Population dynamics

• Population dynamics

  A subfield of ecology that focuses on the study of how the size, structure, and growth of populations of organisms change over time and in response to various environmental factors
• Population dynamics


  • Concerns the factors influencing the expansion, decline, and maintenance of the population to create a total growth rate
  • Three factors that contribute to this growth rate: fertility (birth rate), migration, and mortality
• Factors that will increase the population of a country

  • Births
  • Immigration
• Factors that will decrease the population of a country

  • Death
  • Emigration
• Population Size (N)


  The total number of individuals of a species in a given area at a specific time
• Birth Rate (Natality)

  The number of offspring produced per unit of time within a population
• Death Rate (Mortality)


  The number of individuals that die per unit of time within a population
• Immigration (I)

  The movement of individuals INTO a population
• Emigration (E)

  The movement of individuals OUT of a population
• Population Growth Rate (r)


  The net change in population size per unit of time, calculated as the difference between birth rate and death rate
• Exponential growth


  Where the population size increases rapidly and continuously over time in the absence of limiting factors
• Carrying Capacity (K)


  The maximum population size that an environment can support sustainably over the long term
• Factors Influencing Carrying Capacity

  • Resource availability, habitat space, and environmental conditions
• Logistic Growth


  Characterized by an initial exponential growth phase followed by a stabilization of population size as it approaches carrying capacity
• Density-Dependent Factors


  Factors that have a greater impact as population density increases (e.g., competition, predation, disease)
• Density-Independent Factors


  Factors that affect population growth regardless of population density (e.g., weather events, natural disasters)
• Mutualism

  A positive interaction where two species benefit from their association
• Parasitism

  An interaction where one species (parasite) benefits at the expense of another species (host)
• Commensalism

  An interaction in which one species benefits, while the other is neither helped nor harmed
• Cohort life table


  Cohort is a group born during the same time period
• Static life table


  A snapshot of survival within a population during a short interval of time
• Age distribution


  The proportion of individuals of different ages within a population
• Crude birth rate (CBR)


  Total number of births per 1000 individuals
• Crude death rate (CDR)

  Total number of deaths per 1000 individuals
• Total fertility rate (TFR)


  Average number of births per woman of child-bearing age