A student was investigating the populations of organisms in a garden - Edexcel - GCSE Biology Combined Science - Question 5 - 2019 - Paper 1

Killing the slugs would have an indirect effect on the population of earthworms. Since hedgehogs eat both slugs and earthworms, reducing the slug population would likely lead to an increase in the earthworm population. With fewer slugs, there would be less competition for food resources, allowing the earthworms to thrive. Furthermore, if hedgehogs no longer have slugs to eat, they might turn their attention more towards earthworms, which could also influence the overall balance in the ecosystem. However, in the absence of slugs, the pressure on earthworms from their natural predators (hedgehogs) may diminish, potentially allowing their numbers to increase.