Question

soil layers
o humus or organic
a topsoil
b subsoil
use the diagram to answer the question. when moving underground from the surface, which layer is the first one down having no living organisms?

Explanation:

Analyze the soil layers diagram

The diagram shows three labeled soil horizons from the surface downward:

• O Humus or organic (uppermost layer, containing organic matter and living organisms)
• A Topsoil (second layer, rich in organic matter, roots, and soil organisms)
• B Subsoil (third layer, lower organic content, fewer organisms)

Identify the first layer with no living organisms

• The question asks: "When moving underground from the surface, which layer is the first one down having no living organisms?"
• The O horizon (humus/organic) and A horizon (topsoil) are highly active biological zones containing plant roots, insects, fungi, and bacteria.
• The B horizon (subsoil) is characterized by an accumulation of leached minerals and clay, with extremely low organic matter and a lack of active soil organisms compared to the upper layers.

Determine the correct layer

The B Subsoil layer is the first layer down from the surface that is considered to have no living organisms (or negligible biological activity) compared to the highly active O and A horizons.

Answer:

B Subsoil