Food Chains and Food Webs — Economic Framework

Economic Framework

Diagram conventions

Resource → consumer shows the direction of material and energy transfer in the usual feeding diagram. Read the legend if another convention is specified. A chain selects one path; a web joins several paths.

Roles

Producer: forms organic matter using an external energy source.
Primary consumer: feeds on producers along the stated path.
Higher consumer: feeds after one or more consumer transfers.
Omnivore: can occupy more than one trophic position.
Detrital pathway: begins with dead organic material and connects with other feeding paths.

Three pyramid measures

Numbers: count individuals, regardless of their size. Biomass: standing mass at a time. Energy: transfer over a stated period and area. Inversion of a biomass snapshot does not imply inversion of energy flow.

Transfer calculation

Count arrows, not organisms. Under an explicitly supplied ten-percent assumption, two transfers multiply the initial energy by 0.1 twice. Actual efficiencies need measurement; the approximation is not an exact universal constant.

Response analysis

Change in a predator or resource → possible effect on the next link → indirect effect elsewhere. Check alternative pathways and environmental conditions before asserting a certain outcome. More producer growth can coexist with later oxygen stress if decomposition increases. For a diagram-based question, use the links actually given; do not import a familiar species relationship that the problem has not specified.