Ecology: Practice Questions

Which of the following is considered a biotic factor that can limit the population size of a species within a grassland ecosystem?

A community of organisms undergoes primary succession on a newly formed volcanic island. Which of the following best describes the change in the ratio of Gross Primary Productivity (GPP) to Total Community Respiration (R) as the ecosystem transitions from a pioneer community to a climax community?

A researcher is studying the nitrogen cycle in a waterlogged soil. They observe a significant increase in the release of nitrogen gas \( (N_{2}) \) into the atmosphere. Which process is occurring, and what is the primary ecological condition driving this transformation?

In an aquatic ecosystem, the initial concentration of dissolved oxygen (DO) in a sample is \( 8.2\text{ mg L}^{-1} \). After incubating a second sample in the dark for 5 days at \( 20^{\circ}\text{C} \), the DO drops to \( 3.4\text{ mg L}^{-1} \). A third sample incubated in the light for the same period shows a DO of \( 9.8\text{ mg L}^{-1} \). What is the Gross Primary Productivity (GPP) of this system expressed in terms of oxygen production?

Consider the nitrogen cycle in an anaerobic soil environment such as a wetland. Farmers drain the wetland for agriculture, significantly increasing the oxygen levels in the soil. Which of the following transformations is most likely to decrease in rate as a result of this increased aeration?

Calculate the Net Primary Productivity (NPP) of an ecosystem where the Gross Primary Productivity (GPP) is \( 45,000\text{ kJ m}^{-2}\text{ yr}^{-1} \) and respiration losses (R) are \( 22,000\text{ kJ m}^{-2}\text{ yr}^{-1} \).

Discuss the ecological implications of trophic efficiency being typically only \( 10\% \) for the maximum length of food chains and the total biomass of top predators.