Worked example
In a simplified kelp bed, sea urchins eat kelp and otters eat urchins. Under otherwise similar conditions, fewer otters may mean less predation on urchins. More surviving urchins may graze more kelp. That two-link argument gives a plausible effect on kelp without assuming any immediate or exact population change.
Contrast and common error
In a larger web, urchins may eat several foods and have other predators. A drawn link shows a path, not the fraction of food obtained there. If a model supplies numbers for stored biomass energy, compute the fraction from those numbers rather than applying a fixed transfer percentage.
Transfer check
A model bird eats both caterpillars and seeds. A season reduces caterpillars. Does the diagram imply the bird loses all food? Check: seeds still give another route if they remain available. Their presence in the diagram alone gives no amount.
Try it, then explain it.
Complete a short set without looking at the example. After each answer, explain which evidence or rule supports your decision and why the alternatives do not fit.
Sources & authorship
Original OpenExam explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.
OpenStax Biology 2e 46.2 Energy Flow through Ecosystems