population growth in a closed culture

• Lag phase

  • organisms adjusting to their surroundings
  • taking in water, growing, switching genes on and off, making enzymes
  • active cells but not reproducing
  • numbers do not build up very quickly
  • length of this phase depends on conditions
• exponential growth phase

  • organisms multiply rapidly
  • size of population doubles each generation
  • in bacteria generation time can be only 30 minutes
• stationary phase

  • the rate of reproduction begins to slow
  • some organisms stop reproducing and start to die
  • lack of food
  • waste or metabolites build up
  • births = deaths
  • in a closed system this represents the carrying capacity of the environment
• death phase

  • deaths outnumber births
  • food has run out
  • waste or metabolites at toxic levels
  • in a closed system this would lead to extinction