Lecture 21-11: Insect Population Dynamics 1

Source

Exponential Growth Model

  • Also referred to as the Malthusian growth model. Thomas Malthus introduced this model in An Essay on the Principle of Population published in 1798.
  • The exponential growth model assumes unlimited resources such as food and space.

dN/dt = rN

where:

  • r is the intrinsic growth rate: (births - deaths)/N
  • N is the population size

Exponential Growth (YouTube; 10 minutes)

References: Wikipedia: Exponential Growth, Wikipedia: Malthusian growth model

Logistic Growth Model

  • Also referred to as the Verhulst growth model. This model was developed by Pierre Verhulst in 1838, after he had read Malthus' essay.
  • The logistic model assumes that resource availability limits the number of individuals in a population to constant K, the carrying capacity.

dN/dt = rN *(K-N)/K

where:

  • r is the instrinsic growth rate
  • K is the carrying capacity, the maximum population size that can be sustained by the environment

Logistic Growth (YouTube; 11 minutes)

Reference: Wikipedia: Logistic Growth

r and K Selection

  • r selected organisms produce many offspring = a high reproduction rate (r)
  • K selected organisms produce few offspring, but put significant resources into ensuring their survival

r/K Selection(YouTube; 7 minutes)

Reference: Wikipedia: r/K Selection Theory