IB Biology HL C4.2.11 Energy Pyramids Questions

Interpret and construct energy pyramids from productivity data, calculate trophic transfer or loss, and evaluate multi-level feeding and other model limitations in IB Biology HL C4.2.11.

Exam points

Define and interpret energy pyramids as energy available at each trophic level per unit area per unit time, and identify correct units and trophic labels.
Construct, calculate or compare energy-pyramid bars from productivity or energy-flow data, including percentage transfer or loss between named trophic levels.
Evaluate energy pyramids as models by explaining declining bar widths from trophic transfer and limitations such as multi-level feeding, time variation and omitted pathways.

[Maximum number: 6]

Ecologists sometimes display data from an ecosystem using a diagram called a pyramid of energy. Describe what is shown in pyramids of energy.

pyramid of energy shows the flow of energy from one trophic level to the next (in a community);
units of pyramids of energy are energy per unit area per unit time $/ \mathrm{kJ} \mathrm{m}^{-2} \mathrm{yr}^{-1}$ ;
bar width is proportional to the energy stored (in the biomass) in that trophic level;
the first/lowest trophic level is producers;
second level is primary consumers/herbivores;
third level of secondary consumers/carnivores;
only a small amount (10 to 20 % ) of energy of one level is passed to the next;
bar width/energy stored in the trophic level decreases (proportionally) as you go up each level;
pyramid shows that there is a limit to the length of food chains;

Award any of the above marking points to a correctly drawn and clearly labelled pyramid.

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IB Biology HL C4.2.11 Energy Pyramids Questions question 1