During which phase does population growth occur exponentially due to favorable conditions and intrinsic growth rate depends on nutrients, temperature, and pH?

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

Answer: (C)

The phase where population size increases exponentially under favorable conditions is the log phase, also called the exponential growth phase. In this stage, cells divide at a nearly constant rate because nutrients are abundant, temperature is near optimum, and pH is suitable for enzyme activity and replication. These favorable conditions allow the intrinsic growth rate to be high, so the population doubles in regular, predictable intervals, producing the characteristic rapid rise. Before this phase, cells acclimate with little division during the lag phase; after, resources become limiting and growth slows in the stationary phase, eventually leading to decline in the death phase. The description—exponential growth tied to optimal nutrients, temperature, and pH—fits the log phase best.