Population growth model

• Population growth models


  Theoretical frameworks used by population ecologists to predict how the size of a particular population will change over time under different conditions
• Population growth

  1. Populations are dynamic-increasing and decreasing in response to changes in the biotic and abiotic environments

  2. Look at population growth in the presence of abundant resources

  3. Look at growth where resources are limited

  4. How the environment can act to change birthrates and death rates
• Population growth rate


  The change in number of individuals in a population over time
• Population growth rate equation

  dN/T = rN
• Exponential growth model


  • Condition: In the presence of abundant resources, populations can grow at exponential rates
  • Key concept: The population grows at a constant rate and the size of the population increases exponentially over time, assuming unlimited resources and no constraints on growth
• Exponential growth formula


  dN/dt = rmaxN
• Exponential growth in nature


  • Bacterial population growth in a laboratory setting with unlimited nutrients and ideal conditions
• Logistic growth model


  Condition: Unlike exponential growth, logistic growth considers environmental limitations and resource constraints<|>Key concept: The population initially grows exponentially. However, as the population size N approaches the carrying capacity K, the growth rate slows down and eventually levels off
• Carrying capacity


  The population size at which growth stops<|>Number of individuals of a particular population that the environment can support
• Logistic growth in nature

  • Yeast population growth in a test tube, where growth levels off as the population hits the limit of the available nutrients
• Under the exponential growth model, the population size is predicted to be 453 squirrels in three years
• Logistic growth produces a sigmoidal, or S-shaped growth curve
• Factors affecting population growth

  • Resource availability
  • Competition
  • Carrying capacity
  • Density-dependent factors
  • Environmental conditions
  • Human intervention