Stages of the population growth graph

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  • Stages of the population growth graph
    • Lag Phase
      • 1. Small number reproducing because time needed to:
        • Activate genes
        • Synthesis of enzymes for the medium they are in
        • Remember that , if organisms are in an complex growth medium e.g. xylose or sucrose rather, glucose
        • Cells are growing in size before reproducing
        • Proteins are made e.g. photosynth. e.g. enzymes.
    • Log Phase
      • Maximum growth rate
      • Growth is exponential i.e. numbers double i constant time periods/every generation
      • There are no limiting factors e.g. there is plenty of oxygen/nutrients and waste products aren't poisoning them yet.
    • Stationary phase
      • Growth rate /production is slow
      • Limiting factors are in operation (nutrients/oxygen low or competition for them is very high/waste products of metabolism/toxins/extreme pH killing some cells.
      • Number of new cells = number of dying cells
        • Birth rate = death rate
      • Carrying capacity
    • Decline phase
      • Death of cells exceeds production of new cells
      • Waste products/toxin are rapidly killing cells
      • Become overcrowded and starved of nutrients/oxygen.
      • Occurs when all resources have been used up. e.g.nutrients - toxins
      • Building up/space limited/ disease due to overcrowding

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