Ecosystem ecology: Ponds, Forests and Who Eats Whom

In the paper

Unit 3 carries 4 of the 40 botany marks; with three chapters sharing them, this one averages a little over one mark (MEC publishes weights by unit, not by chapter). The MEC scope line reads: "Ecosystem ecology: Structural and functional aspects of pond and forest ecosystems, Biotic interactions." Expect three kinds of item:

• Recall — the pond zone with no producers, the organisms at a trophic level, the sign pair (+, −) of an interaction.
• Understanding — why the pyramid of energy never inverts, why a pond's pyramid of biomass can, why most of a forest's energy passes through its litter.
• Application — a 10 per cent calculation, or a described pair of organisms (a yellow twiner on a hedge, an orchid on a mango branch) to classify.

This note goes a level deeper than the unit overview, Ecology and environment.