Ecosystems, Terrestrial and Aquatic Biomes: Practice Questions

Which of the following processes in the nitrogen cycle is primarily responsible for converting ammonium \( (NH_4^+) \) into nitrites \( (NO_2^-) \) and subsequently into nitrates \( (NO_3^-) \)?

In a coastal wetland ecosystem, the Net Primary Productivity (NPP) is measured at \( 2,500 \text{ g C/m}^2/\text{yr} \). If the respiration loss \( (R_a) \) by the phytoplankton and aquatic plants is found to be \( 1,800 \text{ g C/m}^2/\text{yr} \), what is the Gross Primary Productivity (GPP) of this ecosystem?

Consider the rule of 10% in ecological pyramids. If the Net Primary Productivity (NPP) of an ecosystem is \( 12,000 \text{ kcal/m}^2/\text{yr} \) and the Respiration (R) by producers is \( 8,000 \text{ kcal/m}^2/\text{yr} \), what is the maximum energy available to the tertiary consumers, assuming a strict 10% transfer efficiency between each trophic level?

A specific terrestrial ecosystem has a Gross Primary Productivity (GPP) of \( 45,000 \text{ kcal/m}^2/\text{yr} \). The producers in this ecosystem lose \( 28,000 \text{ kcal/m}^2/\text{yr} \) to respiration. If the trophic transfer efficiency from producers to primary consumers is \( 12\% \), and from primary consumers to secondary consumers is \( 10\% \), calculate the energy available to the secondary consumers.

In a nitrogen-limited marsh ecosystem, the total annual biomass production is \( 15,000 \text{ kg/ha} \). The plants in this ecosystem have an average energy content of \( 4.5 \text{ kcal/g} \). If the autotrophic respiration \( (R_a) \) accounts for \( 55\% \) of the Gross Primary Productivity (GPP), calculate the total GPP of the marsh in \( \text{kcal/m}^2/\text{yr} \).

In a forest ecosystem, the Gross Primary Productivity (GPP) is measured at \( 32,000 \text{ kcal/m}^2/\text{yr} \) and the Net Primary Productivity (NPP) is \( 14,000 \text{ kcal/m}^2/\text{yr} \). Calculate the amount of energy used by the producers for their own cellular respiration \( (R) \) and explain why this value is always positive.

In a temperate forest food web, the net primary productivity (NPP) is measured at \(8,000\text{ kcal/m}^{2}\text{/yr}\). If respiration losses (R) are \(12,000\text{ kcal/m}^{2}\text{/yr}\), calculate the Gross Primary Productivity (GPP) and estimate the energy available to tertiary consumers.

Unit 1: The Living World: Ecosystems
An ecologist is studying the energy flow in a temperate deciduous forest ecosystem. The net primary productivity (NPP) of the forest is measured at \( 8000 \text{ kcal/m}^2\text{/yr} \). The respiration loss by the producers is estimated to be \( 12000 \text{ kcal/m}^2\text{/yr} \).
(a) Calculate the Gross Primary Productivity (GPP) of this ecosystem. Show your work.
(b) If the secondary consumers in this ecosystem have a net secondary productivity of \( 80 \text{ kcal/m}^2\text{/yr} \), calculate the ecological efficiency between the primary consumers and the secondary consumers, assuming the primary consumers consume \( 1000 \text{ kcal/m}^2\text{/yr} \) of energy from the producers and have a net productivity of \( 800 \text{ kcal/m}^2\text{/yr} \).
(c) Describe two factors that could lead to a decrease in the NPP of this forest ecosystem over time. <\/p>

A coastal temperate rainforest ecosystem is being studied for its carbon sequestration and energy dynamics. Researchers have measured the following data over a one-year period:
- Solar radiation reaching the canopy: \( 1,500,000 \text{ kcal/m}^2/\text{yr} \)
- Gross Primary Productivity (GPP): \( 32,000 \text{ kcal/m}^2/\text{yr} \)
- Net Primary Productivity (NPP): \( 12,000 \text{ kcal/m}^2/\text{yr} \)

(a) Calculate the photosynthetic efficiency of this ecosystem. Show your work.
(b) Calculate the total amount of energy lost as heat through respiration by the primary producers in this forest.
(c) If a secondary consumer in this forest requires \( 450 \text{ kcal/m}^2/\text{yr} \) to maintain its population, and the trophic transfer efficiency from one level to the next is consistently \( 10\% \), determine if the current NPP is sufficient to support a quaternary consumer level that requires \( 5 \text{ kcal/m}^2/\text{yr} \).
(d) Explain how a significant increase in turbidity in the local atmosphere (due to nearby industrial activity) would likely impact the Net Ecosystem Productivity (NEP) of this forest.