Ecology

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Ecology
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Ecology

• Ecology is the study of interactions between
  organisms and their environment.
• Population ecology
• Community ecology
• Ecosystem ecology

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Ecology vs. Environmentalism

• Ecology - the study of interactions between
  organisms and their environment
• Population Ecology relationship between members
  of a species
• Community Ecology the study of groups of
  populations
• Ecosystem Ecology the study of the structure
  and function of physical, chemical and biological
  components of the environment
• Environmentalism - the practical application by
  humans of this understanding. Not all
  environmentalists are ecologists.

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General Model of Nutrient Cycling
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Nitrogen Cycle

• Nitrogen is 78 of the atmosphere, in gaseous
  form N2. It has to be transformed into a usable
  form for all organisms to use.
• Nitrogen fixing bacteria make NH3 from N2 and may
  produce organic compounds with nitrogen, or
  excrete it.
• Other bacteria make nitrite and nitrate (NO3)
  from NH4
• Denitrifying bacteria convert nitrate to N2 for
  release back into the atmosphere.

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Nitrogen cont

• Nitrogen is also a component of fertilizers.
  High ammonia or nitrates in a stream or pond
  means there is probably some nutrient source
  flowing into it, such as animal waste or
  fertilizer.
• Plants and animals need it to make proteins and
  enzymes.

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Nitrogen Cycle
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Phosphorous

• The major source of phosphorous in the ecosystem
  is the weathering of rocks.
• Organisms use phosphorous for phospholipids in
  cell membranes, nucleic acids, and ATP and in
  mineral form for bones.
• Plants pick up dissolved phosphorous from soil
  and use it in cells and as energy.

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Phosphorous cont

• Decomposers return phosphate to the soil by
  decomposition of detritus.
• People put lots of phosphate in the soil when
  they apply fertilizers. If it is applied too
  heavily or at the wrong time, much of it runs off
  into the streams and causes algal blooms.

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Phosphorus Cycle
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Dissolved Oxygen

• Dissolved oxygen levels are an important
  indicator of the health of ponds or streams.
• Low dissolved oxygen usually is from low flow
  and/or high bacterial communities.
• An areator was installed in the Duck Pond to
  increase dissolved oxygen levels and to keep the
  Duck Pond from going anaerobic.

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Typical levels

• Phosphorous levels lt0.1ppm, usually 0.001 ppm
• Silica 0-75 ppm
• Ammonia and nitrate lt10 ug/L normal
• Nitrates lt0.1 to 6 mg/L (produced by ammonia
  breakdown)
• Hardness (sum of calcium and magnesium) ranges
  from 0-320 mg/L.
• Dissolved oxygen 8-9 mg/L saturation

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Exponential and Logistic Growth Curves
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Human population growth
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Carrying Capacity K

• K is the maximum population that a specific
  environment can support.
• Factors affecting carrying capacity include
• Nutrient availability
• Energy
• Water
• Nesting sites if animals
• Sunlight for plants
• Predators
• space

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Exponential Growth

• dN/dt rN dN/dt is pop. growth rate
• Looking at population size during exponential
  growth we use
• Nt Noert
• So if we have 10 duckweeds growing for
• 4 days and r (rate of growth) is 0.2 then
• N4 10 x e(0.2x4) 10 X 2.22 or 22.2 duckweeds
  after 4 days

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• To determine the intrinsic rate of growth
• r ln(Nt/No)
• t
• In the last example
• r ln(22.2/10)
• 4
• r 0.199 or 0.2

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Logistic Growth

• dN/dt rmaxN (K-N)
• K
• Where dN is change in population
• t is time and dt is change in time
• dN/dt is the population growth rate
• K is carrying capacity
• K-N is of extra individuals an environment can
  sustain (effect of crowding or environmental
  resistance)
• rmax is exponential rate of increase
• (K-N)/K is part of K available for population
  growth

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Logistic Growth cont.

• If N is small (K-N)/K is close to 1 and
• population growth is rapid
• If N is large, (K-N)/K population growth is slow
• If N 5 and K 50 and r 1 we have
• 1x50x(50-5)/50 4.5 dN/dt
• If N 45,
• 1x50x(50-45)/50 0.5 dN/dt

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Limitations to growth

• Resource availability
• Sunlight
• Space
• Nutrients
• Pollinators
• Proper environment for growth

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Competition

• Competition between species may be for
• Space
• Sunlight
• Nutrients

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Lemna minor - Duckweed
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Lemna minor

• A very good food source for waterfowl and fish.
• Used in wastewater treatment because of their
  ability to absorb excess nutrients such as
  phosphorus and NH4. Also reduces BOD.

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Salvinia
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Salvinia

• An aquatic fern that is a pest species
• Reproduces only by vegetative reproduction.
• Forms thick mats that damage to irrigation
  equipment, fencing, and boat engines.
• Thick mats can trap and drown children and
  livestock and can cause stagnation of water.

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Today

• Design and carry out an experiment to test the
  effects of varying a resource or other
  environmental factor on Lemna minor with
• the supplies available.
• This will be a two week experiment and a lab
  report will be required at the end of the
  experiment.

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Types of Investigations

• Look at resource limitations
• Figure out the carrying capacity of a specific
  environment for a given species
• Determine optimal nutrient or light levels
• Look at competition among two species of aquatic
  plants.
• Study effects of various water sources

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Notes

• Work in groups of 4 (one lab table)
• 100 mL per container, mark water line w/sharpie
• Set up appropriate controls
• Can use 6 cups per lab group
• Starting amounts
• For growth rate 6 or a spoon full
• For carrying capacity start with more

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Disposal of Duckweed and Salvinia

• Do NOT throw these plants down the drain.
• Leave them on the racks and we will clean them up
  when you are finished.

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Time line

• Start experiment today, finish March 29th
• April 5 First draft due
• April 19 Final Draft of Lab Reports Due