What are ecological pyramids? Explain, with diagrams, upright and inverted pyramids of number and of biomass.

1. 1 · Define in one line. An ecological pyramid shows the number, biomass or energy at successive trophic levels; the base is the producers and the apex the top consumers.
2. 2 · Explain the pyramid of number.
   • Upright in a grassland: millions of plants support only a few top carnivores.
   • Inverted for a big tree with many insects feeding on it.
3. 3 · Explain the pyramid of biomass.
   • Upright on land: biomass falls at higher levels.
   • Inverted in the sea: fish biomass far exceeds phytoplankton biomass.
4. 4 · Draw four pyramids. [Bars labelled PP, PC, SC, TC: upright number (grassland), inverted number (tree), upright biomass (forest), inverted biomass (sea)]
5. 5 · Explain the inversions. Counting ignores size, so one tree can feed thousands of insects; phytoplankton reproduce fast, so a small standing crop feeds a larger biomass.
6. 6 · Link to real life. Coastal fisheries depend on fast-growing phytoplankton that support a larger weight of fish.
7. 7 · Close in one line. So pyramids of number and biomass can be inverted, but the pyramid of energy cannot.

Scoring tip: Label every bar (PP, PC, SC, TC) and name the ecosystem under each pyramid. Unlabelled bars lose the diagram mark.