume relatively little
  plant biomass because they are held in check by a
  variety of factors
• Most terrestrial ecosystems have large standing
  crops despite the large numbers of herbivores

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The green world hypothesis

• proposes several factors that keep herbivores in
  check
• Plants have defenses against herbivores
• Nutrients, not energy supply, usually limit
  herbivores
• Abiotic factors limit herbivores
• Intraspecific competition can limit herbivore
  numbers
• Interspecific interactions check herbivore
  densities

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54.4 Biological and geochemical processes move
nutrients between organic and inorganic parts of
the ecosystem

• Life on Earth
• Depends on the recycling of essential chemical
  elements
• Nutrient circuits that cycle matter through an
  ecosystem
• Involve both biotic and abiotic components and
  are often called biogeochemical cycles

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A General Model of Chemical Cycling

• Gaseous forms of carbon, oxygen, sulfur, and
  nitrogen
• Occur in the atmosphere and cycle globally
• Less mobile elements, including phosphorous,
  potassium, and calcium
• Cycle on a more local level

A general model of nutrient cycling Includes the
main reservoirs of elements and the processes
that transfer elements between reservoirs
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Biogeochemical Cycles

• All elements
• Cycle between organic and inorganic reservoirs

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Biogeochemical Cycles

• The water cycle and the carbon cycle

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Water Cycle (Read Page 1196)
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The Carbon Cycle (Read Page 1196)
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The Nitrogen Cycle (Read Page 1197)
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The Phosphorus Cycle (Read Page 1197)
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Decomposition and Nutrient Cycling Rates

• Decomposers (detritivores) play a key role
• In the general pattern of chemical cycling

• The rates at which nutrients cycle in different
  ecosystems
• Are extremely variable, mostly as a result of
  differences in rates of decomposition

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Vegetation and Nutrient Cycling The Hubbard
Brook Experimental Forest

• The research team constructed a dam on the site
• To monitor water and mineral loss

• Nutrient cycling
• Is strongly regulated by vegetation
• Long-term ecological research projects
• Monitor ecosystem dynamics over relatively long
  periods of time
• The Hubbard Brook Experimental Forest
• Has been used to study nutrient cycling in a
  forest ecosystem since 1963

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Experiment Human Disturbances and how they
effect nutrient cycles

• In one experiment, the trees in one valley were
  cut down
• And the valley was sprayed with herbicides

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Experiment Human Disturbances and how they
effect nutrient cycles

• Net losses of water and minerals were studied
• And found to be greater than in an undisturbed
  area
• These results showed how human activity
• Can affect ecosystems

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54.5 The human population is disrupting chemical
cycles throughout the biosphere

• As the human population has grown in size
• Our activities have disrupted the trophic
  structure, energy flow, and chemical cycling of
  ecosystems in most parts of the world

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Nutrient Enrichment

• In addition to transporting nutrients from one
  location to another
• Humans have added entirely new materials, some of
  them toxins, to ecosystems

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Nutrient Enrichment

• In addition to transporting nutrients from one
  location to another
• Humans have added entirely new materials, some of
  them toxins, to ecosystems

• Agriculture constantly removes nutrients from
  ecosystems
• That would ordinarily be cycled back into the soil

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Nutrient Enrichment

• Nitrogen is the main nutrient lost through
  agriculture
• Thus, agriculture has a great impact on the
  nitrogen cycle
• Industrially produced fertilizer is typically
  used to replace lost nitrogen
• But the effects on an ecosystem can be harmful

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Contamination of Aquatic Ecosystems

• The critical load for a nutrient
• Is the amount of that nutrient that can be
  absorbed by plants in an ecosystem without
  damaging it

• When excess nutrients are added to an ecosystem,
  the critical load is exceeded
• And the remaining nutrients can contaminate
  groundwater and freshwater and marine ecosystems

• Sewage runoff contaminates freshwater (and
  saltwater) ecosystems
• Causing cultural eutrophication, excessive algal
  growth, which can cause significant harm to these
  ecosystems

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This is happening in your backyard!!!!
Click Picture to learn about the NY/NJ Harbor
Estuary studies and action plans
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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

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Acid Precipitation

• By the year 2000
• The entire contiguous United States was affected
  by acid precipitation

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Toxins in the Environment

• Humans release an immense variety of toxic
  chemicals
• Including thousands of synthetics previously
  unknown to nature
• One of the reasons such toxins are so harmful
• Is that they become more concentrated in
  successive trophic levels of a food web

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Biological Magnification

• Toxins concentrate at higher trophic levels
  because at these levels biomass tends to be lower

Polychlorinated Biphenyl (PCB) PCBs belong to a
broad family of man-made organic chemicals known
as chlorinated hydrocarbons. PCBs were
domestically manufactured from 1929 until their
manufacture was banned in 1979. They have a range
of toxicity and vary in consistency from thin,
light-colored liquids to yellow or black waxy
solids. Due to their non-flammability, chemical
stability, high boiling point, and electrical
insulating properties, PCBs were used in hundreds
of industrial and commercial applications
including electrical, heat transfer, and
hydraulic equipment as plasticizers in paints,
plastics, and rubber products in pigments, dyes,
and carbonless copy paper and many other
industrial applications.
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Atmospheric Carbon Dioxide

• One pressing problem caused by human activities
• Is the rising level of atmospheric carbon dioxide

• Due to the increased burning of fossil fuels and
  other human activities
• The concentration of atmospheric CO2 has been
  steadily increasing

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National Geographic Video on Global Warming
Click on picture for 3min video
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The Greenhouse Effect and Global Warming

• The greenhouse effect is caused by many gases,
  but atmospheric CO2 plays a major role
• But is necessary to keep the surface of the Earth
  at a habitable temperature

• Increased levels of atmospheric CO2 are
  magnifying the greenhouse effect
• Which could cause global warming and significant
  climatic change

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Depletion of Atmospheric Ozone

• Life on Earth is protected from the damaging
  effects of UV radiation
• By a protective layer or ozone molecules (O3)
  present in the atmosphere

• Satellite studies of the atmosphere
• Suggest that the ozone layer has been gradually
  thinning since 1975

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The destruction of atmospheric ozone

• Probably results from chlorine-releasing
  pollutants produced by human activity