populations

• Biotic factors


  Living factors; the organisms in an environment
• Abiotic factors


  Non-living factors; the physical and chemical properties of an environment
• Dispersal


  Movement of individuals away from centers of high population density or from their area of origin
• Invasive species


  An introduced (non-native) species that becomes overpopulated and harms its new environment
• Population


  A group of individuals of a single species living in the same general area
• Immigration


  The influx of new individuals from other areas
• Emigration


  The movement of individuals out of a population
• Population size


  The total number of individuals in the population (N)
• Population density


  The number of individuals per unit area or volume
• Population dispersion


  The distribution of individuals in the population
• Random dispersion


  Spatial pattern in which the position of each individual is independent of other individuals
• Clumped dispersion


  Spatial pattern in which individuals aggregate in patches
• Uniform dispersion


  Spatial pattern in which individuals are evenly spaced
• Populations


  • Size
  • Density
  • Dispersion
  • Rate of change in size over time
• Measuring population size and density

  1. Count in subplots

  2. Use an indicator of population size

  3. Use the mark-recapture method
• The same biome in different parts of the world harbors different species with similar characteristics
• Biotic factors affect species distributions through species interactions like predation, parasitism, competition, mutualism, and herbivory
• Abiotic factors affect species distributions through physical characteristics like temperature, water, oxygen, salinity, sunlight, rocks, and soil
• Geographic features like mountains and oceans can act as barriers to dispersal, affecting species distributions
• Species transplants can be used to determine if dispersal is limiting a species' distribution
• Population ecology explores how biotic and abiotic factors influence the abundance, dispersion, and age structure of populations
• Births and immigration add individuals to a population, while deaths and emigration remove individuals
• Population size, density, dispersion, and rate of change are influenced by the ecological needs of the species, the distribution and abundance of resources, and the interactions among individuals in the population