IB ESS SL 2.2.13 Gross and Net Productivity Questions
Distinguish gross productivity from net productivity and interpret ecological production data.
- Syllabus
- First assessment 2026
- Course
- ESS SL
- Level
- SL
Exam points
- define GP and NP, then use NP = GP − R to account for respiratory losses
- explain contrasting GP values from rainfall and temperature patterns shown in environmental data
- calculate consumer gross productivity from dry food eaten minus faecal loss per unit time
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IB ESS SL 2.2.13 Gross and Net Productivity Questions 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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