index Drain Logistic Compete Coop Exclus Interact Oscillat Preypred Netprod
Openaq Pulse Saltmrsh Prairie Fire Lagoon Climax Species Specarea

Logistic Growth

Description:

If a population of microbes grows on a constant-pressure source, it increases exponentially. But the death rate is also increased because of more interactions and crowding, so the population levels off. When the deaths equal the births, the population reaches a steady state.

Examples:

  • Experiment with laboratory mice
  • Populations of people in big cities
    		•  Diagram

    Variables:

    E = constant-pressure energy source
    Q = stored quantity (population)
    K1 = increasing factor
    K4 = decreasing factor

    Equations:

    DQ = K1*E*Q - K4*Q*Q

    Simulation:

    The graph shows the changes of Q over a time period.
    Source code: Logistic.java

    "What if" Experiments:

    Think about a population of mice:

  • If you put many more mice in the cage at the beginning of your experiment, would they all survive or would the population decrease?
  • If you tried the mice experiment with another species which was less sensitive to crowding, which variable would you change?
    		•