Soil microbiology — Compared with the population of bacteria or fungi in typical soils, the population of algae is generally regarded as:

Introduction / Context:
Understanding relative abundances of microbial groups in soil (bacteria, fungi, algae) helps predict ecological roles such as nutrient cycling, aggregation, and primary productivity. While all three occur in many soils, their numbers and biomass differ because of light availability, moisture, organic matter, and aeration.

Given Data / Assumptions:

• Typical surface mineral soils with patchy light exposure.
• No unusual algal blooms or permanently waterlogged photic conditions.
• We compare routine population levels rather than rare special habitats.

Concept / Approach:
Soil bacteria and fungi dominate numerically and functionally in most soils. Algae (including cyanobacteria in many texts) occur primarily on illuminated surfaces or pore spaces near the surface. Because soils are often shaded and light-limited, algal populations are usually lower than bacterial and fungal populations that thrive on organic substrates independent of light.

Step-by-Step Solution:

Verification / Alternative check:
Microbial ecology surveys consistently report higher counts and biomass for bacteria and fungi; algal counts rise mainly in crusts, paddy fields, or very thin illuminated layers after rain.

Why Other Options Are Wrong:

• Generally greater than: contradicts usual soil surveys.
• Equal to: unrealistic given energy constraints and habitat volume.
• None of these: unnecessary because a correct comparative statement is available.

Common Pitfalls:
Generalizing from special cases (e.g., algal crusts, paddy soils) to all soils; the question targets typical soils where light is limiting below the surface.

Final Answer:
generally smaller than