ECOSYSTEMS AND HOW THEY WORK

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CHAPTER 4

• ECOSYSTEMS AND HOW THEY WORK

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Ecology and Life

• Ecology is study of how organisms interact with
  one another and with their nonliving environment
• A species consists of all organisms -living
  things-which can reproduce living offspring
• Populations consist of organisms of same species
  living in same place at same time
• Genetically diverse organisms contribute genes to
  the populations gene pool

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Ecology and Life -2

• Several interacting populations occupying the
  same habitat form a community
• An ecosystem is the communities and their
  nonliving environment all Earths ecosystems
  form the ecosphere
• What are 6 characteristics of living things that
  enable growth, survival and reproduction?

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Reproduction and Evolution

• While asexual reproduction can produce new
  offspring - they are all identical
• Sexual reproduction produces organisms have new
  combinations of parental traits.
• Traits which offer a better chance of survival
  are adaptive and lead to evolution
• Biodiversity refers to all of the variety of
  living organisms and their traits

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Earths Life-support Systems

• Atmosphere consists of inner trophosphere and
  outer stratosphere
• Hydrosphere is liquid, solid gaseous water
• Lithosphere is crust and upper mantle
• Ecosphere is portion of earth where organisms
  interact (atmosphere, hydrosphere, and upper
  lithosphere)

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Sustaining Life on Earth

• Interconnected factors include
• one-way flow of high quality energy from sun
• What is the path?
• Cycling of matter or nutrients through ecosphere
• Gravity permits earth to hold onto all parts of
  ecosphere

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Life is Sustained by Sun

• Sunlight supplies energy for photosynthesis
• Solar energy powers cycling of matter
• Solar energy drives climate and weather systems
• Hydrogen and helium nuclei fuse releasing solar
  energy

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Effects of Solar Radiation

• Solar energy reaching earth is either reflected
  (28) or absorbed (28)
• Absorbed radiation warms, evaporated, cycles, and
  generates winds.
• Less than 1 is captured for photosynthesis these
  reactions produce all organic compounds required
  for all living organisms
• Greenhouse effect - ultimate change of all solar
  radiation to heat (infrared radiation)

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Ecosystem Concepts

• Biomes are large terrestrial regions
  characterized by distinct climate and specific
  life forms.
• Climate is weather - over the long term it
  determines type of life forms in biomes
• Biomes contain many ecosystems
• Aquatic life zones (like biomes) consist of
  freshwater and marine life zones

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Major Components of Ecosystems

• Abiotic - nonliving water, air, nutrients and
  solar energy
• physical factors affecting terrestrial ecosystems
• What are the six factors listed?
• Physical factors affecting aquatic ecosystems
• What are three factors listed?
• Biotic - living components
• Observe how abiotic and biotic components
  interact (fig. 4.9 and 4.10)

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Tolerance

• Each population has range of variations in
  environmental factors that it can tolerate the
  extremes of the range of tolerance are tolerance
  limits.
• Within this range of tolerance are variety of
  conditions which are optimal for success.
• State the law of tolerance
• Some factors limit population growth more than
  others - Name limiting factors in terrestrial and
  aquatic ecosystems

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Biotic Components of Ecosystem

• Producers (autotrophs) transform solar energy
  into chemical energy of bonds of organic
  molecules - Photo (chemo)synthesis
• green plants and aquatic phytoplankton
• Consumers (heterotrophs) cannot synthesize
  organic molecules from scratch - they can
  convert organic molecules from food to other
  organic molecules needed

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Consumers

• Consumers (heterotrophs) obtain energy and
  nutrients from other organisms
• Herbivores - primary consumers
• Secondary tertiary consumers may be
• carnivores - meat-eaters
• omnivores - plant and meat eaters
• scavengers and detritus feeders feed on animals
  already killed or remains of such
• Decomposers - recycle organic molecules and
  release inorganic molecules - biodegradation

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One-way Flow of Energy

• Respiration is release of energy from chemical
  bonds of organic molecules
• Aerobic (w/oxygen) respiration --gt complete
  breakdown of glucose to CO2 water energy
• Anaerobic (w/out oxygen) respiration (also called
  fermentation) --gt incomplete breakdown of glucose
  --gt methane, alcohol or acetic acid
• One-way flow of energy through organisms
• Matter energy recycles through ecosystems

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Food Chains

• Food chain - how nutrients and energy move
  through organisms in ecosystem - who eats who
  (Fig. 4-14)
• trophic levels begin with producers and end with
  decomposers
• Be sure you can identify types of organisms at
  each trophic level, I.e. producers, primary,
  secondary, and tertiary consumers

