Ecology

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Ecology

• Chapter 25
• Botany 004
• April 30/May 1

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Ecology - the study of the interaction of
organisms and their environment (including the
biotic environment)
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Ecology and evolutionary biology are closely
related disciplines an important cause of
evolutionary change is the interaction of
organisms with their environment.
Example Solbrig (1970) demonstrated that
different genotypes of dandelion were selected
for around building foundations versus open lawns
as a result of different mowing regimes.
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Ecology Provides a Scientific Context for
Evaluating Environmental Issues
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Abiotic includes non-living chemical and physical
factors such as

• Light and Temperature
• Water and Nutrients
• Wind / Climate
• Soil / Rocks
• Elevation
• Periodic Disturbances

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Terrestrial Ecosystems are Defined by Temperature
and Moisture
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Interactions

• Includes not only how the environment affects an
  organism, but also how the organism changes its
  environment
• O2, a byproduct of early photosynthetic
  bacteria, produced an aerobic atmosphere.
• Trees sometimes shade the forest floor
  preventing their own progeny from growing.

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Ecological Research Ranges from the Adaptations
of Organisms to the Dynamics of Ecosystems
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Ecology can be Divided into Four Levels of Inquiry

• Organismal Ecology
• Population Ecology
• Community Ecology
• Ecosystem Ecology

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Organismal Ecology Study of the behavioral,
physiological, and morphological ways individuals
meet abiotic challenges

• Seed germination
• Tropisms
• Leaf Drop
• Flowering
• Photoperiodism
• etc.
• The distribution of organisms is limited by their
  tolerance of abiotic challenges

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Population Ecology Study of groups of
individuals of the same species in a particular
place

• Concerned with factors that affect population
  size and composition.
• How and Why do Populations Change over Time?
• Why does a plant grow where it does?
• Why is the density and spacing of individuals in
  the population the way it is?

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Reproductive Strategies Semelparous reproduction
(big-bang) A life history strategy in which
the organism reproduces but once and then dies.
Iteroparous reproduction repeated
reproduction over the course of the life span
White tailed deer - an iteroparous species
Bamboo - a semelparous species
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Community Ecology Study of all organisms that
inhabit a particular area

• Concerned with predation, competition, and other
  interactions that affect community structure and
  composition.
• Pollination
• Symbiosis
• Defense Protection from Pathogens secondary
  metabolites.
• Allelopathy
• Succession
• Nitrogen Fixation
• Many, many others.

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Ecological succession is the transition in
species composition over ecological time. It is
a response to disturbance.
Primary succession begins in a lifeless area
where soil has not yet formed.
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The Pattern of Primary Succession on Glacial
Moraines in Glacier Bay, Alaska
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Figure 53.20 Change in soil nitrogen
concentration during succession after glacial
retreat in Glacier Bay, Alaska
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Figure 53.20 Alders and cottonwoods covering the
hillsides
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Figure 53.20 Spruce coming into the alder and
cottonwood forest
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Figure 53.20 Spruce and hemlock forest
Ecological Monographs Vol. 64, No. 2, pp.
149-175. Mechanisms of Primary Succession
Following Deglaciation at Glacier Bay, Alaska.
F. Stuart Chapin, Lawrence R. Walker, Christopher
L. Fastie, and Lewis C. Sharman
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Secondary succession occurs where an existing
community has been cleared by some event, but
the soil is left intact.
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Ecosystem EcologyStudy of all abiotic factors
as well as communities of organisms in an area

• Concerned with energy flow and chemical recycling
  among biotic and abiotic components.

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The Carbon Cycle and Global Warming
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Depletion of Atmospheric Ozone

• Life on Earth is protected from damaging effects
  of UV radiation by a protective layer or ozone
  molecules in the atmosphere
• Satellite studies suggest that the ozone layer
  has been gradually thinning since 1975

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LE 54-26
350
300
250
200
Ozone layer thickness (Dobson units)
150
100
50
0
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
1955
Year (Average for the month of October)
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• Destruction of atmospheric ozone probably results
  from chlorine-releasing pollutants produced by
  human activity

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LE 54-27
Chlorine from CFCs interacts with ozone (O3),
forming chlorine monoxide (CIO) and oxygen (O2).
Chlorine atoms
O2
O3
Chlorine
CIO
O2
Sunlight causes Cl2O2 to break down into O2 and
free chlorine atoms. The chlorine atoms can begin
the cycle again.
CIO
Two CIO molecules react, forming chlorine
peroxide (Cl2O2).
Cl2O2
Sunlight
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• Scientists first described an ozone hole over
  Antarctica in 1985 it has increased in size as
  ozone depletion has increased

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October 1979
October 2000