Energy & Ecosystems

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  • Energy & Ecosystems
    • Primary Succession
      • The starting point is bare ground (e.g. rock)
      • The introduction of plants/animals into areas that have not previously supported a community
      • First organism to colonise an area = Pioneer Species
        • They form a pioneer community
      • Features of Pioneer Species
        • Early arrivals
        • Can tolerate extreme conditions (e.g. low nutrient levels)
        • Very good means of dispersal (usually by wind)
        • Unable to compete for resources
        • Not influenced by or dependent upon animal species
        • May be able to fix nitrogen and build up soil nutrients
    • Secondary Succession
      • A community is damaged and the soil is left for plants to colonise
      • The re-introduction of organisms into a bare habitat previously occupied by plants and animals
      • If the original vegetation is removed the area is quickly re-colonised by different plants and animals
      • SERES = The different stages in a succession when particular communities dominate
    • How Does Succession Happen?
      • EXAMPLE: In Iceland the island of Surtsey was created by a volcanic eruption
      • Algae and lichen colonised the bare rock
      • Enough soil was produced for larger plants to grow from the build up of dead and decaying organisms
        • These plants succeeded the algae and lichen
      • Larger plants succeeded the smaller plants until a stable community was reached
      • This is a CLIMAX COMMUNITY
      • Sand dunes are interesting because they display all the stages of succession in the same place at the same time
    • Features of Climax Community Species
      • Species found in the end point community
      • Large seeds with a large energy store so seedlings can survive low light intensity
      • Specialised niche
      • Unable to tolerate great fluctuations in the water content of soil
      • Strongly influenced by other organisms
        • Competitors
        • Herbivores
        • Seed dispersal agents
        • Soil micro-organisms

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