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Food Webs

• Food web - network of interconnected food chains
  more complex because one organism is never eaten
  by only one other
• Identify the various trophic levels shown in Fig.
  4.15

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Energy flow and Biomass storage

• Biomass (dry weight of organic matter) is
  transferred between trophic levels - but at each
  level some biomass changes to energy and is lost
• Ecological efficiency compares biomass
  transferred to that converted and lost
• Pyramid of energy flow shows that first trophic
  level has greatest amount of energy - some is
  transferred and some is lost at each level

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Pyramid of Biomass

• This pyramid demonstrates the total amount of
  biomass at each trophic level
• Why is biomass of producers less than that of
  primary consumers in ocean ecosystem?

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Pyramid of Numbers

• The actual number of organisms at each trophic
  level - regardless of size (amount of energy or
  biomass contained)
• Numbers of organisms at first level often
  greatest and fourth level often has least number
  of organisms - unless the producers individually
  contain more biomass

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Primary Productivity

• Gross Primary productivity - rate at which
  producers convert solar energy into chemical
  energy
• Net Primary productivity - accounts for energy
  that produces use for their own respiration -
  biomass lost - so this rate is always less
• Net primary productivity determines carrying
  capacity of species in ecosystems

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Comparisons of net productivity

• Which life zones have the greatest net
  productivity? Why zones have the least?
• Though tropical rain forest have high
  productivity for natural plants, the productivity
  when cleared is much less.
• What effect have humans had on the earths net
  productivity?

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Matter Cycling in Ecosystems

• Nutrients are any atoms, ions or molecules needed
  by organisms to live, grow or reproduce.
• Nutrient cycles (biogeochemical cycles) show how
  elements needed in greatest amounts travel
  through ecosystems

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Hydrologic (water) Cycle

• Main processes
• evaporation -liquid water to water vapor
• transpiration - evaporation from plants
• condensation - water vapor to liquid water
• precipitation - water from air goes to land
• infiltration - water moves into soil
• percolation - water flows downward through soil
• runoff - water flows downward across surface

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Hydrologic Cycle -2

• Cycle powered by solar energy and gravity
• Water vapor measurements absolute vs. relative
  humidity
• Condensation requires condensation nuclei and
  occurs at dew point
• How does surface runoff affect lithosphere?
• Name three ways Man has intervened in water
  cycle.

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Carbon Cycle

• Earths temperature varies with changes in carbon
  dioxide in atmosphere and water
• Producers use CO2 from atmosphere for
  photosynthesis
• Consumers release CO2 to atmosphere
• Carbon of buried organisms may become fossil
  fuels
• Most carbon stored as limestone and in water -
  How has Man disturbed carbon cycle?

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Nitrogen Cycles

• Most is in gas form in atmosphere
• Gaseous nitrogen must be fixed to form ammonia
  or nitrates for plant assimilation
• Plants synthesize nitrogen-containing organic
  molecules - proteins nucleic acids
• Ammonia and nitrates converted back to gas which
  reenters atmosphere
• How has Man intervened in nitrogen cycle?

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Phosphorus Cycle

• There is no gaseous phase for phosphorus
• Phosphorus circulates through water, earths
  crust and living organisms
• Phosphorus is added to land naturally by guano
  and artificially by fertilizer
• Phosphorus is limiting factor in growth of many
  organisms
• How has Man intervened in phosphorus cycle?

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Sulfur Cycle

• Much sulfur stored underground in rocks and
  minerals
• Sulfur enters atmosphere as hydrogen sulfide,
  sulfur dioxide and sulfates
• Water combines with sulfur dioxide to form acid
  rain
• How has Man increased the atmospheric phase of
  the sulfur cycle?

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Ecological Research

• Field research - dirty, difficult and expensive,
  but important new technologies
• Laboratory research - set up model ecosystems
  with controlled variables easier but must be
  coupled with field research
• Systems analysis - computer simulations used to
  make prediction accuracy depends on input

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Ecosystem Services and Sustainability

• Ecosystem services constitute earths natural
  capital one is biological diversity
• genetic diversity - individuals in species vary
  in genetic makeup
• species diversity - habitats contain wide variety
  of different species
• ecological diversity - ecosystems contain wide
  variety of communities

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Ecosystem Services and Sustainability -2

• Ecosystem services provide recycling,
  purification and natural pest control
• Each species results from many adaptations
• Each species provides raw material for future
  adaptation
• Two basic principles of natural ecosystem
  sustainability use renewable solar energy
• and recycle nutrients efficiently