Chapter 56

• Population ecology


  The study of factors that affect population size and how these factors change over space and time
• Population


  A group of interbreeding individuals of the same species occupying the same area at the same time
• Population density


  The number of organisms of a given species in a given unit area or volume
• Methods to quantify population density

  1. Simple visual count

  2. Various sampling devices, traps, and capture techniques
• Problems can arise with different methods; animals may learn to avoid traps or actively seek out food-baited traps
• Patterns of spacing among individuals in a population

  • Clumped
  • Uniform
  • Random
• Clumped individuals


  • Live close together in groups
• Uniform individuals


  • Live at a constant distance from one another
• Random individuals


  • Live at variable and random distances from one another
• Factors that determine a population's size

  • Rate of natality (birth)
  • Rate of fatality (death)
  • Rate of immigration
  • Rate of emigration
• Demography


  The study of the statistics of a population, especially with regard to size and density
• Life tables


  Provide information on the numbers surviving in each age class in a population
• Survivorship curves


  Visualize the patterns of survival and mortality in populations
• Factors that determine a population's growth

  • Age at first reproduction
  • Frequency of reproduction
  • Average number of offspring
  • Length of reproductive lifespan
  • Average death rate
  • Availability of resources
  • Density-dependent factors