Organisms

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Levels Important to Ecology

• Organisms
• Populations
• Communities
• Ecosystems
• Biosphere

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COMMUNITY AND POPULATION ECOLOGY
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Classification of Communities

• Physical appearance.forest, grassland, desert,
  or scrubland.dominant plant species.
• Species diversity.high diversity (tropical rain
  forest or coral reef).low diversity (tundra or
  boreal coniferous forest).
• Niche structure.how many organisms are in each
  trophic level.specialists or generalists.

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Physical Appearance and Biomes
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Community Structure and Diversity
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Species present in a community

• Native species--species present since recorded
  history began. (oak, hazelnut, ferns)
• Invasive species--organisms introduced
  accidentally or intentionally by people.
• Indicator species--organisms that responds
  quickly to environmental stress.

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European Starling
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Starling Range Spread
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Zebra Mussel
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Purple Loosestrife
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Giant Hogweed

• Attack of the Giant Hogweed

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Indicators of Polluted Water

• Tadpole snails and Tubifex worms thrive in the
  low oxygen environments of polluted streams.

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Indicators of Clean Water
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Keystone Species

• A species that maintains the structure of a
  community.
• Sea otters, which prevent sea urchins from
  destroying kelp forests.

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Foundation Species

• A species that restores a community if the
  community is removed.

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Competition

• Two or more individuals scrambling or fighting
  for the same resource.
• Can be within the same species or between species.

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Mutualism
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Commensalism
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Parasitism
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Succession

• Succession is a generally predictable change in
  community composition over time.
• Primary successionthe progression of species
  from bare ground to a climax community. (slow)
• Secondary successionthe restoration of a
  previously existing community from a disturbance.
  (rapid)

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Michigan Examples

• Succession from open fields to oak-pine forest to
  maple-beech forest.
• Succession in lakes filling in to form bogs and
  then meadows.

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Population Terminology

• Population size(birthsimmigration)-(deathsemigr
  ation).
• Intrinsic rate of increase called rrelated to
  birthrate.
• Carrying capacity of the environmentnumber of
  individuals the environment can supportcalled K.
• K also an important part of biological
  resistanceall the factors that restrict
  population growth.

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Age Structure

• Many young individuals usually means rapid growth
  in the future.
• Many older individuals usually means slower
  growth in the future.

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Exponential Vs. Logistic Growth

• Exponential growth involves ever-increasing rates
  of growth produces J-curve.
• Logistic growth starts out like exponential
  growth, but slows down as it reaches K produces
  S-curve.

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r-selected Species
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K-selected Species
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Comparison of ecological roles of r- vs.
K-selected organisms

• Most r-selected organisms are generalists.Excepti
  on parasites.
• Most K-selected organisms are specialists.Excepti
  on humans.

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Next upClimate and Biodiversity
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Pages and Figures to Read

• Compare and contrast r-selected species and
  K-selected species.- examples of each.
• Compare and contrast the characteristics of
  natural systems and human-dominated systems.-
  examples of each.

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Human-Dominated vs. Natural Ecosystems

• Human-dominated ecosystems are
• Much flatter (fewer trophic levels)
• Less diverse.
• Have most of primary productivity directed to
  human consumption.
• Regularly disturbed (plowing, construction, etc.)