Energy & Biomass in Ecosystems (DP IB Environmental Systems & Societies (ESS): HL): Exam Questions

Explain how the first law of thermodynamics is demonstrated in the figure below, as solar energy flows through the primary producers.

Explain how the second law of thermodynamics applies to the food chain shown in the figure below.

Identify four factors that contribute to the controversial nature of using the insecticide DDT.

The figures below show a pyramid of numbers and a pyramid of biomass for a tropical rainforest ecosystem.

Explain how the pyramid of numbers shown above can have fewer producers than consumers.

The figures below show a pyramid of numbers and a pyramid of biomass for a tropical rainforest ecosystem.

State one other type of ecological pyramid that can be used to demonstrate trophic levels within ecosystems.

Evaluate pyramids of numbers as a method of representing trophic levels within ecosystems.

Use the figure below to produce a food chain that includes exactly four trophic levels.

Outline how two named human activities can alter the pyramid structure of the trophic levels within a tropical rainforest ecosystem.

Outline the role of primary producers in ecosystems.

Explain the vulnerability of top carnivores to non-biodegradable toxins.

Only around 1% of the light energy that reaches the Earth’s atmosphere is captured by plants and made available to other organisms in the food chain.

Suggest reasons for this low value.

Define the term gross primary productivity.

Woodlice are detritivorous insects (they feed on the dead remains of plants). A biologist estimated the numbers of woodlice at two different sites in a woodland ecosystem. They also estimated the net primary production of the sites to see if this influenced the numbers of woodlice present. Their results are shown in the table below.

Although net primary production is a measure of plant biomass formed per year, it does not represent the total amount of plant biomass formed per year by photosynthesis.

Explain why.

Explain why there is a greater number of woodlice in site X than site Y.

This woodland ecosystem has a total average gross primary productivity of 20 000 kJ m^-2 y^-1 but the net primary productivity is calculated to be 12 000 kJ m^-2 y^-1.

Calculate how much energy one square metre of this grass loses as heat from respiration in one year.

The figure below shows the energy transfers taking place in a simple food chain. The energy values are all given in kJ m^-3 y^-1.

The efficiency of energy transfer can be calculated using the following equation:

Ecological efficiency = (energy used for new biomass ÷ energy supplied) × 100

Use information in the figure and the equation provided to calculate the efficiency of energy transfer for zooplankton.

Explain how chemoautotrophs contribute to food chains in deep-sea ecosystems.

Describe ecological efficiency.

Distinguish between gross secondary productivity and net secondary productivity.

Suggest why photoautotrophs and chemoautotrophs could coexist in the same ecosystem.

Evaluate the use of food webs as models for studying ecosystems.

Discuss the impacts of persistent or non-biodegradable pollutants, such as DDT or mercury, on ecosystems.

Explain the significance of net primary productivity (NPP) for sustainable food production.

To what extent is entropy responsible for limiting the number of trophic levels in ecosystems?