IB ESS HL 2.2.13 Gross and Net Productivity Question Bank
Distinguish gross productivity from net productivity and interpret ecological production data.
- Syllabus
- First assessment 2026
- Course
- ESS HL
- Level
- HL
Exam points
- identify the ecological process or energy relationship
- apply the correct thermodynamic, productivity or trophic concept
- justify the conclusion from evidence and system boundary
2.2.13—Gross and net productivity question 1
[Maximum number: 7]
Define the terms gross primary productivity (GPP) and net primary productivity (NPP). Explain, with reference to two contrasting biomes, why one biome will be more productive than the other.
Marking guidance:
Award [2 max] for definition of GPP and NPP.
gross primary productivity/GPP is the (total) gain in energy or biomass (per unit area per unit time) by photosynthesis/plants/primary producers;
net primary productivity/NPP is the amount available to consumers in an ecosystem;
that is, the gain in energy or biomass after allowing for respiratory losses/ NPP=GPP-R where R= respiratory loss;
Award [5 max] for explanation of productivity in biomes.
e.g. tropical rainforests:
light/insolation/sunlight and rainfall/precipitation ( 2500 mm per annum) are not limiting/optimal;
and temperatures are high throughout the year;
e.g. deserts:
do not have enough rainfall/precipitation ( 250 mm per annum);
light is not limiting/have high temperatures (in the day);
distribution of rainfall throughout the year is as important as the total amount;
Award [1] for correctly identifying difference in productivity between two biomes. e.g. tropical rainforests have higher rates of productivity than deserts;
other limiting factors e.g. availability of nutrients/plant diversity play a part;
Award [3 max] if two named biomes are not included/used correctly or general responses.
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