IB ESS SL 2.2.17 Ecological Pyramids Questions
Interpret pyramids of numbers, biomass and energy and identify their limitations.
- Syllabus
- First assessment 2026
- Course
- ESS SL
- Level
- SL
Exam points
- distinguish numbers, biomass and productivity pyramids by what they measure, when and in which units
- design pyramid-of-numbers data collection using quadrats or mark-release-recapture and proportional bars
- evaluate a pyramid-of-productivity model using its energy-flow strengths and data-collection limitations
- explain inverted or changing pyramid shapes using organism size, standing stock, seasonality and energy loss
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IB ESS SL 2.2.17 Ecological Pyramids Questions question 1
[Maximum number: 7]
Explain why pyramids of numbers, biomass and productivity may vary in shape for different food chains.
a. pyramids of productivity tend to get smaller at higher levels;
b. this is because energy is lost between trophic levels;
c. seasonal productivity at lower levels could temporarily be smaller;
d. ...but annual productivity should always decrease at higher levels;
e. pyramids of numbers tend to get smaller at higher levels due to losses;
f. ...but may get larger if individuals at lower trophic levels are larger (e.g. trees);
g. pyramids of biomass tend to get smaller at higher levels due to losses;
h. ...but as they reflect standing stock (and not rate of flow) they can be inverted;
i. pyramids may become larger at higher levels if they represent a single food chain in a larger food web;
j. ...because more biomass may be fed in from other food chains;
k. food chain with more trophic levels will have longer shape;
I. pyramids of productivity tend to be pyramid shaped because they show flow of energy over time;
m. ...and because the second law of thermodynamics means energy is lost in the flow;
Note: Alternative valid points describing/explaining why pyramid shape may vary can be credited.
Do not credit vague statements claiming shape will be "different" without explaining in what way it will differ.
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