Energy and ecosystems：練習題

In a specific grassland ecosystem, the Gross Primary Production (GPP) is calculated as \(45,000\,kJ\,m^{-2}\,year^{-1}\). If the respiratory losses (R) of the producers are \(28,000\,kJ\,m^{-2}\,year^{-1}\), what is the Net Primary Production (NPP)?

A researcher is studying the energy flow in a grassland ecosystem. The following annual data was collected:
- Gross Primary Production (GPP): \(7.5 \times 10^4\,kJ\,m^{-2}\)
- Energy used by producers in respiration (R): \(4.8 \times 10^4\,kJ\,m^{-2}\)

What is the Net Primary Production (NPP) and what percentage of the GPP is lost to the environment as heat?

A researcher calculates the energy transfer in a food chain. A primary consumer ingests food with a chemical energy store of \(2,500\,kJ\,m^{-2}\). It loses \(1,100\,kJ\,m^{-2}\) in faeces and urine, and \(950\,kJ\,m^{-2}\) is lost as heat due to respiration. Calculate the net production of the consumer (N).

A specific crop has a Gross Primary Production (GPP) of \(1.2 \times 10^5\,kJ\,m^{-2}\,yr^{-1}\). If the Net Primary Production (NPP) is \(5.4 \times 10^4\,kJ\,m^{-2}\,yr^{-1}\), calculate the energy lost to the environment as heat via respiration and state what percentage of the GPP this represents.

Why is the dry mass, rather than the fresh mass, used to measure the biomass of organisms in an ecosystem?

In an ecosystem, the total chemical energy store in plant biomass within a specific area and time is known as Gross Primary Production (GPP). Once respiratory losses (R) are subtracted, what is the resulting chemical energy store called and what are its two primary uses in the plant?

A farmer grows a crop where the Gross Primary Production is \(9.0 \times 10^4\,kJ\,m^{-2}\,yr^{-1}\). If \(55\%\) of this energy is lost as heat through respiration, calculate the Net Primary Production (NPP) available to the next trophic level.

In an ecosystem, explain why the Net Primary Production (NPP) is always lower than the Gross Primary Production (GPP), referencing the metabolic process involved.

In an agricultural study, researchers estimated the energy transfer between trophic levels in a cattle-based food chain. The following data was collected:
- Gross Primary Production (GPP) of the pasture: \(3.5 \times 10^4\) kJ m\(^{-2}\) yr\(^{-1}\)
- Respiratory losses of the grass (R): \(1.2 \times 10^4\) kJ m\(^{-2}\) yr\(^{-1}\)
- Energy stored in the biomass of cattle (secondary production): \(4.6 \times 10^2\) kJ m\(^{-2}\) yr\(^{-1}\)

a) Calculate the Net Primary Production (NPP) of the pasture. Show your working.
b) Calculate the percentage efficiency of energy transfer from the Net Primary Production of the pasture to the cattle. Give your answer to two decimal places.

A researcher investigated the energy budget of a population of insects. The energy content of the food ingested (I) was measured as \(4.5 \times 10^5\,J\). The energy lost in faeces and urine (F) was \(1.8 \times 10^5\,J\), and the energy lost via respiration (R) was \(2.1 \times 10^5\,J\).

(a) Calculate the Net Production (N) for this population. (1 point)
(b) Calculate the percentage efficiency with which these insects convert ingested energy into biomass. (2 points)
(c) Suggest one reason why the energy lost in faeces is higher in primary consumers (herbivores) than in secondary consumers (carnivores). (2 points)