Predation, Herbivory and Trophic Cascades · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
En anglais

Hunters, herds, and ripple effects

Science · Ecology & Conservation · ages 21-22
Name ______________________   Date ____________

  1. What is herbivory?

    • Animals eating plants
    • Predators eating predators
    • Plants eating insects

  2. In the classic lynx and snowshoe hare trapping record, when do lynx peaks typically occur relative to hare peaks?

    • About 1 to 2 years before the hare peaks
    • At exactly the same time as every hare peak
    • About 1 to 2 years after the hare peaks

  3. Every predator-prey population pair must show regular cycles.

    Circle one:   True   False

  4. In a simple model, crabs limit snail numbers by predation, and snail grazing limits algae. Crabs return after being absent; other conditions stay fixed. What does the model predict?

    • Snails decrease and algae decrease
    • Snails decrease and algae stay unchanged
    • Snails decrease and algae increase

  5. In a simple wolf-deer-tree model, wolves limit deer and deer browsing limits young trees. With other conditions unchanged, what does wolf removal predict?

    • Deer decline and young trees recover
    • Deer surge and young trees decline
    • Deer stay flat and young trees recover

  6. Across replicated plots, fertilizer increases plants, herbivores and predators relative to untreated controls. What conclusion does this result support?

    • The result supports a bottom-up contribution
    • The result shows all levels increased at once
    • The result shows top-down effects are absent

  7. Removing a top predator can only affect its direct prey, never plants two links away.

    Circle one:   True   False

  8. A student excludes predators from one meadow but has no control or repeats. Which improvement best addresses weather, season and fence effects?

    • Repeat exclusions while leaving all comparison meadows unfenced
    • Use replicated controls, including fences that allow predator access
    • Count plants in the same meadow while changing the fence each season
LightMySky · lightmysky.comW1-mt_T0jG4YImZp-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

Hunters, herds, and ripple effects W1-mt_T0jG4YImZp-s1

  1. Animals eating plants · Herbivory is an animal consuming plants or plant parts, such as leaves.
  2. About 1 to 2 years after the hare peaks · In this record, lynx peaks typically follow hare peaks by about 1 to 2 years. This timing is not a rule for every predator-prey system.
  3. False · Some predator-prey populations cycle, but many do not. The lynx and hare record does not establish a universal rule.
  4. Snails decrease and algae increase · The stated model predicts fewer snails when crabs return. Less snail grazing then allows more algae. This prediction depends on the stated links and fixed conditions.
  5. Deer surge and young trees decline · Under the stated assumptions, fewer wolves allow more deer. More browsing then reduces young trees. A real valley need not follow this simple prediction.
  6. The result supports a bottom-up contribution · The response to nutrient addition supports a bottom-up contribution. It does not establish simultaneous increases or rule out top-down effects.
  7. False · Removing a predator can affect plants indirectly by changing herbivore numbers or feeding. The direction and size of the response depend on the food web.
  8. Use replicated controls, including fences that allow predator access · Replicated untreated plots track shared changes. Controls with comparable fencing but predator access test fence effects. A difference supports a predator effect, not exclusive top-down control.
Worksheet · LightMySky