Explain why removing all the predators from a grassland ecosystem would affect the populations of both herbivores and plants.

Eduqas GCSE Biology — 1.6.1 Ecosystems · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

In some areas, large predators such as wolves have been hunted until they no longer exist in a habitat. Scientists have studied the effects this has on the rest of the ecosystem.

Model answer (4 marks)

Without predators the herbivore population would increase because they are no longer being eaten or kept in check. The larger number of herbivores would consume more plants, so the plant population would decrease.

Examiner tips

Use the exact sequence: predators removed → herbivore increase → more plant consumption → plant decrease.
Show cause and effect clearly, linking each step.
Use terms like "kept in check" and "consume more plants" to match the mark scheme.

Common mistakes

Focusing only on predator removal without mentioning herbivore increase.
Using vague language such as "more animals" instead of "herbivore population".
Ignoring the plant response or stating the opposite effect.

Mark scheme (4 marks)

Without predators, the herbivore population would increase
Because herbivores are no longer being eaten / kept in check by predators
The increased number of herbivores would consume more plants
So the plant population would decrease

Key terms in this question

predator · herbivore · population · ecosystem