Question

open response: the graph below depicts the growth of a yeast population in a test tube containing nutrient broth. part a: at what point on the graph would a density - dependent limiting factor have the greatest effect on the population? part b: explain why it would have the greatest effect at this point.

Explanation:

Part A

Step1: Analyze yeast growth phases

Yeast growth typically has lag, log (exponential), and stationary phases. The graph's regions: A (lag), B (log), C (stationary). Density - dependent factors (e.g., competition, waste) act more when population is dense.

Step2: Identify the point

In the stationary phase (point C), population density is highest. So a density - dependent limiting factor has the greatest effect at point C (or the end of the growth curve, where population is most dense).

Part B

Step1: Recall density - dependent factors

Density - dependent factors depend on population size (e.g., competition for nutrients, space; waste accumulation).

Step2: Explain effect at high density

At point C (high population density), yeast cells are numerous. Competition for limited nutrient broth, space, or accumulation of toxic wastes is most intense. More individuals mean more pressure from these factors, so a density - dependent factor (like nutrient depletion or waste buildup) will impact the population most here as resources are scarce and competition is fierce.

Answer:

(Part A): Point C (or the region of highest population density on the graph, typically the stationary phase part of the yeast growth curve)