Effect of Density of Populations (College Board AP Biology)

Figure 1. Bacterial population growth in the presence of two nutrients (nutrient I and nutrient II)

Bacteria can be cultured in media with a carefully controlled nutrient composition. The graph above shows the growth of a bacterial population in a medium with limiting amounts of two nutrients, I and II.

Estimate the maximum population density in for the culture. Using the data, describe what prevents further growth of the bacterial population in the culture.

Using the data, calculate the growth rate in  of the bacterial population between hours 2 and 4.

Identify the preferred nutrient source of the bacteria in the culture over the course of the experiment.

Use the graph to justify your response. Propose ONE advantage of the nutrient preference for an individual bacterium.

Describe how nutrient I most likely regulates the genes for metabolism of nutrient I and the genes for metabolism of nutrient II. Provide TWO reasons that the population does not grow between hours 5 and 6.