Ecology

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Ecology
Energy Flow in Ecosystems
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First Law of ThermodynamicsConservation of Energy

• In short, the law of conservation of energy
  states that energy can not be created or
  destroyed, it can only be changed from one form
  to another or transferred from one body to
  another, but the total amount of energy remains
  constant (the same).

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Energy Flow Sustaining Life on Earth

• The most important factor that controls what
  kinds of organisms and how many live in an
  ecosystem
• One way flow of high quality energy
• The cycling of matter (the earth is a closed
  system)

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The Source of High Quality Energy

• Energy of sun lights and warms the planet
• Supports photosynthesis
• Powers the cycling of matter
• Drives climate and weather that distribute heat
  and H2O

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Primary Productivity

• Primary productivity the rate at which
  photosynthesis ? organic material (food)
• Energy expended Plants use the energy captured
  in photosynthesis for maintenance and growth.
• Primary productivity determines the amount of
  energy available in an ecosystem

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Which Ecosystems are the most productive?
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Terrestrial productivity
0100 100200 200400 400600 600800 gt800
Productivity ranges (g/m2/yr)
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Marine productivity
lt35 3555 5590 gt90
Productivity ranges (g/m2/yr)
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Fate of Primary Productivity

• According to one source
• Humans now use, waste, or destroy about 27 of
  earths total potential NPP
• And 40 of the NPP of the planets terrestrial
  ecosystems

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Components of Ecosystems

• Abiotic cycles
• Producers (autotrophs)
• Source of all food
• Photosynthesis
• Chemosynthesis
• Consumers (heterotrophs)
• Aerobic respiration
• Oxygen
• Anaerobic respiration
• Methane, H2S
• Decomposers
• Matter recyclers
• Release organic compounds into soil and water
  where they can be used by producers

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Autotrophs are producers

• They capture energy and synthesize their own
  organic nutrients.
• They can do this by photosynthesis or
  chemosynthesis.
• Chemosynthetic bacteria get energy and raw
  materials from vents called "smokers" on the
  ocean floor.
• Tube worms rely upon the bacteria that coexist
  with them to make food at the bottom of the
  ocean.

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Autotrophs

• Autotrophs (self-nourishing) are called primary
  producers.
• Photoautotrophs fix energy from the sun and
  store it in complex organic compounds
• green plants
• algae
• some bacteria
• some protists

light
simple inorganic compounds
complex organic compounds
photoautotrophs
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Autotrophs

• Chemoautotrophs are bacteria that oxidize reduced
  inorganic substances (typically sulfur and
  ammonia compounds) and produce complex organic
  compounds.
• Nitrifing bacteria
• Halophiles (found in highly concentrated salt
  lakes)
• Thermophiles (found in hot springs and geysers)

oxygen
complex organic compounds
reduced inorganic compounds
chemoautotrophs
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Heterotrophs are consumers

• Heterotrophs are consumers, they must consume
  preformed organic nutrients synthesized by other
  organisms.

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Heterotrophs

• Heterotrophs (other-nourishing) cannot produce
  their own food directly from sunlight inorganic
  compounds. They require energy previously stored
  in complex molecules.
• Examples of heterotrophs
• Herbivores eat plants
• Carnivores eat meat
• Omnivores eat both plants and meat
• Scavengers eat carrion
• Saprophytes eat dead or decaying material

heat
simple inorganic compounds
complex organic compounds
heterotrophs
this may include several steps, with several
different types of organisms
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Carnivores

• Carnivores can be further divided into groups
• primary carnivore secondary carnivore
• tertiary carnivore
• quaternary carnivore (top)
• The last carnivore in a chain, which is not
  usually eaten by any other carnivore, is often
  referred to as the top carnivore.

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Heterotrophs

• Saprophytes (those that feed on dead material)
  can be divided into two groups
• Detritivore scavengers that feed directly on
  dead stuff
• Decomposers - Digest complex organic chemicals
  into inorganic nutrients that are used by
  producers
• Complete the cycle of matter
• Bacteria and fungi are the main groups of
  decomposers.
• Bacteria are the main feeders on animal material.
• Fungi feed primarily on plants, although bacteria
  also are important in some plant decomposition
  processes.

