Population and Sustainability

  • Created by: ems2001
  • Created on: 12-11-18 09:19
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  • Population and Sustainability
    • Population size is total number of organisms of 1 species in a habitat.
      • This can change over time because of the effects of various factors.
    • Abiotic factors and population size
      • E.g. amount of light, water or space available, and temperature of surroundings.
      • When these are ideal for a species, organisms can grow fast and reproduce successfully.
    • Biotic factors and population size
      • E.g. interspecific and intraspecific competition, and predation.
      • Intraspecific competition
        • Between members of same species.
        • 100% niche overlapping as they require same resources.
        • During stationary phase this competition keeps the population relatively stable.
          • If population size decreases, competition decreases and size can increase.
          • If population size increases, competition increases and size decreases.
      • Interspecific competition
        • Between members of different species.
        • Affects population size and distribution of species'.
        • Niches don't overlap completely, some species have very close niches but not the exact same.
          • Reduced competition so both can survive in same habitat.
            • E.g. Nuthatch and Brown Creeper are birds that forage on the same trees for insects, but one works its way up the tree and the other down, therefore they eat different insects so competition is reduced.
        • Rare to find 2 closely related species in same area as competition would be too great for both to survive.
      • Competitive Exclusion Principle
        • 2 species competing for the same limiting resource in an area cannot coexist.
        • 1 species will be the better competitor and the other will be displaced or excluded.
    • Factors affecting population size
      • Limiting factors
      • Carrying capacity
      • Density dependent mortality factors, e.g. competition for food etc.
      • Density independent mortality factors, e.g. diseases.
    • Population growth curve
      • Lag phase: growth begins slowly from few individuals.
      • Log phase: exponential growth occurs, conditions are ideal, maximum growth rate reached.
      • Stationary phase: growth rate slows as resources become limited (intraspecific competition).
      • Stable phase: carrying capacity reached, population is stable.
      • Death phase: environment can no longer support population.
    • Conservation and Preservation
      • Conservation
        • Wise use.
        • Limited, sustainable, responsible, human development.
        • Human management to protect natural integrity.
        • E.g. woodland management, Marwell Zoo breeding programs.
      • Preservation
        • Untouched.
        • No human development, use or management.
        • E.g. National parks (Studland).
    • Fishing
      • Issues
        • Overfishing
        • Incidental catch of non-target animals (Bycatch)
        • Discards
        • Habitat destruction
        • Illegal, unreported or unregulated fishing
      • Solutions
        • Fishing quotas
          • Set number of fish companies are allowed to catch.
          • Both difficult to monitor and have penalties if not obeyed.
        • Mesh sizes
          • Controlling sizes of holes in nets to allow young fish to escape and keep population alive.
          • Both difficult to monitor and have penalties if not obeyed.
    • Woodland management
      • Issues
        • Logging for products and space
        • Pollution from coal-burning
        • Global warming
      • Solutions
        • Rotational coppicing
        • Selective cutting
        • Control pests

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