5.1.10—Soil and biodiversity
- Syllabus
- First assessment 2026
- Objective
- 5.1.10
- Level
- HL
Explain Why Soil Holds Many Niches
Soil supports diverse organisms because pore size, depth, moisture, oxygen and food create different microhabitats.
Large pores drain and aerate; small pores retain water; surface litter supplies carbon; deeper layers differ in oxygen and chemistry. Microbes, fungi and animals partition these conditions.
A water-filled deep pore favours anaerobic microbes, while an oxygenated surface pore supports aerobic decomposers.
Compaction removes pore space and blocks oxygen and water pathways, reducing the range of soil microhabitats and niches.
Soil life is not evenly distributed; conditions vary over centimetres and depth.