8.4 Effect of Density in Populations

    Cards (15)

    • Population density
      How close individuals within a population live near one another
    • Abundance of food available
      Population can become dense, higher reproductive rate, space is limited
    • Food is limited
      Density of population may decrease, lower reproductive rate, individuals can spread out in limited space
    • Limits to population growth
      • Density dependent factors
      • Density independent factors
    • Density dependent factors
      Abiotic or biotic factors whose effect on population size relies on population densities (e.g. competition for resources, territoriality, disease, predation)
    • Density independent factors
      Abiotic or biotic factors that affect population size regardless of population density (e.g. natural disasters, pollution)
    • A population can produce a density of organisms that exceeds the system's resource availability
    • Logistic growth model
      Population growth that initially starts slowly, immediately followed by exponential and ends with a relatively stable maximum growth, illustrated as an S-shaped curve
    • Carrying capacity
      Maximum number of individuals the environment can sustain
    • Density dependent and density independent limiting factors can cause a population to reach carrying capacity
    • Under certain conditions, a population can temporarily exceed the carrying capacity
    • Fluctuations in population size can naturally occur at or near carrying capacity
    • When density dependent and density independent factors are imposed, a logistic growth model generally ensues
    • Density Independent Factors

      Natural Disasters
      Pollution
    • Density Dependent Factors

      Competition for resources
      Territoriality
      Disease
      Predation
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