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Community Ecology b - PowerPoint PPT Presentation


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Community Ecology. Community Characteristics. Interactions among species Species diversity Trophic structure. Species Diversity . Species richness The total number of different species Species abundance The proportion each species represents of the total individuals in the community.

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Presentation Transcript

Community characteristics
Community Characteristics

  • Interactions among species

  • Species diversity

  • Trophic structure


Species diversity
Species Diversity

  • Species richness

    • The total number of different species

  • Species abundance

    • The proportion each species represents of the total individuals in the community




Species richness
Species Richness

  • Heterogeneous vs homogeneous distribution



Trophic structure
Trophic Structure

  • Feeding relationships between organisms

  • Transfer of food energy through food web

    • Influences community dynamics

    • Producers vs Consumers

  • Primary energy source is sunlight

    • Conversion of this energy source through trophic structure

    • Energy conversion is inefficient

      • Energy enters system as sunlight “lost” as heat

    • Food chain vs food web

      • Illustrates trophic interactions


Trophic structure1
Trophic Structure

  • Producer

    • autotrophic

    • Converts sunlight energy into chemical energy

    • Sun to sugars

  • Consumer

    • Primary consumer

      • Trophic level that feeds on producers

      • herbivores

    • Secondary consumer

      • Trophic level that feeds primarily on primary consumers

      • Typically smaller carnivores

    • Tertiary consumer

      • Trophic level that feeds primarily on secondary consumers

    • Quaternary Consumer

      • Trophic level that feeds primarily on teriary consumers


Trophic structure2
Trophic Structure

  • Detritivores

    • In soil

    • Feed on detritus (dead material)

    • Soil scavengers

    • Earthworms, soil nematodes

  • Decomposers

    • Recycle nutrients

    • Fungus, bacteria


Food chain
Food chain

  • Detritivore

  • Decomposers

  • Omnivores?



Food web1
Food Web

  • Linkage based on trophic levels

  • Species can occupy more than 1 trophic level

  • Diagram complex relationships


Limitations of food chain
Limitations of food chain

  • 4-5 levels (9)

  • Energetic Hypothesis

    • Inefficiency of E transfer

    • 10 % rule

  • Dynamic stability hypothesis

    • Long chains lack stability

    • Magnification of fluctuations in variable environments






Dominant species
Dominant species

  • Species found in highest abundance or biomass in a community

  • Biomass

    • The sum weight of all individuals in a population

  • Important in interspecific interactions

  • Influence abiotic factors

  • Exploit competitive advantage or predator avoidance

    • Ex Invasive species

  • Absence impacts environment

    • Ex chestnut blight (40% of canopy cover)

      • Impacted insect diversity (7 extinct out of 56)

    • Redundancy model of community structure

      • Other tree spp (resources) remained

    • Focus on biotic impact




Keystone species
Keystone Species

  • Not necessarily dominant species in a community

  • Occupy a critical niche occupation that controls the community structure

  • Pisaster vs Mytilus (keystone vs dominant)

    • Offset competitive advantage

    • 15-20 ---5

  • Sea Otter

    • Dynamic stability hypothesis??




Foundation species
Foundation Species

  • ecosystem engineers

  • Influence environment by causing physical changes to the structure of the community

  • Use behavior or biomass


Community stability
Community Stability

  • Ability to resist disturbance

  • Natural disturbances

    • Storm

    • Fire

    • Flood

    • Results in patterns of ecological succession

  • Unnatural

    • Human induced disturbance


Disturbance
Disturbance

  • Any event that that changes a community, removes organisms, alters resources

  • Stability

    • Ability of a community to recover from sisturbance

  • Natural disturbance

  • Unnatural disturbance







Succession
Succession

  • Ecological Succession

    • Progression of change in plant community in recovery progress

  • Primary Succession

    • Ecological succession in communities where extreme disturbance has occurred

    • Soil not intact after disturbance

  • Secondary Succession

    • Ecological succession in communities where less extreme disturbance has occurred

    • Soil intact after disturbance



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