6.4.8(Population growth in a closed culture)

State what is meant by a closed culture

• A population in which all the conditions are set at the start and there is no exchange with the external environment

State the 4 phases in standard growth curve

• Lag phase

• Log phase

• Stationary phase

• Decline phase

Describe the lag phase in the standard growth curve

• Bacteria adjusting to the new conditions

• Takes a while for enzyme production and other molecules needed for production

• rate of reproduction is a little higher than rate of death

Describe the log phase in the standard growth curve

• Favourable reproductive conditions (lots of nutrients, little competition)

• The number of bacteria doubles at regular intervals

• Rate of reproduction is much higher than rate of death

Describe the stationary phase in the standard growth curve

• Rate of reproduction is equal to rate of death

• Bacteria die as not enough nutrients and poisonous waste products begin to build up

Describe the decline phase in the standard growth curve

• Death rate is greater than the reproductive rate

• Nutrients and food is scarce and waste products are at toxic levels

What is the equation to calculate the population of microorganisms

• Number of individuals = Initial number of cells x 2ⁿ (where n is the number of divisions)