OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What happens to soil when earthworms are damaged by ploughing?

1. The soil becomes more fertile

2. The soil becomes compacted

3. The soil retains more water

4. The soil is enriched with organic matter

The correct answer is: The soil becomes compacted

When earthworms are damaged by ploughing, the soil becomes compacted. Earthworms play a crucial role in maintaining soil structure and aeration. They create burrows as they move through the soil, which helps to loosen it and allows air, water, and nutrients to penetrate effectively. When these earthworms are harmed, their burrowing activity is diminished, leading to a reduction in soil aeration and drainage. Consequently, the soil can become denser and more compacted, which can negatively affect plant growth and hinder root development. While the other options such as increased fertility, water retention, and enrichment with organic matter are beneficial processes often associated with healthy earthworm populations, none of these occur when earthworms are damaged. Instead, the loss of earthworm activity primarily leads to compaction, detrimental to overall soil health.