Populations and Communities · Paper 1 — Free Biology HL Practice Questions

A laboratory culture of Paramecium aurelia is grown in a closed flask with limited nutrients. The population grows slowly at first, then accelerates, and finally stabilizes at approximately 500 individuals per mL. Which growth model best describes this population, and why?

A population of sea otters has a carrying capacity ($K$) of 200 individuals. The current population size ($N$) is 50 individuals and the per capita growth rate ($r$) is 0.4 per year. Using the logistic growth model $\dfrac{dN}{dt} = rN\left(\dfrac{K-N}{K}\right)$, what is the current annual growth rate of this population?

In a logistic growth model, a population has reached exactly half its carrying capacity. Which statement correctly describes the per capita growth rate and the carrying capacity at this point?