Unit 2: Ecosystems and Ecology

Topic 2.5: Flows of Energy and Matter Questions

Practice 20 exam-style questions for IB ESS Topic 2.5. Review the question stems below, then unlock the full Question Bank to access markschemes, model answers, and AI grading.

1state1 mark
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State the typical units for a pyramid of biomass.
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2state1 mark
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State the first law of thermodynamics.
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3write1 mark
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Write the formula linking net productivity (NP), gross productivity (GP), and respiration (R).
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4identify1 mark
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A food chain is phytoplankton → zooplankton → sardine → tuna. Identify the primary consumer.
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5state1 mark
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State the second law of thermodynamics.
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6outline4 marks
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Outline the role of producers in ecosystems and explain why they are essential for energy flow.
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7state1 mark
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State the approximate percentage of energy passed on to the next trophic level (the 10% rule).
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8state1 mark
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State what is meant by net productivity (NP).
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9define1 mark
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Define the term energy efficiency in a food chain.
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10outline1 mark
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Outline what is meant by gross productivity (GP).
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11define1 mark
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Define the term productivity as used in ecosystem studies.
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12define1 mark
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Define the term biomass as used in ecological pyramids.
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13state1 mark
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State one reason why biomass is measured as dry mass rather than fresh mass.
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14outline1 mark
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Outline what a pyramid of numbers shows.
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15explain4 marks
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Table 1 shows energy stored as biomass at three trophic levels in a grassland.
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16describe1 mark
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Describe one reason why approximately 90% of energy is lost between trophic levels.
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17calculate1 mark
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Figure 1 includes energy values for the grasshopper and frog. Calculate, as a percentage, the efficiency of energy transfer between grasshopper and frog.
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18calculate1 mark
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Figure 2 includes energy values for shrimp and mackerel. Calculate, as a percentage, the efficiency of energy transfer between shrimp and mackerel.
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19define2 marks
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Define the term pyramid of energy.
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20calculate5 marks
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Figure 1 shows the energy flow through trophic levels in a grassland ecosystem.
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