Which phase is characterized by a balance of cell division and cell death, resulting in no net change in population size?

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

Answer: (C)

The phase described is the stationary phase. In a closed system, nutrients become limited and waste products accumulate, so the rate at which cells divide slows down while the rate at which they die continues, and these two rates balance out. As a result, the total population size remains constant even though individual cells are still alive and some are dividing. Cells shift into maintenance and stress-response modes during this phase, with some cells becoming dormant or entering protective states to endure the unfavorable conditions.

Before this phase, cells may undergo a lag phase where there’s little to no division as they adapt. After, the culture can enter a death phase where death outpaces division and the population declines. The exponential or log phase is characterized by rapid, unchecked division due to abundant nutrients and low accumulated waste.