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Heterotroph Humor
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Heterotrophs
Detritivores vs Decomposers
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Predators of decomposers
Spider
Salamander
Centipede
Puffball
Puffball
Mushroom
Nematodes
Bacteria and archaea
Millipede
Earthworm
Pillbugs
Primary decomposers
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Trophic Levels

• Each organism in an ecosystem is assigned to a
  feeding (Trophic) level based on source of E
• Primary Producers
• Primary Consumers (herbivores, omnivores)
• Secondary Consumer (carnivores)
• Tertiary Consumers (carnivores)
• Detritus feeders and scavengers
• Directly consume tiny fragments of dead stuff
• Decomposers
• Digest complex organic chemicals into inorganic
  nutrients that are used by producers
• Complete the cycle of matter

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Trophic Levels
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General Rules for Energy Flow through Ecosystems

1. Energy is lost as heat
2. Amount of useful energy decreases at higher
   trophic levels
3. At each trophic level, only about 10 of the
   previous level energy remains
4. Thus, only about 1 of NPP ends up as production
   in the third trophic level

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Energy Pyramid

• An energy pyramid provides a means of describing
  the feeding and energy relationships within a
  food chain or web.   
• Each step shows that some energy is stored in
  newly made structures of the organism which eats
  the preceding one.  
• Shows that much of the energy is lost when one
  organism in a food chain eats another.   Most of
  this energy which is lost goes into the
  environment as heat energy.

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Trophic Levels Found on an Energy Pyramid

• The greatest amount of energy is found at the
  base of the pyramid.
• The least amount of energy is found at top of the
  pyramid.

Tertiary consumers
Secondary consumers
Primary consumers
Producers
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Implications of Pyramids.

• Why could the earth support more people if the
  eat at lower trophic levels?
• Why are food chains and webs rarely more than
  four or five trophic levels?
• Why are there so few top level carnivores?
• Why are these species usually the first to suffer
  when the the ecosystems that support them are
  disrupted?

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Biomass

• Energy is sometimes considered in terms of
  biomass the dry weight of tissue of all the
  organisms and organic material in an area.
• Producer organisms represent the greatest amount
  of living tissue or biomass at the bottom of the
  pyramid.  
• There are more plants on Earth than there are
  animals.
• Biolife Massweight
• Bio Mass Weight of living things within an
  ecosystem.

On average, each feeding level only contains 10
of the energy as the one below it, with the
energy that is lost mostly being transformed to
heat. 
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Trophic Levels

• Number of individuals per species

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Trophic Levels

• What if we transformed each species into biomass
  instead of absolute numbers?

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Energy Flow and Matter Cycling in Ecosystems

• Food Chains vs. Food Webs
• KEY There is little if no matter waste in
  natural ecosystems!

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Food chains tend to have few links.
10 8 6 4 2 0
Streams Lakes Terrestrial
Average number of links 3.5
Number of observations
Number of links in food chain
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Food Chain

• A food chain indicates the transfer of energy
  from producers through a series of organisms
  which feed upon each other
• The algae and plants are the producers.
• The aquatic crustaceans are primary consumers
  they eat the producers.
• Fish are secondary consumers they eat the
  primary consumers.
• The raccoons represent the tertiary consumer.

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Food Webs

• A food web is a series of interrelated food
  chains which provides a more accurate picture of
  the feeding relationships in an ecosystem, as
  more than one thing will usually eat a particular
  species.    

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Generalized Food Web of the Antarctic
Note Arrows Go in direction Of energy flow
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Fresh water Food web.
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Food web of the harp seal.
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Biogeochemical (Abiotic) Cycles

• A closed pathway where matter cycles from the
  nonliving environment to living and then back
  again for reuse.
• A key feature in all cycles is that nutrients
  are recycled and reused.
• The overall rate of nutrient movement is
  limited most by decomposition.
• The rate of nutrient loss is a very important
  characteristic in any ecosystem.

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Plants
Overview of Nutrient Cycling
Consumption
Herbivore
Assimilation
Feces or urine
Death
Death
Detritus
Uptake
Soil nutrient pool
Decomposer food web
Loss to erosion or leaching into groundwater
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Water Cycle

• Water has greatest influence of all non-living
  components
• Transpiration evaporation from leaves of
  plants
• Driven by sun
• Causes wind currents

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Carbon Cycle

• Combustion
• Burning- CO2
• Fossil fuels -hydrocarbons

• Photosynthesis and Cellular respiration
• O2 ? ? CO2

• Erosion
• CaCO3 ? shells ? limestone

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Nitrogen Cycle

• 78 N gas in atmosphere
• unusable

• Nitrogen fixation N2 3H ?2NH3
• Bacteria in soil
• Limits plant growth

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Nitrogen Cycle

• Ammonification
• Decomposition by bacteria during decay

• Bacteria can fix nitrogen which means they
  break apart nitrogen gas and convert it into
  ammonia or ammonium.

• Assimilation
• Absorption and incorporation of nitrogen by plants

• Nitrification
• Ammonia to nitrates and nitrites by bacteria
• Then can be assimilated by plants

• Denitrification
• Denitrifying bacteria converts nitrates back into
  N2

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Phosphorous Cycle

• No gaseous component (from land to sediment and
  back to land only)
• Erosion ?releases phosphate? soil ?plants
• Decomposers ?phosphate ? soil
• Deposited in oceanic sediment ? unavailable for
  years
• Fertilizers, run off containing animal wastes,
  and sewage ?aquatic ecosystems

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