During which growth phase is the population size constant with some cells dying and others dividing?

• A. Log
• B. Stationary
• C. Lag
• D. Death

Answer: (B)

In this situation, the key idea is that a closed culture reaches a balance between growth and death. During the stationary phase, nutrients become limited and waste products accumulate, so cells can’t keep dividing indefinitely. Yet some cells continue to divide while others die, and these opposing processes roughly offset each other, so the total population size remains about the same.

This isn’t the case in the lag phase, where cells are adapting and not yet multiplying much; nor in the log (exponential) phase, where cells are dividing rapidly and the population grows quickly; nor in the death phase, where death outpaces division and the population declines.