Question

use the diagram to answer the question: which layer typically does not contain living organisms?

soil layers
o humus or organic
a topsoil
b subsoil
c parent material
r bedrock

parent layer
subsoils
topsoil
humus

Explanation:

Analyze the characteristics of soil layers

The soil profile consists of several horizons:

• O Horizon (Humus or organic): Rich in organic matter, plant litter, and active decomposers.
• A Horizon (Topsoil): High concentration of organic matter and microorganisms; where most plant roots and soil organisms live.
• B Horizon (Subsoil): Contains clay and mineral deposits, with fewer organisms and deep roots.
• C Horizon (Parent material): Consists of weathered rock fragments with virtually no organic matter or biological activity.
• R Horizon (Bedrock): Solid rock layer.

Evaluate the given options

• humus: Highly active biologically.
• topsoil: Highly active biologically.
• subsoils: Contains some deep roots and microbes, but far less than topsoil.
• parent layer (C Horizon): Located deep underground, consisting of partially disintegrated rock with almost no organic nutrients, water, or oxygen to support living organisms.

Answer:

• parent layer (Correct answer)
• subsoils
• topsoil
• humus