Food Chains and Food Webs — Revision Notes

⚡ 30-Second Revision

Revision checked 17 October 2026.

Arrows usually run food → consumer.
Webs contain multiple paths.
Omnivores can occupy different trophic positions.
Biomass stock differs from energy flow.
Count transfers, and qualify cascade predictions.

2-Minute Revision

A chain is one pathway through a web. Detritus links dead material to consumers and decomposing organisms. A bird eating seeds and herbivorous insects has different trophic positions along those paths. Energy declines through transfers; a small producer standing biomass can still support consumers through rapid turnover. Apply ten-percent transfer only as the stated exercise assumption.

5-Minute Revision

Original drill: A diagram contains plants → insects → birds and plants → birds. The bird occupies the primary-consumer position on the direct seed path and a higher position on the insect path. Removing insects does not establish that all birds disappear because another food path exists, although its adequacy is unknown.

Explain the difference between a possible alternative and proof that the population is unaffected. Add dead leaves as a detrital input and show why the network extends beyond the living-plant chain.

Vyyuha Quick Recall

WEB: Who eats whom; Energy transfers; Biomass versus flow. Use the three checks before interpreting a diagram.