Which phase represents the end of the growth cycle with a decline in population?

The phase that signifies the end of the growth cycle with a decline in the population is the Death Phase. During this stage, the number of viable cells decreases as the waste products accumulate and resources become insufficient to support cell growth. Factors such as nutrient depletion and toxic byproducts cause many cells to die, leading to a net decline in the overall population.

In contrast, the Lag Phase is primarily characterized by the adaptation of microorganisms to their new environment, where there is little to no cell division and population growth does not occur yet. The Exponential Phase, also known as the log phase, sees cells dividing at a constant rate, leading to rapid population increase. The Stationary Phase is when the growth rate slows and stabilizes due to limitations in resources or accumulation of waste, resulting in a balance between cell division and death, but it does not represent a decline. Thus, the Death Phase distinctly marks the transition to a declining population, primarily due to negative environmental factors impacting cell viability.