Make a Conditional Web Prediction
Separate a plausible pathway effect from a guaranteed population count.
Supplied materials
- Use the supplied fictional observations or model. Paper and pencil are optional; spoken answers are welcome. No equipment or real experiment is needed.
Learn the idea
When a food source becomes less available, follow its outgoing arrows to identify consumers whose shown food is reduced. Indirect effects can follow additional arrows. But a web alone does not tell whether animals switch foods, how much remains, or what happens to births and survival. Phrase a prediction conditionally and identify missing information.
The supplied fictional web is grass → grasshopper → frog → hawk and grass → rabbit → hawk, plus pond insects → frog. If grasshoppers decline, frogs lose some food on one route but retain pond insects. A hawk could be affected through frogs, yet rabbits are another shown food source. The diagram supports possible pathways; it does not establish that any named population must decline by a particular percentage.
- Draw all six food-to-consumer arrows.
- Mark the reduced grasshopper → frog route.
- Trace the possible indirect frog → hawk link.
- List the frog and hawk alternatives and write a prediction with a missing-amount limit.
See the method in action
Frogs could have less food if reduced grasshoppers are not replaced by pond insects. That could affect hawks through frogs, but the hawk’s rabbit route remains. No exact population change follows from these arrows alone.
Check your reasoning
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See the answer and explanation
Frog food on one route decreases; pond-insect availability is needed to assess the total effect.
The changed grasshopper link reduces one food route. The supplied alternative and missing quantities limit the prediction.
Take it further
Remove pond insects from the web too. Frogs now have no remaining shown food source, but the diagram still does not give an exact frog count or rule out unlisted real-world food sources.
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